#431

画面上でのテストは完了．
移行にす早さが求められるので，準備ができたらマージする．

Reviewed-on: #430
Co-authored-by: miteruzo <miteruzo@naver.com>

backend/app/controllers/materials_controller.rb

@@ -70,7 +70,10 @@ class MaterialsController < ApplicationController
         .find_by(id: params[:id])
     return head :not_found unless material
 
-    wiki_page_body = material.tag&.tag_name('ja')&.wiki_page&.current_revision&.body
+    wiki_page_body =
+        TagDescription
+        .find_by(tag_id: material.tag_id, language_code: locale.language_code)
+        &.body
 
     render json: MaterialRepr.base(material, host: request.base_url,
                                    language_code: locale.language_code).merge(wiki_page_body:)

backend/app/controllers/nico_tags_controller.rb

@@ -26,7 +26,7 @@ class NicoTagsController < ApplicationController
         ExternalTag
         .joins("LEFT JOIN (#{ post_tag_max_sql }) post_tag_max " \
                'ON post_tag_max.external_tag_id = external_tags.id')
-        .includes(linked_tags: { tag_names: :wiki_page })
+        .includes(linked_tags: [:tag_names, :tag_descriptions])
     if name
       q = q.where(('external_tags.name LIKE ? ' +
                    "OR CONCAT(external_tags.platform, ':', external_tags.name) LIKE ?"),

backend/app/controllers/posts_controller.rb

@@ -53,7 +53,7 @@ class PostsController < ApplicationController
         .reselect('posts.*', Arel.sql("#{ updated_at_all_sql } AS updated_at_all"))
         .preload(:external_tags, :uploaded_user, :parents, :children,
                  post_tags: [:sections, { tag: [:deerjikists, :materials,
-                                                { tag_names: :wiki_page }] }])
+                                                :tag_names, :tag_descriptions] }])
         .with_attached_thumbnail
 
     q = q.where('posts.url LIKE ?', "%#{ url }%") if url
@@ -111,7 +111,7 @@ class PostsController < ApplicationController
         filtered_posts(locale)
         .preload(:uploaded_user, :parents, :children,
                  post_tags: [:sections, { tag: [:deerjikists, :materials,
-                                                { tag_names: :wiki_page }] }])
+                                                :tag_names, :tag_descriptions] }])
         .with_attached_thumbnail
         .order('RAND()')
         .first
@@ -198,7 +198,7 @@ class PostsController < ApplicationController
         Post
         .includes(:uploaded_user, :parents, :children,
                   post_tags: [:sections, { tag: [:deerjikists, :materials,
-                                                 { tag_names: :wiki_page }] }])
+                                                 :tag_names, :tag_descriptions] }])
         .with_attached_thumbnail
         .find_by(id: params[:id])
     return head :not_found unless post

backend/app/controllers/tag_descriptions_controller.rb

@@ -1,14 +1,18 @@
 class TagDescriptionsController < ApplicationController
   def show
-    description = TagDescription.find_by(tag_id: params[:id], language_code: 'ja')
+    locale = resolve_locale!
+    description = TagDescription.find_by(tag_id: params[:id], language_code: locale.language_code)
     return head :not_found unless description
 
     render json: representation(description)
   end
 
   def show_by_title
-    tag_name = TagName.find_by(language_code: 'ja', name: params[:name].to_s.strip)
+    locale = resolve_locale!
-    description = tag_name&.tag && TagDescription.find_by(tag: tag_name.tag, language_code: 'ja')
+    tag_name = TagName.find_by(
+        language_code: locale.language_code, name: params[:name].to_s.strip)
+    description = tag_name&.tag && TagDescription.find_by(
+        tag: tag_name.tag, language_code: locale.language_code)
     return head :not_found unless description
 
     render json: representation(description)
@@ -21,18 +25,19 @@ class TagDescriptionsController < ApplicationController
     body = params[:body].to_s
     return render_unprocessable_entity('本文は必須です．', field: :body) if body.blank?
 
+    locale = resolve_locale!
     tag = Tag.find_by(id: params[:id])
     return head :not_found unless tag
 
-    description = TagDescription.find_by(tag:, language_code: 'ja')
+    description = TagDescription.find_by(tag:, language_code: locale.language_code)
 
     if description
-      TagDescriptionOperation.update!(tag:, body:, updated_by_user: current_user)
+      TagDescriptionOperation.update!(locale, tag:, body:, updated_by_user: current_user)
       description.reload
       render json: representation(description)
     else
-      TagDescriptionOperation.create!(tag:, body:, created_by_user: current_user)
+      TagDescriptionOperation.create!(locale, tag:, body:, created_by_user: current_user)
-      description = TagDescription.find_by!(tag:, language_code: 'ja')
+      description = TagDescription.find_by!(tag:, language_code: locale.language_code)
       render json: representation(description), status: :created
     end
   rescue ActiveRecord::RecordInvalid => e

backend/app/controllers/tag_groups_controller.rb

@@ -0,0 +1,43 @@
+class TagGroupsController < ApplicationController
+  def index
+    locale = resolve_locale!
+    groups = TagGroup.includes(:created_by_user, :updated_by_user).order(:id)
+    render json: TagGroupRepr.many(locale, groups.to_a)
+  end
+
+  def show
+    locale = resolve_locale!
+    group = TagGroup.includes(:created_by_user, :updated_by_user).find_by(id: params[:id])
+    return head :not_found unless group
+
+    render json: TagGroupRepr.one(locale, group)
+  end
+
+  def create
+    return head :unauthorized unless current_user
+    return head :forbidden unless current_user.gte_member?
+
+    locale = resolve_locale!
+    group = TagGroupOperation.create!(locale, **write_attributes, actor: current_user)
+    render json: TagGroupRepr.one(locale, group), status: :created
+  end
+
+  def update
+    return head :unauthorized unless current_user
+    return head :forbidden unless current_user.gte_member?
+
+    locale = resolve_locale!
+    group = TagGroup.find_by(id: params[:id])
+    return head :not_found unless group
+
+    TagGroupOperation.update!(locale, group:, **write_attributes, actor: current_user)
+    render json: TagGroupRepr.one(locale, group.reload)
+  end
+
+  private
+
+  def write_attributes
+    { name: params[:name], description: params[:description],
+      members: params[:members], placements: params[:placements] }
+  end
+end

backend/app/controllers/tag_versions_controller.rb

@@ -51,7 +51,7 @@ class TagVersionsController < ApplicationController
 
       tags_by_id =
           Tag
-          .includes(:tag_names, :materials, tag_names: :wiki_page)
+          .includes(:tag_names, :materials, :tag_descriptions, parents: :tag_descriptions)
           .where(id: all_parent_tag_ids)
           .index_by(&:id)
 

backend/app/controllers/tags_controller.rb

@@ -175,7 +175,7 @@ class TagsController < ApplicationController
     tags_by_id =
         Tag
         .joins(:tag_names)
-        .includes(:tag_names, :materials, tag_names: :wiki_page)
+        .includes(:tag_names, :materials, :tag_descriptions, parents: :tag_descriptions)
         .where(tag_names: { language_code: locale.language_code, primary_flg: true },
                id: tag_ids)
         .index_by(&:id)
@@ -238,7 +238,7 @@ class TagsController < ApplicationController
     base =
         Tag
         .joins(:tag_names)
-        .includes(:tag_names, :materials, tag_names: :wiki_page)
+        .includes(:tag_names, :materials, :tag_descriptions, parents: :tag_descriptions)
         .where(tag_names: { language_code: locale.language_code, primary_flg: true },
                deprecated_at: nil)
     base = base.where('tags.post_count > 0') if present_only
@@ -282,7 +282,7 @@ class TagsController < ApplicationController
     tag =
         Tag
         .joins(:tag_names)
-        .includes(:tag_names, :materials, tag_names: :wiki_page)
+        .includes(:tag_names, :materials, :tag_descriptions, parents: :tag_descriptions)
         .find_by(id: params[:id],
                  tag_names: { language_code: locale.language_code, primary_flg: true })
     return render json: TagRepr.base(tag, language_code: locale.language_code) if tag
@@ -302,7 +302,7 @@ class TagsController < ApplicationController
     tag =
         Tag
         .joins(:tag_names)
-        .includes(:tag_names, :materials, tag_names: :wiki_page)
+        .includes(:tag_names, :materials, :tag_descriptions, parents: :tag_descriptions)
         .find_by(tag_names: { name:, language_code: locale.language_code, primary_flg: true })
     return render json: TagRepr.base(tag, language_code: locale.language_code) if tag
 
@@ -320,7 +320,7 @@ class TagsController < ApplicationController
 
     tag = 
         Tag.joins(:tag_names)
-        .includes(:tag_names, tag_names: :wiki_page)
+        .includes(:tag_names, :tag_descriptions, parents: :tag_descriptions)
         .find_by(id: params[:id],
                  tag_names: { language_code: locale.language_code, primary_flg: true })
     return head :not_found unless tag
@@ -340,7 +340,7 @@ class TagsController < ApplicationController
     tag =
         Tag
         .joins(:tag_names)
-        .includes(:tag_names, tag_names: :wiki_page)
+        .includes(:tag_names, :tag_descriptions, parents: :tag_descriptions)
         .find_by(tag_names: { name:, language_code: locale.language_code, primary_flg: true })
     return head :not_found unless tag
 
@@ -359,7 +359,7 @@ class TagsController < ApplicationController
     tag =
         Tag
         .joins(:tag_names)
-        .includes(:tag_names, tag_names: :wiki_page)
+        .includes(:tag_names, :tag_descriptions, parents: :tag_descriptions)
         .find_by(id: params[:id],
                  tag_names: { language_code: locale.language_code, primary_flg: true })
     return head :not_found unless tag
@@ -424,7 +424,7 @@ class TagsController < ApplicationController
     tag =
         Tag
         .joins(:tag_names)
-        .includes(:tag_names, :materials, tag_names: :wiki_page)
+        .includes(:tag_names, :materials, :tag_descriptions, parents: :tag_descriptions)
         .find_by(tag_names: { name:, language_code: locale.language_code, primary_flg: true })
     return head :not_found unless tag
 
@@ -770,31 +770,15 @@ class TagsController < ApplicationController
       TagVersioning.ensure_snapshot!(old_owner_tag, created_by_user: current_user)
     end
 
-    current_tag_name.wiki_page&.update!(tag_name_id: promoted_tag_name.id)
+    current_tag_name&.update!(primary_flg: false, auto_generated: false)
-    current_tag_name.association(:wiki_page).reset
+    promoted_tag_name.update!(tag:, primary_flg: true, auto_generated: false)
-
+    tag.association(:tag_names).reset
-    current_tag_name.update!(canonical_id: promoted_tag_name.id,
-                             primary_flg: false, auto_generated: false)
-    promoted_tag_name.update!(tag:, canonical_id: nil, primary_flg: true, auto_generated: false)
-
-    TagName.where(tag:,
-                  language_code: current_tag_name.language_code,
-                  primary_flg: false)
-           .where.not(id: promoted_tag_name.id)
-           .find_each do |alias_tag_name|
-      alias_tag_name.update!(canonical_id: promoted_tag_name.id, primary_flg: false)
-    end
-
-    tag.update!(tag_name_id: promoted_tag_name.id)
-    current_tag_name.association(:wiki_page).reset
-    current_tag_name.association(:tag).reset
-    current_tag_name.reload.update!(canonical_id: promoted_tag_name.id, primary_flg: false)
 
     return unless old_owner_tag && old_owner_tag != tag
 
     record_tag_version!(old_owner_tag.reload, event_type: :update,
                         created_by_user: current_user,
-                        language_code: current_tag_name.language_code)
+                        language_code: promoted_tag_name.language_code)
   end
 
   def update_aliases! locale, tag, alias_names
@@ -802,20 +786,15 @@ class TagsController < ApplicationController
 
     affected_tags = [tag]
 
-    primary_tag_name = TagName.find_by!(tag:,
-                                        language_code: locale.language_code,
-                                        primary_flg: true)
     current_aliases = tag.tag_names.where(language_code: locale.language_code,
                                           primary_flg: false).to_a
 
-    current_aliases.each do |alias_tag_name|
+    requested_aliases = TagName.where(
-      next if alias_names.include?(alias_tag_name.name)
+        language_code: locale.language_code, name: alias_names)
-
+        .includes(:tag).index_by(&:name)
-      affected_tags << alias_tag_name.tag
-    end
 
     alias_names.each do |alias_name|
-      alias_tag_name = TagName.find_by(language_code: locale.language_code, name: alias_name)
+      alias_tag_name = requested_aliases[alias_name]
       if alias_tag_name&.primary? && alias_tag_name.tag_id && alias_tag_name.tag_id != tag.id
         alias_tag_name.errors.add(:name, 'その名前は既に使はれてゐます．')
         raise ActiveRecord::RecordInvalid, alias_tag_name
@@ -823,7 +802,8 @@ class TagsController < ApplicationController
       affected_tags << alias_tag_name&.tag
     end
 
-    affected_tags.compact.uniq.each do |affected_tag|
+    affected_tags = affected_tags.compact.uniq(&:id)
+    affected_tags.each do |affected_tag|
       TagVersioning.ensure_snapshot!(affected_tag, created_by_user: current_user,
                                      language_code: locale.language_code)
     end
@@ -831,19 +811,21 @@ class TagsController < ApplicationController
     current_aliases.each do |alias_tag_name|
       next if alias_names.include?(alias_tag_name.name)
 
-      alias_tag_name.update!(canonical_id: nil, tag_id: nil)
+      alias_tag_name.destroy!
     end
 
     alias_names.each do |alias_name|
-      alias_tag_name = TagName.find_or_initialize_by(
+      alias_tag_name = requested_aliases[alias_name] || TagName.new(
           language_code: locale.language_code,
           name: alias_name)
       alias_tag_name.script_code = locale.script_code
-      alias_tag_name.update!(tag:, primary_flg: false, auto_generated: false,
+      alias_tag_name.update!(tag:, primary_flg: false, auto_generated: false)
-                             canonical_id: primary_tag_name.id)
     end
 
-    affected_tags.compact.uniq.each do |affected_tag|
+    affected_tags.each do |affected_tag|
+      # update_all records this Tag after its parent relationships are updated.
+      next if affected_tag.id == tag.id
+
       record_tag_version!(affected_tag, event_type: :update,
                           created_by_user: current_user,
                           language_code: locale.language_code)

backend/app/controllers/wiki_pages_controller.rb

@@ -1,107 +1,126 @@
 class WikiPagesController < ApplicationController
-  rescue_from Wiki::Commit::Conflict, with: :render_wiki_conflict
+  # 互換性のための Facade API
+
+  rescue_from TagDescriptionOperation::Conflict, with: :render_wiki_conflict
 
   def index
-    # 互換性のための化石リソース
+    locale = resolve_locale!
-    # TODO: ヘルプおよびタグ・グループ追加後に，
-    # TODO: タグ説明とヘルプ、タグ・グループから取得する作りに変更する．
-    #
-    title = params[:title].to_s.strip
-    descriptions = TagDescription.where(language_code: 'ja')
-        .includes(tag: :tag_names)
-    pages = unmigrated_wiki_pages.includes(tag_name: :tag)
 
+    title = params[:title].to_s.strip
+    descriptions =
+        TagDescription
+        .where(language_code: locale.language_code)
+        .includes(tag: :tag_names)
+
+    descriptions = descriptions.order(updated_at: :desc, id: :asc)
+    tag_groups = TagGroup.order(updated_at: :desc, id: :asc)
     if title.present?
       pattern = "%#{ ApplicationRecord.sanitize_sql_like(title) }%"
-      descriptions = descriptions.joins(tag: :tag_names)
+      descriptions =
-          .where(tag_names: { language_code: 'ja', primary_flg: true })
+          descriptions.joins(tag: :tag_names)
+          .where(tag_names: { language_code: locale.language_code, primary_flg: true })
           .where('tag_names.name LIKE ?', pattern).limit(20)
-      pages = pages.where('tag_names.name LIKE ?', pattern).limit(20)
+      tag_groups = tag_groups.where(
+          'CONCAT(?, name) LIKE ? OR CONCAT(?, name) LIKE ?',
+          TagGroupRepr::PREFIX, pattern, 'tag_group:', pattern).limit(20)
     end
 
-    json = descriptions.map { |description| WikiPageRepr.tag_description(description) }
+    json = descriptions.map { |description| WikiPageRepr.tag_description(locale, description) }
-    json.concat(WikiPageRepr.base(pages))
+    json.concat(tag_groups.map { WikiPageRepr.tag_group(_1) })
+    json.sort_by! do |row|
+      [-row['updated_at'].to_f, row.fetch('resource_type'), row.fetch('id')]
+    end
     json = json.first(20) if title.present?
     render json:
   end
 
   def show
-    tag_description = TagDescription.find_by(id: params[:id])
+    locale = resolve_locale!
+    tag_description = TagDescription.find_by(id: params[:id], language_code: locale.language_code)
 
-    return render_wiki_page_by_tag_description tag_description if tag_description
+    return render_wiki_page_by_tag_description locale, tag_description if tag_description
 
-    page = WikiPage.joins(:tag_name)
+    tag_group = TagGroup.find_by(id: params[:id])
-                   .includes(tag_name: :tag)
+    return render_tag_group locale, tag_group if tag_group
-                   .find_by(id: params[:id])
 
-    render_wiki_page_or_404 page
+    head :not_found
   end
 
   def show_by_title
+    locale = resolve_locale!
     title = params[:title].to_s.strip
 
-    tag_description = tag_description_by_title(title)
+    if (name = TagGroupRepr.name_from_title(title))
+      tag_group = TagGroup.find_by(name:)
+      return render_tag_group locale, tag_group if tag_group
+      return head :not_found
+    end
 
-    return render_wiki_page_by_tag_description tag_description if tag_description
+    tag_description = tag_description_by_title(locale, title)
 
-    page = WikiPage.joins(:tag_name)
+    return render_wiki_page_by_tag_description locale, tag_description if tag_description
-                   .includes(tag_name: :tag)
-                   .find_by(tag_name: { name: title })
 
-    render_wiki_page_or_404 page
+    head :not_found
   end
 
   def exists
-    return head :no_content if TagDescription.exists?(id: params[:id])
+    locale = resolve_locale!
+    if TagDescription.exists?(id: params[:id], language_code: locale.language_code)
+      return head :no_content
+    end
+    return head :no_content if TagGroup.exists?(id: params[:id])
 
-    head WikiPage.exists?(id: params[:id]) ? :no_content : :not_found
+    head :not_found
   end
 
   def exists_by_title
+    locale = resolve_locale!
     title = params[:title].to_s.strip
-    return head :no_content if tag_description_by_title(title)
+    if (name = TagGroupRepr.name_from_title(title))
+      exists = TagGroup.exists?(name:)
+      return head exists ? :no_content : :not_found
+    end
 
-    exists = WikiPage.joins(:tag_name).exists?(tag_names: { name: title })
+    return head :no_content if tag_description_by_title(locale, title)
-    head exists ? :no_content : :not_found
+
+    head :not_found
   end
 
   def diff
     id = params[:id]
     return render_bad_request('id は必須です．') if id.blank?
 
+    locale = resolve_locale!
+
     from = params[:from].presence
     to = params[:to].presence
 
-    description = TagDescription.find_by(id:)
+    description = TagDescription.find_by(id:, language_code: locale.language_code)
     if description
       versions = description_versions(description)
       from_rev = from && versions.find(from)
       to_rev = to ? versions.find(to) : versions.find_by!(version_no: description.version_no)
-      resource = WikiPageRepr.tag_description(description)
+      resource = WikiPageRepr.tag_description(locale, description)
     else
-      page = WikiPage.joins(:tag_name).includes(tag_name: :tag).find(id)
+      tag_group = TagGroup.find_by(id:)
-      from_rev = from && page.wiki_revisions.find(from)
+      if tag_group
-      to_rev = to ? page.wiki_revisions.find(to) : page.current_revision
+        from_rev = from && group_version(tag_group, from)
-      if ((from_rev && !from_rev.content?) || !to_rev&.content?)
+        to_rev = to ? group_version(tag_group, to) : current_group_version(tag_group)
-        return render_unprocessable_entity('差分を表示できない版です．')
+        return head :not_found if (from && !from_rev) || !to_rev
+
+        from_body = from_rev && render_group_version(locale, from_rev)
+        to_body = render_group_version(locale, to_rev)
+        resource = { 'id' => tag_group.id,
+                     'title' => "#{ TagGroupRepr::PREFIX }#{ tag_group.name }",
+                     'deprecated_at' => nil }
+      else
+        return head :not_found
       end
-      resource = WikiPageRepr.base(page)
     end
 
-    diffs = Diff::LCS.sdiff(from_rev&.body&.lines || [], to_rev.body.lines)
+    from_body ||= from_rev&.body
-    diff_json = diffs.map { |change|
+    to_body ||= to_rev.body
-      case change.action
+    diff_json = wiki_diff(from_body, to_body)
-      when ?=
-        { type: 'context', content: change.old_element }
-      when ?!
-        [{ type: 'removed', content: change.old_element },
-         { type: 'added', content: change.new_element }]
-      when ?+
-        { type: 'added', content: change.new_element }
-      when ?-
-        { type: 'removed', content: change.old_element }
-      end
-    }.flatten.compact
 
     render json: { wiki_page_id:      resource.fetch('id'),
                    title:             resource.fetch('title'),
@@ -109,6 +128,8 @@ class WikiPagesController < ApplicationController
                    older_revision_id: from_rev&.id,
                    newer_revision_id: to_rev.id,
                    diff:              diff_json }
+  rescue TagGroupMarkdownRenderer::UnsupportedStructure => error
+    render_unprocessable_entity(error.message)
   end
 
   def create
@@ -122,30 +143,37 @@ class WikiPagesController < ApplicationController
     return render_unprocessable_entity('タイトルは必須です．', field: :title) if title.blank?
     return render_unprocessable_entity('本文は必須です．', field: :body) if body.blank?
 
-    page = if title.include?(':')
+    locale = resolve_locale!
-      ApplicationRecord.transaction do
-        tag_name = TagName.find_or_create_by!(language_code: 'ja', name: title) do |name|
-          name.script_code = 'Jpan'
-          name.primary_flg = true
-          name.auto_generated = false
-        end
 
-        Wiki::Commit.create_legacy_content!(
+    if (name = TagGroupRepr.name_from_title(title))
-            tag_name:, body:, created_by_user: current_user, message:)
+      parsed = TagGroupMarkdownParser.parse(locale, body:, group: nil)
-      end
+      group = TagGroupOperation.create!(
-    else
+          locale, name:, **parsed.except(:compatibility_body), actor: current_user,
-      tag_name = TagName.find_by(language_code: 'ja', name: title)
+          require_compatibility: true)
-      return render_unprocessable_entity field: :title unless tag_name&.tag
+      version = current_group_version(group)
-
+      return render_group_representation(TagGroupRepr.one(locale, group), version,
-      TagDescriptionOperation.create!(
+                                         status: :created)
-          tag: tag_name.tag, body:, created_by_user: current_user, message:)
     end
 
-    render json: WikiPageRepr.base(page), status: :created
+    description =
+        if title.include?(':')
+          return render_unprocessable_entity field: :title
+        else
+          tag_name = TagName.find_by(language_code: locale.language_code, name: title)
+          return render_unprocessable_entity field: :title unless tag_name&.tag
+
+          TagDescriptionOperation.create!(
+              locale,
+              tag: tag_name.tag, body:, created_by_user: current_user, message:)
+        end
+
+    render json: WikiPageRepr.tag_description(locale, description), status: :created
   rescue ActiveRecord::RecordInvalid => e
     render_validation_error e.record
   rescue ActiveRecord::RecordNotUnique
     render_record_not_unique
+  rescue TagGroupMarkdownParser::InvalidDocument => error
+    render_unprocessable_entity(error.message)
   end
 
   def update
@@ -158,93 +186,177 @@ class WikiPagesController < ApplicationController
     return render_unprocessable_entity('タイトルは必須です．', field: :title) if title.blank?
     return render_unprocessable_entity('本文は必須です．', field: :body) if body.blank?
 
-    page = WikiPage.find(params[:id])
+    locale = resolve_locale!
+
+    group = TagGroup.find_by(id: params[:id])
+    if (name = TagGroupRepr.name_from_title(title))
+      return head :not_found unless group
+
+      parsed = TagGroupMarkdownParser.parse(locale, body:, group:)
+      TagGroupOperation.update!(
+          locale, group:, name:, **parsed.except(:compatibility_body), actor: current_user,
+          require_compatibility: true)
+      return head :ok
+    end
+
+    return render_unprocessable_entity field: :title if title.include?(':')
+    description = TagDescription.find_by(id: params[:id], language_code: locale.language_code)
+    unless description
+      return render_unprocessable_entity field: :title if group
+      return head :not_found
+    end
+
+    tag = description.tag
+    tag_name = tag.tag_name(locale.language_code)
+    return render_unprocessable_entity field: :title unless tag_name
+    return render_unprocessable_entity field: :title if tag_name.name.include?(':')
+
     base_revision_id = params[:base_revision_id].presence
 
     ApplicationRecord.transaction do
-      page.lock!
+      tag.lock!
-
+      old_title = tag_name.name
-      old_title = page.title
+      if title != old_title
-
-      tag = page.tag_name.tag
-
-      if tag && title != old_title
         TagVersioning.ensure_snapshot!(tag, created_by_user: current_user)
       end
 
-      page.tag_name.update!(name: title) if title != old_title
+      tag_name.update!(name: title) if title != old_title
 
       message = params[:message].presence
-      Wiki::Commit.content!(page:,
+      TagDescriptionOperation.update!(locale, tag:, body:, updated_by_user: current_user,
-                            body:,
+                                      message:, base_revision_id:)
-                            created_user: current_user,
-                            message:,
-                            base_revision_id:)
 
-      if tag && title != old_title
+      if title != old_title
         tag.reload
         TagVersionRecorder.record!(tag:, event_type: :update, created_by_user: current_user)
       end
     end
 
     head :ok
+  rescue ActiveRecord::RecordInvalid => e
+    render_validation_error e.record
+  rescue ActiveRecord::RecordNotUnique
+    render_record_not_unique
+  rescue TagGroupMarkdownParser::InvalidDocument => error
+    render_unprocessable_entity(error.message)
   end
 
   def changes
+    locale = resolve_locale!
+
     id = params[:id].presence
-    description = id && TagDescription.find_by(id:)
+    description = id && TagDescription.find_by(id:, language_code: locale.language_code)
     if description
-      return render json: description_changes(TagDescription.where(id: description.id))
+      return render json: description_changes(locale, TagDescription.where(id: description.id))
     end
 
-    pages = id ? WikiPage.where(id:) : unmigrated_wiki_pages
+    tag_group = id && TagGroup.find_by(id:)
-    revisions = WikiRevision.joins(wiki_page: :tag_name)
+    if tag_group
-        .where(wiki_page_id: pages.select(:id))
+      return render json: tag_group_changes(TagGroupVersion.where(tag_group_id: tag_group.id))
-        .includes(:created_user, wiki_page: { tag_name: :tag })
+    end
-        .order(id: :desc).limit(200)
+
-    json = revisions.map { |rev|
+    json = []
-      { revision_id: rev.id,
-        pred: rev.base_revision_id,
-        succ: nil,
-        wiki_page: { id: rev.wiki_page_id,
-                     title: rev.wiki_page.title,
-                     deprecated_at: rev.wiki_page.deprecated_at },
-        user: rev.created_user && { id: rev.created_user.id, name: rev.created_user.name },
-        kind: rev.kind,
-        message: rev.message,
-        timestamp: rev.created_at }
-    }
     unless id
-      json.concat(description_changes(TagDescription.where(language_code: 'ja')))
+      json.concat(tag_group_changes(TagGroupVersion.all))
-      json.sort_by! { |row| -row[:revision_id] }
+      json.concat(description_changes(locale,
+                                      TagDescription.where(language_code: locale.language_code)))
+      json = json.each_with_index.sort_by do |row, index|
+        [-row.fetch(:timestamp).to_f, index]
+      end.map(&:first)
     end
     render json: json.first(200)
   end
 
   private
 
-  def render_wiki_page_or_404 page
+  def render_tag_group locale, group
-    return head :not_found unless page
+    version = if params[:version].present?
-
+      group_version(group, params[:version])
-    rev = find_revision(page)
+    else
-    return head :not_found unless rev
+      current_group_version(group)
-
-    if rev.redirect?
-      return (
-          redirect_to wiki_page_by_title_path(title: rev.redirect_page.title),
-                      status: :moved_permanently)
     end
+    return head :not_found unless version
 
-    body = rev.body
+    representation =
-    revision_id = rev.id
+        if params[:version].present?
-    pred = page.pred_revision_id(revision_id)
+          TagGroupRepr.historical(locale, version)
-    succ = page.succ_revision_id(revision_id)
+        else
-    updated_at = rev.created_at
+          TagGroupRepr.one(locale, group)
-
+        end
-    render json: WikiPageRepr.base(page).merge(body:, revision_id:, pred:, succ:, updated_at:)
+    render_group_representation(representation, version)
   end
 
-  def render_wiki_page_by_tag_description description
+  def render_group_version locale, version
+    representation = TagGroupRepr.historical(locale, version)
+    TagGroupMarkdownRenderer.render(representation)
+  end
+
+  def render_group_representation representation, version, body: nil, status: :ok
+    body ||= TagGroupMarkdownRenderer.render(representation)
+    versions = TagGroupVersion.where(tag_group_id: version.tag_group_id)
+    pred = versions.find_by(version_no: version.version_no - 1)&.id
+    succ = versions.find_by(version_no: version.version_no + 1)&.id
+    updated_at = version.created_at
+    render json: {
+        'id' => version.tag_group_id,
+        'resource_type' => 'tag_group',
+        'title' => "#{ TagGroupRepr::PREFIX }#{ representation.fetch('name') }",
+        'deprecated_at' => nil,
+        'body' => body,
+        'revision_id' => version.id,
+        'pred' => pred,
+        'succ' => succ,
+        'updated_at' => updated_at }, status:
+  rescue TagGroupMarkdownRenderer::UnsupportedStructure => error
+    render_unprocessable_entity(error.message)
+  end
+
+  def current_group_version group
+    TagGroupVersion.find_by(tag_group_id: group.id, version_no: group.version_no)
+  end
+
+  def group_version group, version_id
+    TagGroupVersion.find_by(tag_group_id: group.id, id: version_id)
+  end
+
+  def wiki_diff from_body, to_body
+    diffs = Diff::LCS.sdiff(from_body.to_s.lines, to_body.to_s.lines)
+    diffs.map { |change|
+      case change.action
+      when ?=
+        { type: 'context', content: change.old_element }
+      when ?!
+        [{ type: 'removed', content: change.old_element },
+         { type: 'added', content: change.new_element }]
+      when ?+
+        { type: 'added', content: change.new_element }
+      when ?-
+        { type: 'removed', content: change.old_element }
+      end
+    }.flatten.compact
+  end
+
+  def tag_group_changes versions
+    rows = versions.includes(:created_by_user).order(id: :desc).limit(200).to_a
+    groups = TagGroup.where(id: rows.map(&:tag_group_id).uniq).index_by(&:id)
+    predecessors = TagGroupVersion.where(tag_group_id: groups.keys,
+                                         version_no: rows.map { _1.version_no - 1 })
+        .pluck(:tag_group_id, :version_no, :id)
+        .to_h { |group_id, number, version_id| [[group_id, number], version_id] }
+    rows.map do |version|
+      group = groups.fetch(version.tag_group_id)
+      user = version.created_by_user
+      { revision_id: version.id,
+        pred: predecessors[[group.id, version.version_no - 1]],
+        succ: nil,
+        wiki_page: { id: group.id, title: "#{ TagGroupRepr::PREFIX }#{ version.name }",
+                     deprecated_at: nil },
+        user: user && { id: user.id, name: user.name },
+        kind: 'content', message: nil, timestamp: version.created_at }
+    end
+  end
+
+  def render_wiki_page_by_tag_description locale, description
     versions = description_versions(description)
     historical = params[:version].present?
     rev = historical ? versions.find_by(id: params[:version]) :
@@ -255,7 +367,7 @@ class WikiPagesController < ApplicationController
     succ = versions.find_by(version_no: rev.version_no + 1)&.id
     body = historical ? rev.body : description.body
     updated_at = historical ? rev.created_at : description.updated_at
-    render json: WikiPageRepr.tag_description(description).merge(
+    render json: WikiPageRepr.tag_description(locale, description).merge(
         body:, revision_id: rev.id, pred:, succ:, updated_at:)
   end
 
@@ -264,20 +376,14 @@ class WikiPagesController < ApplicationController
                                 language_code: description.language_code)
   end
 
-  def tag_description_by_title title
+  def tag_description_by_title locale, title
     TagDescription.joins(tag: :tag_names)
-        .find_by(language_code: 'ja', tag_names: { language_code: 'ja', name: title })
+        .find_by(language_code: locale.language_code,
+                 tag_names: { language_code: locale.language_code, name: title })
   end
 
-  def unmigrated_wiki_pages
+  def description_changes locale, descriptions
-    descriptions = TagDescription.where(language_code: 'ja')
+    versions = TagDescriptionVersion.where(language_code: locale.language_code,
-    WikiPage.joins(:tag_name).where.not(id: descriptions.select(:id))
-        .where('tag_names.tag_id IS NULL OR tag_names.tag_id NOT IN (?)',
-               descriptions.select(:tag_id))
-  end
-
-  def description_changes descriptions
-    versions = TagDescriptionVersion.where(language_code: 'ja',
                                            tag_id: descriptions.select(:tag_id))
         .order(id: :desc).limit(200).to_a
     return [] if versions.empty?
@@ -286,7 +392,7 @@ class WikiPagesController < ApplicationController
         .includes(tag: :tag_names).index_by(&:tag_id)
     users = User.where(id: versions.map(&:created_by_user_id)).index_by(&:id)
     predecessors = TagDescriptionVersion.where(
-        language_code: 'ja', tag_id: by_tag.keys,
+        language_code: locale.language_code, tag_id: by_tag.keys,
         version_no: versions.map { |version| version.version_no - 1 })
         .pluck(:tag_id, :version_no, :id)
         .to_h { |tag_id, version_no, id| [[tag_id, version_no], id] }
@@ -296,7 +402,7 @@ class WikiPagesController < ApplicationController
       { revision_id: version.id,
         pred: predecessors[[version.tag_id, version.version_no - 1]],
         succ: nil,
-        wiki_page: { id: description.id, title: description.tag.name('ja'),
+        wiki_page: { id: description.id, title: description.tag.name(locale.language_code),
                      deprecated_at: description.tag.deprecated_at },
         user: user && { id: user.id, name: user.name },
         kind: 'content',
@@ -305,14 +411,6 @@ class WikiPagesController < ApplicationController
     end
   end
 
-  def find_revision page
-    if params[:version].present?
-      page.wiki_revisions.find_by(id: params[:version])
-    else
-      page.current_revision
-    end
-  end
-
   def render_wiki_conflict err
     render json: { error: 'conflict', message: err.message }, status: :conflict
   end

backend/app/models/external_tag.rb

@@ -1,4 +1,6 @@
 class ExternalTag < ApplicationRecord
+  before_create { SharedResourceIdAllocator.assign!(self) }
+
   enum :platform, nico: 'nico'
   validates :platform, presence: true, inclusion: { in: ExternalTag.platforms.keys }
 

backend/app/models/locale.rb

@@ -13,14 +13,13 @@ class Locale < ApplicationRecord
   def generate_tag_names!
     ApplicationRecord.transaction do
       tag_ids = TagName.where(language_code:, primary_flg: true).pluck(:tag_id)
-      Tag.where.not(id: tag_ids).find_each do
+      Tag.where.not(id: tag_ids).includes(:tag_names).find_each do
         TagName.create!(tag_id: _1.id,
                         language_code:,
                         name: TagName.generate_name(self, _1, _1.tag_name('ja')),
                         script_code:,
                         primary_flg: true,
-                        auto_generated: true,
+                        auto_generated: true)
-                        canonical_id: nil)
       end
     end
   end

backend/app/models/tag.rb

@@ -2,6 +2,8 @@ require 'set'
 
 
 class Tag < ApplicationRecord
+  before_create { SharedResourceIdAllocator.assign!(self) }
+
   class NicoTagNormalisationError < ArgumentError
     ;
   end
@@ -51,6 +53,7 @@ class Tag < ApplicationRecord
   has_many :tag_versions
 
   has_many :tag_names
+  has_many :tag_descriptions
 
   attribute :version_no, :integer, default: 1
 
@@ -88,7 +91,6 @@ class Tag < ApplicationRecord
     end
   end
   def name(language_code) = tag_name(language_code)&.name
-  def wiki_page = tag_name('ja')&.wiki_page
 
   def system?
     tag_name('ja')&.name.in?(SYSTEM_TAG_NAMES)
@@ -96,7 +98,13 @@ class Tag < ApplicationRecord
 
   def deprecated? = deprecated_at?
 
-  def has_wiki = wiki_page.present?
+  def has_description? language_code:
+    if tag_descriptions.loaded?
+      tag_descriptions.any? { _1.language_code == language_code }
+    else
+      tag_descriptions.exists?(language_code:)
+    end
+  end
 
   def material_id = materials.first&.id
 
@@ -251,16 +259,13 @@ class Tag < ApplicationRecord
       name = name.to_s.strip
 
       ApplicationRecord.transaction do
-        tn = TagName.find_or_create_by!(language_code:, name:) do
+        tn = TagName.find_by(language_code:, name:)
-          _1.script_code = locale.script_code
+        next tn.tag if tn
-          _1.primary_flg = true
-        end
 
-        tag = tn.tag
+        tag = Tag.create!(category:)
-        next tag if tag
+        tn = TagName.create!(tag:, language_code:, name:,
-
+                             script_code: locale.script_code, primary_flg: true,
-        tag = Tag.create!(tag_name_id: tn.id, category:)
+                             auto_generated: false)
-        tn.update!(tag:, primary_flg: true, canonical_id: nil, auto_generated: false)
         generate_tag_names!(locale, tag, tn)
         tag.association(:tag_names).reset
 
@@ -294,20 +299,18 @@ class Tag < ApplicationRecord
             end
           end
 
-          source_tag_name = source_tag.tag_name('ja')
+          if source_tag.tag_descriptions.exists?
-
+            source_tag.errors.add(:base, :invalid)
-          if source_tag_name.wiki_page.present?
+            raise ActiveRecord::RecordInvalid, source_tag
-            raise ActiveRecord::RecordInvalid.new(source_tag_name)
           end
 
           TagVersioning.record!(source_tag, event_type: :discard, created_by_user:)
-          source_tag.tag_names.update_all(tag_id: target_tag.id, primary_flg: false,
+          target_languages = target_tag.tag_names.where(primary_flg: true).pluck(:language_code)
-                                          updated_at: Time.current)
+          source_tag.tag_names.where(language_code: target_languages)
+              .update_all(primary_flg: false, auto_generated: false, updated_at: Time.current)
+          source_tag.tag_names.update_all(tag_id: target_tag.id, updated_at: Time.current)
           source_tag.destroy!
 
-          source_tag_name.update_columns(canonical_id: target_tag.tag_name_id,
-                                         updated_at: Time.current)
-
           TagVersioning.record!(target_tag, event_type: :update, created_by_user:)
         end
 
@@ -367,8 +370,7 @@ class Tag < ApplicationRecord
                           name: TagName.generate_name(locale, tag, base_tag_name),
                           script_code:,
                           primary_flg: true,
-                          auto_generated: true,
+                          auto_generated: true)
-                          canonical_id: nil)
         end
       end
     end

backend/app/models/tag_description.rb

@@ -1,3 +1,5 @@
 class TagDescription < ApplicationRecord
+  before_create { SharedResourceIdAllocator.assign!(self) }
+
   belongs_to :tag
 end

backend/app/models/tag_description_version.rb

@@ -1,3 +1,3 @@
 class TagDescriptionVersion < ApplicationRecord
-  ;
+  before_create { SharedResourceIdAllocator.assign!(self) }
 end

backend/app/models/tag_group.rb

@@ -0,0 +1,27 @@
+class TagGroup < ApplicationRecord
+  before_create { SharedResourceIdAllocator.assign!(self) }
+  before_destroy :delete_current_structure!
+
+  belongs_to :created_by_user, class_name: 'User', optional: true
+  belongs_to :updated_by_user, class_name: 'User', optional: true
+
+  has_many :tag_group_tags, dependent: :delete_all
+  has_many :tags, through: :tag_group_tags
+  has_many :tag_group_groups, dependent: :delete_all
+  has_many :child_tag_groups, through: :tag_group_groups
+  has_many :placements, -> { order(:position) },
+           class_name: 'TagGroupPlacement', dependent: :delete_all
+  has_many :versions, -> { order(:version_no) },
+           class_name: 'TagGroupVersion'
+
+  validates :name, presence: true, uniqueness: true, length: { maximum: 255 }
+  validates :version_no, numericality: { only_integer: true, greater_than: 0 }
+
+  private
+
+  def delete_current_structure!
+    placements.reorder(position: :desc).each(&:delete)
+    tag_group_tags.delete_all
+    tag_group_groups.delete_all
+  end
+end

backend/app/models/tag_group_group.rb

@@ -0,0 +1,7 @@
+class TagGroupGroup < ApplicationRecord
+  self.primary_key = [:tag_group_id, :child_tag_group_id]
+
+  belongs_to :tag_group
+  belongs_to :child_tag_group, class_name: 'TagGroup'
+  belongs_to :created_by_user, class_name: 'User', optional: true
+end

backend/app/models/tag_group_placement.rb

@@ -0,0 +1,9 @@
+class TagGroupPlacement < ApplicationRecord
+  self.primary_key = [:tag_group_id, :position]
+
+  belongs_to :tag_group
+  belongs_to :tag, optional: true
+  belongs_to :child_tag_group, class_name: 'TagGroup', optional: true
+  belongs_to :created_by_user, class_name: 'User', optional: true
+  belongs_to :updated_by_user, class_name: 'User', optional: true
+end

backend/app/models/tag_group_tag.rb

@@ -0,0 +1,7 @@
+class TagGroupTag < ApplicationRecord
+  self.primary_key = [:tag_group_id, :tag_id]
+
+  belongs_to :tag_group
+  belongs_to :tag
+  belongs_to :created_by_user, class_name: 'User', optional: true
+end

backend/app/models/tag_group_version.rb

@@ -0,0 +1,9 @@
+class TagGroupVersion < ApplicationRecord
+  include VersionRecord
+
+  before_create { SharedResourceIdAllocator.assign!(self) }
+
+  belongs_to :tag_group
+
+  scope :ordered, -> { order(:version_no) }
+end

backend/app/models/tag_name.rb

@@ -1,14 +1,12 @@
 class TagName < ApplicationRecord
   belongs_to :language, foreign_key: :language_code, primary_key: :code
-  belongs_to :tag, optional: true
+  belongs_to :tag
-  has_one :wiki_page
 
   validates :name, presence: true,
                    length: { maximum: 255 },
                    uniqueness: { scope: :language_code }
 
   validate :alias_name_must_not_have_prefix
-  validate :alias_must_not_have_wiki_page
   validate :name_must_be_sanitised
   validate :name_mustnt_start_with_nico
   validate :generated_name_must_be_reserved
@@ -21,14 +19,16 @@ class TagName < ApplicationRecord
 
     tns = TagName.where(language_code: locale.language_code, name: names).index_by(&:name)
 
+    primary_names = TagName.where(
+        language_code: locale.language_code, tag_id: tns.values.map(&:tag_id),
+        primary_flg: true).pluck(:tag_id, :name).to_h
+
     names.map { |name|
       tag_name = tns[name]
-      if !tag_name || tag_name.primary? || tag_name.tag_id.nil?
+      if !tag_name || tag_name.primary?
         name
       else
-        TagName.find_by(language_code: locale.language_code,
+        primary_names[tag_name.tag_id] || name
-                        tag_id: tag_name.tag_id,
-                        primary_flg: true)&.name || name
       end
     }.uniq
   end
@@ -53,12 +53,6 @@ class TagName < ApplicationRecord
     end
   end
 
-  def alias_must_not_have_wiki_page
-    if !(primary?) && wiki_page
-      errors.add :primary_flg, 'Wiki 参照がある名前はエーリアスになれません．'
-    end
-  end
-
   def name_must_be_sanitised
     if name? && name != TagNameSanitisationRule.sanitise(name)
       errors.add :name, '名前に使用できない文字が含まれてゐます．'

backend/app/models/tag_name_sanitisation_rule.rb

@@ -16,37 +16,36 @@ class TagNameSanitisationRule < ApplicationRecord
 
     def apply!
       Language.find_each do |language|
-        TagName.where(language:).find_each do |tn|
+        TagName.where(language:).find_each do |candidate|
-          name = sanitise(tn.name)
-          next if name == tn.name
-
           TagName.transaction do
+            tn = TagName.find_by(id: candidate.id)
+            next unless tn
+
+            name = sanitise(tn.name)
+            next if name == tn.name
+
             existing_tn = TagName.find_by(language:, name:)
-            if existing_tn
+            source_tag = tn.tag
-              unless existing_tn.primary_flg
+            target_tag = existing_tn ? existing_tn.tag : source_tag
-                existing_tn = TagName.find_by!(language:,
+            [source_tag, target_tag].uniq(&:id).sort_by(&:id).each(&:lock!)
-                                               tag_id: existing_tn.tag_id,
+            TagVersioning.ensure_snapshot!(source_tag, created_by_user: nil)
-                                               primary_flg: true)
+
+            if existing_tn && target_tag != source_tag
+              Tag.merge_tags!(target_tag, source_tag)
+              tn.reload.destroy!
+            elsif existing_tn
+              if tn.primary?
+                existing_tn.destroy!
+                tn.update_columns(name:, updated_at: Time.current)
+              else
+                tn.destroy!
               end
-              next if existing_tn.id == tn.id
+            else
-
+              # TagName 側の自動サニタイズを回避
-              existing_tag = existing_tn.tag
+              tn.update_columns(name:, updated_at: Time.current)
-              source_tag = tn.tag
-
-              if existing_tag
-                Tag.merge_tags!(existing_tag, source_tag) if tn.tag
-              elsif source_tag
-                tn.update_columns(tag_id: nil, updated_at: Time.current)
-                source_tag.update_columns(tag_name_id: existing_tn.id, updated_at: Time.current)
-                existing_tn.update_columns(tag_id: source_tag.id, updated_at: Time.current)
-              end
-              tn.destroy!
-
-              next
             end
 
-            # TagName 側の自動サニタイズを回避
+            TagVersioning.record!(target_tag, event_type: :update, created_by_user: nil)
-            tn.update_columns(name:, updated_at: Time.current)
           end
         end
       end

backend/app/models/user.rb

@@ -13,10 +13,10 @@ class User < ApplicationRecord
   has_many :ip_addresses, through: :user_ips
   has_many :user_post_views, dependent: :destroy
   has_many :viewed_posts, through: :user_post_views, source: :post
-  has_many :created_wiki_pages,
+  has_many :created_tag_descriptions, class_name: 'TagDescription',
-           class_name: 'WikiPage', foreign_key: :created_user_id, dependent: :nullify
+           foreign_key: :created_by_user_id, dependent: :nullify
-  has_many :updated_wiki_pages,
+  has_many :updated_tag_descriptions, class_name: 'TagDescription',
-           class_name: 'WikiPage', foreign_key: :updated_user_id, dependent: :nullify
+           foreign_key: :updated_by_user_id, dependent: :nullify
 
   def viewed?(post) = user_post_views.exists?(post_id: post.id)
 

backend/app/models/wiki_line.rb

@@ -1,15 +0,0 @@
-class WikiLine < ApplicationRecord
-  has_many :wiki_revision_lines, dependent: :restrict_with_exception
-
-  validates :sha256, presence: true, uniqueness: true, length: { is: 64 }
-  validates :body, presence: true
-
-  def self.upsert_by_body! body
-    sha = Digest::SHA256.hexdigest(body)
-    now = Time.current
-
-    upsert(sha256: sha, body:, created_at: now, updated_at: now)
-
-    find_by!(sha256: sha)
-  end
-end

backend/app/models/wiki_page.rb

@@ -1,58 +0,0 @@
-require 'set'
-
-
-class WikiPage < ApplicationRecord
-  include MyDiscard
-
-  has_many :wiki_revisions, dependent: :destroy
-  belongs_to :created_user, class_name: 'User'
-  belongs_to :updated_user, class_name: 'User'
-
-  has_many :redirected_from_revisions,
-           class_name: 'WikiRevision',
-           foreign_key: :redirect_page_id,
-           dependent: :nullify
-
-  has_many :wiki_versions
-
-  attribute :version_no, :integer, default: 1
-
-  belongs_to :tag_name
-  validates :tag_name, presence: true
-  validates :body, presence: true
-
-  def title = tag_name.name
-  def deprecated_at = tag_name.tag&.deprecated_at
-
-  def title= val
-    (self.tag_name ||= build_tag_name).name = val
-  end
-
-  def current_revision = wiki_revisions.order(id: :desc).first
-
-  def resolve_redirect limit: 10
-    page = self
-    visited = Set.new
-
-    limit.times do
-      return page if visited.include?(page.id)
-
-      visited.add(page.id)
-
-      rev = page.current_revision
-      return page if !(rev&.redirect?) || !(rev.redirect_page)
-
-      page = rev.redirect_page
-    end
-
-    page
-  end
-
-  def pred_revision_id revision_id
-    wiki_revisions.where('id < ?', revision_id).order(id: :desc).limit(1).pick(:id)
-  end
-
-  def succ_revision_id revision_id
-    wiki_revisions.where('id > ?', revision_id).order(id: :asc).limit(1).pick(:id)
-  end
-end

backend/app/models/wiki_revision.rb

@@ -1,55 +0,0 @@
-class WikiRevision < ApplicationRecord
-  belongs_to :wiki_page
-  belongs_to :base_revision, class_name: 'WikiRevision', optional: true
-  belongs_to :created_user, class_name: 'User'
-  belongs_to :redirect_page, class_name: 'WikiPage', optional: true
-
-  has_many :wiki_revision_lines, dependent: :delete_all
-  has_many :wiki_lines, through: :wiki_revision_lines
-
-  enum :kind, content: 0, redirect: 1
-
-  validates :kind, presence: true
-  validates :lines_count, numericality: { only_integer: true, greater_than_or_equal_to: 0 }
-  validates :tree_sha256, length: { is: 64 }, allow_nil: true
-
-  validate :kind_consistency
-
-  def body
-    return unless content?
-
-    wiki_revision_lines
-        .includes(:wiki_line)
-        .order(:position)
-        .map { |rev| rev.wiki_line.body }
-        .join("\n")
-  end
-
-  private
-
-  def kind_consistency
-    if content?
-      if tree_sha256.blank?
-        errors.add(:tree_sha256, '種類がページの場合は必須です．') 
-      end
-
-      if redirect_page_id.present?
-        errors.add(:redirect_page_id, '種類がページの場合は空である必要があります．')
-      end
-    end
-
-    if redirect?
-      if redirect_page_id.blank?
-        errors.add(:redirect_page_id, '種類がリダイレクトの場合は必須です．')
-      end
-
-      if tree_sha256.present?
-        errors.add(:tree_sha256, '種類がリダイレクトの場合は空である必要があります．')
-      end
-
-      if lines_count.to_i > 0
-        errors.add(:lines_count, '種類がリダイレクトの場合は 0 である必要があります．')
-      end
-    end
-  end
-end

backend/app/models/wiki_revision_line.rb

@@ -1,8 +0,0 @@
-class WikiRevisionLine < ApplicationRecord
-  belongs_to :wiki_revision
-  belongs_to :wiki_line
-
-  validates :position, presence: true,
-                       numericality: { only_integer: true, greater_than_or_equal_to: 0 }
-  validates :position, uniqueness: { scope: :wiki_revision_id }
-end

backend/app/models/wiki_version.rb

@@ -1,8 +0,0 @@
-class WikiVersion < ApplicationRecord
-  include VersionRecord
-
-  belongs_to :wiki_page
-
-  validates :title, presence: true
-  validates :body, presence: true
-end

backend/app/representations/tag_group_repr.rb

@@ -0,0 +1,205 @@
+module TagGroupRepr
+  PREFIX = 'タググループ:'
+
+  module_function
+
+  def name_from_title title
+    prefix = [PREFIX, 'tag_group:'].find { title.downcase.start_with?(_1) }
+    title[prefix.length..] if prefix
+  end
+
+  def many locale, groups
+    ids = groups.map(&:id)
+    return [] if ids.empty?
+
+    tag_members = TagGroupTag.where(tag_group_id: ids)
+        .group_by(&:tag_group_id)
+    group_members = TagGroupGroup.where(tag_group_id: ids)
+        .group_by(&:tag_group_id)
+    placements = TagGroupPlacement.where(tag_group_id: ids).order(:position)
+        .group_by(&:tag_group_id)
+
+    target_ids =
+        tag_members.values.flatten.map(&:tag_id) +
+        placements.values.flatten.filter_map(&:tag_id)
+    child_ids =
+        group_members.values.flatten.map(&:child_tag_group_id) +
+        placements.values.flatten.filter_map(&:child_tag_group_id)
+    tags = Tag.select(:id, :category).where(id: target_ids.uniq).index_by(&:id)
+    names =
+        TagName
+        .where(tag_id: target_ids.uniq,
+               language_code: locale.language_code,
+               primary_flg: true)
+        .pluck(:tag_id, :name)
+        .to_h
+    child_groups = TagGroup.where(id: child_ids.uniq).index_by(&:id)
+
+    groups.map do |group|
+      group_json(group,
+                 tag_members.fetch(group.id, []),
+                 group_members.fetch(group.id, []),
+                 placements.fetch(group.id, []), tags, names, child_groups)
+    end
+  end
+
+  def one locale, group
+    many(locale, [group]).first
+  end
+
+  def tag_group wiki_page
+    { 'id' => wiki_page.id,
+      'title' => "#{ PREFIX }#{ wiki_page.name }",
+      'deprecated_at' => nil,
+      'created_at' => wiki_page.created_at,
+      'updated_at' => wiki_page.updated_at }
+  end
+
+  def current_version group
+    TagGroupVersion.find_by(tag_group_id: group.id, version_no: group.version_no)
+  end
+
+  def historical locale, version
+    members = Array(version.members)
+    placements = Array(version.placements)
+    tag_references = members.filter_map { |member| member['tag_id'] } +
+        collect_ids(placements, 'tag_id')
+    group_references = members.filter_map { |member| member['tag_group_id'] } +
+        collect_ids(placements, 'tag_group_id')
+    tag_versions = historical_tag_versions(tag_references)
+    group_versions = historical_group_versions(group_references)
+    tag_version_numbers = members.filter_map do |member|
+      next unless member['tag_id']
+
+      [member.fetch('tag_id'), member.fetch('version_no')]
+    end.to_h
+    group_version_numbers = members.filter_map do |member|
+      next unless member['tag_group_id']
+
+      [member.fetch('tag_group_id'), member.fetch('version_no')]
+    end.to_h
+    historical_members = members.map do |member|
+      historical_member(locale, member, tag_versions, group_versions)
+    end
+    historical_placements = placements.map do |node|
+      historical_placement(locale, node, tag_versions, group_versions,
+                           tag_version_numbers, group_version_numbers)
+    end
+    { 'id' => version.tag_group_id,
+      'name' => version.name,
+      'description' => version.description,
+      'version_no' => version.version_no,
+      'members' => historical_members,
+      'placements' => historical_placements,
+      'created_at' => version.created_at,
+      'updated_at' => version.created_at,
+      'created_by_user' => user_json(version.created_by_user),
+      'updated_by_user' => user_json(version.created_by_user) }
+  end
+
+  def group_json group, tag_members, group_members, rows, tags, names, child_groups
+    tree = placement_tree(rows, tags, names, child_groups)
+    members = tag_members.sort_by(&:tag_id).map do |member|
+      { 'tag' => tag_json(tags.fetch(member.tag_id), names[member.tag_id]) }
+    end
+    members.concat(group_members.sort_by(&:child_tag_group_id).map do |member|
+      { 'tag_group' => group_json_reference(child_groups.fetch(member.child_tag_group_id)) }
+    end)
+    { 'id' => group.id,
+      'name' => group.name,
+      'description' => group.description,
+      'version_no' => group.version_no,
+      'members' => members,
+      'placements' => tree,
+      'created_at' => group.created_at,
+      'updated_at' => group.updated_at,
+      'created_by_user' => user_json(group.created_by_user),
+      'updated_by_user' => user_json(group.updated_by_user) }
+  end
+
+  def user_json user
+    UserRepr.base(user) if user
+  end
+
+  def placement_tree rows, tags, names, child_groups
+    by_parent = rows.group_by(&:parent_position)
+    build = lambda do |parent|
+      by_parent.fetch(parent, []).sort_by(&:position).map do |row|
+        node = if row.tag_id
+          { 'tag' => tag_json(tags.fetch(row.tag_id), names[row.tag_id]) }
+        elsif row.child_tag_group_id
+          { 'tag_group' => group_json_reference(child_groups.fetch(row.child_tag_group_id)) }
+        else
+          { 'section_name' => row.section_name, 'description' => row.description }
+        end
+        node.merge('children' => build.call(row.position))
+      end
+    end
+    build.call(nil)
+  end
+
+  def tag_json tag, name
+    { 'id' => tag.id, 'name' => name, 'category' => tag.category }
+  end
+
+  def group_json_reference group
+    { 'id' => group.id, 'name' => group.name }
+  end
+
+  def collect_ids nodes, key
+    nodes.flat_map do |node|
+      [node[key], *collect_ids(Array(node['children']), key)].compact
+    end
+  end
+
+  def historical_tag_versions ids
+    TagVersion.where(tag_id: ids.uniq).to_a.index_by do |version|
+      [version.tag_id, version.version_no]
+    end
+  end
+
+  def historical_group_versions ids
+    TagGroupVersion.where(tag_group_id: ids.uniq).to_a.index_by do |version|
+      [version.tag_group_id, version.version_no]
+    end
+  end
+
+  def historical_member locale, member, tag_versions, group_versions
+    if member['tag_id']
+      id = member.fetch('tag_id')
+      version = tag_versions.fetch([id, member.fetch('version_no')])
+      { 'tag' => { 'id' => id, 'name' => version_name(locale, version),
+                   'category' => version.category } }
+    else
+      id = member.fetch('tag_group_id')
+      version = group_versions.fetch([id, member.fetch('version_no')])
+      { 'tag_group' => { 'id' => id, 'name' => version.name } }
+    end
+  end
+
+  def historical_placement locale, node, tag_versions, group_versions,
+                           tag_version_numbers, group_version_numbers
+    result = if node['tag_id']
+      id = node.fetch('tag_id')
+      version_no = tag_version_numbers.fetch(id)
+      version = tag_versions.fetch([id, version_no])
+      { 'tag' => { 'id' => id, 'name' => version_name(locale, version),
+                   'category' => version.category } }
+    elsif node['tag_group_id']
+      id = node.fetch('tag_group_id')
+      version_no = group_version_numbers.fetch(id)
+      version = group_versions.fetch([id, version_no])
+      { 'tag_group' => { 'id' => id, 'name' => version.name } }
+    else
+      { 'section_name' => node.fetch('section_name'), 'description' => node['description'] }
+    end
+    result.merge('children' => Array(node['children']).map do |child|
+      historical_placement(locale, child, tag_versions, group_versions,
+                           tag_version_numbers, group_version_numbers)
+    end)
+  end
+
+  def version_name locale, version
+    version.names[locale.language_code]&.fetch('name')
+  end
+end

backend/app/representations/tag_repr.rb

@@ -3,21 +3,28 @@
 
 module TagRepr
   BASE = { only: [:id, :category, :post_count, :created_at, :updated_at, :deprecated_at],
-           methods: [:has_wiki, :material_id, :has_deerjikists] }.freeze
+           methods: [:material_id, :has_deerjikists] }.freeze
 
   module_function
 
   def base tag, language_code: 'ja'
-    tag.as_json(BASE).merge(name: name_for(tag, language_code),
+    tag.as_json(BASE).merge('has_wiki' => tag.has_description?(language_code:),
+                            name: name_for(tag, language_code),
                             aliases: tag.snapshot_aliases(language_code),
                             parents: tag.parents.map { inline(_1, language_code:) })
   end
 
   def inline tag, language_code: 'ja'
-    tag.as_json(BASE).merge(name: name_for(tag, language_code), aliases: [], parents: [])
+    tag.as_json(BASE).merge('has_wiki' => tag.has_description?(language_code:),
+                            name: name_for(tag, language_code), aliases: [], parents: [])
   end
 
-  def many(tags, language_code: 'ja') = tags.map { |tag| base(tag, language_code:) }
+  def many tags, language_code: 'ja'
+    records = tags.to_a
+    ActiveRecord::Associations::Preloader.new(
+        records:, associations: [:tag_descriptions, { parents: :tag_descriptions }]).call
+    records.map { |tag| base(tag, language_code:) }
+  end
 
   def name_for tag, language_code
     tag.name(language_code) || (tag.system? ? tag.name('ja') : nil)

backend/app/representations/wiki_page_repr.rb

@@ -2,18 +2,14 @@
 
 
 module WikiPageRepr
-  BASE = { methods: [:title, :deprecated_at] }.freeze
-
   module_function
 
-  def base wiki_page
+  def tag_description locale, description
-    wiki_page.as_json(BASE)
-  end
-
-  def tag_description description
     tag = description.tag
+
     { 'id' => description.id,
-      'tag_name_id' => tag.tag_name('ja')&.id,
+      'resource_type' => 'tag_description',
+      'tag_name_id' => tag.tag_name(locale.language_code)&.id,
       'body' => description.body,
       'created_user_id' => description.created_by_user_id,
       'updated_user_id' => description.updated_by_user_id,
@@ -21,11 +17,11 @@ module WikiPageRepr
       'updated_at' => description.updated_at,
       'discarded_at' => nil,
       'version_no' => description.version_no,
-      'title' => tag.name('ja'),
+      'title' => tag.name(locale.language_code),
       'deprecated_at' => tag.deprecated_at }
   end
 
-  def many wiki_pages
+  def tag_group tag_group
-    wiki_pages.map { |p| base(p) }
+    TagGroupRepr.tag_group(tag_group).merge('resource_type' => 'tag_group')
   end
 end

backend/app/services/post_create_plan.rb

@@ -95,14 +95,10 @@ class PostCreatePlan
   def build_default_tag_specs locale, direct_tag_specs
     default_tag_specs = []
     if direct_tag_specs.length < 10 && direct_tag_specs.none? { _1[:name] == TAGME_TAG_NAME }
-      default_tag_specs << {
+      default_tag_specs << { name: TAGME_TAG_NAME, category: :meta }
-          name: TAGME_TAG_NAME,
-          category: :meta }
     end
     if direct_tag_specs.none? { deerjikist_tag_spec?(locale, _1) }
-      default_tag_specs << {
+      default_tag_specs << { name: NO_DEERJIKIST_TAG_NAME, category: :meta }
-          name: NO_DEERJIKIST_TAG_NAME,
-          category: :meta }
     end
 
     default_tag_specs
@@ -117,9 +113,9 @@ class PostCreatePlan
   end
 
   def validate_new_tag_spec! locale, spec
-    tag_name = TagName.new(name: spec[:name], language_code: locale.language_code,
-                           script_code: locale.script_code, primary_flg: true)
     tag = Tag.new(category: spec[:category])
+    tag_name = TagName.new(tag:, name: spec[:name], language_code: locale.language_code,
+                           script_code: locale.script_code, primary_flg: true)
     return if tag_name.valid? && tag.valid?
 
     post = Post.new
@@ -140,10 +136,10 @@ class PostCreatePlan
     end
     expanded_parent_specs =
         Tag.expand_parent_tags(existing_snapshot_tags)
-           .reject(&:deprecated?)
+        .reject(&:deprecated?)
-           .map { |tag|
+        .map { |tag|
-             { name: tag.name(locale.language_code),
+          { name: tag.name(locale.language_code),
-               category: tag.category.to_sym }
+            category: tag.category.to_sym }
         }
     merge_tag_specs(snapshot_tag_specs + expanded_parent_specs)
   end
@@ -164,9 +160,10 @@ class PostCreatePlan
   def existing_tags_by_name locale
     @existing_tags_by_name ||= begin
       names = tag_names.map { canonical_tag_name_without_sections(locale, _1) }.uniq
-      TagName.where(language_code: locale.language_code, primary_flg: true, name: names)
+      TagName
-             .includes(:tag)
+          .where(language_code: locale.language_code, primary_flg: true, name: names)
-             .each_with_object({ }) { |tag_name, tags| tags[tag_name.name] = tag_name.tag }
+          .includes(:tag)
+          .each_with_object({ }) { |tag_name, tags| tags[tag_name.name] = tag_name.tag }
     end
   end
 

backend/app/services/shared_resource_id_allocator.rb

@@ -0,0 +1,91 @@
+require 'digest'
+
+
+class SharedResourceIdAllocator
+  SPACES = {
+      'tags' => ['tags', 'external_tags'],
+      'wiki' => ['tag_descriptions', 'tag_groups'],
+      'wiki_history' => ['tag_description_versions', 'tag_group_versions'] }.freeze
+  HISTORY_IDS = {
+      'tags' => [
+          ['tag_versions', 'tag_id'],
+          ['nico_tag_versions', 'tag_id'],
+          ['tag_description_versions', 'tag_id']],
+      'wiki' => [['tag_group_versions', 'tag_group_id']] }.freeze
+  LOCK_TIMEOUT = 10
+
+  def self.assign! record
+    space, tables = SPACES.find { |_name, names| names.include?(record.class.table_name) }
+    raise ArgumentError, 'Unknown shared ID resource' unless tables
+
+    connection = record.class.connection
+    transaction = record.class.current_transaction
+    unless transaction.open?
+      raise ActiveRecord::ActiveRecordError, 'Shared ID requires a transaction'
+    end
+
+    database = connection.pool.db_config.database
+    name = "btrc:ids:#{ Digest::SHA256.hexdigest(database)[0, 16] }:#{ space }"
+    quoted_name = connection.quote(name)
+    acquired = record.class.uncached do
+      connection.select_value("SELECT GET_LOCK(#{ quoted_name }, #{ LOCK_TIMEOUT })")
+    end
+    unless acquired.to_i == 1
+      raise ActiveRecord::LockWaitTimeout, "Shared ID lock unavailable: #{ space }"
+    end
+
+    release = lambda do
+      result = record.class.uncached do
+        connection.select_value("SELECT RELEASE_LOCK(#{ quoted_name })")
+      end
+      unless result.to_i == 1
+        raise ActiveRecord::ActiveRecordError, "Shared ID lock release failed: #{ space }"
+      end
+    end
+    begin
+      transaction.after_commit(&release)
+      transaction.after_rollback(&release)
+    rescue StandardError
+      release.call
+      raise
+    end
+
+    # 明示-tic な Id. 指定は許可する．
+    return if record.id.present?
+
+    next_id = record.class.uncached do
+      historical_max = HISTORY_IDS.fetch(space, []).map { |table, column|
+        quoted_table = connection.quote_table_name(table)
+        quoted_column = connection.quote_column_name(column)
+        connection.select_value("SELECT MAX(#{ quoted_column }) FROM #{ quoted_table }").to_i
+      }.max.to_i
+
+      [next_ids(connection, tables).max, historical_max + 1].max
+    end
+
+    record.id = next_id
+  end
+
+  def self.next_ids connection, tables
+    expiry = connection.select_value('SELECT @@SESSION.information_schema_stats_expiry').to_i
+    begin
+      connection.execute('SET SESSION information_schema_stats_expiry = 0')
+      quoted_tables = tables.map { connection.quote(_1) }.join(', ')
+      rows = connection.select_all(<<~SQL).to_a
+        SELECT TABLE_NAME, ENGINE, AUTO_INCREMENT
+        FROM information_schema.tables
+        WHERE TABLE_SCHEMA = DATABASE() AND TABLE_NAME IN (#{ quoted_tables })
+      SQL
+      persistent = rows.all? do |row|
+        row['ENGINE'] == 'InnoDB' && row['AUTO_INCREMENT'].to_i.positive?
+      end
+      unless rows.size == tables.size && persistent
+        raise ActiveRecord::ActiveRecordError, 'Persistent InnoDB counters are required'
+      end
+      rows.map { _1.fetch('AUTO_INCREMENT').to_i }
+    ensure
+      connection.execute("SET SESSION information_schema_stats_expiry = #{ expiry }")
+    end
+  end
+  private_class_method :next_ids
+end

backend/app/services/tag_description_operation.rb

@@ -1,54 +1,67 @@
 class TagDescriptionOperation
-  LANGUAGE_CODE = 'ja'
+  class Conflict < StandardError
+    ;
+  end
 
-  def self.create!(tag:, body:, created_by_user:, message: nil)
+  def self.create! locale, tag:, body:, created_by_user:, message: nil
     ApplicationRecord.transaction do
       tag.lock!
       raise ActiveRecord::RecordNotUnique if TagDescription.exists?(
-          tag_id: tag.id, language_code: LANGUAGE_CODE)
+          tag_id: tag.id, language_code: locale.language_code)
 
-      page = Wiki::CompatibilityWriter.create!(
+      description = TagDescription.new(tag:, language_code: locale.language_code)
-          tag_name: tag.tag_name(LANGUAGE_CODE), body:, created_by_user:, message:)
+      body = normalise_body!(description, body)
-      revision = page.wiki_revisions.order(id: :desc).first
+      record_version!(description:, body:, user: created_by_user)
-      record_version!(tag:, revision:, body:, user: created_by_user,
+
-                      description: nil)
+      description
-      page
     end
   end
 
-  def self.update!(tag:, body:, updated_by_user:, message: nil,
+  def self.update! locale, tag:, body:, updated_by_user:, message: nil, base_revision_id: nil
-                   base_revision_id: nil)
     ApplicationRecord.transaction do
       tag.lock!
       description = TagDescription.lock.find_by!(
-          tag_id: tag.id, language_code: LANGUAGE_CODE)
+          tag_id: tag.id, language_code: locale.language_code)
-      page = WikiPage.lock.find(description.id)
+      body = normalise_body!(description, body)
-      revision = Wiki::CompatibilityWriter.update!(
+      latest = TagDescriptionVersion.find_by(
-          page:, body:, updated_by_user:, message:,
+          tag_id: tag.id, language_code: locale.language_code,
-          base_revision_id:)
+          version_no: description.version_no)
-      next unless revision
+      if base_revision_id.present? && latest&.id != base_revision_id.to_i
+        raise Conflict, '競合が発生してゐます．'
+      end
+      next if latest && normalise_body(description.body) == body
 
-      record_version!(tag:, revision:, body: revision.body,
+      record_version!(description:, body:, user: updated_by_user)
-                      user: updated_by_user, description:)
-      revision
     end
   end
 
-  def self.record_version! tag:, revision:, body:, user:, description:
+  def self.record_version! description:, body:, user:
-    version_no = description ? description.version_no + 1 : 1
+    creating = description.new_record?
+    version_no = creating ? 1 : description.version_no + 1
+    description.created_by_user_id = user.id if creating
+    description.update!(body:, version_no:, updated_by_user_id: user.id)
     TagDescriptionVersion.create!(
-        id: revision.id, tag_id: tag.id, language_code: LANGUAGE_CODE,
+        tag_id: description.tag_id, language_code: description.language_code,
-        version_no:, event_type: description ? 'update' : 'create', body:,
+        version_no:, event_type: creating ? 'create' : 'update', body:,
-        created_by_user_id: user.id, created_at: revision.created_at)
+        source_language_code: description.source_language_code,
-    if description
+        source_version_no: description.source_version_no,
-      description.update!(body:, version_no:, updated_by_user_id: user.id)
+        created_by_user_id: user.id, created_at: Time.current)
-    else
-      TagDescription.create!(
-          id: revision.wiki_page_id, tag_id: tag.id,
-          language_code: LANGUAGE_CODE, version_no:, body:,
-          created_by_user_id: user.id, updated_by_user_id: user.id)
-    end
   end
-
   private_class_method :record_version!
+
+  def self.normalise_body body
+    body.to_s.gsub(/\r\n?/, "\n")
+        .encode('UTF-8', invalid: :replace, undef: :replace, replace: '🖕')
+        .sub(/\n+\z/, '')
+  end
+  private_class_method :normalise_body
+
+  def self.normalise_body! description, body
+    normalised = normalise_body(body)
+    return normalised if normalised.present?
+
+    description.errors.add(:body, :blank)
+    raise ActiveRecord::RecordInvalid, description
+  end
+  private_class_method :normalise_body!
 end

backend/app/services/tag_group_markdown_parser.rb

@@ -0,0 +1,178 @@
+require 'kramdown'
+
+class TagGroupMarkdownParser
+  PREFIX = TagGroupRepr::PREFIX
+
+  class InvalidDocument < StandardError
+    ;
+  end
+
+  def self.parse(locale, body:, group: nil)
+    new(body:, group:).parse(locale)
+  end
+
+  def initialize(body:, group:)
+    @body = body.to_s.gsub(/\r\n?/, "\n")
+    @group = group
+  end
+
+  def parse locale
+    parse_body = @body.gsub(/([^\n])\n([\x23]{1,6}[ \t]+\S)/, "\\1\n\n\\2")
+    root = Kramdown::Document.new(parse_body, input: 'GFM', auto_ids: false).root
+    placements = []
+    description_parts = []
+    headings = []
+
+    root.children.each do |node|
+      case node.type
+      when :blank
+        next
+      when :header
+        level = node.options.fetch(:level)
+        name = inline_text(node).strip
+        invalid!('Section 名は必須です．') if name.blank?
+
+        headings.pop while headings.any? && headings.last.fetch(:level) >= level
+        parent = headings.last&.fetch(:node)
+        section = { 'section_name' => name, 'description' => nil,
+                    'children' => [] }
+        (parent ? parent.fetch('children') : placements) << section
+        headings << { level:, node: section }
+      when :p
+        text = inline_markdown(node).strip
+        next if text.empty?
+
+        if headings.any?
+          section = headings.last.fetch(:node)
+          section['description'] = [section['description'], text].compact.join("\n\n")
+        else
+          description_parts << text
+        end
+      when :ul
+        invalid!('未対応のリスト項目があります．') if node.attr.any?
+        target = headings.any? ? headings.last.fetch(:node).fetch('children') : placements
+        target.concat(node.children.map { parse_list_item(locale, _1) })
+      else
+        invalid!("未対応の Markdown 構文 #{ node.type.inspect } です．")
+      end
+    end
+
+    description = description_parts.presence&.join("\n\n")
+    { description:, placements:, members: build_members(placements),
+      compatibility_body: @body.sub(/\n+\z/, '') }
+  rescue Kramdown::Error => error
+    invalid!("Markdown を解析できません：#{ error.message }")
+  end
+
+  private
+
+  def parse_list_item locale, item
+    invalid!('リスト項目ではありません．') unless item.type == :li
+    invalid!('未対応のリスト項目があります．') if item.attr.any?
+
+    nested, own = item.children.partition { |child| child.type == :ul }
+    invalid!('順序付きリストは使用できません．') if own.any? { _1.type == :ol }
+    own.reject! { _1.type == :blank }
+    invalid!('未対応のリスト項目があります．') unless own.all? do |child|
+      [:p, :text].include?(child.type)
+    end
+    invalid!('リスト項目は一つの段落で指定してください．') if own.size != 1
+
+    label = own.map { inline_text(_1) }.join(' ').strip
+    invalid!('空のリスト項目は使用できません．') if label.blank?
+
+    node =
+        if (group_name = TagGroupRepr.name_from_title(label))
+          group_name = group_name.strip
+          child_group = TagGroup.find_by(name: group_name)
+          invalid!("Tag Group #{ group_name.inspect } を解決できません．") unless child_group
+          invalid!('自分自身を含めることはできません．') if child_group.id == @group&.id
+          { 'tag_group_id' => child_group.id }
+        elsif label.end_with?(':', '：')
+          section_name = label.sub(/[:：]\z/, '').strip
+          invalid!('Section 名は必須です．') if section_name.blank?
+          { 'section_name' => section_name, 'description' => nil }
+        else
+          { 'tag_id' => resolve_tag(locale, label) }
+        end
+
+    node['children'] = nested.flat_map do |list|
+      invalid!('未対応の入れ子リストです．') unless list.type == :ul
+      list.children.map { parse_list_item(locale, _1) }
+    end
+    node
+  end
+
+  def resolve_tag locale, name
+    names = TagName.where(language_code: locale.language_code, name:).to_a
+    tag_ids = names.filter_map(&:tag_id).uniq
+    invalid!("Tag #{ name.inspect } を解決できません．") if tag_ids.empty?
+    invalid!("Tag 名 #{ name.inspect } が曖昧です．") if tag_ids.many?
+
+    tag_ids.first
+  end
+
+  def build_members(nodes)
+    references = []
+    visit = lambda do |items|
+      items.each do |node|
+        references << node.slice('tag_id', 'tag_group_id') if
+            node.key?('tag_id') || node.key?('tag_group_id')
+        visit.call(node.fetch('children'))
+      end
+    end
+    visit.call(nodes)
+    references.uniq
+  end
+
+  def inline_text(node)
+    if node.attr.any?
+      invalid!("未対応のインライン構文 #{ node.type.inspect } です．")
+    end
+
+    case node.type
+    when :text
+      node.value.to_s
+    when :p, :header
+      node.children.map { inline_text(_1) }.join
+    else
+      invalid!("未対応のインライン構文 #{ node.type.inspect } です．")
+    end
+  end
+
+  def inline_markdown(node)
+    case node.type
+    when :text
+      node.value.to_s
+    when :codespan
+      text = node.value.to_s
+      longest = text.scan(/`+/).map(&:length).max || 0
+      delimiter = '`' * (longest + 1)
+      padded = text.start_with?('`', ' ') || text.end_with?('`', ' ')
+      content = padded ? " #{ text } " : text
+      "#{ delimiter }#{ content }#{ delimiter }"
+    when :softbreak
+      "\n"
+    when :br
+      "  \n"
+    when :p
+      node.children.map { inline_markdown(_1) }.join
+    when :a
+      href = node.attr.fetch('href')
+      label = node.children.map { inline_markdown(_1) }.join
+      title = node.attr['title']&.gsub('"', '\\"')
+      suffix = title ? " \"#{ title }\"" : ''
+      "[#{ label }](#{ href }#{ suffix })"
+    when :em
+      "*#{ node.children.map { inline_markdown(_1) }.join }*"
+    when :strong
+      "**#{ node.children.map { inline_markdown(_1) }.join }**"
+    else
+      invalid!("未対応の説明文構文 #{ node.type.inspect } です．")
+    end
+  end
+
+  def invalid! message
+    raise InvalidDocument, message
+  end
+end

backend/app/services/tag_group_markdown_renderer.rb

@@ -0,0 +1,123 @@
+class TagGroupMarkdownRenderer
+  class UnsupportedStructure < StandardError
+    ;
+  end
+
+  def self.render group
+    new(group).render
+  end
+
+  def initialize group
+    @group = group
+  end
+
+  def render
+    placements = @group.fetch('placements')
+    validate_membership!(placements)
+    blocks = []
+    if @group['description'].present?
+      blocks << clean_text(@group['description'])
+    end
+
+    first_section = placements.index { _1.key?('section_name') }
+
+    if first_section
+      if placements.drop(first_section).any? { !_1.key?('section_name') }
+        raise UnsupportedStructure,
+            '見出し Section の後に最上位 Placement は配置できません．'
+      end
+
+      if first_section.positive?
+        blocks << render_list(placements.take(first_section), 0)
+      end
+
+      blocks.concat(placements.drop(first_section).map { render_heading(_1, 2) })
+    elsif placements.any?
+      blocks << render_list(placements, 0)
+    end
+
+    blocks.compact.reject(&:empty?).join("\n").sub(/\n+\z/, '')
+  end
+
+  private
+
+  def validate_membership! placements
+    placed = placement_members(placements).uniq.sort
+    members = @group.fetch('members').map { |member|
+      if member['tag']
+        ['tag', member.fetch('tag').fetch('id')]
+      else
+        ['tag_group', member.fetch('tag_group').fetch('id')]
+      end
+    }.uniq.sort
+    missing = members - placed
+    if missing.any?
+      raise UnsupportedStructure, '掲載位置のない membership は Markdown にできません．'
+    end
+  end
+
+  def placement_members nodes
+    nodes.flat_map do |node|
+      own = if node['tag']
+        [['tag', node.fetch('tag').fetch('id')]]
+      elsif node['tag_group']
+        [['tag_group', node.fetch('tag_group').fetch('id')]]
+      else
+        []
+      end
+      own + placement_members(node.fetch('children'))
+    end
+  end
+
+  def render_heading section, level
+    header = "#{ '#' * level } #{ clean_text(section.fetch('section_name')) }"
+    blocks = [header]
+    blocks << clean_text(section['description']) if section['description'].present?
+    children = section.fetch('children')
+    section_indexes = children.each_index.select { |index| children[index].key?('section_name') }
+    if section_indexes.any?
+      first_section = section_indexes.first
+      if children[first_section..].any? { !_1.key?('section_name') }
+        raise UnsupportedStructure,
+              '見出し Section と兄弟 Placement の交互配置は Markdown にできません．'
+      end
+      list_nodes = children[0...first_section]
+      blocks << render_list(list_nodes, 0) if list_nodes.any?
+      blocks.concat(children[first_section..].map { render_heading(_1, level + 1) })
+    elsif children.any?
+      blocks << render_list(children, 0)
+    end
+    blocks.join("\n")
+  end
+
+  def render_list nodes, depth
+    nodes.map do |node|
+      indent = '  ' * depth
+      if node.key?('section_name')
+        raise UnsupportedStructure,
+            'リスト内 Section の説明文は Markdown にできません．' if node['description'].present?
+
+        children = node.fetch('children')
+        head = "#{ indent }- #{ clean_text(node.fetch('section_name')) }:"
+        tail = render_list(children, depth + 1) if children.any?
+        [head, tail].compact.join("\n")
+      else
+        label = if node['tag']
+          node.fetch('tag').fetch('name')
+        else
+          "#{ TagGroupRepr::PREFIX }#{ node.fetch('tag_group').fetch('name') }"
+        end
+        raise UnsupportedStructure, '名称のない Placement は Markdown にできません．' if label.blank?
+
+        head = "#{ indent }- #{ clean_text(label) }"
+        children = node.fetch('children')
+        tail = render_list(children, depth + 1) if children.any?
+        [head, tail].compact.join("\n")
+      end
+    end.join("\n")
+  end
+
+  def clean_text value
+    value.to_s.gsub(/\r\n?/, "\n").lines.map(&:rstrip).join("\n").strip
+  end
+end

backend/app/services/tag_group_operation.rb

@@ -0,0 +1,362 @@
+class TagGroupOperation
+  MAX_PLACEMENT_DEPTH = 5
+
+  def self.create!(locale, name:, description:, members:, placements:, actor:,
+                   require_compatibility: false)
+    ApplicationRecord.transaction do
+      group = TagGroup.new(version_no: 1, created_by_user: actor,
+                           updated_by_user: actor)
+      attributes = prepare!(locale:, group:, name:, description:, members:, placements:)
+      group.assign_attributes(name: attributes.fetch(:name),
+                              description: attributes.fetch(:description))
+      group.save!
+      persist_structure!(group:, attributes:, actor:)
+      validate_compatibility!(locale, group) if require_compatibility
+      persist_version!(group:, attributes:, actor:, event_type: 'create')
+      group
+    end
+  end
+
+  def self.update!(locale, group:, name:, description:, members:, placements:, actor:,
+                   require_compatibility: false)
+    ApplicationRecord.transaction do
+      group.lock!
+      attributes = prepare!(locale:, group:, name:, description:, members:, placements:)
+      if unchanged?(group, attributes)
+        validate_compatibility!(locale, group) if require_compatibility
+        next group
+      end
+
+      group.update!(name: attributes.fetch(:name),
+                    description: attributes.fetch(:description),
+                    version_no: group.version_no + 1,
+                    updated_by_user: actor)
+      persist_structure!(group:, attributes:, actor:)
+      validate_compatibility!(locale, group) if require_compatibility
+      persist_version!(group:, attributes:, actor:, event_type: 'update')
+      group
+    end
+  end
+
+  def self.validate_compatibility! locale, group
+    TagGroupMarkdownRenderer.render(TagGroupRepr.one(locale, group))
+  rescue TagGroupMarkdownRenderer::UnsupportedStructure => error
+    invalid!(group, :base, error.message)
+  end
+  private_class_method :validate_compatibility!
+
+  def self.prepare!(locale:, group:, name:, description:, members:, placements:)
+    record = group
+    normalized_name = name.to_s.strip
+    invalid!(record, :name, 'グループ名は必須です．') if normalized_name.blank?
+    if normalized_name.length > 255
+      invalid!(record, :name, 'グループ名は 255 文字以内で入力してください．')
+    end
+    invalid!(record, :description, '説明文は文字列で入力してください．') unless
+        description.nil? || description.is_a?(String)
+
+    record.name = normalized_name
+    record.description = description
+    unless record.valid?
+      raise ActiveRecord::RecordInvalid, record
+    end
+
+    member_rows = normalize_members(record, members)
+    placement_tree = normalize_placements(record, placements)
+    validate_references!(locale, record, member_rows, placement_tree)
+    validate_containment!(record, member_rows)
+    { name: normalized_name, description:, members: member_rows,
+      placements: placement_tree }
+  end
+  private_class_method :prepare!
+
+  def self.unchanged?(group, attributes)
+    unless (group.name_in_database == attributes.fetch(:name) &&
+            group.description_in_database == attributes.fetch(:description))
+      return false
+    end
+
+    members = TagGroupTag.where(tag_group_id: group.id).pluck(:tag_id)
+        .map { { 'tag_id' => _1 } }
+    members.concat(TagGroupGroup.where(tag_group_id: group.id)
+        .pluck(:child_tag_group_id).map { { 'tag_group_id' => _1 } })
+    requested_members = attributes.fetch(:members).map do |member|
+      member.except('version_no')
+    end
+    return false unless members.to_set == requested_members.to_set
+
+    rows = TagGroupPlacement.where(tag_group_id: group.id).order(:position)
+        .group_by(&:parent_position)
+    build = lambda do |parent_position|
+      rows.fetch(parent_position, []).map do |row|
+        node = if row.tag_id
+          { 'tag_id' => row.tag_id }
+        elsif row.child_tag_group_id
+          { 'tag_group_id' => row.child_tag_group_id }
+        else
+          { 'section_name' => row.section_name, 'description' => row.description }
+        end
+        node.merge('children' => build.call(row.position))
+      end
+    end
+    build.call(nil) == comparable_placements(attributes.fetch(:placements))
+  end
+  private_class_method :unchanged?
+
+  def self.comparable_placements(nodes)
+    nodes.map do |node|
+      result = node.dup
+      result['description'] = node['description'] if node.key?('section_name')
+      result['children'] = comparable_placements(node.fetch('children'))
+      result
+    end
+  end
+  private_class_method :comparable_placements
+
+  def self.normalize_members(record, members)
+    invalid!(record, :members, 'members は配列で指定してください．') unless members.is_a?(Array)
+
+    result = members.map do |member|
+      member = stringify_keys(member)
+      unless member.is_a?(Hash) && member.keys.one? &&
+             (member.key?('tag_id') || member.key?('tag_group_id'))
+        invalid!(record, :members, '各 member は tag_id または tag_group_id を一つ指定してください．')
+      end
+      key = member.keys.first
+      id = integer_id(record, member.fetch(key), :members)
+      { key => id }
+    end
+    invalid!(record, :members, 'membership に重複があります．') unless result.uniq == result
+    result
+  end
+  private_class_method :normalize_members
+
+  def self.normalize_placements(record, placements)
+    invalid!(record, :placements, 'placements は配列で指定してください．') unless
+        placements.is_a?(Array)
+
+    normalize_placement_nodes(record, placements, 1)
+  end
+  private_class_method :normalize_placements
+
+  def self.normalize_placement_nodes(record, nodes, depth)
+    if depth > MAX_PLACEMENT_DEPTH && nodes.any?
+      invalid!(record, :placements, '配置の深さは 5 階層までです．')
+    end
+
+    nodes.map do |raw_node|
+      node = stringify_keys(raw_node)
+      unless node.is_a?(Hash) && node.key?('children')
+        invalid!(record, :placements, '各 Placement に children 配列が必要です．')
+      end
+      children = node.delete('children')
+      unless children.is_a?(Array)
+        invalid!(record, :placements, 'children は配列で指定してください．')
+      end
+
+      kinds = ['tag_id', 'tag_group_id', 'section_name'].select { node.key?(_1) }
+      invalid!(record, :placements, 'Placement の種類を一つ指定してください．') unless
+          kinds.one?
+      kind = kinds.first
+      allowed = [kind, 'description']
+      invalid!(record, :placements, '不明な Placement 項目があります．') unless
+          (node.keys - allowed).empty?
+
+      case kind
+      when 'tag_id', 'tag_group_id'
+        node[kind] = integer_id(record, node.fetch(kind), :placements)
+        if node['description'].present?
+          invalid!(record, :placements, 'Tag / Tag Group Placement に説明文は指定できません．')
+        end
+        node.delete('description')
+      when 'section_name'
+        section_name = node.fetch(kind)
+        unless section_name.is_a?(String) && section_name.strip.present? &&
+               section_name.length <= 255
+          invalid!(record, :placements, 'Section 名は 1〜255 文字で入力してください．')
+        end
+        node[kind] = section_name.strip
+        unless node['description'].nil? || node['description'].is_a?(String)
+          invalid!(record, :placements, 'Section の説明文は文字列で入力してください．')
+        end
+      end
+
+      node['children'] = normalize_placement_nodes(record, children, depth + 1)
+      node
+    end
+  end
+  private_class_method :normalize_placement_nodes
+
+  def self.validate_references!(locale, record, members, placements)
+    membership = members.to_set
+    placed = placement_references(placements).uniq
+    missing = placed - membership.to_a
+    invalid!(record, :placements, 'Placement の対象は membership に含めてください．') if
+        missing.any?
+
+    tag_ids = members.filter_map { _1['tag_id'] }
+    group_ids = members.filter_map { _1['tag_group_id'] }
+    tags = Tag.where(id: tag_ids).index_by(&:id)
+    groups = TagGroup.where(id: group_ids).index_by(&:id)
+    invalid!(record, :members, '存在しない Tag が含まれています．') if
+        tags.size != tag_ids.uniq.size
+    invalid!(record, :members, '存在しない Tag Group が含まれています．') if
+        groups.size != group_ids.uniq.size
+
+    tag_versions = TagVersion.where(tag_id: tag_ids).pluck(:tag_id, :version_no).to_set
+    group_versions = TagGroupVersion.where(tag_group_id: group_ids)
+        .pluck(:tag_group_id, :version_no).to_set
+    tag_names = TagName.where(
+        tag_id: tag_ids, language_code: locale.language_code, primary_flg: true)
+        .pluck(:tag_id).uniq
+
+    members.each do |member|
+      if member.key?('tag_id')
+        id = member.fetch('tag_id')
+        invalid!(record, :members, :invalid) unless
+            tag_names.include?(id)
+        version_no = tags.fetch(id).version_no
+        unless tag_versions.include?([id, version_no])
+          invalid!(record, :members, "Tag ##{ id } の Version がありません．")
+        end
+        member['version_no'] = version_no
+      else
+        id = member.fetch('tag_group_id')
+        version_no = groups.fetch(id).version_no
+        unless group_versions.include?([id, version_no])
+          invalid!(record, :members, "Tag Group ##{ id } の Version がありません．")
+        end
+        member['version_no'] = version_no
+      end
+    end
+  end
+  private_class_method :validate_references!
+
+  def self.validate_containment!(record, members)
+    target_id = record.id
+    return unless target_id
+
+    children = members.filter_map { _1['tag_group_id'] }
+    edges = TagGroupGroup.pluck(:tag_group_id, :child_tag_group_id)
+        .group_by(&:first).transform_values { _1.map(&:last) }
+    edges[target_id] = children
+    visiting = Set.new
+    visited = Set.new
+    visit = lambda do |group_id|
+      invalid!(record, :members, 'Tag Group の循環包含はできません．') if
+          group_id == target_id && visiting.include?(group_id)
+      return if visited.include?(group_id)
+
+      visiting.add(group_id)
+      edges.fetch(group_id, []).each do |child_id|
+        invalid!(record, :members, 'Tag Group の循環包含はできません．') if
+            child_id == target_id
+        visit.call(child_id)
+      end
+      visiting.delete(group_id)
+      visited.add(group_id)
+    end
+    children.each { visit.call(_1) }
+  end
+  private_class_method :validate_containment!
+
+  def self.persist_structure!(group:, attributes:, actor:)
+    tag_members = TagGroupTag.where(tag_group_id: group.id).index_by(&:tag_id)
+    group_members = TagGroupGroup.where(tag_group_id: group.id).index_by(&:child_tag_group_id)
+    attributes.fetch(:members).each do |member|
+      if member.key?('tag_id')
+        next if tag_members.delete(member.fetch('tag_id'))
+
+        TagGroupTag.create!(tag_group_id: group.id, tag_id: member.fetch('tag_id'),
+                            created_by_user: actor)
+      else
+        next if group_members.delete(member.fetch('tag_group_id'))
+
+        TagGroupGroup.create!(tag_group_id: group.id,
+                              child_tag_group_id: member.fetch('tag_group_id'),
+                              created_by_user: actor)
+      end
+    end
+    existing = TagGroupPlacement.where(tag_group_id: group.id).index_by(&:position)
+    persist_placements!(group:, nodes: attributes.fetch(:placements), actor:, existing:)
+    existing.values.sort_by(&:position).reverse_each(&:delete)
+    tag_members.each_value(&:delete)
+    group_members.each_value(&:delete)
+  end
+  private_class_method :persist_structure!
+
+  def self.persist_placements!(group:, nodes:, actor:, existing:, parent_position: nil,
+                               next_position: [0])
+    nodes.each do |node|
+      next_position[0] += 1
+      position = next_position[0]
+      row = existing.delete(position) || TagGroupPlacement.new(
+          tag_group_id: group.id, position:, created_by_user: actor)
+      row.assign_attributes(
+          parent_position:,
+          section_name: node['section_name'], description: node['description'],
+          tag_id: node['tag_id'], child_tag_group_id: node['tag_group_id'])
+      if row.new_record? || row.changed?
+        row.updated_by_user = actor
+        row.save!
+      end
+      persist_placements!(group:, nodes: node.fetch('children'), actor:, existing:,
+                          parent_position: position, next_position:)
+    end
+  end
+  private_class_method :persist_placements!
+
+  def self.persist_version!(group:, attributes:, actor:, event_type:)
+    TagGroupVersion.create!(tag_group: group, version_no: group.version_no,
+                            event_type:, name: group.name,
+                            description: group.description,
+                            members: attributes.fetch(:members),
+                            placements: attributes.fetch(:placements),
+                            created_by_user: actor)
+  end
+  private_class_method :persist_version!
+
+  def self.placement_references(nodes)
+    nodes.flat_map do |node|
+      own = if node.key?('tag_id')
+        [{ 'tag_id' => node.fetch('tag_id') }]
+      elsif node.key?('tag_group_id')
+        [{ 'tag_group_id' => node.fetch('tag_group_id') }]
+      else
+        []
+      end
+      own + placement_references(node.fetch('children'))
+    end
+  end
+  private_class_method :placement_references
+
+  def self.stringify_keys(value)
+    case value
+    when ActionController::Parameters
+      value.to_unsafe_h.deep_stringify_keys
+    when Hash
+      value.deep_stringify_keys
+    else
+      value
+    end
+  end
+  private_class_method :stringify_keys
+
+  def self.integer_id(record, value, attribute)
+    integer = if value.is_a?(Integer)
+      value
+    elsif value.is_a?(String) && value.match?(/\A[0-9]+\z/)
+      value.to_i
+    end
+    invalid!(record, attribute, 'ID は正の整数で指定してください．') unless integer
+    invalid!(record, attribute, 'ID は正の整数で指定してください．') unless integer.positive?
+    integer
+  end
+  private_class_method :integer_id
+
+  def self.invalid!(record, attribute, message)
+    record.errors.add(attribute, message)
+    raise ActiveRecord::RecordInvalid, record
+  end
+  private_class_method :invalid!
+end

backend/app/services/wiki/commit.rb

@@ -1,160 +0,0 @@
-require 'digest'
-
-
-module Wiki
-  class Commit
-    class Conflict < StandardError
-      ;
-    end
-
-    def self.create_content! tag_name:, body:, created_by_user:, message: nil
-      if tag_name.tag && tag_name.language_code == 'ja'
-        return TagDescriptionOperation.create!(
-            tag: tag_name.tag, body:, created_by_user:, message:)
-      end
-
-      create_legacy_content!(tag_name:, body:, created_by_user:, message:)
-    end
-
-    def self.create_legacy_content! tag_name:, body:, created_by_user:, message: nil
-      normalised = normalise_body(body)
-
-      page = WikiPage.new(tag_name:,
-                          body: normalised,
-                          created_user: created_by_user,
-                          updated_user: created_by_user)
-
-      if normalised.blank?
-        page.errors.add(:body, :blank)
-        raise ActiveRecord::RecordInvalid, page
-      end
-
-      ActiveRecord::Base.transaction do
-        page.save!
-
-        new(page:, created_user: created_by_user).content!(
-            body: normalised,
-            message:,
-            base_revision_id: nil)
-
-        page
-      end
-    end
-
-    def self.content! page:, body:, created_user:, message: nil, base_revision_id: nil
-      description = TagDescription.find_by(id: page.id)
-      if description
-        return TagDescriptionOperation.update!(
-            tag: description.tag, body:, updated_by_user: created_user,
-            message:, base_revision_id:)
-      end
-
-      legacy_content!(page:, body:, created_user:, message:, base_revision_id:)
-    end
-
-    def self.legacy_content! page:, body:, created_user:, message: nil,
-                             base_revision_id: nil
-      new(page:, created_user:).content!(body:, message:, base_revision_id:)
-    end
-
-    def self.redirect! page:, redirect_page:, created_user:, message: nil, base_revision_id: nil
-      new(page:, created_user:).redirect!(redirect_page:, message:, base_revision_id:)
-    end
-
-    def initialize page:, created_user:
-      @page = page
-      @created_user = created_user
-    end
-
-    def content! body:, message:, base_revision_id:
-      normalised = self.class.normalise_body(body)
-      if normalised.blank?
-        @page.errors.add(:body, :blank)
-        raise ActiveRecord::RecordInvalid, @page
-      end
-
-      lines = split_lines(normalised)
-
-      line_shas = lines.map { |line| Digest::SHA256.hexdigest(line) }
-      tree_sha = Digest::SHA256.hexdigest(line_shas.join(','))
-
-      ActiveRecord::Base.transaction do
-        @page.lock!
-
-        if base_revision_id.present?
-          current_id = @page.wiki_revisions.maximum(:id)
-          if current_id && current_id != base_revision_id.to_i
-            raise Conflict,
-                "競合が発生してゐます" +
-                "（現在の Id.：#{ current_id }，ベース Id.：#{ base_revision_id }）．"
-          end
-        end
-
-        line_id_by_sha = upsert_lines!(lines, line_shas)
-        line_ids = line_shas.map { |sha| line_id_by_sha.fetch(sha) }
-        @page.update!(body: normalised)
-
-        WikiVersionRecorder.record!(
-            page: @page,
-            event_type: @page.wiki_versions.exists? ? :update : :create,
-            reason: message,
-            created_by_user: @created_user)
-
-        rev = WikiRevision.create!(
-            wiki_page:        @page,
-            base_revision_id:,
-            created_user:     @created_user,
-            kind:             :content,
-            redirect_page_id: nil,
-            message:,
-            lines_count:      lines.length,
-            tree_sha256:      tree_sha)
-
-        rows = line_ids.each_with_index.map do |line_id, pos|
-          { wiki_revision_id: rev.id, wiki_line_id: line_id, position: pos }
-        end
-        WikiRevisionLine.insert_all!(rows) if rows.any?
-        rev
-      end
-    end
-
-    def redirect!(redirect_page:, message:, base_revision_id:) = raise '廃止しました．'
-
-    def self.normalise_body body
-      s = body.to_s
-      s.gsub!(/\r\n?/, "\n")
-      s.encode('UTF-8', invalid: :replace, undef: :replace, replace: '🖕')
-      s.gsub(/\n+$/, '')
-    end
-
-    private
-
-    def split_lines(body) = body.split("\n")
-
-    def upsert_lines! lines, line_shas
-      now = Time.current
-
-      id_by_sha = WikiLine.where(sha256: line_shas).pluck(:sha256, :id).to_h
-
-      missing_by_sha = { }
-
-      line_shas.each_with_index do |sha, i|
-        next if id_by_sha.key?(sha)
-        next if missing_by_sha.key?(sha)
-
-        missing_by_sha[sha] = {
-            sha256:     sha,
-            body:       lines[i],
-            created_at: now,
-            updated_at: now }
-      end
-
-      if missing_by_sha.any?
-        WikiLine.upsert_all(missing_by_sha.values)
-        id_by_sha = WikiLine.where(sha256: line_shas).pluck(:sha256, :id).to_h
-      end
-
-      id_by_sha
-    end
-  end
-end

backend/app/services/wiki/compatibility_writer.rb

@@ -1,33 +0,0 @@
-module Wiki
-  class CompatibilityWriter
-    def self.create! tag_name:, body:, created_by_user:, message: nil
-      Commit.create_legacy_content!(
-          tag_name:, body:, created_by_user:, message:)
-    end
-
-    def self.update! page:, body:, updated_by_user:, message: nil,
-                     base_revision_id: nil
-      normalised = Commit.normalise_body(body)
-      if normalised.blank?
-        return Commit.legacy_content!(
-            page:, body: normalised, created_user: updated_by_user, message:,
-            base_revision_id:)
-      end
-
-      if base_revision_id.present?
-        current_id = page.wiki_revisions.maximum(:id)
-        if current_id && current_id != base_revision_id.to_i
-          raise Commit::Conflict,
-              "競合が発生してゐます" +
-              "（現在の Id.：#{ current_id }，ベース Id.：#{ base_revision_id }）．"
-        end
-      end
-
-      return if Commit.normalise_body(page.body) == normalised
-
-      Commit.legacy_content!(
-          page:, body: normalised, created_user: updated_by_user, message:,
-          base_revision_id:)
-    end
-  end
-end

backend/app/services/wiki_version_recorder.rb

@@ -1,21 +0,0 @@
-class WikiVersionRecorder < VersionRecorder
-  def self.record! page:, event_type:, reason: nil, created_by_user:
-    new(page:, event_type:, reason:, created_by_user:).record!
-  end
-
-  def initialize page:, event_type:, reason: nil, created_by_user:
-    @reason = reason
-    super(record: page, event_type:, created_by_user:)
-  end
-
-  private
-
-  def version_class = WikiVersion
-  def version_association = :wiki_versions
-  def record_key = :wiki_page
-
-  def snapshot_attributes = {
-      title: @record.title,
-      body: @record.body,
-      reason: @reason }
-end

backend/config/routes.rb

@@ -1,4 +1,6 @@
 Rails.application.routes.draw do
+  resources :tag_groups, only: [:index, :show, :create, :update]
+
   resources :nico_tags, path: 'tags/nico', only: [:index, :show, :update]
 
   scope 'tags/:parent_id/children', controller: :tag_children do

backend/db/migrate/20261008000000_create_tag_groups.rb

@@ -0,0 +1,149 @@
+class CreateTagGroups < ActiveRecord::Migration[8.0]
+  def change
+    # 翻訳系は上流の Translation リソースが未完のため保留
+
+    create_table :tag_groups do |t|
+      t.integer :version_no, null: false
+      t.string :name, limit: 255, null: false
+      t.text :description
+      t.references :created_by_user, foreign_key: { to_table: :users }
+      t.references :updated_by_user, foreign_key: { to_table: :users }
+      t.timestamps
+
+      t.check_constraint 'version_no > 0', name: 'chk_tag_groups_version_no_positive'
+      t.index :name, unique: true
+    end
+
+    create_table :tag_group_tags, primary_key: [:tag_group_id, :tag_id] do |t|
+      t.references :tag_group, null: false, foreign_key: true, index: false
+      t.references :tag, null: false, foreign_key: true
+      t.references :created_by_user, foreign_key: { to_table: :users }
+      t.datetime :created_at, null: false
+    end
+
+    create_table :tag_group_groups, primary_key: [:tag_group_id, :child_tag_group_id] do |t|
+      t.references :tag_group, null: false, foreign_key: true, index: false
+      t.references :child_tag_group,
+                   null: false, foreign_key: { to_table: :tag_groups }
+      t.references :created_by_user, foreign_key: { to_table: :users }
+      t.datetime :created_at, null: false
+
+      t.check_constraint 'tag_group_id <> child_tag_group_id',
+                         name: 'chk_tag_group_groups_tag_group_id_not_child_tag_group_id'
+    end
+
+    create_table :tag_group_placements, primary_key: [:tag_group_id, :position] do |t|
+      t.references :tag_group, null: false, foreign_key: true, index: false
+      t.integer :position, null: false
+      t.integer :parent_position
+      t.string :section_name, limit: 255
+      t.text :description
+      t.references :tag
+      t.references :child_tag_group
+      t.references :created_by_user, foreign_key: { to_table: :users }
+      t.references :updated_by_user, foreign_key: { to_table: :users }
+      t.timestamps
+
+      t.foreign_key :tag_group_placements,
+                    column: [:tag_group_id, :parent_position],
+                    primary_key: [:tag_group_id, :position]
+
+      t.foreign_key :tag_group_tags,
+                    column: [:tag_group_id, :tag_id],
+                    primary_key: [:tag_group_id, :tag_id]
+
+      t.foreign_key :tag_group_groups,
+                    column: [:tag_group_id, :child_tag_group_id],
+                    primary_key: [:tag_group_id, :child_tag_group_id]
+
+      t.check_constraint 'position > parent_position',
+                         name: 'chk_tag_group_placements_position_gt_parent_position'
+
+      t.check_constraint ('((section_name IS NOT NULL AND tag_id IS NULL AND child_tag_group_id IS NULL) OR ' +
+                          '(section_name IS NULL AND tag_id IS NOT NULL AND child_tag_group_id IS NULL) OR ' +
+                          '(section_name IS NULL AND tag_id IS NULL AND child_tag_group_id IS NOT NULL)) AND ' +
+                          '(section_name IS NOT NULL OR description IS NULL)'),
+                         name: 'chk_tag_group_placements_references_exclusive'
+    end
+
+    create_table :tag_group_versions do |t|
+      t.references :tag_group, null: false
+      t.integer :version_no, null: false
+      t.string :event_type, null: false
+      t.string :name, limit: 255, null: false
+      t.text :description
+      t.json :members, null: false
+      t.json :placements, null: false
+      t.references :created_by_user
+      t.datetime :created_at, null: false
+
+      t.check_constraint 'version_no > 0',
+                         name: 'chk_tag_group_versions_version_no_positive'
+      t.index [:tag_group_id, :version_no], unique: true
+
+      add_members_constraint!(t)
+      add_placements_constraint!(t)
+    end
+  end
+
+  private
+
+  def add_members_constraint! t
+    schema = { type: 'array',
+               uniqueItems: true,
+               items: member_schema }
+
+    quoted_schema = connection.quote(JSON.generate(schema))
+
+    t.check_constraint "JSON_SCHEMA_VALID(#{ quoted_schema }, members)", 
+                       name: 'chk_tag_group_versions_members_schema'
+  end
+
+  def member_schema
+    { oneOf: [tag_member_schema, group_member_schema] }
+  end
+
+  def tag_member_schema
+    { type: 'object',
+      required: ['tag_id', 'version_no'],
+      properties: { tag_id: { type: 'integer', minimum: 1 },
+                    version_no: { type: 'integer', minimum: 1 } },
+      additionalProperties: false }
+  end
+
+  def group_member_schema
+    { type: 'object',
+      required: ['tag_group_id', 'version_no'],
+      properties: { tag_group_id: { type: 'integer', minimum: 1 },
+                    version_no: { type: 'integer', minimum: 1 } },
+      additionalProperties: false }
+  end
+
+  def add_placements_constraint! t
+    schema = { type: 'array', items: placement_schema(5) }
+
+    quoted_schema = connection.quote(JSON.generate(schema))
+
+    t.check_constraint "JSON_SCHEMA_VALID(#{ quoted_schema }, placements)",
+                       name: 'chk_tag_group_versions_placements_schema'
+  end
+
+  def placement_schema rest
+    { type: 'object',
+      required: ['children'],
+      properties: { section_name: { type: 'string' },
+                    description: { type: ['string', 'null'] },
+                    tag_id: { type: 'integer', minimum: 1 },
+                    tag_group_id: { type: 'integer', minimum: 1 },
+                    children: if rest > 1
+                                { type: 'array', items: placement_schema(rest - 1) }
+                              else
+                                { type: 'array', maxItems: 0 }
+                              end },
+      oneOf: [{ required: ['section_name'] },
+              { required: ['tag_id'] },
+              { required: ['tag_group_id'] }],
+      dependencies: { description: ['section_name'] },
+      additionalProperties: false }
+  end
+end

backend/db/migrate/20261008010000_migrate_tag_groups_from_wiki_pages.rb

@@ -0,0 +1,518 @@
+class MigrateTagGroupsFromWikiPages < ActiveRecord::Migration[8.0]
+  PREFIX = 'タググループ:'
+
+  def up
+    require 'json'
+    require 'time'
+    require 'kramdown'
+    require 'kramdown-parser-gfm'
+
+    assert_empty_destination!
+
+    pages = connection.select_all(<<~SQL).to_a
+      SELECT
+        wp.id
+      , wp.created_user_id
+      , wp.updated_user_id
+      , wp.created_at
+      , wp.updated_at
+      , wp.discarded_at
+      , tn.name
+      FROM
+        wiki_pages wp
+        INNER JOIN
+          tag_names tn
+          ON
+            tn.id = wp.tag_name_id
+      WHERE
+        tn.language_code = 'ja'
+        AND tn.name LIKE #{ quote("#{ PREFIX }%") }
+      ORDER BY
+        wp.id
+    SQL
+
+    return if pages.empty?
+
+    pages.each do |page|
+      if page['discarded_at']
+        say "Wiki ##{ page.fetch('id') }: 破棄済みですが，Revision の移行を継続します．"
+      end
+    end
+
+    tag_ids = load_tag_ids
+    page_ids = pages.map { |page| page.fetch('id').to_i }
+
+    revisions = connection.select_all(<<~SQL).to_a
+      SELECT
+        wr.id
+      , wr.wiki_page_id
+      , wr.kind
+      , wr.redirect_page_id
+      , wr.created_user_id
+      , wr.created_at
+      FROM
+        wiki_revisions wr
+      WHERE
+        wr.wiki_page_id IN (#{ page_ids.join(', ') })
+      ORDER BY
+        wr.wiki_page_id
+      , wr.id
+    SQL
+
+    revisions_by_page = revisions.group_by { |row| row.fetch('wiki_page_id').to_i }
+
+    pages = pages.select do |page|
+      page_id = page.fetch('id').to_i
+      if revisions_by_page.fetch(page_id, []).empty?
+        # tag_groups.version_no > 0 のため，Revision 0 件の Wiki は作成しない．
+        say "Wiki ##{ page_id }: Revision が 0 件のため移行対象から除外します．"
+        false
+      else
+        true
+      end
+    end
+
+    return if pages.empty?
+
+    group_ids = pages.to_h { |page| [page.fetch('name'), page.fetch('id').to_i] }
+    revision_history = pages.to_h do |page|
+      page_id = page.fetch('id').to_i
+      history = revisions_by_page.fetch(page_id).each_with_index.map do |revision, index|
+        { 'id' => revision.fetch('id').to_i,
+          'version_no' => index + 1,
+          'created_at' => revision.fetch('created_at') }
+      end
+      [page_id, history]
+    end
+
+    tag_history = connection.select_all(<<~SQL).to_a.group_by { |row| row.fetch('tag_id').to_i }
+      SELECT
+        tag_id
+      , version_no
+      , created_at
+      FROM
+        tag_versions
+      ORDER BY
+        tag_id
+      , created_at
+      , version_no
+    SQL
+
+    prepared = { }
+    pages.each do |page|
+      page_id = page.fetch('id').to_i
+      history = revisions_by_page.fetch(page_id)
+
+      prepared[page_id] = history.each_with_index.map do |revision, index|
+        context = "Wiki ##{ page_id } / Revision ##{ revision.fetch('id') }"
+        body = revision_body(revision.fetch('id').to_i)
+
+        if revision.fetch('kind').to_i == 1
+          destination = revision['redirect_page_id']
+          description = "旧 Wiki のリダイレクト先: Wiki ##{ destination }"
+          placements = []
+          members = []
+          say "#{ context }: リダイレクトを説明文として移行します．"
+        else
+          begin
+            description, placements = parse_wiki(body, tag_ids, group_ids, context)
+            validate_tree!(placements, context)
+            members = build_members(placements, revision.fetch('created_at'),
+                                    tag_history, revision_history, context)
+          rescue StandardError => error
+            # 解析できない版も捨てず，当時の Markdown を説明文として保存する．
+            say "#{ context }: 構造化を保留し，本文を保存します (#{ error.message })．"
+            description = body
+            placements = []
+            members = []
+          end
+        end
+
+        { revision:, version_no: index + 1, description:, members:, placements:, body: }
+      end
+    end
+
+    # 自己包含は禁止されてゐるため，当該版は原文の保存を優先する．
+    prepared.each do |group_id, versions|
+      current = versions.last
+      next unless current.fetch(:members).any? { |member| member['tag_group_id'] == group_id }
+
+      say "Tag Group ##{ group_id }: 直接の自己参照を検出したため，現行構造化を保留します．"
+      current[:description] = current.fetch(:body)
+      current[:members] = []
+      current[:placements] = []
+    end
+
+    begin
+      validate_current_groups!(prepared)
+    rescue StandardError => error
+      say "Tag Group の包含関係に問題がありますが，移行を継続します (#{ error.message })．"
+    end
+
+    # 移行先の書込みはすべて検証の後．DDL は含めない．
+    connection.transaction do
+      pages.each do |page|
+        page_id = page.fetch('id').to_i
+        current = prepared.fetch(page_id).last
+
+        insert_row('tag_groups', {
+            id: page_id,
+            # page.version_no ではなく，この Wiki に紐付く Revision の総数．
+            version_no: revisions_by_page.fetch(page_id).size,
+            name: page.fetch('name').delete_prefix(PREFIX),
+            description: current.fetch(:description),
+            created_by_user_id: page.fetch('created_user_id'),
+            updated_by_user_id: page.fetch('updated_user_id'),
+            created_at: page.fetch('created_at'),
+            updated_at: page.fetch('updated_at') })
+      end
+
+      pages.each do |page|
+        page_id = page.fetch('id').to_i
+        name = page.fetch('name').delete_prefix(PREFIX)
+
+        prepared.fetch(page_id).each do |item|
+          revision = item.fetch(:revision)
+
+          insert_row('tag_group_versions', {
+              id: revision.fetch('id'),
+              tag_group_id: page_id,
+              version_no: item.fetch(:version_no),
+              event_type: item.fetch(:version_no) == 1 ? 'create' : 'update',
+              name:,
+              description: item.fetch(:description),
+              members: JSON.generate(item.fetch(:members)),
+              placements: JSON.generate(item.fetch(:placements)),
+              created_by_user_id: revision.fetch('created_user_id'),
+              created_at: revision.fetch('created_at') })
+        end
+      end
+
+      pages.each do |page|
+        page_id = page.fetch('id').to_i
+        current = prepared.fetch(page_id).last
+        revision = current.fetch(:revision)
+
+        current.fetch(:members).each do |member|
+          if member.key?('tag_id')
+            insert_row('tag_group_tags', {
+                tag_group_id: page_id,
+                tag_id: member.fetch('tag_id'),
+                created_by_user_id: revision.fetch('created_user_id'),
+                created_at: revision.fetch('created_at') })
+          else
+            insert_row('tag_group_groups', {
+                tag_group_id: page_id,
+                child_tag_group_id: member.fetch('tag_group_id'),
+                created_by_user_id: revision.fetch('created_user_id'),
+                created_at: revision.fetch('created_at') })
+          end
+        end
+      end
+
+      pages.each do |page|
+        page_id = page.fetch('id').to_i
+        current = prepared.fetch(page_id).last
+        revision = current.fetch(:revision)
+        position = 0
+
+        append = -> nodes, parent_position do
+          nodes.each do |node|
+            position += 1
+            own_position = position
+
+            insert_row('tag_group_placements', {
+                tag_group_id: page_id,
+                position: own_position,
+                parent_position:,
+                section_name: node['section_name'],
+                description: node['description'],
+                tag_id: node['tag_id'],
+                child_tag_group_id: node['tag_group_id'],
+                created_by_user_id: revision.fetch('created_user_id'),
+                updated_by_user_id: revision.fetch('created_user_id'),
+                created_at: revision.fetch('created_at'),
+                updated_at: revision.fetch('created_at') })
+
+            append.(node.fetch('children'), own_position)
+          end
+        end
+
+        append.(current.fetch(:placements), nil)
+      end
+    end
+  end
+
+  def down
+    raise ActiveRecord::IrreversibleMigration, '戻せません．'
+  end
+
+  private
+
+  def assert_empty_destination!
+    ['tag_groups', 'tag_group_versions', 'tag_group_tags',
+     'tag_group_groups', 'tag_group_placements'].each do |table|
+      count = connection.select_value("SELECT COUNT(*) FROM #{ table }").to_i
+      raise "#{ table } が空ではありません．" if count.positive?
+    end
+  end
+
+  # 解決は tag_names.name -> tag_names.tag_id のみ．
+  # tags.tag_name_id は読まない．
+  def load_tag_ids
+    rows = connection.select_all(<<~SQL).to_a
+      SELECT
+        name
+      , tag_id
+      FROM
+        tag_names
+      WHERE
+        language_code = 'ja'
+        AND tag_id IS NOT NULL
+    SQL
+
+    rows.each_with_object({ }) do |row, by_name|
+      name = row.fetch('name')
+      id = row.fetch('tag_id').to_i
+      by_name[name] ||= []
+      by_name[name] << id unless by_name[name].include?(id)
+    end
+  end
+
+  def revision_body revision_id
+    connection.select_rows(<<~SQL).flatten.join("\n")
+      SELECT
+        wl.body
+      FROM
+        wiki_revision_lines wrl
+        INNER JOIN wiki_lines wl ON wl.id = wrl.wiki_line_id
+      WHERE
+        wrl.wiki_revision_id = #{ Integer(revision_id) }
+      ORDER BY
+        wrl.position
+    SQL
+  end
+
+  def parse_wiki markdown, tag_ids, group_ids, context
+    root = Kramdown::Document.new(markdown, input: 'GFM').root
+    placements = []
+    description_parts = []
+    headings = []
+
+    root.children.each_with_index do |node, index|
+      case node.type
+      when :blank
+        next
+      when :header
+        level = node.options.fetch(:level)
+        name = inline_text(node).strip
+        raise "#{ context }: 名前のない見出しがあります．" if name.empty?
+
+        headings.pop while headings.any? && headings.last.first >= level
+        parent = headings.last&.last
+        section = { 'section_name' => name, 'description' => nil, 'children' => [] }
+        (parent ? parent.fetch('children') : placements) << section
+        headings << [level, section]
+      when :p
+        text = inline_markdown(node).strip
+        next if text.empty?
+
+        if headings.any?
+          heading = headings.last.last
+          heading['description'] = [heading['description'], text].compact.join("\n\n")
+        else
+          description_parts << text
+        end
+      when :ul, :ol
+        if headings.any? && see_also_heading?(headings.last.last.fetch('section_name'))
+          heading = headings.last.last
+          raw = original_block(markdown, root.children, index)
+          heading['description'] = [heading['description'], raw].compact.join("\n\n")
+        else
+          target = headings.any? ? headings.last.last.fetch('children') : placements
+          target.concat(node.children.map { |item| parse_list_item(item, tag_ids, group_ids, context) })
+        end
+      else
+        raise "#{ context }: 未対応の Markdown 構文 #{ node.type.inspect }"
+      end
+    end
+
+    [description_parts.empty? ? nil : description_parts.join("\n\n"), placements]
+  end
+
+  def see_also_heading? name
+    ['see also', '関連項目'].include?(name.strip.downcase.sub(/[:：]\z/, ''))
+  end
+
+  def original_block markdown, siblings, index
+    current = siblings.fetch(index)
+    start_line = current.options[:location]
+    raise 'Markdown block の位置が不明です．' unless start_line
+
+    following = siblings[(index + 1)..].find do |node|
+      node.options[:location] && node.options[:location] > start_line
+    end
+    end_line = following ? following.options.fetch(:location) - 1 : markdown.lines.length
+    markdown.lines[(start_line - 1)...end_line].join.strip
+  end
+
+  def parse_list_item item, tag_ids, group_ids, context
+    raise "#{ context }: リスト項目ではありません．" if item.type != :li
+
+    nested, own = item.children.partition { |child| [:ul, :ol].include?(child.type) }
+    own.reject! { |child| child.type == :blank }
+    unless own.all? { |child| [:p, :text, :a, :codespan].include?(child.type) }
+      raise "#{ context }: 未対応のリスト項目があります．"
+    end
+
+    label = own.map { |child| inline_text(child) }.join(' ').strip
+    raise "#{ context }: 空のリスト項目があります．" if label.empty?
+
+    node =
+        if group_ids.key?(label)
+          { 'tag_group_id' => group_ids.fetch(label) }
+        elsif tag_ids.key?(label)
+          ids = tag_ids.fetch(label)
+          unless ids.one?
+            raise "#{ context }: タグ名 #{ label.inspect } が複数の ID を指します：#{ ids.inspect }"
+          end
+          { 'tag_id' => ids.first }
+        elsif label.end_with?(':', '：')
+          name = label.sub(/[:：]\z/, '')
+          raise "#{ context }: 空の区分名があります．" if name.empty?
+          if see_also_heading?(name) && nested.any?
+            raise "#{ context }: リスト内の See also は説明文への保管処理が未実装です．"
+          end
+          { 'section_name' => name, 'description' => nil }
+        else
+          raise "#{ context }: 解決不能なリスト項目 #{ label.inspect }"
+        end
+
+    node['children'] = nested.flat_map do |list|
+      list.children.map { |child| parse_list_item(child, tag_ids, group_ids, context) }
+    end
+
+    node
+  end
+
+  def inline_text node
+    case node.type
+    when :text, :codespan
+      node.value.to_s
+    when :softbreak, :br
+      ' '
+    when :a, :p, :header, :em, :strong, :span, :li
+      node.children.map { |child| inline_text(child) }.join
+    else
+      raise "未対応のインライン構文 #{ node.type.inspect }"
+    end
+  end
+
+  def inline_markdown node
+    case node.type
+    when :text
+      node.value.to_s
+    when :codespan
+      "`#{ node.value }`"
+    when :softbreak
+      "\n"
+    when :br
+      "  \n"
+    when :p
+      node.children.map { |child| inline_markdown(child) }.join
+    when :a
+      href = node.attr.fetch('href')
+      "[#{ node.children.map { |child| inline_markdown(child) }.join }](#{ href })"
+    when :em
+      "*#{ node.children.map { |child| inline_markdown(child) }.join }*"
+    when :strong
+      "**#{ node.children.map { |child| inline_markdown(child) }.join }**"
+    else
+      raise "未対応のインライン構文 #{ node.type.inspect }"
+    end
+  end
+
+  def validate_tree! nodes, context, depth = 1
+    raise "#{ context }: 配置の深さが 5 を超えてゐます．" if depth > 5 && nodes.any?
+
+    nodes.each do |node|
+      name = node['section_name']
+      if name && name.length > 255
+        raise "#{ context }: 区分名が 255 文字を超えてゐます．"
+      end
+      validate_tree!(node.fetch('children'), context, depth + 1)
+    end
+  end
+
+  def build_members nodes, date, tag_history, group_history, context
+    ids_of_tags = []
+    ids_of_groups = []
+
+    visit = -> items do
+      items.each do |node|
+        ids_of_tags << node['tag_id'] if node.key?('tag_id')
+        ids_of_groups << node['tag_group_id'] if node.key?('tag_group_id')
+        visit.(node.fetch('children'))
+      end
+    end
+    visit.(nodes)
+
+    tags = ids_of_tags.uniq.map do |id|
+      { 'tag_id' => id,
+        'version_no' => version_at(tag_history[id], date, context, "Tag ##{ id }") }
+    end
+
+    groups = ids_of_groups.uniq.map do |id|
+      { 'tag_group_id' => id,
+        'version_no' => version_at(group_history[id], date, context, "TagGroup ##{ id }") }
+    end
+
+    tags + groups
+  end
+
+  def version_at history, date, context, target
+    raise "#{ context }: #{ target } の履歴が存在しません．" unless history&.any?
+
+    timestamp = Time.parse(date.to_s)
+    candidates = history.select do |row|
+      Time.parse(row.fetch('created_at').to_s) <= timestamp
+    end
+    if candidates.empty?
+      raise "#{ context }: #{ target } は #{ date } 時点で存在しません．"
+    end
+
+    candidates.max_by { |row|
+      [Time.parse(row.fetch('created_at').to_s), row.fetch('version_no').to_i]
+    }.fetch('version_no').to_i
+  end
+
+  def validate_current_groups! prepared
+    edges = { }
+    prepared.each do |group_id, versions|
+      edges[group_id] = versions.last.fetch(:members)
+                              .filter_map { |member| member['tag_group_id'] }
+    end
+
+    visiting = { }
+    visited = { }
+    visit = -> group_id do
+      raise "Tag Group の循環参照を検出しました：#{ group_id }" if visiting[group_id]
+      return if visited[group_id]
+
+      visiting[group_id] = true
+      edges.fetch(group_id, []).each { |child_id| visit.(child_id) }
+      visiting.delete(group_id)
+      visited[group_id] = true
+    end
+
+    edges.keys.each { |group_id| visit.(group_id) }
+  end
+
+  def quote(value) = connection.quote(value)
+
+  def insert_row table, values
+    columns = values.keys.join(', ')
+    payload = values.values.map { |value| quote(value) }.join(', ')
+    execute "INSERT INTO #{ table } (#{ columns }) VALUES (#{ payload })"
+  end
+end

backend/db/migrate/20261015000000_drop_wiki_pages.rb

@@ -0,0 +1,9 @@
+class DropWikiPages < ActiveRecord::Migration[8.0]
+  def change
+    drop_table :wiki_versions
+    drop_table :wiki_revision_lines
+    drop_table :wiki_lines
+    drop_table :wiki_revisions
+    drop_table :wiki_pages
+  end
+end

backend/db/migrate/20261015003000_remove_tag_name_id_from_tags.rb

@@ -0,0 +1,11 @@
+class RemoveTagNameIdFromTags < ActiveRecord::Migration[8.0]
+  def up
+    remove_foreign_key :tags, column: :tag_name_id
+    remove_foreign_key :tag_names, column: :canonical_id
+
+    remove_column :tags, :tag_name_id
+    remove_column :tag_names, :canonical_id
+  end
+
+  def down = raise ActiveRecord::IrreversibleMigration, '戻せません．'
+end

backend/db/migrate/20261015010000_delete_name_for_wiki_from_tag_names.rb

@@ -0,0 +1,15 @@
+class DeleteNameForWikiFromTagNames < ActiveRecord::Migration[8.0]
+  def up
+    execute <<~SQL
+      DELETE
+      FROM
+        tag_names
+      WHERE
+        tag_id IS NULL
+    SQL
+
+    change_column_null :tag_names, :tag_id, false
+  end
+
+  def down = raise ActiveRecord::IrreversibleMigration, '戻せません．'
+end

backend/db/schema.rb

@@ -10,7 +10,7 @@
 #
 # It's strongly recommended that you check this file into your version control system.
 
-ActiveRecord::Schema[8.0].define(version: 2026_10_05_000000) do
+ActiveRecord::Schema[8.0].define(version: 2026_10_15_010000) do
   create_table "active_storage_attachments", charset: "utf8mb4", collation: "utf8mb4_0900_ai_ci", force: :cascade do |t|
     t.string "name", null: false
     t.string "record_type", null: false
@@ -483,6 +483,80 @@ ActiveRecord::Schema[8.0].define(version: 2026_10_05_000000) do
     t.check_constraint "`version_no` > 0", name: "chk_tag_descriptions_version_no_positive"
   end
 
+  create_table "tag_group_groups", primary_key: ["tag_group_id", "child_tag_group_id"], charset: "utf8mb4", collation: "utf8mb4_0900_ai_ci", force: :cascade do |t|
+    t.bigint "tag_group_id", null: false
+    t.bigint "child_tag_group_id", null: false
+    t.bigint "created_by_user_id"
+    t.datetime "created_at", null: false
+    t.index ["child_tag_group_id"], name: "index_tag_group_groups_on_child_tag_group_id"
+    t.index ["created_by_user_id"], name: "index_tag_group_groups_on_created_by_user_id"
+    t.check_constraint "`tag_group_id` <> `child_tag_group_id`", name: "chk_tag_group_groups_tag_group_id_not_child_tag_group_id"
+  end
+
+  create_table "tag_group_placements", primary_key: ["tag_group_id", "position"], charset: "utf8mb4", collation: "utf8mb4_0900_ai_ci", force: :cascade do |t|
+    t.bigint "tag_group_id", null: false
+    t.integer "position", null: false
+    t.integer "parent_position"
+    t.string "section_name"
+    t.text "description"
+    t.bigint "tag_id"
+    t.bigint "child_tag_group_id"
+    t.bigint "created_by_user_id"
+    t.bigint "updated_by_user_id"
+    t.datetime "created_at", null: false
+    t.datetime "updated_at", null: false
+    t.index ["child_tag_group_id"], name: "index_tag_group_placements_on_child_tag_group_id"
+    t.index ["created_by_user_id"], name: "index_tag_group_placements_on_created_by_user_id"
+    t.index ["tag_group_id", "child_tag_group_id"], name: "fk_rails_7342b54ced"
+    t.index ["tag_group_id", "parent_position"], name: "fk_rails_3af6ee71ca"
+    t.index ["tag_group_id", "tag_id"], name: "fk_rails_365dc60759"
+    t.index ["tag_id"], name: "index_tag_group_placements_on_tag_id"
+    t.index ["updated_by_user_id"], name: "index_tag_group_placements_on_updated_by_user_id"
+    t.check_constraint "(((`section_name` is not null) and (`tag_id` is null) and (`child_tag_group_id` is null)) or ((`section_name` is null) and (`tag_id` is not null) and (`child_tag_group_id` is null)) or ((`section_name` is null) and (`tag_id` is null) and (`child_tag_group_id` is not null))) and ((`section_name` is not null) or (`description` is null))", name: "chk_tag_group_placements_references_exclusive"
+    t.check_constraint "`position` > `parent_position`", name: "chk_tag_group_placements_position_gt_parent_position"
+  end
+
+  create_table "tag_group_tags", primary_key: ["tag_group_id", "tag_id"], charset: "utf8mb4", collation: "utf8mb4_0900_ai_ci", force: :cascade do |t|
+    t.bigint "tag_group_id", null: false
+    t.bigint "tag_id", null: false
+    t.bigint "created_by_user_id"
+    t.datetime "created_at", null: false
+    t.index ["created_by_user_id"], name: "index_tag_group_tags_on_created_by_user_id"
+    t.index ["tag_id"], name: "index_tag_group_tags_on_tag_id"
+  end
+
+  create_table "tag_group_versions", charset: "utf8mb4", collation: "utf8mb4_0900_ai_ci", force: :cascade do |t|
+    t.bigint "tag_group_id", null: false
+    t.integer "version_no", null: false
+    t.string "event_type", null: false
+    t.string "name", null: false
+    t.text "description"
+    t.json "members", null: false
+    t.json "placements", null: false
+    t.bigint "created_by_user_id"
+    t.datetime "created_at", null: false
+    t.index ["created_by_user_id"], name: "index_tag_group_versions_on_created_by_user_id"
+    t.index ["tag_group_id", "version_no"], name: "index_tag_group_versions_on_tag_group_id_and_version_no", unique: true
+    t.index ["tag_group_id"], name: "index_tag_group_versions_on_tag_group_id"
+    t.check_constraint "`version_no` > 0", name: "chk_tag_group_versions_version_no_positive"
+    t.check_constraint "json_schema_valid(_utf8mb4'{\"type\":\"array\",\"items\":{\"type\":\"object\",\"required\":[\"children\"],\"properties\":{\"section_name\":{\"type\":\"string\"},\"description\":{\"type\":[\"string\",\"null\"]},\"tag_id\":{\"type\":\"integer\",\"minimum\":1},\"tag_group_id\":{\"type\":\"integer\",\"minimum\":1},\"children\":{\"type\":\"array\",\"items\":{\"type\":\"object\",\"required\":[\"children\"],\"properties\":{\"section_name\":{\"type\":\"string\"},\"description\":{\"type\":[\"string\",\"null\"]},\"tag_id\":{\"type\":\"integer\",\"minimum\":1},\"tag_group_id\":{\"type\":\"integer\",\"minimum\":1},\"children\":{\"type\":\"array\",\"items\":{\"type\":\"object\",\"required\":[\"children\"],\"properties\":{\"section_name\":{\"type\":\"string\"},\"description\":{\"type\":[\"string\",\"null\"]},\"tag_id\":{\"type\":\"integer\",\"minimum\":1},\"tag_group_id\":{\"type\":\"integer\",\"minimum\":1},\"children\":{\"type\":\"array\",\"items\":{\"type\":\"object\",\"required\":[\"children\"],\"properties\":{\"section_name\":{\"type\":\"string\"},\"description\":{\"type\":[\"string\",\"null\"]},\"tag_id\":{\"type\":\"integer\",\"minimum\":1},\"tag_group_id\":{\"type\":\"integer\",\"minimum\":1},\"children\":{\"type\":\"array\",\"items\":{\"type\":\"object\",\"required\":[\"children\"],\"properties\":{\"section_name\":{\"type\":\"string\"},\"description\":{\"type\":[\"string\",\"null\"]},\"tag_id\":{\"type\":\"integer\",\"minimum\":1},\"tag_group_id\":{\"type\":\"integer\",\"minimum\":1},\"children\":{\"type\":\"array\",\"maxItems\":0}},\"oneOf\":[{\"required\":[\"section_name\"]},{\"required\":[\"tag_id\"]},{\"required\":[\"tag_group_id\"]}],\"dependencies\":{\"description\":[\"section_name\"]},\"additionalProperties\":false}}},\"oneOf\":[{\"required\":[\"section_name\"]},{\"required\":[\"tag_id\"]},{\"required\":[\"tag_group_id\"]}],\"dependencies\":{\"description\":[\"section_name\"]},\"additionalProperties\":false}}},\"oneOf\":[{\"required\":[\"section_name\"]},{\"required\":[\"tag_id\"]},{\"required\":[\"tag_group_id\"]}],\"dependencies\":{\"description\":[\"section_name\"]},\"additionalProperties\":false}}},\"oneOf\":[{\"required\":[\"section_name\"]},{\"required\":[\"tag_id\"]},{\"required\":[\"tag_group_id\"]}],\"dependencies\":{\"description\":[\"section_name\"]},\"additionalProperties\":false}}},\"oneOf\":[{\"required\":[\"section_name\"]},{\"required\":[\"tag_id\"]},{\"required\":[\"tag_group_id\"]}],\"dependencies\":{\"description\":[\"section_name\"]},\"additionalProperties\":false}}',`placements`)", name: "chk_tag_group_versions_placements_schema"
+    t.check_constraint "json_schema_valid(_utf8mb4'{\"type\":\"array\",\"uniqueItems\":true,\"items\":{\"oneOf\":[{\"type\":\"object\",\"required\":[\"tag_id\",\"version_no\"],\"properties\":{\"tag_id\":{\"type\":\"integer\",\"minimum\":1},\"version_no\":{\"type\":\"integer\",\"minimum\":1}},\"additionalProperties\":false},{\"type\":\"object\",\"required\":[\"tag_group_id\",\"version_no\"],\"properties\":{\"tag_group_id\":{\"type\":\"integer\",\"minimum\":1},\"version_no\":{\"type\":\"integer\",\"minimum\":1}},\"additionalProperties\":false}]}}',`members`)", name: "chk_tag_group_versions_members_schema"
+  end
+
+  create_table "tag_groups", charset: "utf8mb4", collation: "utf8mb4_0900_ai_ci", force: :cascade do |t|
+    t.integer "version_no", null: false
+    t.string "name", null: false
+    t.text "description"
+    t.bigint "created_by_user_id"
+    t.bigint "updated_by_user_id"
+    t.datetime "created_at", null: false
+    t.datetime "updated_at", null: false
+    t.index ["created_by_user_id"], name: "index_tag_groups_on_created_by_user_id"
+    t.index ["name"], name: "index_tag_groups_on_name", unique: true
+    t.index ["updated_by_user_id"], name: "index_tag_groups_on_updated_by_user_id"
+    t.check_constraint "`version_no` > 0", name: "chk_tag_groups_version_no_positive"
+  end
+
   create_table "tag_implications", charset: "utf8mb4", collation: "utf8mb4_0900_ai_ci", force: :cascade do |t|
     t.bigint "tag_id", null: false
     t.bigint "parent_tag_id", null: false
@@ -504,17 +578,15 @@ ActiveRecord::Schema[8.0].define(version: 2026_10_05_000000) do
   end
 
   create_table "tag_names", charset: "utf8mb4", collation: "utf8mb4_0900_ai_ci", force: :cascade do |t|
-    t.bigint "tag_id"
+    t.bigint "tag_id", null: false
     t.string "language_code", limit: 16, null: false
     t.string "name", null: false
     t.string "script_code", limit: 4, null: false
     t.boolean "primary_flg", null: false
     t.boolean "auto_generated", default: false, null: false
-    t.bigint "canonical_id"
     t.datetime "created_at", null: false
     t.datetime "updated_at", null: false
     t.virtual "primary_tag_id", type: :bigint, as: "(case when `primary_flg` then `tag_id` else NULL end)"
-    t.index ["canonical_id"], name: "index_tag_names_on_canonical_id"
     t.index ["language_code", "name"], name: "index_tag_names_on_language_code_and_name", unique: true
     t.index ["primary_tag_id", "language_code"], name: "index_tag_names_on_primary_tag_id_and_language_code", unique: true
     t.index ["script_code"], name: "fk_rails_dd783b3d1c"
@@ -551,7 +623,6 @@ ActiveRecord::Schema[8.0].define(version: 2026_10_05_000000) do
   end
 
   create_table "tags", charset: "utf8mb4", collation: "utf8mb4_0900_ai_ci", force: :cascade do |t|
-    t.bigint "tag_name_id", null: false
     t.string "category", default: "general", null: false
     t.datetime "deprecated_at"
     t.datetime "created_at", null: false
@@ -559,7 +630,6 @@ ActiveRecord::Schema[8.0].define(version: 2026_10_05_000000) do
     t.integer "post_count", default: 0, null: false
     t.integer "version_no", null: false
     t.index ["deprecated_at"], name: "index_tags_on_deprecated_at"
-    t.index ["tag_name_id"], name: "index_tags_on_tag_name_id", unique: true
     t.check_constraint "(`deprecated_at` is null) or (`category` <> _utf8mb4'nico')", name: "chk_tags_deprecated_at_not_nico"
     t.check_constraint "`version_no` > 0", name: "chk_tags_version_no_positive"
   end
@@ -699,76 +769,6 @@ ActiveRecord::Schema[8.0].define(version: 2026_10_05_000000) do
     t.index ["banned_at"], name: "index_users_on_banned_at"
   end
 
-  create_table "wiki_lines", charset: "utf8mb4", collation: "utf8mb4_0900_ai_ci", force: :cascade do |t|
-    t.string "sha256", limit: 64, null: false
-    t.text "body", null: false
-    t.datetime "created_at", null: false
-    t.datetime "updated_at", null: false
-    t.index ["sha256"], name: "index_wiki_lines_on_sha256", unique: true
-  end
-
-  create_table "wiki_pages", charset: "utf8mb4", collation: "utf8mb4_0900_ai_ci", force: :cascade do |t|
-    t.bigint "tag_name_id", null: false
-    t.text "body", null: false
-    t.bigint "created_user_id", null: false
-    t.bigint "updated_user_id", null: false
-    t.datetime "created_at", null: false
-    t.datetime "updated_at", null: false
-    t.datetime "discarded_at"
-    t.integer "version_no", null: false
-    t.index ["created_user_id"], name: "index_wiki_pages_on_created_user_id"
-    t.index ["discarded_at"], name: "index_wiki_pages_on_discarded_at"
-    t.index ["tag_name_id"], name: "index_wiki_pages_on_tag_name_id", unique: true
-    t.index ["updated_user_id"], name: "index_wiki_pages_on_updated_user_id"
-    t.check_constraint "`version_no` > 0", name: "chk_wiki_pages_version_no_positive"
-  end
-
-  create_table "wiki_revision_lines", charset: "utf8mb4", collation: "utf8mb4_0900_ai_ci", force: :cascade do |t|
-    t.bigint "wiki_revision_id", null: false
-    t.integer "position", null: false
-    t.bigint "wiki_line_id", null: false
-    t.index ["wiki_line_id"], name: "index_wiki_revision_lines_on_wiki_line_id"
-    t.index ["wiki_revision_id", "position"], name: "index_wiki_revision_lines_on_wiki_revision_id_and_position", unique: true
-    t.index ["wiki_revision_id", "wiki_line_id"], name: "index_wiki_revision_lines_on_wiki_revision_id_and_wiki_line_id"
-    t.index ["wiki_revision_id"], name: "index_wiki_revision_lines_on_wiki_revision_id"
-  end
-
-  create_table "wiki_revisions", charset: "utf8mb4", collation: "utf8mb4_0900_ai_ci", force: :cascade do |t|
-    t.bigint "wiki_page_id", null: false
-    t.bigint "base_revision_id"
-    t.bigint "created_user_id", null: false
-    t.integer "kind", default: 0, null: false
-    t.bigint "redirect_page_id"
-    t.string "message"
-    t.integer "lines_count", default: 0, null: false
-    t.string "tree_sha256", limit: 64
-    t.datetime "created_at", null: false
-    t.datetime "updated_at", null: false
-    t.index ["base_revision_id"], name: "index_wiki_revisions_on_base_revision_id"
-    t.index ["created_user_id"], name: "index_wiki_revisions_on_created_user_id"
-    t.index ["kind"], name: "index_wiki_revisions_on_kind"
-    t.index ["redirect_page_id"], name: "index_wiki_revisions_on_redirect_page_id"
-    t.index ["tree_sha256"], name: "index_wiki_revisions_on_tree_sha256"
-    t.index ["wiki_page_id", "id"], name: "index_wiki_revisions_on_wiki_page_id_and_id"
-    t.index ["wiki_page_id"], name: "index_wiki_revisions_on_wiki_page_id"
-  end
-
-  create_table "wiki_versions", charset: "utf8mb4", collation: "utf8mb4_0900_ai_ci", force: :cascade do |t|
-    t.bigint "wiki_page_id", null: false
-    t.integer "version_no", null: false
-    t.string "event_type", null: false
-    t.string "title", null: false
-    t.text "body", null: false
-    t.text "reason"
-    t.datetime "created_at", null: false
-    t.bigint "created_by_user_id"
-    t.index ["created_by_user_id"], name: "index_wiki_versions_on_created_by_user_id"
-    t.index ["wiki_page_id", "version_no"], name: "index_wiki_versions_on_wiki_page_id_and_version_no", unique: true
-    t.index ["wiki_page_id"], name: "index_wiki_versions_on_wiki_page_id"
-    t.check_constraint "`event_type` in (_utf8mb4'create',_utf8mb4'update',_utf8mb4'discard',_utf8mb4'restore')", name: "wiki_versions_event_type_valid"
-    t.check_constraint "`version_no` > 0", name: "wiki_versions_version_no_positive"
-  end
-
   add_foreign_key "active_storage_attachments", "active_storage_blobs", column: "blob_id"
   add_foreign_key "active_storage_variant_records", "active_storage_blobs", column: "blob_id"
   add_foreign_key "gekanator_ai_runs", "gekanator_question_suggestions"
@@ -823,16 +823,28 @@ ActiveRecord::Schema[8.0].define(version: 2026_10_05_000000) do
   add_foreign_key "tag_descriptions", "tags"
   add_foreign_key "tag_descriptions", "users", column: "created_by_user_id"
   add_foreign_key "tag_descriptions", "users", column: "updated_by_user_id"
+  add_foreign_key "tag_group_groups", "tag_groups"
+  add_foreign_key "tag_group_groups", "tag_groups", column: "child_tag_group_id"
+  add_foreign_key "tag_group_groups", "users", column: "created_by_user_id"
+  add_foreign_key "tag_group_placements", "tag_group_groups", column: ["tag_group_id", "child_tag_group_id"], primary_key: ["tag_group_id", "child_tag_group_id"]
+  add_foreign_key "tag_group_placements", "tag_group_placements", column: ["tag_group_id", "parent_position"], primary_key: ["tag_group_id", "position"]
+  add_foreign_key "tag_group_placements", "tag_group_tags", column: ["tag_group_id", "tag_id"], primary_key: ["tag_group_id", "tag_id"]
+  add_foreign_key "tag_group_placements", "tag_groups"
+  add_foreign_key "tag_group_placements", "users", column: "created_by_user_id"
+  add_foreign_key "tag_group_placements", "users", column: "updated_by_user_id"
+  add_foreign_key "tag_group_tags", "tag_groups"
+  add_foreign_key "tag_group_tags", "tags"
+  add_foreign_key "tag_group_tags", "users", column: "created_by_user_id"
+  add_foreign_key "tag_groups", "users", column: "created_by_user_id"
+  add_foreign_key "tag_groups", "users", column: "updated_by_user_id"
   add_foreign_key "tag_implications", "tags"
   add_foreign_key "tag_implications", "tags", column: "parent_tag_id"
   add_foreign_key "tag_names", "languages", column: "language_code", primary_key: "code"
   add_foreign_key "tag_names", "scripts", column: "script_code", primary_key: "code"
-  add_foreign_key "tag_names", "tag_names", column: "canonical_id"
   add_foreign_key "tag_names", "tags"
   add_foreign_key "tag_similarities", "tags"
   add_foreign_key "tag_similarities", "tags", column: "target_tag_id"
   add_foreign_key "tag_versions", "users", column: "created_by_user_id"
-  add_foreign_key "tags", "tag_names"
   add_foreign_key "theatre_comments", "theatres"
   add_foreign_key "theatre_comments", "users"
   add_foreign_key "theatre_programmes", "posts"
@@ -857,15 +869,4 @@ ActiveRecord::Schema[8.0].define(version: 2026_10_05_000000) do
   add_foreign_key "user_post_views", "posts"
   add_foreign_key "user_post_views", "users"
   add_foreign_key "user_theme_slots", "users"
-  add_foreign_key "wiki_pages", "tag_names"
-  add_foreign_key "wiki_pages", "users", column: "created_user_id"
-  add_foreign_key "wiki_pages", "users", column: "updated_user_id"
-  add_foreign_key "wiki_revision_lines", "wiki_lines"
-  add_foreign_key "wiki_revision_lines", "wiki_revisions"
-  add_foreign_key "wiki_revisions", "users", column: "created_user_id"
-  add_foreign_key "wiki_revisions", "wiki_pages"
-  add_foreign_key "wiki_revisions", "wiki_pages", column: "redirect_page_id"
-  add_foreign_key "wiki_revisions", "wiki_revisions", column: "base_revision_id"
-  add_foreign_key "wiki_versions", "users", column: "created_by_user_id"
-  add_foreign_key "wiki_versions", "wiki_pages"
 end

backend/lib/tasks/export_nico.rake

@@ -3,8 +3,8 @@ namespace :nico do
   task export: :environment do
     require 'open3'
 
-    mysql_user = ENV.fetch('MYSQL_USER')
+    mysql_user = ENV.fetch('NIZIKA_NICO_MYSQL_USER')
-    mysql_pass = ENV.fetch('MYSQL_PASS')
+    mysql_pass = ENV.fetch('NIZIKA_NICO_MYSQL_PASS')
     nizika_nico_path = ENV.fetch('NIZIKA_NICO_PATH')
 
     videos = Post.where('url LIKE ?', '%nicovideo.jp/watch/%').pluck(:url).filter_map {
@@ -14,7 +14,7 @@ namespace :nico do
     next if videos.empty?
 
     _, stderr, status = Open3.capture3(
-        { 'MYSQL_USER' => mysql_user, 'MYSQL_PASS' => mysql_pass },
+        { 'NIZIKA_NICO_MYSQL_USER' => mysql_user, 'NIZIKA_NICO_MYSQL_PASS' => mysql_pass },
         'python3', '-m', 'tracked_videos.put_bulk_upsert', *videos,
         chdir: nizika_nico_path)
 

backend/lib/tasks/migrate_help_pages.rake

@@ -0,0 +1,51 @@
+namespace :help do
+  desc 'ヘルプ移行'
+  task migrate: :environment do
+    help_path = ENV.fetch('BTRC_HUB_HELP_PATH')
+    abort 'ヘルプ置場指定してね．' if help_path.blank?
+
+    # ファイルがすでに存在する場合は通さなぃ．
+    abort 'ファイル消してね．' if Dir.glob("#{ help_path }/*").present?
+
+    # 現状物理削除はなぃはず
+    pages = 
+        WikiPage
+        .joins(:tag_name)
+        .where(tag_names: { tag_id: nil, language_code: 'ja' })
+        .where.not("tag_names.name LIKE 'タググループ:%'")
+
+    puts "移行対象: #{pages.count} 件"
+    abort '移行対象がありません．' if pages.empty?
+
+    pages.find_each do |page|
+      puts page.body
+      puts page.title
+
+      puts 'この identifier は何にする?'
+      identifier = $stdin.gets.chomp
+      Dir.mkdir "#{ help_path }/#{ identifier }"
+      Dir.mkdir "#{ help_path }/#{ identifier }/editions"
+      Dir.mkdir "#{ help_path }/#{ identifier }/editions/ja"
+
+      last_file_name = ''
+      WikiVersion.where(wiki_page_id: page.id).order(:version_no).each do |ver|
+        last_file_name, last_file_name_no = last_file_name.split('.')
+
+        file_name = ver.created_at.strftime('%Y-%m-%d')
+        if file_name == last_file_name
+          file_name += ".#{ (last_file_name_no || 1).to_i + 1 }"
+        end
+
+        body = "# #{ ver.title.sub(/^ヘルプ:/, '') }\n\n#{ ver.body }"
+        File.write "#{ help_path }/#{ identifier }/editions/ja/#{ file_name }.mdx", body
+
+        last_file_name = file_name
+      end
+
+      article_meta = { 'identifier' => identifier,
+                       'canonical_language' => 'ja',
+                       'languages' => { 'ja' => { 'current_edition' => last_file_name } } }
+      File.write "#{ help_path }/#{ identifier }/article.yml", article_meta.to_yaml
+    end
+  end
+end

backend/lib/tasks/sync_nico.rake

@@ -54,11 +54,11 @@ namespace :nico do
           .find_each(&:destroy!)
     end
 
-    mysql_user = ENV['MYSQL_USER']
+    mysql_user = ENV['NIZIKA_NICO_MYSQL_USER']
-    mysql_pass = ENV['MYSQL_PASS']
+    mysql_pass = ENV['NIZIKA_NICO_MYSQL_PASS']
     nizika_nico_path = ENV['NIZIKA_NICO_PATH']
     stdout, stderr, status = Open3.capture3(
-        { 'MYSQL_USER' => mysql_user, 'MYSQL_PASS' => mysql_pass },
+        { 'NIZIKA_NICO_MYSQL_USER' => mysql_user, 'NIZIKA_NICO_MYSQL_PASS' => mysql_pass },
         'python3', "#{ nizika_nico_path }/get_videos.py")
 
     unless status.success?

backend/spec/db/tag_description_migration_spec.rb

@@ -1,34 +0,0 @@
-require 'rails_helper'
-require_relative '../../db/migrate/20261003010000_migrate_tag_descriptions_from_wiki_pages'
-
-RSpec.describe 'Tag description migration identity' do
-  it 'preserves every revision ID and repeated body in an independent sequence' do
-    user = create_member_user!
-    tag_name = create(:tag_name, name: 'description_migration')
-    page = Wiki::Commit.create_content!(
-        tag_name:, body: 'A', created_by_user: user)
-    revisions = [page.current_revision]
-    ['A', 'B', 'B', 'A'].each do |body|
-      revisions << Wiki::Commit.content!(
-          page:, body:, created_user: user, base_revision_id: revisions.last.id)
-    end
-    tag = create(:tag, primary_tag_name: tag_name)
-    legacy_state = [page.reload.attributes, revisions.map(&:attributes)]
-    expect(page.wiki_versions.count).to eq(3)
-
-    migration = MigrateTagDescriptionsFromWikiPages.new
-    migration.suppress_messages { migration.up }
-
-    versions = TagDescriptionVersion.where(tag_id: tag.id, language_code: 'ja')
-        .order(:version_no)
-    expect(versions.pluck(:id)).to eq(revisions.map(&:id))
-    expect(versions.pluck(:version_no)).to eq([1, 2, 3, 4, 5])
-    expect(versions.pluck(:body)).to eq(['A', 'A', 'B', 'B', 'A'])
-    expect(versions.pluck(:created_by_user_id)).to eq([user.id] * 5)
-    expect(versions.pluck(:created_at)).to eq(revisions.map(&:created_at))
-    expect(TagDescription.find(page.id)).to have_attributes(
-        tag_id: tag.id, language_code: 'ja', version_no: 5, body: 'A')
-    expect([page.reload.attributes, revisions.map { |revision| revision.reload.attributes }])
-        .to eq(legacy_state)
-  end
-end

backend/spec/db/tag_group_constraints_spec.rb

@@ -0,0 +1,110 @@
+require 'rails_helper'
+
+RSpec.describe 'Tag group persistence constraints' do
+  include TagGroupRecords
+
+  let!(:user) { create_member_user! }
+  let!(:tag) { group_tag('制約確認') }
+  let!(:group_id) do
+    seed_group(
+        name: '制約確認',
+        members: [{ 'tag_id' => tag.id, 'version_no' => tag.version_no }])
+  end
+
+  def placement attributes
+    insert_group_row('tag_group_placements', {
+        tag_group_id: group_id, position: 1,
+        created_at: Time.current, updated_at: Time.current }.merge(attributes))
+  end
+
+  def reject_statement
+    before_state = group_state
+    expect { yield }.to raise_error(ActiveRecord::StatementInvalid)
+    expect(group_state).to eq(before_state)
+  end
+
+  it 'allows membership without placement' do
+    expect(group_rows('tag_group_tags', tag_group_id: group_id).size).to eq(1)
+    expect(group_rows('tag_group_placements', tag_group_id: group_id)).to be_empty
+  end
+
+  it 'allows repeated Tag placements with unique membership' do
+    placement(tag_id: tag.id)
+    placement(tag_id: tag.id, position: 2)
+    expect(group_rows('tag_group_tags', tag_group_id: group_id).size).to eq(1)
+    expect(group_rows('tag_group_placements', tag_group_id: group_id).size).to eq(2)
+  end
+
+  it 'rejects duplicate Tag membership' do
+    reject_statement do
+      insert_group_row('tag_group_tags', {
+          tag_group_id: group_id, tag_id: tag.id, created_at: Time.current })
+    end
+  end
+
+  it 'rejects duplicate child membership' do
+    child_id = seed_group(name: '子')
+    attributes = { tag_group_id: group_id, child_tag_group_id: child_id,
+                   created_at: Time.current }
+    insert_group_row('tag_group_groups', attributes)
+    reject_statement { insert_group_row('tag_group_groups', attributes) }
+  end
+
+  it 'rejects direct self membership' do
+    reject_statement do
+      insert_group_row('tag_group_groups', {
+          tag_group_id: group_id, child_tag_group_id: group_id, created_at: Time.current })
+    end
+  end
+
+  it 'rejects a placement without a kind' do
+    reject_statement { placement({ }) }
+  end
+
+  it 'rejects simultaneous Section and Tag kinds' do
+    reject_statement { placement(section_name: '区分', tag_id: tag.id) }
+  end
+
+  it 'rejects a description attached to a Tag placement' do
+    reject_statement { placement(tag_id: tag.id, description: '不正') }
+  end
+
+  it 'allows an optional description on a Section' do
+    placement(section_name: '区分', description: '説明')
+    expect(group_rows('tag_group_placements', tag_group_id: group_id).sole)
+        .to include('section_name' => '区分', 'description' => '説明')
+  end
+
+  it 'rejects a Tag placement absent from membership' do
+    other = group_tag('非メンバー')
+    reject_statement { placement(tag_id: other.id) }
+  end
+
+  it 'rejects a missing parent placement' do
+    reject_statement { placement(section_name: '子', parent_position: 9) }
+  end
+
+  it 'rejects a child ordered before its parent' do
+    placement(section_name: '親', position: 2)
+    reject_statement { placement(section_name: '子', position: 1, parent_position: 2) }
+  end
+
+  it 'rejects duplicate group names' do
+    reject_statement { seed_group(name: '制約確認') }
+  end
+
+  it 'rejects a missing mandatory group name' do
+    reject_statement { seed_group(name: nil) }
+  end
+
+  it 'rejects a six-level snapshot' do
+    nodes = []
+    6.times { nodes = [{ 'tag_id' => tag.id, 'children' => nodes }] }
+    reject_statement do
+      insert_group_row('tag_group_versions', {
+          tag_group_id: group_id, version_no: 2, event_type: 'update', name: '制約確認',
+          members: [{ 'tag_id' => tag.id, 'version_no' => tag.version_no }].to_json,
+          placements: nodes.to_json, created_at: Time.current })
+    end
+  end
+end

backend/spec/db/tag_name_constraints_spec.rb

@@ -1,11 +1,17 @@
 require 'rails_helper'
 
 RSpec.describe 'TagName database invariants' do
-  def insert_name!(**attributes)
+  def insert_name! **attributes
-    TagName.insert_all!([{ name: 'constraint_name', language_code: 'ja',
+    defaults = {
-                          script_code: 'Jpan', primary_flg: true,
+        tag_id: create(:tag, primary_tag_name: nil).id,
-                          created_at: Time.current, updated_at: Time.current,
+        name: 'constraint_name',
-                          **attributes }])
+        language_code: 'ja',
+        script_code: 'Jpan',
+        primary_flg: true,
+        created_at: Time.current,
+        updated_at: Time.current }
+
+    TagName.insert_all!([defaults.merge(attributes)])
   end
 
   it 'defaults persisted names to human-confirmed provenance' do
@@ -33,4 +39,9 @@ RSpec.describe 'TagName database invariants' do
         .to raise_error(ActiveRecord::RecordNotUnique)
     expect(TagName.where(tag:, language_code: 'ja', primary_flg: true).count).to eq(1)
   end
+
+  it 'rejects a name without a tag' do
+    expect { insert_name!(tag_id: nil) }
+        .to raise_error(ActiveRecord::NotNullViolation)
+  end
 end

backend/spec/db/wiki_removal_spec.rb

@@ -0,0 +1,23 @@
+require 'rails_helper'
+
+RSpec.describe 'Schema after Wiki removal' do
+  it 'has no legacy Wiki tables or name indirection columns' do
+    connection = ApplicationRecord.connection
+    ['wiki_pages', 'wiki_revisions', 'wiki_lines', 'wiki_revision_lines', 'wiki_versions']
+        .each do |table|
+      expect(connection.table_exists?(table)).to be(false)
+    end
+    expect(connection.column_exists?(:tags, :tag_name_id)).to be(false)
+    expect(connection.column_exists?(:tag_names, :canonical_id)).to be(false)
+  end
+
+  it 'requires TagName ownership while keeping the native resources and history' do
+    connection = ApplicationRecord.connection
+    expect(TagName.columns_hash.fetch('tag_id').null).to be(false)
+    expect(connection.foreign_key_exists?(:tag_names, :tags)).to be(true)
+    ['tag_descriptions', 'tag_description_versions', 'tag_groups', 'tag_group_versions']
+        .each do |table|
+      expect(connection.table_exists?(table)).to be(true)
+    end
+  end
+end

backend/spec/factories/tag_names.rb

@@ -6,6 +6,8 @@ FactoryBot.define do
     auto_generated { false }
     sequence(:name) { |number| "tag-#{ SecureRandom.hex(4) }-#{ number }" }
 
+    association :tag, primary_tag_name: nil
+
     trait :alias do
       primary_flg { false }
     end

backend/spec/factories/tags.rb

@@ -4,7 +4,7 @@ FactoryBot.define do
       primary_name { nil }
       primary_tag_name do
         attributes = primary_name.nil? ? { } : { name: primary_name }
-        build(:tag_name, **attributes)
+        build(:tag_name, tag: nil, **attributes)
       end
     end
 
@@ -12,17 +12,16 @@ FactoryBot.define do
     post_count { 0 }
 
     after(:build) do |tag, evaluator|
+      next unless evaluator.primary_tag_name
+
       evaluator.primary_tag_name.primary_flg = true
+      evaluator.primary_tag_name.tag = tag
       tag.tag_names.target << evaluator.primary_tag_name
     end
 
-    before(:create) do |tag, evaluator|
-      evaluator.primary_tag_name.save!
-      # Compatibility write only; ownership is established through tag_id below.
-      tag.tag_name_id = evaluator.primary_tag_name.id
-    end
-
     after(:create) do |tag, evaluator|
+      next unless evaluator.primary_tag_name
+
       evaluator.primary_tag_name.update!(tag:, primary_flg: true)
 
       Locale.where(deprecated_at: nil).order(:language_code, :created_at, :script_code).to_a

backend/spec/factories/wiki_pages.rb

@@ -1,9 +0,0 @@
-FactoryBot.define do
-  factory :wiki_page do
-    title { "TestPage" }
-    association :created_user, factory: :user
-    association :updated_user, factory: :user
-
-    body { ' ' }
-  end
-end

backend/spec/models/shared_tag_ids_spec.rb

@@ -0,0 +1,37 @@
+require 'rails_helper'
+
+RSpec.describe 'Shared Tag and ExternalTag IDs', type: :model do
+  it 'allocates distinct increasing IDs across the two tables' do
+    tag = create(:tag)
+    external = create(:external_tag)
+    next_tag = create(:tag)
+
+    expect(external.id).to be > tag.id
+    expect(next_tag.id).to be > external.id
+  end
+
+  it 'does not reuse physically deleted IDs in either table' do
+    tag = create(:tag)
+    external = create(:external_tag)
+    TagName.where(tag_id: tag.id).delete_all
+    tag.destroy!
+    external.destroy!
+
+    expect(create(:tag).id).to be > external.id
+    expect(create(:external_tag).id).to be > external.id
+  end
+
+  it 'retains existing overlapping IDs without renumbering on update or insert' do
+    tag = create(:tag)
+    external = create(:external_tag)
+    external.update_columns(id: tag.id)
+    tag.update!(category: :meta)
+    external.update!(name: 'updated_external')
+    before_tag = tag.reload.attributes
+    before_external = external.reload.attributes
+
+    expect(create(:tag).id).to be > tag.id
+    expect(tag.reload.attributes).to eq(before_tag)
+    expect(external.reload.attributes).to eq(before_external)
+  end
+end

backend/spec/models/tag_group_spec.rb

@@ -0,0 +1,48 @@
+require 'rails_helper'
+
+RSpec.describe TagGroup, type: :model do
+  let(:actor) { create_member_user! }
+
+  def create_group name:, members: [], placements: []
+    TagGroupOperation.create!(
+        Locale.nipponese, name:, description: nil, members:, placements:, actor:)
+  end
+
+  it 'retains version IDs and snapshots after destroying an empty group' do
+    group = create_group(name: 'history owner')
+    versions = group.versions.order(:version_no).map(&:attributes)
+
+    expect { group.destroy! }.to change(described_class, :count).by(-1)
+        .and change(TagGroupVersion, :count).by(0)
+
+    expect(TagGroupVersion.where(tag_group_id: group.id).order(:version_no).map(&:attributes))
+        .to eq(versions)
+    expect(TagGroupRepr.historical(
+        Locale.nipponese, TagGroupVersion.find(versions.first.fetch('id'))))
+        .to include('id' => group.id, 'name' => 'history owner', 'members' => [])
+  end
+
+  it 'destroys a group with nested placements and child membership, retaining history' do
+    child = create_group(name: 'child group')
+
+    parent = create_group(
+        name: 'parent group',
+        members: [{ 'tag_group_id' => child.id }],
+        placements: [{ 'section_name' => 'section', 'description' => nil,
+                       'children' => [{ 'tag_group_id' => child.id, 'children' => [] }] }])
+
+    versions = parent.versions.order(:version_no).map(&:attributes)
+
+    expect { parent.destroy! }
+        .to change(TagGroup, :count).by(-1)
+        .and change(TagGroupVersion, :count).by(0)
+
+    expect(TagGroupVersion.where(tag_group_id: parent.id)
+        .order(:version_no).map(&:attributes)).to eq(versions)
+
+    expect(child.reload).to be_persisted
+    expect(TagGroupPlacement.where(tag_group_id: parent.id)).to be_empty
+    expect(TagGroupTag.where(tag_group_id: parent.id)).to be_empty
+    expect(TagGroupGroup.where(tag_group_id: parent.id)).to be_empty
+  end
+end

backend/spec/models/tag_name_sanitisation_rule_spec.rb

@@ -34,6 +34,66 @@ RSpec.describe TagNameSanitisationRule, type: :model do
       described_class.create!(priority: 10, source_pattern: 'foo_', replacement: 'foo')
     end
 
+    [:primary, :alias].each do |source_kind|
+      it "keeps the primary identity when a #{ source_kind } collides within its Tag" do
+        tag = create(:tag, primary_name: source_kind == :primary ? 'temporary' : 'foobar')
+        primary = tag.tag_name('ja')
+        alias_name = create(:tag_name, :alias, tag:,
+                             name: source_kind == :primary ? 'foobar' : 'temporary_alias')
+        source = source_kind == :primary ? primary : alias_name
+        source.update_columns(name: 'foo_bar')
+
+        expect { described_class.apply! }.to change(TagName, :count).by(-1)
+            .and change(Tag, :count).by(0)
+
+        expect(primary.reload).to have_attributes(
+            name: 'foobar', primary_flg: true, tag_id: tag.id)
+        expect(TagName.exists?(alias_name.id)).to be(false)
+        expect(TagName.where(tag:, language_code: 'ja', primary_flg: true))
+            .to contain_exactly(primary)
+        expect(tag.tag_versions.order(:version_no).last.names.fetch('ja'))
+            .to include('name' => 'foobar', 'aliases' => [])
+      end
+    end
+
+    it 'deduplicates colliding aliases without changing the primary name' do
+      tag = create(:tag, primary_name: 'primary')
+      primary = tag.tag_name('ja')
+      kept = create(:tag_name, :alias, tag:, name: 'foobar')
+      removed = create(:tag_name, :alias, tag:, name: 'temporary_alias')
+      removed.update_columns(name: 'foo_bar')
+
+      described_class.apply!
+
+      expect(primary.reload).to have_attributes(name: 'primary', primary_flg: true)
+      expect(kept.reload.tag_id).to eq(tag.id)
+      expect(TagName.exists?(removed.id)).to be(false)
+      expect(tag.tag_versions.order(:version_no).last.names.fetch('ja').fetch('aliases'))
+          .to eq([{ 'name' => 'foobar', 'script_code' => 'Jpan' }])
+    end
+
+    it 'rolls back a collision merge when the source owns a description' do
+      user = create_member_user!
+      target = create(:tag, primary_name: 'foobar')
+      source = create(:tag, primary_name: 'temporary')
+      TagDescriptionOperation.create!(
+          Locale.nipponese, tag: source, body: 'retained', created_by_user: user)
+      source.tag_name('ja').update_columns(name: 'foo_bar')
+      post = create(:post)
+      PostTag.create!(post:, tag: source)
+      models = [Tag, TagName, TagVersion, TagDescription, TagDescriptionVersion, PostTag]
+      snapshots = models.map { |model| model.order(*Array(model.primary_key)).map(&:attributes) }
+
+      expect { described_class.apply! }.to raise_error(ActiveRecord::RecordInvalid)
+
+      after_state = models.map do |model|
+        model.order(*Array(model.primary_key)).map(&:attributes)
+      end
+      expect(after_state).to eq(snapshots)
+      expect(post.reload.tags).to contain_exactly(source)
+      expect(target.reload.name('ja')).to eq('foobar')
+    end
+
     context 'when only another language has the sanitised name' do
       include_context 'English locale'
 
@@ -98,25 +158,6 @@ RSpec.describe TagNameSanitisationRule, type: :model do
       end
     end
 
-    context 'when the source tag_name has a tag and the existing one has no tag' do
-      let!(:existing) { create(:tag_name, name: 'foobar') }
-      let!(:source_tag) { create(:tag, primary_name: 'tmp', category: :general) }
-      let!(:source_tag_name_id) { primary_tag_name_for(source_tag, 'ja').id }
-
-      before do
-        primary_tag_name_for(source_tag, 'ja').update_columns(
-            name: 'foo_bar', updated_at: Time.current)
-      end
-
-      it 'moves the tag to the existing tag_name' do
-        described_class.apply!
-        expect(existing.reload).to have_attributes(
-            tag_id: source_tag.id, language_code: 'ja', primary_flg: true)
-        expect(primary_tag_name_for(source_tag, 'ja')).to eq(existing)
-        expect(primary_tag_name_for(source_tag.reload, 'ja')).to eq(existing)
-        expect(TagName.unscoped.exists?(source_tag_name_id)).to be(false)
-      end
-    end
 
     context 'when the sanitised name is an alias of an existing tag' do
       let!(:existing_tag) { create(:tag) }

backend/spec/models/tag_name_spec.rb

@@ -22,16 +22,23 @@ RSpec.describe TagName, type: :model do
     expect(duplicate.errors.of_kind?(:name, :taken)).to be(true)
   end
 
-  it 'creates Nipponese factory names without requiring a tag' do
+  it 'creates Nipponese factory names with an owning tag' do
     name = create(:tag_name)
 
     expect(name.reload).to have_attributes(
         language_code: 'ja', script_code: 'Jpan', primary_flg: true,
-        auto_generated: false, tag_id: nil)
+        auto_generated: false, tag_id: name.tag.id)
+  end
+
+  it 'rejects an ownerless name at model and database boundaries' do
+    name = build(:tag_name, tag: nil)
+    expect(name).to be_invalid
+    expect { name.save!(validate: false) }.to raise_error(ActiveRecord::NotNullViolation)
   end
 
   it 'defaults ordinary persisted human names to confirmed provenance' do
-    name = described_class.create!(name: 'ordinary_human_name', language_code: 'ja',
+    name = described_class.create!(tag: create(:tag, primary_tag_name: nil),
+                                   name: 'ordinary_human_name', language_code: 'ja',
                                    script_code: 'Jpan', primary_flg: true)
 
     expect(name.reload.auto_generated).to be(false)
@@ -46,7 +53,7 @@ RSpec.describe TagName, type: :model do
     expect(name.tag).to eq(tag)
     expect(described_class.find_by!(tag_id: tag.id, language_code: 'ja', primary_flg: true))
         .to eq(name)
-    expect(tag.reload.tag_name_id).to eq(name.id)
+    expect(tag.reload.tag_name('ja')&.id).to eq(name.id)
   end
 
   it 'creates a complete ordinary tag factory under the active Nipponese language' do
@@ -96,19 +103,14 @@ RSpec.describe TagName, type: :model do
   end
 
   describe '.canonicalise' do
-    it 'leaves detached aliases unchanged' do
-      create(:tag_name, :alias, name: 'detached_alias')
 
-      expect(described_class.canonicalise(Locale.nipponese, ['detached_alias']))
-          .to eq(['detached_alias'])
-    end
 
-    it 'does not resolve a detached alias through another detached primary' do
+    it 'resolves an alias to its owning primary name' do
-      create(:tag_name, :alias, name: 'detached_alias')
+      tag = create(:tag, primary_name: 'canonical')
-      create(:tag_name, name: 'unrelated_detached_primary')
+      create(:tag_name, :alias, tag:, name: 'alias')
 
-      expect(described_class.canonicalise(Locale.nipponese, ['detached_alias']))
+      expect(described_class.canonicalise(Locale.nipponese, ['alias', 'unknown']))
-          .to eq(['detached_alias'])
+          .to eq(['canonical', 'unknown'])
     end
 
     it 'resolves the primary name of the alias language on the same tag' do
@@ -119,7 +121,7 @@ RSpec.describe TagName, type: :model do
       english_primary.update!(name: 'english_primary', auto_generated: false)
       english_alias = create(:tag_name, :alias, tag:, name: 'english_alias',
                                                  language_code: 'en', script_code: 'Latn')
-      representative_id = tag.tag_name_id
+      representative_id = tag.tag_name('ja')&.id
 
       primary = described_class.find_by!(tag_id: english_alias.tag_id,
                                          language_code: english_alias.language_code,
@@ -128,7 +130,7 @@ RSpec.describe TagName, type: :model do
       expect(primary).to eq(english_primary)
       expect(described_class.canonicalise(locale, [english_alias.name]))
           .to eq([english_primary.name])
-      expect(tag.reload.tag_name_id).to eq(representative_id)
+      expect(tag.reload.tag_name('ja')&.id).to eq(representative_id)
     end
 
     it 'resolves only aliases in the requested language' do

backend/spec/models/tag_repr_spec.rb

@@ -0,0 +1,50 @@
+require 'rails_helper'
+
+RSpec.describe TagRepr do
+  let(:tag) { create(:tag) }
+
+  def description_for record
+    TagDescription.create!(tag: record, language_code: 'ja', body: '', version_no: 1)
+  end
+
+  it 'keeps has_wiki boolean for the selected language in base and inline' do
+    description_for(tag)
+    [:base, :inline].each do |method|
+      expect(described_class.public_send(method, tag).as_json.fetch('has_wiki')).to be(true)
+      expect(described_class.public_send(method, tag, language_code: 'en')
+          .as_json.fetch('has_wiki')).to be(false)
+    end
+  end
+
+  it 'uses the same language for a tag and its parents' do
+    parent = create(:tag)
+    description_for(tag)
+    description_for(parent)
+    TagImplication.create!(tag:, parent_tag: parent)
+    ['ja', 'en'].each do |language_code|
+      row = described_class.base(tag, language_code:).as_json
+      expected = language_code == 'ja'
+      expect(row.fetch('has_wiki')).to be(expected)
+      expect(row.fetch('parents').sole.fetch('has_wiki')).to be(expected)
+    end
+  end
+
+  it 'preloads existence checks for many tags and their parents without Wiki reads' do
+    parent = create(:tag)
+    description_for(parent)
+    records = Array.new(3) do
+      create(:tag).tap { TagImplication.create!(tag: _1, parent_tag: parent) }
+    end
+    description_for(records.first)
+    queries = []
+    subscriber = ->(*args) { queries << args.last.fetch(:sql) }
+    rows = nil
+    ActiveSupport::Notifications.subscribed(subscriber, 'sql.active_record') do
+      rows = described_class.many(records).as_json
+    end
+    expect(rows.map { _1.fetch('has_wiki') }).to eq([true, false, false])
+    expect(rows.map { _1.fetch('parents').sole.fetch('has_wiki') }).to eq([true] * 3)
+    expect(queries.grep(/\bSELECT\b.*\btag_descriptions\b/im).size).to be <= 2
+    expect(queries.grep(/\bwiki_(pages|revisions|versions)\b/i)).to be_empty
+  end
+end

backend/spec/models/tag_spec.rb

@@ -1,6 +1,42 @@
 require 'rails_helper'
 
 RSpec.describe Tag, type: :model do
+  include WikiRecords
+  describe '#has_description?' do
+    let(:tag) { create(:tag) }
+
+    it 'checks the requested language and treats an empty description as present' do
+      TagDescription.create!(tag:, language_code: 'ja', body: '', version_no: 1)
+      expect(tag.has_description?(language_code: 'ja')).to be(true)
+      expect(tag.has_description?(language_code: 'en')).to be(false)
+    end
+
+    it 'returns false without a description' do
+      expect(tag.has_description?(language_code: 'ja')).to be(false)
+    end
+
+
+    it 'reuses preloaded descriptions without reading Wiki or querying again' do
+      TagDescription.create!(tag:, language_code: 'ja', body: '', version_no: 1)
+      loaded = Tag.includes(:tag_descriptions).find(tag.id)
+      queries = []
+      subscriber = ->(*args) { queries << args.last.fetch(:sql) }
+      ActiveSupport::Notifications.subscribed(subscriber, 'sql.active_record') do
+        expect(loaded.has_description?(language_code: 'ja')).to be(true)
+        expect(loaded.has_description?(language_code: 'en')).to be(false)
+      end
+      expect(queries).to be_empty
+    end
+
+    it 'keeps language selection generic without enabling another Language record' do
+      tag.association(:tag_descriptions).target = [
+          TagDescription.new(tag:, language_code: 'en', body: '', version_no: 1)]
+      tag.association(:tag_descriptions).loaded!
+      expect(tag.has_description?(language_code: 'en')).to be(true)
+      expect(tag.has_description?(language_code: 'ja')).to be(false)
+    end
+  end
+
   describe 'external tag separation' do
     ['nico:reserved', 'NiCo:reserved'].each do |name|
       it "rejects the reserved prefix #{ name } for internal tags" do
@@ -293,38 +329,7 @@ RSpec.describe Tag, type: :model do
             .where(tag_names: { name: 'atomic_english_name' })).to be_empty
       end
 
-      it 'keeps a detached requested name detached if generation fails' do
-        pending '日本語以外の Locale 有効化は別課題で実装する'
-        locale
-        detached = create(:tag_name, :alias, name: 'atomic_detached',
-                                           language_code: 'en', script_code: 'Latn')
-        original_tag_count = described_class.count
-        allow(TagName).to receive(:generate_name).and_raise('generation failed')
 
-        expect {
-          described_class.find_or_create_by_tag_name!(
-              locale, detached.name, category: :general)
-        }.to raise_error('generation failed')
-
-        expect(described_class.count).to eq(original_tag_count)
-        expect(detached.reload).to have_attributes(tag_id: nil, primary_flg: false)
-      end
-
-      it 'promotes a detached alias into the requested primary name' do
-        pending '日本語以外の Locale 有効化は別課題で実装する'
-        locale
-        detached = create(:tag_name, :alias, name: 'detached_english',
-                                           language_code: 'en', script_code: 'Latn')
-
-        tag = described_class.find_or_create_by_tag_name!(
-            locale, detached.name, category: :general)
-
-        expect(detached.reload).to have_attributes(
-            tag_id: tag.id, primary_flg: true, canonical_id: nil,
-            auto_generated: false)
-        expect(TagName.where(tag:, language_code: 'en', primary_flg: true))
-            .to contain_exactly(detached)
-      end
 
       it 'creates separate tag identities for the same name in different languages' do
         pending '日本語以外の Locale 有効化は別課題で実装する'
@@ -349,7 +354,7 @@ RSpec.describe Tag, type: :model do
         pending '日本語以外の Locale 有効化は別課題で実装する'
         locale
         tag = create(:tag, primary_name: '日本語代表名')
-        representative_id = tag.tag_name_id
+        representative_id = tag.tag_name('ja')&.id
         english = primary_tag_name_for(tag, 'en')
         english.update!(name: 'english_primary', auto_generated: false)
 
@@ -357,7 +362,7 @@ RSpec.describe Tag, type: :model do
             locale, english.name, category: :general)
 
         expect(found).to eq(tag)
-        expect(tag.reload.tag_name_id).to eq(representative_id)
+        expect(tag.reload.tag_name('ja')&.id).to eq(representative_id)
         expect(english.reload.tag_id).to eq(tag.id)
       end
 
@@ -389,22 +394,10 @@ RSpec.describe Tag, type: :model do
       expect(primary_tag_name_for(tag, 'ja').auto_generated).to be(false)
     end
 
-    it 'promotes a detached Nipponese alias into a human-confirmed primary' do
-      detached = create(:tag_name, :alias, name: 'detached_nipponese')
-
-      tag = described_class.find_or_create_by_tag_name!(
-          Locale.nipponese, detached.name, category: :general)
-
-      expect(detached.reload).to have_attributes(
-          tag_id: tag.id, primary_flg: true, canonical_id: nil,
-          auto_generated: false)
-      expect(TagName.where(tag:, language_code: 'ja', primary_flg: true))
-          .to contain_exactly(detached)
-    end
 
     it 'reuses the owning tag for an alias without changing its category' do
       tag = create(:tag, category: :character)
-      representative_id = tag.tag_name_id
+      representative_id = tag.tag_name('ja')&.id
       alias_name = create(:tag_name, :alias, name: 'lookup_alias', tag:)
       expect(alias_name.reload).to have_attributes(
           tag_id: tag.id,
@@ -418,7 +411,7 @@ RSpec.describe Tag, type: :model do
 
       expect(found).to eq(tag)
       expect(found.category).to eq('character')
-      expect(tag.reload.tag_name_id).to eq(representative_id)
+      expect(tag.reload.tag_name('ja')&.id).to eq(representative_id)
     end
 
     it 'reuses the owning tag through another alias' do
@@ -642,7 +635,7 @@ RSpec.describe Tag, type: :model do
       let!(:wiki_page) do
         admin = create_admin_user!
 
-        Wiki::Commit.create_content!(
+        seed_description(
             tag_name: source_tag_name,
             body: 'source wiki body',
             created_by_user: admin,

backend/spec/models/user_spec.rb

@@ -0,0 +1,25 @@
+require 'rails_helper'
+
+RSpec.describe User, type: :model do
+  it 'nullifies description authorship without deleting native content or history' do
+    author = create_member_user!
+    editor = create_member_user!
+    tag = create(:tag)
+    description = TagDescriptionOperation.create!(
+        Locale.nipponese, tag:, body: 'initial', created_by_user: author)
+    TagDescriptionOperation.update!(
+        Locale.nipponese, tag:, body: 'edited', updated_by_user: editor)
+    versions = TagDescriptionVersion.where(tag_id: tag.id).order(:version_no)
+    snapshots = versions.map(&:attributes)
+
+    expect(author.created_tag_descriptions).to contain_exactly(description)
+    expect(editor.updated_tag_descriptions).to contain_exactly(description)
+    expect { author.destroy! }.to change(TagDescription, :count).by(0)
+        .and change(TagDescriptionVersion, :count).by(0)
+    expect(description.reload).to have_attributes(
+        body: 'edited', created_by_user_id: nil, updated_by_user_id: editor.id)
+    expect { editor.destroy! }.not_to change(TagDescription, :count)
+    expect(description.reload.updated_by_user_id).to be_nil
+    expect(versions.reload.map(&:attributes)).to eq(snapshots)
+  end
+end

backend/spec/requests/materials_spec.rb

@@ -178,6 +178,7 @@ RSpec.describe 'Materials API', type: :request do
   end
 
   describe 'GET /materials/:id' do
+    include WikiRecords
     let!(:tag) do
       create(:tag, primary_name: 'material_show', category: :material)
     end
@@ -205,6 +206,54 @@ RSpec.describe 'Materials API', type: :request do
       get '/materials/999999999'
       expect(response).to have_http_status(:not_found)
     end
+
+    def get_material_without_legacy_reads
+      queries = []
+      subscriber = lambda do |*args|
+        sql = args.last.fetch(:sql)
+        if sql.match?(/\bSELECT\b/i) && sql.match?(/\bwiki_(pages|revisions|versions)\b/i)
+          queries << sql
+        end
+      end
+      ActiveSupport::Notifications.subscribed(subscriber, 'sql.active_record') do
+        get "/materials/#{ material.id }"
+      end
+      expect(response).to have_http_status(:ok)
+      expect(queries).to be_empty
+    end
+
+    it 'reads the description even when the stored version has different content' do
+      page = seed_description(tag_name: tag.tag_name('ja'), body: 'legacy body',
+                            created_by_user: member_user)
+      TagDescription.find_by!(tag_id: tag.id, language_code: 'ja')
+          .update!(body: 'description body')
+      get_material_without_legacy_reads
+      expect(json.fetch('wiki_page_body')).to eq('description body')
+      expect(current_description_version(page).body).to eq('legacy body')
+    end
+
+    it 'uses tag_id rather than description Id. without a Wiki page' do
+      description = TagDescription.create!(tag:, language_code: 'ja',
+                                           body: 'independent body', version_no: 1)
+      get_material_without_legacy_reads
+      expect(json.fetch('wiki_page_body')).to eq('independent body')
+      expect(json.fetch('tag').fetch('has_wiki')).to be(true)
+    end
+
+    it 'returns nil when only description history remains' do
+      seed_description(tag_name: tag.tag_name('ja'), body: 'legacy only',
+                     created_by_user: member_user)
+      TagDescription.where(tag_id: tag.id).delete_all
+      get_material_without_legacy_reads
+      expect(json.fetch('wiki_page_body')).to be_nil
+      expect(json.fetch('tag').fetch('has_wiki')).to be(false)
+    end
+
+    it 'returns nil for an untagged material' do
+      material.update!(tag: nil)
+      get_material_without_legacy_reads
+      expect(json.fetch('wiki_page_body')).to be_nil
+    end
   end
 
   describe 'POST /materials' do

backend/spec/requests/tag_description_wiki_spec.rb

@@ -1,36 +1,24 @@
 require 'rails_helper'
 
 RSpec.describe 'Tag description Wiki compatibility', type: :request do
+  include WikiRecords
   let!(:user) { create_member_user! }
   let!(:tag_name) { create(:tag_name, name: 'description_contract') }
-  let!(:page) do
+  let!(:tag) { tag_name.tag }
-    Wiki::Commit.create_content!(
-        tag_name:, body: 'old-revision', created_by_user: user)
-  end
-  let!(:revisions) do
-    first = page.current_revision
-    second = Wiki::Commit.content!(page:, body: 'old-second', created_user: user)
-    third = Wiki::Commit.content!(page:, body: 'old-third', created_user: user)
-    [first, second, third]
-  end
-  let!(:tag) { create(:tag, primary_tag_name: tag_name) }
   let!(:versions) do
-    revisions.each_with_index.map do |revision, index|
+    ['A', 'A', 'new-version'].each_with_index.map do |body, index|
       TagDescriptionVersion.create!(
-          id: revision.id, tag_id: tag.id, language_code: 'ja',
+          tag_id: tag.id, language_code: 'ja', version_no: index + 1,
-          version_no: index + 1, event_type: index.zero? ? 'create' : 'update',
+          event_type: index.zero? ? 'create' : 'update', body:,
-          body: index == 2 ? 'new-version' : 'A',
+          created_by_user_id: user.id, created_at: Time.current)
-          created_by_user_id: user.id, created_at: revision.created_at)
     end
   end
   let!(:description) do
     TagDescription.create!(
-        id: page.id, tag:, language_code: 'ja', version_no: 3, body: 'new',
+        tag:, language_code: 'ja', version_no: 3, body: 'new',
         created_by_user_id: user.id, updated_by_user_id: user.id)
   end
 
-  before { page.update_columns(body: 'old') }
-
   # Observe real SELECTs, including cached queries, only during the request.
   def without_legacy_reads
     queries = []
@@ -69,7 +57,7 @@ RSpec.describe 'Tag description Wiki compatibility', type: :request do
     it 'does not fall back to a revision absent from new history' do
       versions.first.destroy!
       without_legacy_reads do
-        get "/wiki/#{ description.id }", params: { version: revisions.first.id }
+        get "/wiki/#{ description.id }", params: { version: versions.first.id }
       end
       expect(response).to have_http_status(:not_found)
     end
@@ -131,16 +119,6 @@ RSpec.describe 'Tag description Wiki compatibility', type: :request do
                              'pred' => versions.first.id, 'succ' => versions.last.id)
     end
 
-    it 'ignores changes to same-title legacy content and revision metadata' do
-      get "/wiki/title/#{ tag_name.name }"
-      original = json
-      page.update_columns(body: 'changed legacy body')
-      revisions.last.update_columns(message: 'legacy message', created_at: 1.day.ago)
-      revisions.last.wiki_lines.update_all(body: 'changed legacy revision')
-      get "/wiki/title/#{ tag_name.name }"
-      expect(json).to eq(original)
-      expect(json.fetch('body')).to eq('new')
-    end
   end
 
   describe 'exists' do
@@ -154,28 +132,6 @@ RSpec.describe 'Tag description Wiki compatibility', type: :request do
       expect(response).to have_http_status(:no_content)
     end
 
-    context 'without a legacy page' do
-      before do
-        WikiVersion.where(wiki_page_id: page.id).delete_all
-        page.destroy!
-      end
-
-      it 'recognises the description ID alone' do
-        get "/wiki/#{ description.id }/exists"
-        expect(response).to have_http_status(:no_content)
-      end
-
-      it 'recognises the TagName alone' do
-        get "/wiki/title/#{ tag_name.name }/exists"
-        expect(response).to have_http_status(:no_content)
-      end
-
-      it 'shows the description by title' do
-        get "/wiki/title/#{ tag_name.name }"
-        expect(response).to have_http_status(:ok)
-        expect(json).to include('body' => 'new', 'revision_id' => versions.last.id)
-      end
-    end
   end
 
   describe 'diff' do
@@ -228,39 +184,8 @@ RSpec.describe 'Tag description Wiki compatibility', type: :request do
                                                       'title' => tag_name.name)
     end
 
-    it 'ignores legacy-only revisions and metadata changes' do
-      get '/wiki/changes', params: { id: description.id }
-      original = json
-      revisions.first.update_columns(message: 'legacy changed', created_at: 1.day.ago)
-      WikiRevision.create!(
-          wiki_page: page, created_user: user, kind: :content,
-          tree_sha256: Digest::SHA256.hexdigest('legacy only'), lines_count: 0)
-      get '/wiki/changes', params: { id: description.id }
-      expect(json).to eq(original)
-      expect(json.map { |row| row.fetch('revision_id') }).to eq(versions.reverse.map(&:id))
-    end
   end
 
-  describe 'mixed changes' do
-    it 'includes unmigrated history and ignores migrated legacy-only revisions' do
-      legacy_page = Wiki::Commit.create_content!(
-          tag_name: create(:tag_name, name: 'Help_mixed'),
-          body: 'help', created_by_user: user)
-      legacy_revision = legacy_page.current_revision
-      extra = WikiRevision.create!(
-          wiki_page: page, created_user: user, kind: :content,
-          tree_sha256: Digest::SHA256.hexdigest('legacy only'), lines_count: 0)
-
-      get '/wiki/changes'
-      expect(response).to have_http_status(:ok)
-      migrated = json.select { |row| row.fetch('wiki_page').fetch('id') == description.id }
-      expect(migrated.map { |row| row.fetch('revision_id') }).to eq(versions.reverse.map(&:id))
-      expect(json.map { |row| row.fetch('revision_id') }).not_to include(extra.id)
-      expect(json).to include(include(
-          'revision_id' => legacy_revision.id,
-          'wiki_page' => include('id' => legacy_page.id, 'title' => 'Help_mixed')))
-    end
-  end
 
   describe 'index' do
     [nil, 'description_contract'].each do |title|

backend/spec/requests/tag_description_wiki_write_spec.rb

@@ -1,273 +1,93 @@
 require 'rails_helper'
 
-RSpec.describe 'Tag description Wiki dual writes', type: :request do
+RSpec.describe 'Tag description Wiki facade writes', type: :request do
+  include WikiRecords
   let!(:user) { create_member_user! }
-  let!(:tag_name) { create(:tag_name, name: 'description_write') }
+  let!(:tag) { create(:tag, primary_name: 'description_write') }
-  let(:tag) { create(:tag, primary_tag_name: tag_name) }
   let(:headers) { { 'X-Transfer-Code' => user.inheritance_code } }
 
   def stored_state
-    [WikiPage, WikiRevision, WikiVersion, TagDescription, TagDescriptionVersion,
+    [Tag, TagName, TagVersion, TagDescription, TagDescriptionVersion].map do |model|
-     TagName, TagVersion].map do |model|
       model.order(:id).map(&:attributes)
     end
   end
 
-  # Fail after a real INSERT/UPDATE, exercising rollback rather than a mock write.
+  it 'creates a native description and exposes its version ID as revision ID' do
-  def fail_save model
+    expect do
-    failure = Class.new(StandardError)
+      post '/wiki', params: { title: tag.name('ja'), body: 'initial' }, headers: headers
-    callback = ->(_record) { raise failure, 'injected persistence failure' }
+    end.to change(TagDescription, :count).by(1)
-    model.set_callback(:save, :after, callback)
+        .and change(TagDescriptionVersion, :count).by(1)
-    expect { yield }.to raise_error(failure)
+    expect(response).to have_http_status(:created)
-  ensure
+    description = TagDescription.find(json.fetch('id'))
-    model.skip_callback(:save, :after, callback)
+    expect(description).to have_attributes(tag_id: tag.id, body: 'initial', version_no: 1)
+    get "/wiki/#{ description.id }"
+    expect(json.fetch('revision_id')).to eq(current_description_version(description).id)
   end
 
-  describe 'POST /wiki' do
+  context 'with an existing description' do
-    before { tag }
+    let!(:description) do
+      TagDescriptionOperation.create!(
+          Locale.nipponese, tag:, body: 'before', created_by_user: user)
+    end
+    let!(:first_version) { current_description_version(description) }
 
-    def create_description
+    def update_description body: 'after', title: tag.name('ja'), base: first_version.id
-      post '/wiki', params: { title: tag_name.name, body: 'initial', message: 'create' },
+      put "/wiki/#{ description.id }", params: { title:, body:, base_revision_id: base },
-           headers: headers
+          headers: headers
     end
 
-    it 'creates both current records and histories with a shared revision ID' do
+    it 'records a body change without changing resource identity or old history' do
-      expect { create_description }
+      snapshot = first_version.attributes
-          .to change(WikiPage, :count).by(1)
+      expect { update_description }.to change(TagDescriptionVersion, :count).by(1)
-          .and change(WikiRevision, :count).by(1)
+      expect(response).to have_http_status(:ok)
-          .and change(WikiVersion, :count).by(1)
+      expect(description.reload).to have_attributes(body: 'after', version_no: 2)
-          .and change(TagDescription, :count).by(1)
+      expect(first_version.reload.attributes).to eq(snapshot)
-          .and change(TagDescriptionVersion, :count).by(1)
+      expect(current_description_version(description)).to have_attributes(
-      expect(response).to have_http_status(:created)
+          body: 'after', event_type: 'update', created_by_user_id: user.id)
-
-      page = WikiPage.find(json.fetch('id'))
-      description = TagDescription.find_by!(tag_id: tag.id, language_code: 'ja')
-      version = TagDescriptionVersion.find_by!(tag_id: tag.id, language_code: 'ja')
-      expect(description).to have_attributes(id: page.id, body: 'initial', version_no: 1)
-      expect(version).to have_attributes(
-          id: page.current_revision.id, body: 'initial', version_no: 1,
-          event_type: 'create', created_by_user_id: user.id)
-      expect(page.body).to eq(description.body)
-      expect(page.current_revision.body).to eq(version.body)
-      expect(page.wiki_versions.last.body).to eq(version.body)
     end
 
-    ['missing_description', 'orphan_description'].each do |title|
+    ['before', "before\r\n\r\n"].each do |body|
-      it "rejects the bare title #{ title } without writing any resource" do
+      it "does not write for normalised-equivalent body #{ body.inspect }" do
-        create(:tag_name, name: title) if title == 'orphan_description'
         before_state = stored_state
-
+        update_description(body:)
-        post '/wiki', params: { title:, body: 'initial' }, headers: headers
+        expect(response).to have_http_status(:ok)
-
-        expect(response).to have_http_status(:unprocessable_entity)
-        expect(json).to include('type' => 'validation_error')
         expect(stored_state).to eq(before_state)
       end
     end
 
-    it 'creates a namespaced legacy Wiki resource without a Tag' do
+    it 'records a title-only edit in Tag history without adding body history' do
-      expect do
+      snapshot = description.attributes
-        post '/wiki', params: { title: 'Help:description_write', body: 'legacy' },
+      expect { update_description(body: 'before', title: 'renamed') }
-             headers: headers
+          .to change(TagVersion, :count).by(2)
-      end.to change(WikiPage, :count).by(1)
-          .and change(WikiRevision, :count).by(1)
-          .and change(WikiVersion, :count).by(1)
-          .and change(TagDescription, :count).by(0)
           .and change(TagDescriptionVersion, :count).by(0)
-
-      expect(response).to have_http_status(:created)
-      page = WikiPage.find(json.fetch('id'))
-      expect(page.tag_name.tag).to be_nil
-      expect(page.body).to eq('legacy')
-      expect(page.current_revision.body).to eq('legacy')
-    end
-
-    it 'creates only legacy Wiki for a namespaced title with an existing Tag' do
-      namespaced_name = create(:tag_name, name: 'help:foo')
-      namespaced_tag = create(:tag, primary_tag_name: namespaced_name)
-
-      expect do
-        post '/wiki', params: { title: namespaced_name.name, body: 'legacy' },
-             headers: headers
-      end.to change(WikiPage, :count).by(1)
-          .and change(WikiRevision, :count).by(1)
-          .and change(WikiVersion, :count).by(1)
-          .and change(TagName, :count).by(0)
-          .and change(TagDescription, :count).by(0)
-          .and change(TagDescriptionVersion, :count).by(0)
-
-      expect(response).to have_http_status(:created)
-      page = WikiPage.find(json.fetch('id'))
-      expect(page).to have_attributes(tag_name_id: namespaced_name.id, body: 'legacy')
-      expect(page.tag_name.tag).to eq(namespaced_tag)
-      expect(page.current_revision.body).to eq('legacy')
-      expect(page.wiki_versions.last.body).to eq('legacy')
-    end
-
-    [WikiPage, WikiRevision, WikiVersion, TagDescription, TagDescriptionVersion].each do |model|
-      it "rolls back both systems when #{ model.name } persistence fails" do
-        tag_name
-        before_state = stored_state
-        aggregate_failures do
-          fail_save(model) { create_description }
-          expect(stored_state).to eq(before_state)
-        end
-      end
-    end
-  end
-
-  describe 'PUT /wiki/:id' do
-    let!(:page) do
-      tag
-      Wiki::Commit.create_content!(
-          tag_name:, body: 'before', created_by_user: user)
-    end
-    let!(:first_revision) { page.current_revision }
-
-    let!(:description) do
-      TagDescription.find_by!(tag_id: tag.id, language_code: 'ja')
-    end
-
-    def update_description body: 'after', title: tag_name.name, base: first_revision.id
-      put "/wiki/#{ page.id }",
-          params: { title:, body:, message: 'edit', base_revision_id: base },
-          headers: headers
-    end
-
-    it 'increments the independent description sequence and shares revision identity' do
-      expect(page.reload.version_no).to eq(1)
-      expect(description.version_no).to eq(1)
-      expect { update_description }
-          .to change(WikiRevision, :count).by(1)
-          .and change(WikiVersion, :count).by(1)
-          .and change(TagDescriptionVersion, :count).by(1)
       expect(response).to have_http_status(:ok)
-
+      expect(tag.reload.name('ja')).to eq('renamed')
-      revision = page.reload.current_revision
+      expect(description.reload.attributes).to eq(snapshot)
-      version = TagDescriptionVersion.find(revision.id)
-      expect(description.reload).to have_attributes(body: 'after', version_no: 2)
-      expect(version).to have_attributes(
-          body: 'after', version_no: 2, event_type: 'update', created_by_user_id: user.id)
-      expect(page).to have_attributes(body: 'after', version_no: 2)
-      expect(revision.body).to eq(version.body)
-      expect(page.wiki_versions.order(:version_no).last.body).to eq(version.body)
     end
 
-    it 'uses description identity even when its Wiki TagName no longer owns the Tag' do
+    ['conflicting body', 'after'].each do |body|
-      tag_name.update_columns(tag_id: nil)
+      it "rejects a stale revision even for #{ body } without a partial rename" do
-
+        update_description
-      expect { update_description }
-          .to change(WikiRevision, :count).by(1)
-          .and change(WikiVersion, :count).by(1)
-          .and change(TagDescriptionVersion, :count).by(1)
-
-      expect(response).to have_http_status(:ok)
-      expect(description.reload).to have_attributes(body: 'after', version_no: 2)
-      expect(TagDescriptionVersion.find(page.reload.current_revision.id))
-          .to have_attributes(tag_id: tag.id, body: 'after', version_no: 2)
-    end
-
-    it 'does not add body history for a title-only update' do
-      revision_count = WikiRevision.count
-      wiki_version_count = WikiVersion.count
-      description_version_count = TagDescriptionVersion.count
-      wiki_version_no = page.reload.version_no
-      description_version_no = description.version_no
-      current_revision_id = page.current_revision.id
-      page_state = page.attributes
-      description_state = description.attributes
-
-      update_description(body: 'before', title: 'Help:description_renamed')
-
-      expect(response).to have_http_status(:ok)
-      expect(tag_name.reload.name).to eq('Help:description_renamed')
-      expect(WikiRevision.count).to eq(revision_count)
-      expect(WikiVersion.count).to eq(wiki_version_count)
-      expect(TagDescriptionVersion.count).to eq(description_version_count)
-      expect(page.reload).to have_attributes(body: 'before', version_no: wiki_version_no)
-      expect(page.current_revision.id).to eq(current_revision_id)
-      expect(page.reload.attributes).to eq(page_state)
-      expect(description.reload).to have_attributes(
-          body: 'before', version_no: description_version_no)
-      expect(description.reload.attributes).to eq(description_state)
-    end
-
-    it 'does not add body history for a TagName rename through tags' do
-      revision_count = WikiRevision.count
-      wiki_version_count = WikiVersion.count
-      description_version_count = TagDescriptionVersion.count
-      page_version_no = page.reload.version_no
-      current_revision_id = page.current_revision.id
-
-      patch "/tags/#{ tag.id }",
-            params: { name: 'description_tag_renamed' },
-            headers: headers
-
-      expect(response).to have_http_status(:ok)
-      expect(tag_name.reload.name).to eq('description_tag_renamed')
-      expect(WikiRevision.count).to eq(revision_count)
-      expect(WikiVersion.count).to eq(wiki_version_count)
-      expect(TagDescriptionVersion.count).to eq(description_version_count)
-      expect(page.reload.version_no).to eq(page_version_no)
-      expect(page.current_revision.id).to eq(current_revision_id)
-      expect(description.reload).to have_attributes(
-          body: 'before', version_no: 1)
-    end
-
-    it 'keeps both systems and the title unchanged on a stale revision conflict' do
-      update_description(body: 'current body', base: first_revision.id)
-      expect(response).to have_http_status(:ok)
-
-      stale_revision_id = first_revision.id
-      before_state = stored_state
-
-      update_description(
-          body: 'conflicting body',
-          title: 'conflicting_rename',
-          base: stale_revision_id)
-
-      expect(response).to have_http_status(:conflict)
-      expect(stored_state).to eq(before_state)
-      expect(tag_name.reload.name).not_to eq('conflicting_rename')
-    end
-
-    [WikiPage, WikiRevision, WikiVersion, TagDescription, TagDescriptionVersion].each do |model|
-      it "rolls back both systems when #{ model.name } persistence fails" do
-        before_state = stored_state
-        aggregate_failures do
-          fail_save(model) do
-            update_description(body: 'rollback body', title: 'rollback_rename')
-          end
-          expect(stored_state).to eq(before_state)
-        end
-      end
-    end
-
-    [['identical body', 'before'],
-     ['normalised-equivalent body', "before\n\n"]].each do |label, body|
-      it "does not write histories for #{ label }" do
-        before_state = stored_state
-        page_state = page.reload.attributes
-        description_state = description.reload.attributes
-        current_revision_id = page.current_revision.id
-        wiki_lines = WikiLine.order(:id).map(&:attributes)
-        revision_lines = WikiRevisionLine.order(:id).map(&:attributes)
-        page_version_no = page.version_no
-        description_version_no = description.version_no
-
-        update_description(body:)
-
         expect(response).to have_http_status(:ok)
-        expect(WikiRevision.count).to eq(before_state[1].length)
+        before_state = stored_state
-        expect(WikiVersion.count).to eq(before_state[2].length)
+        update_description(body:, title: 'conflicting rename')
-        expect(TagDescriptionVersion.count).to eq(before_state[4].length)
+        expect(response).to have_http_status(:conflict)
-        expect(page.reload.version_no).to eq(page_version_no)
+        expect(stored_state).to eq(before_state)
-        expect(description.reload.version_no).to eq(description_version_no)
+      end
-        expect(page.current_revision.id).to eq(current_revision_id)
+    end
-        expect(page.reload.attributes).to eq(page_state)
+
-        expect(description.reload.attributes).to eq(description_state)
+    [TagDescription, TagDescriptionVersion].each do |model|
-        expect(WikiLine.order(:id).map(&:attributes)).to eq(wiki_lines)
+      it "rolls back the rename and body after #{ model.name } persistence fails" do
-        expect(WikiRevisionLine.order(:id).map(&:attributes)).to eq(revision_lines)
+        before_state = stored_state
+        failure = Class.new(StandardError)
+        callback = ->(_record) { raise failure }
+        model.set_callback(:save, :after, callback)
+        begin
+          expect { update_description(title: 'rollback rename') }.to raise_error(failure)
+          expect(stored_state).to eq(before_state)
+        ensure
+          model.skip_callback(:save, :after, callback)
+        end
       end
     end
   end

backend/spec/requests/tag_descriptions_spec.rb

@@ -1,6 +1,8 @@
 require 'rails_helper'
 
 RSpec.describe 'Tag description native API', type: :request do
+  include WikiRecords
+  include TagGroupRecords
   let!(:author) { create_member_user! }
   let(:editor) { create(:user, :member, name: 'description editor') }
   let(:tag_name) { create(:tag_name, name: 'native_description') }
@@ -9,8 +11,7 @@ RSpec.describe 'Tag description native API', type: :request do
   let(:endpoint) { "/tags/#{ tag.id }/description" }
 
   def stored_state
-    [WikiPage, WikiRevision, WikiVersion, TagDescription, TagDescriptionVersion,
+    [TagDescription, TagDescriptionVersion, TagName, TagVersion].map do |model|
-     WikiLine, WikiRevisionLine, TagName, TagVersion].map do |model|
       model.order(:id).map(&:attributes)
     end
   end
@@ -84,7 +85,7 @@ RSpec.describe 'Tag description native API', type: :request do
   describe 'native reads' do
     let!(:description) do
       TagDescription.create!(
-          id: tag.id + 1_000_000, tag:, language_code: 'ja', body: 'native current',
+          tag:, language_code: 'ja', body: 'native current',
           version_no: 1, created_by_user_id: author.id, updated_by_user_id: editor.id)
     end
     let!(:version) do
@@ -95,15 +96,14 @@ RSpec.describe 'Tag description native API', type: :request do
     let(:name_endpoint) { "/tags/name/#{ tag_name.name }/description" }
 
     it 'reads the current resource by Tag ID without a WikiPage' do
-      expect(description.id).not_to eq(tag.id)
-      expect(WikiPage.exists?(id: description.id)).to be(false)
       without_legacy_reads { native_get(endpoint) }
       expect(response).to have_http_status(:ok)
       expect_current(description)
     end
 
     it 'does not interpret a compatibility handle as a Tag ID' do
-      other_tag = create(:tag, id: description.id, primary_name: 'handle_collision')
+      other_tag = create(:tag, primary_name: 'handle_collision')
+      description.update_columns(id: other_tag.id)
       other = TagDescription.create!(
           tag: other_tag, language_code: 'ja', body: 'other current', version_no: 1,
           created_by_user_id: author.id, updated_by_user_id: author.id)
@@ -153,32 +153,6 @@ RSpec.describe 'Tag description native API', type: :request do
       expect_current(description)
     end
 
-    [:id, :name].each do |lookup|
-      it "ignores divergent legacy body and history for #{ lookup } lookup" do
-        page = WikiPage.create!(
-            id: description.id, tag_name:, body: 'old current',
-            created_user: author, updated_user: author)
-        revision = WikiRevision.create!(
-            wiki_page: page, created_user: author, kind: :content,
-            lines_count: 1, tree_sha256: Digest::SHA256.hexdigest('old revision'))
-        line = WikiLine.create!(body: 'old revision', sha256: revision.tree_sha256)
-        WikiRevisionLine.create!(wiki_revision: revision, wiki_line: line, position: 0)
-        WikiVersionRecorder.record!(page:, event_type: :create, created_by_user: author)
-        path = lookup == :id ? endpoint : name_endpoint
-        action = lookup == :id ? 'show' : 'show_by_title'
-
-        without_legacy_reads { native_get(path, action:) }
-        expect(response).to have_http_status(:ok)
-        expect_current(description)
-        original = json
-        page.update_columns(body: 'changed old current')
-        line.update_columns(body: 'changed old revision')
-        revision.update_columns(message: 'changed old history', created_at: 1.day.ago)
-        without_legacy_reads { native_get(path, action:) }
-        expect(response).to have_http_status(:ok)
-        expect(json).to eq(original)
-      end
-    end
   end
 
   describe 'missing native resources' do
@@ -206,35 +180,24 @@ RSpec.describe 'Tag description native API', type: :request do
     context 'without an existing description' do
       before { tag }
 
-      it 'creates both current resources and histories with matching compatibility IDs' do
+
+      it 'creates native history that is immediately available through the facade' do
         expect { native_write(body: 'created natively') }
             .to change(TagDescription, :count).by(1)
             .and change(TagDescriptionVersion, :count).by(1)
-            .and change(WikiPage, :count).by(1)
-            .and change(WikiRevision, :count).by(1)
-            .and change(WikiVersion, :count).by(1)
         expect(response).to have_http_status(:created)
         description = TagDescription.find_by!(tag_id: tag.id, language_code: 'ja')
-        page = WikiPage.find(description.id)
-        revision = page.current_revision
-        version = TagDescriptionVersion.find(revision.id)
-        expect(description).to have_attributes(
-            body: 'created natively', version_no: 1,
-            created_by_user_id: editor.id, updated_by_user_id: editor.id)
-        expect(version).to have_attributes(
-            tag_id: tag.id, language_code: 'ja', body: description.body,
-            version_no: 1, event_type: 'create', created_by_user_id: editor.id)
-        expect(page).to have_attributes(tag_name_id: tag_name.id, body: description.body)
-        expect(revision.body).to eq(version.body)
-        expect(page.wiki_versions.last.body).to eq(version.body)
         expect_current(description)
-
+        version = current_description_version(description)
+        expect(version).to have_attributes(
+            body: 'created natively', version_no: 1, event_type: 'create',
+            created_by_user_id: editor.id)
         get "/wiki/#{ description.id }"
         expect(response).to have_http_status(:ok)
         expect(json).to include('body' => description.body, 'revision_id' => version.id)
       end
 
-      [WikiPage, WikiRevision, WikiVersion, TagDescription, TagDescriptionVersion].each do |model|
+      [TagDescription, TagDescriptionVersion].each do |model|
         it "rolls back native create when #{ model.name } persistence fails" do
           headers
           before_state = stored_state
@@ -249,7 +212,7 @@ RSpec.describe 'Tag description native API', type: :request do
     context 'with an existing description' do
       let!(:page) do
         tag
-        Wiki::Commit.create_content!(tag_name:, body: 'before', created_by_user: author)
+        seed_description(tag_name:, body: 'before', created_by_user: author)
       end
       let!(:description) do
         TagDescription.find_by!(tag_id: tag.id, language_code: 'ja')
@@ -259,22 +222,20 @@ RSpec.describe 'Tag description native API', type: :request do
         expect(page.reload.version_no).to eq(1)
         expect(description.version_no).to eq(1)
         expect { native_write(body: 'after') }
-            .to change(WikiRevision, :count).by(1)
+            .to change(TagDescriptionVersion, :count).by(1)
-            .and change(WikiVersion, :count).by(1)
-            .and change(TagDescriptionVersion, :count).by(1)
         expect(response).to have_http_status(:ok)
         expect(description.reload).to have_attributes(
             body: 'after', version_no: 2,
             created_by_user_id: author.id, updated_by_user_id: editor.id)
         expect(page.reload).to have_attributes(body: 'after', version_no: 2)
 
-        revision = page.current_revision
+        revision = current_description_version(page)
         version = TagDescriptionVersion.find(revision.id)
         expect(version).to have_attributes(
             tag_id: tag.id, language_code: 'ja', version_no: 2, event_type: 'update',
             body: 'after', created_by_user_id: editor.id)
         expect(revision.body).to eq(version.body)
-        expect(page.wiki_versions.order(:version_no).last.body).to eq(version.body)
+        expect(description_versions(page).order(:version_no).last.body).to eq(version.body)
         get "/wiki/#{ description.id }"
         expect(response).to have_http_status(:ok)
         expect(json).to include('body' => 'after', 'revision_id' => version.id)
@@ -285,7 +246,7 @@ RSpec.describe 'Tag description native API', type: :request do
           before_state = stored_state
           page_state = page.reload.attributes
           description_state = description.reload.attributes
-          current_revision_id = page.current_revision.id
+          current_revision_id = current_description_version(page).id
 
           native_write(body:)
 
@@ -293,11 +254,11 @@ RSpec.describe 'Tag description native API', type: :request do
           expect(stored_state).to eq(before_state)
           expect(page.reload.attributes).to eq(page_state)
           expect(description.reload.attributes).to eq(description_state)
-          expect(page.current_revision.id).to eq(current_revision_id)
+          expect(current_description_version(page).id).to eq(current_revision_id)
         end
       end
 
-      [WikiPage, WikiRevision, WikiVersion, TagDescription, TagDescriptionVersion].each do |model|
+      [TagDescription, TagDescriptionVersion].each do |model|
         it "rolls back native update when #{ model.name } persistence fails" do
           headers
           before_state = stored_state

backend/spec/requests/tag_group_locale_spec.rb

@@ -0,0 +1,122 @@
+require 'rails_helper'
+
+RSpec.describe 'Tag group locale contracts', type: :request do
+  include TagGroupRecords
+  include_context 'Ainu locale contract'
+
+  let!(:user) { create_member_user! }
+  let!(:tag) { create(:tag, primary_name: 'japanese_member') }
+  let!(:ainu_name) { add_ainu_name(tag, 'ainu_member') }
+  let(:headers) { { 'X-Transfer-Code' => user.inheritance_code } }
+  let(:members) { [{ 'tag_id' => tag.id }] }
+  let(:placements) do
+    [{ 'section_name' => 'section', 'description' => nil, 'children' => [
+        { 'tag_id' => tag.id, 'children' => [
+            { 'tag_id' => tag.id, 'children' => [] }] }] }]
+  end
+  let!(:group) do
+    TagVersioning.ensure_snapshot!(tag, created_by_user: user)
+    TagGroupOperation.create!(
+        ainu_locale, name: 'locale group', description: nil, members:, placements:, actor: user)
+  end
+
+  it 'uses selected-language names in native collection and nested placements' do
+    ["/tag_groups/#{ group.id }", '/tag_groups'].each do |path|
+      get path, params: { locale: 'ain' }
+      expect(response).to have_http_status(:ok)
+      representation = json.is_a?(Array) ? json.sole : json
+      expect(representation.fetch('members').sole.fetch('tag').fetch('name'))
+          .to eq('ainu_member')
+      node = representation.fetch('placements').sole.fetch('children').sole
+      expect(node.fetch('tag').fetch('name')).to eq('ainu_member')
+      expect(node.fetch('children').sole.fetch('tag').fetch('name')).to eq('ainu_member')
+      expect(response.body).not_to include('japanese_member')
+    end
+  end
+
+  it 'uses snapshot names recursively for history and current names for the latest view' do
+    version = group.versions.sole
+    ainu_name.update!(name: 'renamed_ainu')
+    get "/wiki/#{ group.id }", params: { locale: 'ain' }
+    expect(response).to have_http_status(:ok)
+    expect(json.fetch('body')).to include('renamed_ainu')
+    get "/wiki/#{ group.id }", params: { locale: 'ain', version: version.id }
+    expect(response).to have_http_status(:ok)
+    expect(json.fetch('body').scan('ainu_member').length).to eq(2)
+    expect(json.fetch('body')).not_to include('renamed_ainu', 'japanese_member')
+    get "/wiki/#{ group.id }/diff", params: { locale: 'ain', from: version.id }
+    expect(response).to have_http_status(:ok)
+    expect(json.fetch('diff').map { _1.fetch('type') }.uniq).to eq(['context'])
+  end
+
+  ['タググループ:', 'tag_group:', 'TAG_GROUP:'].each do |prefix|
+    it "round trips #{ prefix } through create, lookup, search and update" do
+      post '/wiki', params: {
+          locale: 'ain', title: "#{ prefix }parent", body: '- tag_group:locale group' },
+          headers: headers
+      expect(response).to have_http_status(:created)
+      id = json.fetch('id')
+      expect(json.fetch('body')).to include('タググループ:locale group')
+      path = "/wiki/title/#{ CGI.escapeURIComponent("#{ prefix }parent") }"
+      get path, params: { locale: 'ain' }
+      expect(response).to have_http_status(:ok)
+      expect(json.fetch('id')).to eq(id)
+      get "#{ path }/exists", params: { locale: 'ain' }
+      expect(response).to have_http_status(:no_content)
+      get '/wiki/search', params: { locale: 'ain', title: "#{ prefix }parent" }
+      expect(json.map { _1.fetch('id') }).to eq([id])
+      put "/wiki/#{ id }", params: {
+          locale: 'ain', title: "#{ prefix }renamed", body: '- ainu_member' }, headers: headers
+      expect(response).to have_http_status(:ok)
+      get "/tag_groups/#{ id }", params: { locale: 'ain' }
+      expect(json.fetch('members').sole.fetch('tag').fetch('name')).to eq('ainu_member')
+    end
+  end
+
+  it 'resolves Markdown names in the requested language and rolls back invalid input' do
+    parsed = TagGroupMarkdownParser.parse(ainu_locale, body: '- ainu_member')
+    expect(parsed.fetch(:members)).to eq(members)
+    expect do
+      TagGroupMarkdownParser.parse(ainu_locale, body: '- japanese_member')
+    end.to raise_error(TagGroupMarkdownParser::InvalidDocument)
+    before_state = group_state
+    put "/wiki/#{ group.id }", params: {
+        locale: 'ain', title: 'タググループ:partial rename', body: '- japanese_member' },
+        headers: headers
+    expect(response).to have_http_status(:unprocessable_entity)
+    expect(group_state).to eq(before_state)
+  end
+
+  it 'passes locale into native validation and facade compatibility checks' do
+    post '/tag_groups', params: {
+        locale: 'ain', name: 'native', description: nil, members:, placements: },
+        headers:, as: :json
+    expect(response).to have_http_status(:created)
+    id = json.fetch('id')
+    expect(json.fetch('members').sole.fetch('tag').fetch('name')).to eq('ainu_member')
+    get "/wiki/#{ id }", params: { locale: 'ain' }
+    expect(response).to have_http_status(:ok)
+    body = json.fetch('body')
+    put "/wiki/#{ id }", params: { locale: 'ain', title: 'tag_group:native', body: },
+        headers: headers
+    expect(response).to have_http_status(:ok)
+    expect(TagGroup.find(id).version_no).to eq(1)
+  end
+
+  it 'does not substitute current or Japanese names for a missing historical language' do
+    other = create(:tag, primary_name: 'historical_japanese')
+    TagVersioning.ensure_snapshot!(other, created_by_user: user)
+    old_group = TagGroupOperation.create!(
+        Locale.nipponese, name: 'old group', description: nil,
+        members: [{ 'tag_id' => other.id }],
+        placements: [{ 'tag_id' => other.id, 'children' => [] }], actor: user)
+    add_ainu_name(other, 'current_ainu')
+    version = old_group.versions.sole
+    representation = TagGroupRepr.historical(ainu_locale, version)
+    expect(representation.fetch('members').sole.fetch('tag').fetch('name')).to be_nil
+    expect(representation.fetch('placements').sole.fetch('tag').fetch('name')).to be_nil
+    get "/wiki/#{ old_group.id }", params: { locale: 'ain', version: version.id }
+    expect(response).to have_http_status(:unprocessable_entity)
+    expect(response.body).not_to include('historical_japanese', 'current_ainu')
+  end
+end

backend/spec/requests/tag_group_markdown_spec.rb

@@ -0,0 +1,148 @@
+require 'rails_helper'
+
+RSpec.describe 'Tag group Markdown round trips through the Wiki facade', type: :request do
+  include TagGroupRecords
+
+  let!(:user) { create_member_user! }
+  let!(:series) { group_tag('ぼざろクリーチャーシリーズ') }
+  let!(:deer) { group_tag('洗澡鹿') }
+  let!(:nizika) { group_tag('伊地知ニジカ') }
+  let!(:wanted) { group_tag('タグ希望') }
+  let!(:character) { group_tag('キャラクター名希望') }
+  let!(:music) { group_tag('楽曲情報希望') }
+  let!(:bot) { group_tag('bot操作') }
+  let!(:unknown) { group_tag('ニジラー情報不詳') }
+  let!(:child_id) { seed_group(name: '伊地知ニジカ亜種', description: '子の説明') }
+
+  before { I18n.locale = :ja }
+
+  def tag_node tag, children = []
+    { 'tag_id' => tag.id, 'children' => children }
+  end
+
+  def tag_member tag
+    { 'tag_id' => tag.id, 'version_no' => tag.version_no }
+  end
+
+  def check_round_trip placements:, members:, markdown:, description: nil
+    id = seed_group(name: '変換元', placements:, members:, description:)
+    without_group_legacy_reads { get group_title_path('変換元') }
+    expect(response).to have_http_status(:ok)
+    expect(json).to include('id' => id)
+    body = json.fetch('body')
+    expect(body).not_to include("\r")
+    expect(body.lines.map(&:chomp)).to all(satisfy { |line| line == line.rstrip })
+    # A trailing LF or a blank line between blocks is semantically irrelevant.
+    expect(body.lines.map(&:chomp).reject(&:empty?)).to eq(
+        markdown.lines.map(&:chomp).reject(&:empty?))
+
+    post '/wiki', params: { title: 'タググループ:再解析', body: },
+         headers: { 'X-Transfer-Code' => user.inheritance_code }
+    expect(response).to have_http_status(:created)
+    parsed = group_rows('tag_groups', name: '再解析').sole
+    expect_group_snapshot(parsed.fetch('id'), number: 1, placements:, members:, description:)
+  end
+
+  it 'renders a list Section under a Tag with two-space indentation' do
+    check_round_trip(
+        members: [series, deer].map { tag_member(_1) },
+        placements: [tag_node(series, [
+            { 'section_name' => '伊地知ニジカ亜種', 'description' => nil,
+              'children' => [tag_node(deer)] }])],
+        markdown: <<~MARKDOWN)
+          - ぼざろクリーチャーシリーズ
+            - 伊地知ニジカ亜種:
+              - 洗澡鹿
+        MARKDOWN
+  end
+
+  it 'renders a child Tag Group distinctly from its parent Tags' do
+    check_round_trip(
+        members: [tag_member(series), tag_member(nizika),
+                  { 'tag_group_id' => child_id, 'version_no' => 1 }],
+        placements: [tag_node(series, [tag_node(nizika, [
+            { 'tag_group_id' => child_id, 'children' => [] }])])],
+        markdown: <<~MARKDOWN)
+          - ぼざろクリーチャーシリーズ
+            - 伊地知ニジカ
+              - タググループ:伊地知ニジカ亜種
+        MARKDOWN
+  end
+
+  it 'renders top-level heading Sections, descriptions and ordered nested Tags' do
+    check_round_trip(
+        description: '全体の説明',
+        members: [wanted, character, music, bot, unknown].map { tag_member(_1) },
+        placements: [
+            { 'section_name' => '要求', 'description' => '要求の説明',
+              'children' => [tag_node(wanted, [tag_node(character), tag_node(music)])] },
+            { 'section_name' => '情報', 'description' => nil,
+              'children' => [tag_node(bot), tag_node(unknown)] }],
+        markdown: <<~MARKDOWN)
+          全体の説明
+
+          ## 要求
+          要求の説明
+
+          - タグ希望
+            - キャラクター名希望
+            - 楽曲情報希望
+
+          ## 情報
+          - bot操作
+          - ニジラー情報不詳
+        MARKDOWN
+  end
+
+  it 'renders nested heading Sections and all repeated Tag placements' do
+    check_round_trip(
+        members: [tag_member(deer)],
+        placements: [
+            { 'section_name' => '親', 'description' => '親の説明', 'children' => [
+                tag_node(deer),
+                { 'section_name' => '子', 'description' => '子の説明',
+                  'children' => [tag_node(deer)] }] }],
+        markdown: <<~MARKDOWN)
+          ## 親
+          親の説明
+
+          - 洗澡鹿
+
+          ### 子
+          子の説明
+
+          - 洗澡鹿
+        MARKDOWN
+  end
+
+  it 'round trips a top-level list followed by heading Sections' do
+    check_round_trip(
+        members: [tag_member(series), tag_member(deer)],
+        placements: [tag_node(series),
+                     { 'section_name' => '区分', 'description' => nil,
+                       'children' => [tag_node(deer)] }],
+        markdown: "- ぼざろクリーチャーシリーズ\n\n## 区分\n\n- 洗澡鹿")
+  end
+
+  it 'rejects mixed top-level heading Sections and Tags without losing structure' do
+    id = seed_group(
+        name: '混在構造', members: [tag_member(series)],
+        placements: [
+            { 'section_name' => '区分', 'description' => nil, 'children' => [] },
+            tag_node(series)])
+
+    get group_title_path('混在構造')
+
+    expect(response).to have_http_status(:unprocessable_entity)
+    expect(group_rows('tag_groups', id:).sole.fetch('id')).to eq(id)
+  end
+
+  it 'rejects membership without a placement instead of omitting it' do
+    id = seed_group(name: '未配置構造', members: [tag_member(series)])
+
+    get group_title_path('未配置構造')
+
+    expect(response).to have_http_status(:unprocessable_entity)
+    expect(group_rows('tag_groups', id:).sole.fetch('id')).to eq(id)
+  end
+end

backend/spec/requests/tag_group_wiki_spec.rb

@@ -0,0 +1,179 @@
+require 'rails_helper'
+
+RSpec.describe 'Tag group Wiki facade reads', type: :request do
+  include WikiRecords
+  include TagGroupRecords
+
+  let!(:user) { create_member_user! }
+  let!(:old_tag) { group_tag('旧タグ') }
+  let!(:new_tag) { group_tag('新タグ') }
+  let!(:page) { create_markdown_group('読取り契約', '- 旧タグ') }
+  let!(:first_revision) { page.versions.sole }
+  let!(:last_revision) do
+    parsed = TagGroupMarkdownParser.parse(Locale.nipponese, body: '- 新タグ')
+    TagGroupOperation.update!(
+        Locale.nipponese,
+        group: page, name: page.name, actor: user,
+        **parsed.slice(:description, :members, :placements))
+    page.versions.order(:version_no).last
+  end
+
+  before { I18n.locale = :ja }
+
+  [:id, :title].each do |lookup|
+    context "with #{ lookup } lookup" do
+      let(:path) { lookup == :id ? "/wiki/#{ page.id }" : group_title_path('読取り契約') }
+
+      it 'reads current structure without consulting migrated Wiki tables' do
+        without_group_legacy_reads { get path }
+        expect(response).to have_http_status(:ok)
+        expect(json).to include(
+            'id' => page.id, 'title' => 'タググループ:読取り契約',
+            'revision_id' => last_revision.id, 'pred' => first_revision.id, 'succ' => nil)
+        expect(json.fetch('body').strip).to eq('- 新タグ')
+      end
+
+      it 'reads the old snapshot rather than current membership or placement' do
+        without_group_legacy_reads { get path, params: { version: first_revision.id } }
+        expect(response).to have_http_status(:ok)
+        expect(json.fetch('body').strip).to eq('- 旧タグ')
+        expect(json).to include(
+            'revision_id' => first_revision.id, 'pred' => nil, 'succ' => last_revision.id,
+            'updated_at' => first_revision.created_at.iso8601(3))
+      end
+
+      it 'checks existence without consulting migrated Wiki tables' do
+        without_group_legacy_reads { get "#{ path }/exists" }
+        expect(response).to have_http_status(:no_content)
+      end
+
+      it 'does not fall back to legacy history when a group version is missing' do
+        group_connection.execute(
+            "DELETE FROM tag_group_versions WHERE id = #{ first_revision.id }")
+        without_group_legacy_reads { get path, params: { version: first_revision.id } }
+        expect(response).to have_http_status(:not_found)
+      end
+    end
+  end
+
+  ['/wiki', '/wiki/search'].each do |path|
+    it "lists migrated groups once with current titles at #{ path }" do
+      get path, params: { title: 'タググループ:読取り' }
+      expect(response).to have_http_status(:ok)
+      rows = json.select { _1.fetch('title') == 'タググループ:読取り契約' }
+      expect(rows.size).to eq(1)
+      expect(rows.sole).to include('id' => page.id)
+      expect(response.body).not_to include('legacy stale')
+    end
+  end
+
+  it 'combines Tag Groups and Tag Descriptions without Help in the unfiltered list' do
+    TagDescriptionOperation.create!(
+        Locale.nipponese, tag: new_tag, body: 'tag description', created_by_user: user)
+    get '/wiki'
+    expect(response).to have_http_status(:ok)
+    expect(json.map { _1.fetch('title') }).to include(
+        'タググループ:読取り契約', '新タグ')
+  end
+
+
+  it 'finds groups by a partial prefix of their displayed title' do
+    get '/wiki', params: { title: 'タググル' }
+
+    expect(response).to have_http_status(:ok)
+    expect(json.map { _1.fetch('title') }).to include('タググループ:読取り契約')
+    expect(json.find { _1.fetch('title') == 'タググループ:読取り契約' })
+        .to include('updated_at' => be_present)
+  end
+
+  it 'does not restore a stale namespaced Wiki page after a group rename' do
+    group = create_markdown_group('旧名称', '正本')
+    TagGroupOperation.update!(
+        Locale.nipponese,
+        group:, name: '新名称', description: '正本', members: [], placements: [], actor: user)
+
+    get group_title_path('旧名称')
+    expect(response).to have_http_status(:not_found)
+    get "#{ group_title_path('旧名称') }/exists"
+    expect(response).to have_http_status(:not_found)
+    get group_title_path('新名称')
+    expect(response).to have_http_status(:ok)
+    expect(json.fetch('body').strip).to eq('正本')
+  end
+
+  it 'orders mixed resource history by timestamp rather than independent IDs' do
+    TagDescriptionOperation.create!(
+        Locale.nipponese, tag: new_tag, body: 'description', created_by_user: user)
+    TagGroupVersion.update_all(created_at: 3.days.ago)
+    TagDescriptionVersion.update_all(created_at: 1.day.ago)
+
+    get '/wiki/changes'
+
+    expect(response).to have_http_status(:ok)
+    timestamps = json.map { Time.iso8601(_1.fetch('timestamp')) }
+    expect(timestamps).to eq(timestamps.sort.reverse)
+    titles = json.map { _1.dig('wiki_page', 'title') }
+    expect(titles.index('新タグ')).to be < titles.index('タググループ:読取り契約')
+  end
+
+  it 'renders nullable group editors without raising' do
+    group_connection.execute(
+        "UPDATE tag_groups SET created_by_user_id = NULL, updated_by_user_id = NULL " +
+        "WHERE id = #{ page.id }")
+    group_connection.execute(
+        "UPDATE tag_group_versions SET created_by_user_id = NULL " +
+        "WHERE tag_group_id = #{ page.id }")
+
+    get "/tag_groups/#{ page.id }"
+    expect(response).to have_http_status(:ok)
+    expect(json).to include('created_by_user' => nil, 'updated_by_user' => nil)
+    get "/wiki/title/#{ CGI.escapeURIComponent('タググループ:読取り契約') }"
+    expect(response).to have_http_status(:ok)
+  end
+
+  it 'reads group version IDs, editor and timestamps in scoped changes' do
+    without_group_legacy_reads { get '/wiki/changes', params: { id: page.id } }
+    expect(response).to have_http_status(:ok)
+    expect(json.map { _1.fetch('revision_id') }).to eq([last_revision.id, first_revision.id])
+    expect(json.first).to include(
+        'pred' => first_revision.id, 'succ' => nil, 'kind' => 'content',
+        'timestamp' => last_revision.created_at.iso8601(3),
+        'user' => { 'id' => user.id, 'name' => user.name },
+        'wiki_page' => include('id' => page.id, 'title' => 'タググループ:読取り契約'))
+  end
+
+
+  [false, true].each do |explicit|
+    it "diffs structured snapshots with #{ explicit ? 'explicit' : 'current' } target" do
+      params = { from: first_revision.id }
+      params[:to] = last_revision.id if explicit
+      without_group_legacy_reads { get "/wiki/#{ page.id }/diff", params: }
+      expect(response).to have_http_status(:ok)
+      expect(json).to include(
+          'wiki_page_id' => page.id, 'older_revision_id' => first_revision.id,
+          'newer_revision_id' => last_revision.id)
+      differences = json.fetch('diff').map { [_1.fetch('type'), _1.fetch('content').strip] }
+      expect(differences).to include(['removed', '- 旧タグ'], ['added', '- 新タグ'])
+    end
+  end
+
+  it 'does not use a version belonging to another group' do
+    other_id = seed_group(name: '別グループ', description: '別本文')
+    other_version = group_version(other_id, 1)
+    get group_title_path('読取り契約'), params: { version: other_version.fetch('id') }
+    expect(response).to have_http_status(:not_found)
+    get "/wiki/#{ page.id }/diff",
+        params: { from: other_version.fetch('id'), to: last_revision.id }
+    expect(response).to have_http_status(:not_found)
+  end
+
+  it 'resolves a group without any compatibility Wiki page' do
+    id = seed_group(name: '独立グループ', description: '独立した説明')
+    without_group_legacy_reads { get group_title_path('独立グループ') }
+    expect(response).to have_http_status(:ok)
+    expect(json).to include('id' => id, 'title' => 'タググループ:独立グループ')
+    expect(json.fetch('body').strip).to eq('独立した説明')
+  end
+
+
+end

backend/spec/requests/tag_group_wiki_write_spec.rb

@@ -0,0 +1,298 @@
+require 'rails_helper'
+
+RSpec.describe 'Tag group Wiki facade writes', type: :request do
+  include TagGroupRecords
+  include ActiveSupport::Testing::TimeHelpers
+
+  let!(:user) { create_member_user! }
+  let!(:tag) { group_tag('洗澡鹿') }
+  let!(:other_tag) { group_tag('伊地知ニジカ') }
+  let(:headers) { { 'X-Transfer-Code' => user.inheritance_code } }
+  let(:members) { [{ 'tag_id' => tag.id, 'version_no' => tag.version_no }] }
+  let(:placements) { [{ 'tag_id' => tag.id, 'children' => [] }] }
+
+  before { I18n.locale = :ja }
+
+  def create_group title: 'タググループ:新規', body: '- 洗澡鹿', request_headers: headers
+    post '/wiki', params: { title:, body: }, headers: request_headers
+  end
+
+  def expect_rejected_without_writes
+    before_state = group_state
+    yield
+    aggregate_failures do
+      expect(response).to have_http_status(:unprocessable_entity)
+      expect(group_state).to eq(before_state)
+      expect(response.media_type).to eq('application/json')
+      expect(response.body).not_to be_empty
+      next if response.body.empty?
+
+      expect(json).to include(
+          'type' => 'validation_error', 'errors' => a_kind_of(Hash),
+          'base_errors' => a_kind_of(Array))
+    end
+  end
+
+  it 'creates the group, snapshot and native version history' do
+    expect { create_group }
+        .to change(TagGroup, :count).by(1)
+        .and change(TagGroupVersion, :count).by(1)
+    expect(response).to have_http_status(:created)
+    group = group_rows('tag_groups', name: '新規').sole
+    expect(json).to include('id' => group.fetch('id'), 'title' => 'タググループ:新規')
+    expect_group_snapshot(group.fetch('id'), number: 1, members:, placements:)
+    version = group_version(group.fetch('id'), 1)
+    expect(version).to include('event_type' => 'create', 'created_by_user_id' => user.id)
+    expect(group).to include('created_by_user_id' => user.id, 'updated_by_user_id' => user.id)
+    get group_title_path('新規')
+    expect(response).to have_http_status(:ok)
+    expect(json.fetch('body')).to eq('- 洗澡鹿')
+  end
+
+  it 'keeps repeated placements but only one membership and one snapshot member' do
+    create_group(body: "- 洗澡鹿\n# 再掲\n- 洗澡鹿")
+    expect(response).to have_http_status(:created)
+    id = group_rows('tag_groups', name: '新規').sole.fetch('id')
+    expect_group_snapshot(
+        id, number: 1, members:,
+        placements: placements + [
+            { 'section_name' => '再掲', 'description' => nil, 'children' => placements }])
+  end
+
+  it 'resolves a Japanese alias through tag_names.tag_id' do
+    create(:tag_name, :alias, tag:, name: '鹿の別名')
+    create_group(body: '- 鹿の別名')
+    expect(response).to have_http_status(:created)
+    id = group_rows('tag_groups', name: '新規').sole.fetch('id')
+    expect_group_snapshot(id, number: 1, members:, placements:)
+    get group_title_path('新規')
+    expect(response).to have_http_status(:ok)
+    expect(json.fetch('body').strip).to eq('- 洗澡鹿')
+  end
+
+  {
+      'unknown Tag' => '- 解決不能',
+      'unknown Tag Group' => '- タググループ:存在しない',
+      'empty Section' => '- :',
+      'unsupported placement syntax' => "```\n洗澡鹿\n```",
+      'six levels' => "- 洗澡鹿\n  - 洗澡鹿\n    - 洗澡鹿\n      - 洗澡鹿\n" +
+          "        - 洗澡鹿\n          - 洗澡鹿",
+      'blank body' => '',
+      'normalised blank body' => "\r\n\r\n" }.each do |label, body|
+    it "rejects #{ label } without fallback or partial create" do
+      expect_rejected_without_writes { create_group(body:) }
+    end
+  end
+
+  ['', 'タググループ:', "タググループ:#{ '長' * 256 }"].each do |title|
+    it "rejects an invalid required title of length #{ title.length }" do
+      expect_rejected_without_writes { create_group(title:) }
+    end
+  end
+
+  it 'rejects a duplicate group name even without a matching legacy Wiki' do
+    seed_group(name: '新規', description: '既存')
+    expect_rejected_without_writes { create_group }
+  end
+
+  it 'accepts the existing five-level placement depth boundary' do
+    body = (0...5).map { "#{ '  ' * _1 }- 洗澡鹿" }.join("\n")
+    create_group(body:)
+    expect(response).to have_http_status(:created)
+    id = group_rows('tag_groups', name: '新規').sole.fetch('id')
+    tree = []
+    5.times { tree = [{ 'tag_id' => tag.id, 'children' => tree }] }
+    expect_group_snapshot(id, number: 1, members:, placements: tree)
+  end
+
+  context 'updating a migrated group' do
+    let!(:page) { create_markdown_group('更新', '- 洗澡鹿') }
+    let!(:old_revision) { page.versions.order(:version_no).last }
+
+
+    def update_group body: '- 伊地知ニジカ', title: 'タググループ:更新', request_headers: headers
+      put "/wiki/#{ page.id }", params: { title:, body: }, headers: request_headers
+    end
+
+    [1, 3].each do |repetitions|
+      it "keeps identical Markdown unchanged after #{ repetitions } Wiki PUTs" do
+        body = group_markdown(page)
+        travel_to(1.hour.from_now) do
+          expect_noop_group_update(group_id: page.id) do
+            repetitions.times do
+              update_group(body:)
+              expect(response).to have_http_status(:ok)
+            end
+          end
+        end
+      end
+    end
+
+    it 'keeps identical Markdown unchanged with a stale base_revision_id' do
+      update_group
+      expect(response).to have_http_status(:ok)
+      body = group_markdown(page)
+      expect(page.versions.order(:version_no).last.id).not_to eq(old_revision.id)
+
+      travel_to(1.hour.from_now) do
+        expect_noop_group_update(group_id: page.id) do
+          put "/wiki/#{ page.id }",
+              params: { title: "タググループ:#{ page.name }", body:, base_revision_id: old_revision.id },
+              headers: headers
+        end
+      end
+    end
+
+    it 'keeps the original editor on identical Markdown from another member' do
+      editor = create(:user, :member)
+      body = group_markdown(page)
+      travel_to(1.hour.from_now) do
+        expect_noop_group_update(group_id: page.id) do
+          update_group(body:, request_headers: { 'X-Transfer-Code' => editor.inheritance_code })
+        end
+      end
+    end
+
+    it 'does not add history for Wiki content already changed through Native' do
+      changed_members = [{ 'tag_id' => other_tag.id }]
+      changed_placements = [{ 'tag_id' => other_tag.id, 'children' => [] }]
+      put "/tag_groups/#{ page.id }",
+          params: { name: '更新', description: nil,
+                    members: changed_members, placements: changed_placements },
+          headers:, as: :json
+      expect(response).to have_http_status(:ok)
+      expect_group_snapshot(
+          page.id, number: 2,
+          members: [{ 'tag_id' => other_tag.id, 'version_no' => other_tag.version_no }],
+          placements: changed_placements)
+      body = group_markdown(page)
+      expect(body).to eq('- 伊地知ニジカ')
+
+      travel_to(1.hour.from_now) do
+        expect_noop_group_update(group_id: page.id) { update_group(body:) }
+      end
+    end
+
+    it 'replaces current membership and placement, retaining the old snapshot' do
+      old = group_version(page.id, 1)
+      update_group
+      expect(response).to have_http_status(:ok)
+      expect_group_snapshot(
+          page.id, number: 2,
+          members: [{ 'tag_id' => other_tag.id, 'version_no' => other_tag.version_no }],
+          placements: [{ 'tag_id' => other_tag.id, 'children' => [] }])
+      expect(group_version(page.id, 1)).to eq(old)
+      expect(group_version(page.id, 2)).to include(
+          'event_type' => 'update', 'created_by_user_id' => user.id)
+      expect(group_markdown(page).strip).to eq('- 伊地知ニジカ')
+      expect(page.versions.count).to eq(2)
+    end
+
+    it 'accepts the current base_revision_id used by the existing frontend' do
+      put "/wiki/#{ page.id }",
+          params: { title: "タググループ:#{ page.name }", body: '- 伊地知ニジカ',
+                    base_revision_id: old_revision.id }, headers: headers
+      expect(response).to have_http_status(:ok)
+      expect(group_rows('tag_groups', id: page.id).sole.fetch('version_no')).to eq(2)
+    end
+
+    it 'ignores a stale base_revision_id without rejecting the update' do
+      update_group
+      expect(response).to have_http_status(:ok)
+
+      put "/wiki/#{ page.id }",
+          params: { title: "タググループ:#{ page.name }", body: '- 洗澡鹿',
+                    base_revision_id: old_revision.id }, headers: headers
+
+      expect(response).to have_http_status(:ok)
+      expect(group_rows('tag_groups', id: page.id).sole.fetch('version_no')).to eq(3)
+      expect(group_markdown(page).strip).to eq('- 洗澡鹿')
+    end
+
+    it 'records the editor and update time' do
+      editor = create(:user, :member, name: '編輯者')
+      travel_to(Time.current + 1.hour) do
+        update_group(request_headers: { 'X-Transfer-Code' => editor.inheritance_code })
+        expect(response).to have_http_status(:ok)
+        current = group_rows('tag_groups', id: page.id).sole
+        version = group_version(page.id, 2)
+        expect(current).to include('updated_by_user_id' => editor.id)
+        expect(version).to include('created_by_user_id' => editor.id)
+        expect(current.fetch('updated_at')).to be_within(1.second).of(Time.current)
+        expect(version.fetch('created_at')).to be_within(1.second).of(Time.current)
+      end
+    end
+
+    ['- 不明なタグ', '- タググループ:不明', '', '- :'].each do |body|
+      it "rejects invalid update #{ body.inspect } atomically" do
+        expect_rejected_without_writes { update_group(body:) }
+      end
+    end
+
+    it 'rejects direct self inclusion' do
+      expect_rejected_without_writes { update_group(body: '- タググループ:更新') }
+    end
+
+    it 'rejects indirect cyclic membership' do
+      seed_group(
+          name: '子', members: [{ 'tag_group_id' => page.id, 'version_no' => 1 }],
+          placements: [{ 'tag_group_id' => page.id, 'children' => [] }])
+      expect_rejected_without_writes { update_group(body: '- タググループ:子') }
+    end
+
+    it 'rejects duplicate rename without retaining a partial title or version' do
+      seed_group(name: '既存', description: '既存')
+      expect_rejected_without_writes { update_group(title: 'タググループ:既存') }
+    end
+  end
+
+  [:create, :update].each do |operation|
+    context "#{ operation } access and atomicity" do
+      let!(:page) do
+        next unless operation == :update
+
+        create_markdown_group('更新', '- 洗澡鹿')
+      end
+      let!(:child_id) { seed_group(name: '子グループ', description: '子') }
+
+      def write_group operation, request_headers
+        body = "- 伊地知ニジカ\n- タググループ:子グループ"
+        if operation == :create
+          create_group(body:, request_headers:)
+        else
+          put "/wiki/#{ page.id }",
+              params: { title: 'タググループ:更新', body: }, headers: request_headers
+        end
+      end
+
+      [nil, :guest, :banned].each do |role|
+        it "rejects #{ role || 'anonymous' } without writes" do
+          actor = case role
+          when :guest then create(:user, :guest)
+          when :banned then create(:user, :member, :banned)
+          end
+          request_headers = actor ? { 'X-Transfer-Code' => actor.inheritance_code } : { }
+          before_state = group_state
+          write_group(operation, request_headers)
+          expect(response).to have_http_status(role ? :forbidden : :unauthorized)
+          expect(group_state).to eq(before_state)
+        end
+      end
+
+      it 'rejects a banned IP even for a member' do
+        IpAddress.create!(ip_address: IPAddr.new('127.0.0.1').hton, banned_at: Time.current)
+        before_state = group_state
+        write_group(operation, headers)
+        expect(response).to have_http_status(:forbidden)
+        expect(group_state).to eq(before_state)
+      end
+
+      tables = TagGroupRecords::GROUP_TABLES
+      tables.each do |table|
+        it "rolls back all writes after a real #{ table } write fails" do
+          expect_atomic_group_write(table) { write_group(operation, headers) }
+        end
+      end
+    end
+  end
+end

backend/spec/requests/tag_group_write_integrity_spec.rb

@@ -0,0 +1,204 @@
+require 'rails_helper'
+
+RSpec.describe 'Tag group write integrity', type: :request do
+  include WikiRecords
+  include TagGroupRecords
+  include ActiveSupport::Testing::TimeHelpers
+
+  let!(:user) { create_member_user! }
+  let!(:tag) { group_tag('洗澡鹿') }
+  let!(:other_tag) { group_tag('伊地知ニジカ') }
+  let(:headers) { { 'X-Transfer-Code' => user.inheritance_code } }
+  let(:members) { [{ 'tag_id' => tag.id, 'version_no' => tag.version_no }] }
+  let(:placements) { [{ 'tag_id' => tag.id, 'children' => [] }] }
+
+  before { I18n.locale = :ja }
+
+  def native_payload name: '更新', nodes: placements, member_rows: members
+    { name:, description: nil, members: member_rows.map do |member|
+      member.except('version_no')
+    end, placements: nodes }
+  end
+
+  def put_wiki id, title:, body: '- 伊地知ニジカ', base: nil
+    put "/wiki/#{ id }", params: { title:, body:, base_revision_id: base }, headers: headers
+  end
+
+  def expect_no_writes
+    before_state = group_state
+    yield
+    expect(response).to have_http_status(:unprocessable_entity)
+    expect(group_state).to eq(before_state)
+  end
+
+  context 'resource identity' do
+
+    it 'rejects an unprefixed update to an independent group' do
+      id = seed_group(name: '独立', members:, placements:)
+      expect_no_writes { put_wiki(id, title: '独立') }
+    end
+
+
+    it 'renames the group and its facade title through the operation' do
+      page = create_markdown_group('更新', '- 洗澡鹿')
+
+      put_wiki(page.id, title: 'タググループ:改名')
+
+      expect(response).to have_http_status(:ok)
+      expect(TagGroup.find(page.id)).to have_attributes(name: '改名', version_no: 2)
+      expect("タググループ:#{ page.reload.name }").to eq('タググループ:改名')
+      expect(group_markdown(page)).to eq('- 伊地知ニジカ')
+    end
+
+
+
+    it 'keeps a description update separate from a colliding group' do
+      page = seed_description(
+          tag_name: tag.tag_name('ja'), body: 'description before', created_by_user: user)
+      description = TagDescription.find_by!(tag_id: tag.id)
+      id = seed_group(name: '更新', id: description.id, members:, placements:)
+      group_before = TagGroup.find(id).attributes
+
+      put_wiki(id, title: '洗澡鹿', body: 'description after')
+
+      expect(response).to have_http_status(:ok)
+      expect(TagDescription.find(id).body).to eq('description after')
+      expect(page.reload.body).to eq('description after')
+      expect(TagGroup.find(id).attributes).to eq(group_before)
+    end
+
+  end
+
+
+  it 'rolls back a facade create when its saved structure cannot be rendered' do
+    allow(TagGroupMarkdownRenderer).to receive(:render)
+        .and_raise(TagGroupMarkdownRenderer::UnsupportedStructure, 'unsupported')
+    expect_no_writes do
+      post '/wiki', params: { title: 'タググループ:新規', body: '- 洗澡鹿' }, headers: headers
+    end
+  end
+
+  it 'rolls back a facade update when its saved structure cannot be rendered' do
+    id = seed_group(name: '更新', members:, placements:)
+    allow(TagGroupMarkdownRenderer).to receive(:render)
+        .and_raise(TagGroupMarkdownRenderer::UnsupportedStructure, 'unsupported')
+    expect_no_writes { put_wiki(id, title: 'タググループ:改名') }
+  end
+
+  context 'identifier Markdown' do
+    ['[洗澡鹿](https://example.com)', '*洗澡鹿*', '**洗澡鹿**', '`洗澡鹿`',
+     '![洗澡鹿](https://example.com/image.png)',
+     '[タググループ:子](https://example.com)', '*区分*:',
+     '[区分](https://example.com):'].each do |label|
+      [:create, :update].each do |operation|
+        it "rejects decorated #{ label } on #{ operation } without writes" do
+          seed_group(name: '子', description: '子')
+          id = seed_group(name: '更新', members:, placements:)
+          expect_no_writes do
+            if operation == :create
+              post '/wiki', params: { title: 'タググループ:新規', body: "- #{ label }" },
+                   headers: headers
+            else
+              put_wiki(id, title: 'タググループ:更新', body: "- #{ label }")
+            end
+          end
+        end
+      end
+    end
+
+    ['# [区分](https://example.com)', '# *区分*', '# `区分`', '# 区分 {#custom}',
+     '# ![区分](https://example.com/image.png)'].each do |heading|
+      it "rejects a decorated heading #{ heading } without writes" do
+        expect_no_writes do
+          post '/wiki', params: { title: 'タググループ:新規', body: "#{ heading }\n- 洗澡鹿" },
+               headers: headers
+        end
+      end
+    end
+
+    it 'preserves allowed markup in group and heading descriptions' do
+      description = '[参照](https://example.com "リンクの説明") と *強調* と ``a`b``'
+      body = "#{ description }\n\n# 区分\n#{ description }\n\n- 洗澡鹿"
+      post '/wiki', params: { title: 'タググループ:説明構文', body: }, headers: headers
+
+      expect(response).to have_http_status(:created)
+      id = json.fetch('id')
+      version = group_version(id, 1)
+      expect(version.fetch('description')).to eq(description)
+      expect(version.fetch('placements').sole.fetch('description')).to eq(description)
+    end
+  end
+
+  context 'structure audit information' do
+    let!(:child_id) { seed_group(name: '子', description: '子') }
+    let(:members) do
+      [{ 'tag_id' => tag.id, 'version_no' => tag.version_no },
+       { 'tag_group_id' => child_id, 'version_no' => 1 }]
+    end
+    let(:placements) do
+      [{ 'tag_id' => tag.id, 'children' => [
+          { 'tag_group_id' => child_id, 'children' => [] }] }]
+    end
+    let!(:id) { seed_group(name: '更新', members:, placements:) }
+    let!(:editor) { create(:user, :member) }
+    let(:headers) { { 'X-Transfer-Code' => editor.inheritance_code } }
+
+    it 'keeps all membership and placement audit fields on a name-only edit' do
+      before_rows = group_state.slice('tag_group_tags', 'tag_group_groups', 'tag_group_placements')
+      travel_to(1.hour.from_now) do
+        put "/tag_groups/#{ id }", params: native_payload(name: '改名'), headers:, as: :json
+      end
+
+      expect(response).to have_http_status(:ok)
+      expect(group_state.slice(*before_rows.keys)).to eq(before_rows)
+      expect(group_version(id, 2)).to include('name' => '改名', 'members' => members)
+    end
+
+    it 'keeps membership and placement audit fields on a description-only edit' do
+      before_rows = group_state.slice('tag_group_tags', 'tag_group_groups', 'tag_group_placements')
+      travel_to(1.hour.from_now) do
+        put "/tag_groups/#{ id }",
+            params: native_payload.merge(description: '説明を追加'), headers:, as: :json
+      end
+
+      expect(response).to have_http_status(:ok)
+      expect(group_state.slice(*before_rows.keys)).to eq(before_rows)
+      expect(group_version(id, 2)).to include('description' => '説明を追加', 'members' => members)
+    end
+
+    it 'rolls back membership removal and placement edits on a version persistence failure' do
+      new_members = [{ 'tag_id' => tag.id }]
+      new_nodes = [{ 'tag_id' => tag.id, 'children' => [] }]
+      expect_atomic_group_write('tag_group_versions') do
+        put "/tag_groups/#{ id }",
+            params: native_payload(nodes: new_nodes, member_rows: new_members), headers:, as: :json
+      end
+    end
+
+    it 'changes only added or removed membership and keeps placement creation audit' do
+      tag_row = TagGroupTag.find([id, tag.id]).attributes
+      placement_row = TagGroupPlacement.find([id, 1]).attributes
+      new_members = [{ 'tag_id' => tag.id }, { 'tag_id' => other_tag.id }]
+      new_nodes = [{ 'tag_id' => tag.id, 'children' => [
+          { 'tag_id' => other_tag.id, 'children' => [] }] }]
+      child_row = TagGroupPlacement.find([id, 2]).attributes
+      travel_to(1.hour.from_now) do
+        put "/tag_groups/#{ id }",
+            params: native_payload(nodes: new_nodes, member_rows: new_members), headers:, as: :json
+      end
+
+      expect(response).to have_http_status(:ok)
+      expect(TagGroupTag.find([id, tag.id]).attributes).to eq(tag_row)
+      expect(TagGroupGroup.exists?(tag_group_id: id, child_tag_group_id: child_id)).to be(false)
+      expect(TagGroupTag.find([id, other_tag.id]).created_by_user_id).to eq(editor.id)
+      expect(TagGroupPlacement.find([id, 1]).attributes).to eq(placement_row)
+      changed = TagGroupPlacement.find([id, 2])
+      expect(changed).to have_attributes(
+          tag_id: other_tag.id, child_tag_group_id: nil, updated_by_user_id: editor.id,
+          created_at: child_row.fetch('created_at'),
+          created_by_user_id: child_row.fetch('created_by_user_id'))
+      expect(changed.updated_at).to be > child_row.fetch('updated_at')
+      expect(group_version(id, 1).fetch('members')).to eq(members)
+    end
+  end
+end

backend/spec/requests/tag_groups_spec.rb

@@ -0,0 +1,447 @@
+require 'rails_helper'
+
+RSpec.describe 'Tag group native API', type: :request do
+  include TagGroupRecords
+  include ActiveSupport::Testing::TimeHelpers
+
+  let!(:user) { create_member_user! }
+  let!(:group_id) { seed_group(name: '専用API', description: '説明') }
+
+  before { I18n.locale = :ja }
+
+  def expect_native_group value
+    expect(value).to include(
+        'id' => group_id, 'name' => '専用API', 'description' => '説明',
+        'version_no' => 1, 'members' => [], 'placements' => [],
+        'created_by_user' => UserRepr.base(user), 'updated_by_user' => UserRepr.base(user))
+    current = group_rows('tag_groups', id: group_id).sole
+    expect(value).to include(
+        'created_at' => current.fetch('created_at').iso8601(3),
+        'updated_at' => current.fetch('updated_at').iso8601(3))
+  end
+
+  it 'serves the collection as JSON without reading Wiki tables' do
+    without_group_legacy_reads { get '/tag_groups' }
+    expect(response).to have_http_status(:ok)
+    expect(response.media_type).to eq('application/json')
+    expect(json).to be_a(Array)
+    expect_native_group(json.find { _1.fetch('id') == group_id })
+  end
+
+  it 'serves an independent group as JSON without reading Wiki tables' do
+    without_group_legacy_reads { get "/tag_groups/#{ group_id }" }
+    expect(response).to have_http_status(:ok)
+    expect(response.media_type).to eq('application/json')
+    expect_native_group(json)
+  end
+
+  it 'provides the confirmed PUT update route' do
+    route = Rails.application.routes.recognize_path("/tag_groups/#{ group_id }", method: :put)
+    expect(route).to include(action: 'update', id: group_id.to_s)
+  end
+
+  [:create, :update].each do |operation|
+    [nil, :guest, :banned].each do |role|
+      it "rejects #{ role || 'anonymous' } native #{ operation } without writes" do
+        actor = case role
+        when :guest then create(:user, :guest)
+        when :banned then create(:user, :member, :banned)
+        end
+        headers = actor ? { 'X-Transfer-Code' => actor.inheritance_code } : { }
+        before_state = group_state
+        if operation == :create
+          post '/tag_groups', params: { }, headers:, as: :json
+        else
+          put "/tag_groups/#{ group_id }", params: { }, headers:, as: :json
+        end
+        expect(response).to have_http_status(role ? :forbidden : :unauthorized)
+        expect(group_state).to eq(before_state)
+      end
+    end
+
+    it "rejects a banned IP for native #{ operation }" do
+      IpAddress.create!(ip_address: IPAddr.new('127.0.0.1').hton, banned_at: Time.current)
+      headers = { 'X-Transfer-Code' => user.inheritance_code }
+      before_state = group_state
+      if operation == :create
+        post '/tag_groups', params: { }, headers:, as: :json
+      else
+        put "/tag_groups/#{ group_id }", params: { }, headers:, as: :json
+      end
+      expect(response).to have_http_status(:forbidden)
+      expect(group_state).to eq(before_state)
+    end
+  end
+
+  context 'structured membership and placements' do
+    let!(:tag) { group_tag('掲載タグ') }
+    let!(:unplaced) { group_tag('未掲載タグ') }
+    let!(:child_id) { seed_group(name: '子', description: '子の説明') }
+    let(:headers) { { 'X-Transfer-Code' => user.inheritance_code } }
+    let(:members) do
+      [{ 'tag_id' => tag.id }, { 'tag_group_id' => child_id }, { 'tag_id' => unplaced.id }]
+    end
+    let(:snapshot_members) do
+      [{ 'tag_id' => tag.id, 'version_no' => tag.version_no },
+       { 'tag_group_id' => child_id, 'version_no' => 1 },
+       { 'tag_id' => unplaced.id, 'version_no' => unplaced.version_no }]
+    end
+    let(:placements) do
+      [{ 'section_name' => '区分', 'description' => '区分の説明', 'children' => [
+          { 'tag_id' => tag.id, 'children' => [
+              { 'tag_group_id' => child_id, 'children' => [] }] },
+          { 'tag_id' => tag.id, 'children' => [] }] }]
+    end
+    let(:payload) { { name: '構造化', description: '全体の説明', members:, placements: } }
+
+    def native_write operation, attributes = payload
+      if operation == :create
+        post '/tag_groups', params: attributes, headers:, as: :json
+      else
+        put "/tag_groups/#{ group_id }", params: attributes, headers:, as: :json
+      end
+    end
+
+    def expect_structured_response
+      tag_repr = { 'id' => tag.id, 'name' => '掲載タグ', 'category' => tag.category }
+      unplaced_repr = { 'id' => unplaced.id, 'name' => '未掲載タグ',
+                        'category' => unplaced.category }
+      expect(json.fetch('members')).to contain_exactly(
+          include('tag' => include(tag_repr)),
+          include('tag' => include(unplaced_repr)),
+          include('tag_group' => include('id' => child_id, 'name' => '子')))
+      expect(json.fetch('placements')).to match([
+          include('section_name' => '区分', 'description' => '区分の説明', 'children' => [
+              include('tag' => include(tag_repr), 'children' => [
+                  include('tag_group' => include('id' => child_id, 'name' => '子'),
+                          'children' => [])]),
+              include('tag' => include(tag_repr), 'children' => [])])])
+    end
+
+    [:create, :update].each do |operation|
+      it "#{ operation }s structured data and keeps unplaced membership" do
+        previous = group_version(group_id, 1)
+        native_write(operation)
+        expect(response).to have_http_status(operation == :create ? :created : :ok)
+        id = operation == :create ? json.fetch('id') : group_id
+        number = operation == :create ? 1 : 2
+        expect_group_snapshot(
+            id, number:, members: snapshot_members, placements:, description: '全体の説明')
+        expect(group_version(group_id, 1)).to eq(previous)
+        get "/tag_groups/#{ id }"
+        expect(response).to have_http_status(:ok)
+        expect(json).to include(
+            'id' => id, 'name' => '構造化', 'description' => '全体の説明', 'version_no' => number,
+            'created_by_user' => UserRepr.base(user), 'updated_by_user' => UserRepr.base(user))
+        expect_structured_response
+      end
+
+      {
+          'blank name' => { name: '' },
+          'missing name' => { name: nil },
+          'oversized name' => { name: '長' * 256 },
+          'duplicate name' => { name: '子' },
+          'placement without a kind' => { placements: [{ children: [] }] },
+          'empty Section name' => { placements: [{ section_name: '', children: [] }] } }
+          .each do |label, invalid|
+        it "rejects #{ label } on #{ operation } without partial writes" do
+          before_state = group_state
+          native_write(operation, payload.merge(invalid))
+          aggregate_failures do
+            expect(response).to have_http_status(:unprocessable_entity)
+            expect(group_state).to eq(before_state)
+          end
+        end
+      end
+
+      it "rejects multiple placement kinds on #{ operation }" do
+        before_state = group_state
+        invalid = [{ tag_id: tag.id, section_name: '不正', children: [] }]
+        native_write(operation, payload.merge(placements: invalid))
+        expect(response).to have_http_status(:unprocessable_entity)
+        expect(group_state).to eq(before_state)
+      end
+
+      it "rejects a missing referenced Tag on #{ operation }" do
+        missing = Tag.maximum(:id).to_i + 1
+        before_state = group_state
+        native_write(operation, payload.merge(
+            members: [{ tag_id: missing }], placements: [{ tag_id: missing, children: [] }]))
+        expect(response).to have_http_status(:unprocessable_entity)
+        expect(group_state).to eq(before_state)
+      end
+
+      it "rejects a missing referenced group on #{ operation }" do
+        missing = group_rows('tag_groups').map { _1.fetch('id') }.max + 1
+        before_state = group_state
+        native_write(operation, payload.merge(
+            members: [{ tag_group_id: missing }],
+            placements: [{ tag_group_id: missing, children: [] }]))
+        expect(response).to have_http_status(:unprocessable_entity)
+        expect(group_state).to eq(before_state)
+      end
+
+      it "rejects six descendant placement levels on #{ operation }" do
+        nodes = []
+        6.times { nodes = [{ tag_id: tag.id, children: nodes }] }
+        before_state = group_state
+        native_write(operation, payload.merge(placements: nodes))
+        expect(response).to have_http_status(:unprocessable_entity)
+        expect(group_state).to eq(before_state)
+      end
+    end
+
+    it 'preserves membership-only data in structured reads without inventing placements' do
+      id = seed_group(name: '未掲載のみ', members: [snapshot_members.last])
+      without_group_legacy_reads { get "/tag_groups/#{ id }" }
+      expect(response).to have_http_status(:ok)
+      expect(json.fetch('placements')).to eq([])
+      expect(json.fetch('members')).to match([
+          include('tag' => include('id' => unplaced.id, 'name' => '未掲載タグ'))])
+    end
+
+    it 'rejects indirect containment cycles' do
+      parent = seed_group(
+          name: '親', members: [{ 'tag_group_id' => group_id, 'version_no' => 1 }])
+      before_state = group_state
+      native_write(:update, payload.merge(
+          members: [{ tag_group_id: parent }], placements: []))
+      expect(response).to have_http_status(:unprocessable_entity)
+      expect(group_state).to eq(before_state)
+    end
+
+    it 'rejects direct containment even without a corresponding placement' do
+      before_state = group_state
+      native_write(:update, payload.merge(
+          members: [{ tag_group_id: group_id }], placements: []))
+      expect(response).to have_http_status(:unprocessable_entity)
+      expect(group_state).to eq(before_state)
+    end
+
+    it 'preserves list Section descriptions in native structured data' do
+      nodes = [{ tag_id: tag.id, children: [
+          { section_name: 'リスト内区分', description: '消してはいけない説明', children: [] }] }]
+      native_write(:update, payload.merge(placements: nodes))
+      expect(response).to have_http_status(:ok)
+      expect(group_version(group_id, 2).fetch('placements')).to eq(
+          JSON.parse(nodes.to_json))
+      get "/tag_groups/#{ group_id }"
+      expect(response).to have_http_status(:ok)
+      section = json.fetch('placements').sole.fetch('children').sole
+      expect(section).to include(
+          'section_name' => 'リスト内区分', 'description' => '消してはいけない説明')
+    end
+
+    context 'compatibility writes for representable structures' do
+      let(:group_id) do
+        seed_group(name: '専用API', description: '説明')
+      end
+      let(:members) { [{ 'tag_id' => tag.id }, { 'tag_group_id' => child_id }] }
+      let(:snapshot_members) do
+        [{ 'tag_id' => tag.id, 'version_no' => tag.version_no },
+         { 'tag_group_id' => child_id, 'version_no' => 1 }]
+      end
+
+      it 'treats identical native content with unplaced membership as a no-op' do
+        unplaced_payload = payload.merge(
+            name: '専用API', members: members + [{ 'tag_id' => unplaced.id }])
+        native_write(:update, unplaced_payload)
+        expect(response).to have_http_status(:ok)
+        expect_group_snapshot(
+            group_id, number: 2, description: '全体の説明', placements:,
+            members: snapshot_members + [
+                { 'tag_id' => unplaced.id, 'version_no' => unplaced.version_no }])
+
+        travel_to(1.hour.from_now) do
+          expect_noop_group_update(group_id:) do
+            native_write(:update, unplaced_payload)
+          end
+        end
+      end
+
+      context 'no-op updates against synchronised state' do
+        let(:synchronised_payload) do
+          { name: '構造化', description: '全体の説明',
+            members: [{ 'tag_id' => tag.id }, { 'tag_group_id' => child_id }], placements: }
+        end
+        let(:additional_tag) { group_tag('追加対象タグ') }
+
+        before do
+          native_write(:update, synchronised_payload)
+          expect(response).to have_http_status(:ok)
+          expect(group_markdown(TagGroup.find(group_id)))
+              .to include('- 掲載タグ', '- タググループ:子')
+        end
+
+        [1, 3].each do |repetitions|
+          it "keeps identical native content unchanged after #{ repetitions } PUTs" do
+            travel_to(1.hour.from_now) do
+              expect_noop_group_update(group_id:) do
+                repetitions.times do
+                  native_write(:update, synchronised_payload)
+                  expect(response).to have_http_status(:ok)
+                end
+              end
+            end
+          end
+        end
+
+        it 'treats membership order alone as a no-op' do
+          travel_to(1.hour.from_now) do
+            expect_noop_group_update(group_id:) do
+              native_write(:update, synchronised_payload.merge(
+                  members: synchronised_payload.fetch(:members).reverse))
+            end
+          end
+        end
+
+        it 'keeps the original editor when another member submits identical content' do
+          editor = create(:user, :member)
+          travel_to(1.hour.from_now) do
+            expect_noop_group_update(group_id:) do
+              put "/tag_groups/#{ group_id }", params: synchronised_payload,
+                  headers: { 'X-Transfer-Code' => editor.inheritance_code }, as: :json
+            end
+          end
+        end
+
+        it 'does not add history for Native content already changed through Wiki' do
+          put "/wiki/#{ group_id }",
+              params: { title: 'タググループ:構造化', body: '- 未掲載タグ' }, headers: headers
+          expect(response).to have_http_status(:ok)
+          expect(group_markdown(TagGroup.find(group_id))).to eq('- 未掲載タグ')
+          same_content = {
+              name: '構造化', description: nil, members: [{ 'tag_id' => unplaced.id }],
+              placements: [{ 'tag_id' => unplaced.id, 'children' => [] }] }
+          expect_group_snapshot(
+              group_id, number: 3, description: nil,
+              members: [{ 'tag_id' => unplaced.id, 'version_no' => unplaced.version_no }],
+              placements: same_content.fetch(:placements))
+
+          travel_to(1.hour.from_now) do
+            expect_noop_group_update(group_id:) do
+              native_write(:update, same_content)
+            end
+          end
+        end
+
+        ['name', 'description', 'membership addition', 'membership removal',
+         'Section name', 'Section description', 'placement order', 'placement hierarchy']
+            .each do |change|
+          it "records a real #{ change } change in native history" do
+            changed = synchronised_payload.deep_dup
+            section = changed.fetch(:placements).first
+            children = section.fetch('children')
+            case change
+            when 'name' then changed[:name] = '実際の改名'
+            when 'description' then changed[:description] = '実際の説明変更'
+            when 'membership addition'
+              expect(changed.fetch(:members)).not_to include('tag_id' => additional_tag.id)
+              changed[:members] << { 'tag_id' => additional_tag.id }
+              children << { 'tag_id' => additional_tag.id, 'children' => [] }
+            when 'membership removal'
+              changed[:members].reject! { _1.key?('tag_group_id') }
+              children.first['children'] = []
+            when 'Section name' then section['section_name'] = '別区分'
+            when 'Section description' then section['description'] = '別の区分説明'
+            when 'placement order' then children.reverse!
+            when 'placement hierarchy'
+              children << children.first.fetch('children').pop
+            end
+
+            old_versions = group_rows('tag_group_versions', tag_group_id: group_id)
+            group = TagGroup.find(group_id)
+            number = group.version_no
+            travel_to(1.hour.from_now) { native_write(:update, changed) }
+
+            expect(response).to have_http_status(:ok)
+            expected_members = changed.fetch(:members).map do |member|
+              target = if member.key?('tag_id')
+                Tag.find(member.fetch('tag_id'))
+              else
+                TagGroup.find(member.fetch('tag_group_id'))
+              end
+              member.merge('version_no' => target.version_no)
+            end
+            expect_group_snapshot(
+                group_id, number: number + 1, members: expected_members,
+                placements: changed.fetch(:placements), description: changed.fetch(:description))
+            expect(group.reload.name).to eq(changed.fetch(:name))
+            versions = group_rows('tag_group_versions', tag_group_id: group_id)
+            expect(versions.size).to eq(old_versions.size + 1)
+            expect(versions.select { _1.fetch('version_no') <= number }).to eq(old_versions)
+            get group_title_path(changed.fetch(:name))
+            expect(response).to have_http_status(:ok)
+            expect(json.fetch('body')).to eq(group_markdown(group))
+          end
+        end
+      end
+
+      it 'creates native state and its native history' do
+        expect { native_write(:create) }
+            .to change(TagGroup, :count).by(1)
+            .and change(TagGroupVersion, :count).by(1)
+        expect(response).to have_http_status(:created)
+        expect_group_snapshot(
+            json.fetch('id'), number: 1, members: snapshot_members,
+            placements:, description: '全体の説明')
+      end
+
+      [:create, :update].each do |operation|
+        it "synchronises Wiki current state and histories on native #{ operation }" do
+          native_write(operation)
+          expect(response).to have_http_status(operation == :create ? :created : :ok)
+          id = operation == :create ? json.fetch('id') : group_id
+          number = operation == :create ? 1 : 2
+          expect_group_snapshot(
+              id, number:, members: snapshot_members, placements:, description: '全体の説明')
+          expect(TagGroup.find(id).versions.count).to eq(number)
+          get group_title_path('構造化')
+          expect(response).to have_http_status(:ok)
+          expect(json.fetch('body')).to include('全体の説明', '# 区分', '- 掲載タグ')
+        end
+
+        TagGroupRecords::GROUP_TABLES
+            .each do |table|
+          it "rolls back native #{ operation } after #{ table } writes" do
+            expect_atomic_group_write(table) { native_write(operation) }
+          end
+        end
+      end
+
+      it 'assigns the next group ID above the existing maximum' do
+        child_id
+        expected_id = [TagGroup.maximum(:id).to_i, TagDescription.maximum(:id).to_i].max + 1
+        native_write(:create)
+        expect(response).to have_http_status(:created)
+        expect(json.fetch('id')).to be >= expected_id
+      end
+
+      TagGroupRecords::GROUP_TABLES.each do |table|
+        it "rolls back native creation after #{ table } writes" do
+          expect_atomic_group_write(table) { native_write(:create) }
+        end
+      end
+
+      it 'updates a native group through Wiki and then reads structured current data' do
+        native_write(:create)
+        expect(response).to have_http_status(:created)
+        id = json.fetch('id')
+        previous = group_version(id, 1)
+        put "/wiki/#{ id }",
+            params: { title: 'タググループ:構造化', body: '- 未掲載タグ' }, headers: headers
+        expect(response).to have_http_status(:ok)
+        expect_group_snapshot(
+            id, number: 2,
+            members: [{ 'tag_id' => unplaced.id, 'version_no' => unplaced.version_no }],
+            placements: [{ 'tag_id' => unplaced.id, 'children' => [] }])
+        expect(group_version(id, 1)).to eq(previous)
+        get "/tag_groups/#{ id }"
+        expect(response).to have_http_status(:ok)
+        expect(json).to include('version_no' => 2)
+        expect(json.fetch('members')).to match([
+            include('tag' => include('id' => unplaced.id, 'name' => '未掲載タグ'))])
+      end
+    end
+  end
+end

backend/spec/requests/tag_resource_ids_spec.rb

@@ -0,0 +1,61 @@
+require 'rails_helper'
+
+RSpec.describe 'Tag resource ID allocation', type: :request do
+  include WikiRecords
+  let!(:user) { create_member_user! }
+  let(:headers) { { 'X-Transfer-Code' => user.inheritance_code } }
+
+  def create_description name
+    tag = create(:tag, primary_name: name)
+    post '/wiki', params: { title: tag.name('ja'), body: 'description' }, headers: headers
+    expect(response).to have_http_status(:created)
+    TagDescription.find(json.fetch('id'))
+  end
+
+  def create_group name
+    post '/tag_groups', params: { name:, members: [], placements: [] }, headers:, as: :json
+    expect(response).to have_http_status(:created)
+    TagGroup.find(json.fetch('id'))
+  end
+
+  it 'shares resource and revision IDs while keeping independent version numbers' do
+    description = create_description('first')
+    group = create_group('second')
+    other = create_description('third')
+    expect([description.id, group.id, other.id]).to eq(
+        [description.id, group.id, other.id].sort.uniq)
+    versions = [current_description_version(description), group.versions.sole,
+                current_description_version(other)]
+    expect(versions.map(&:id)).to eq(versions.map(&:id).sort.uniq)
+    expect(versions.map(&:version_no)).to eq([1, 1, 1])
+    [description, group, other].zip(versions).each do |resource, version|
+      get "/wiki/#{ resource.id }"
+      expect(response).to have_http_status(:ok)
+      expect(json.fetch('revision_id')).to eq(version.id)
+    end
+  end
+
+  it 'does not reuse a deleted description ID for a group or vice versa' do
+    description = create_description('deleted')
+    description.destroy!
+    group = create_group('deleted group')
+    expect(group.id).to be > description.id
+    group.destroy!
+    expect(create_description('replacement').id).to be > group.id
+  end
+
+  it 'preserves resource and old revision identity on an update' do
+    description = create_description('stable')
+    original_resource_id = description.id
+    original = current_description_version(description)
+    snapshot = original.attributes
+    put "/wiki/#{ description.id }",
+        params: { title: 'stable', body: 'after', base_revision_id: original.id },
+        headers: headers
+    expect(response).to have_http_status(:ok)
+    expect(description.reload.id).to eq(original_resource_id)
+    expect(description.reload).to have_attributes(body: 'after', version_no: 2)
+    expect(original.reload.attributes).to eq(snapshot)
+    expect(current_description_version(description).id).to be > original.id
+  end
+end

backend/spec/requests/tag_versions_spec.rb

@@ -1,6 +1,7 @@
 require 'rails_helper'
 
 RSpec.describe 'TagVersions API', type: :request do
+  include WikiRecords
   let(:member) { create(:user, :member, name: 'version member') }
 
   let!(:tag) { create(:tag, primary_name: 'tag_versions_target', category: :general) }
@@ -240,18 +241,19 @@ RSpec.describe 'TagVersions API', type: :request do
       wiki_tag = create(:tag, primary_tag_name: wiki_tag_name, category: :general)
 
       wiki_page =
-          Wiki::Commit.create_content!(
+          seed_description(
               tag_name: wiki_tag_name,
               body: 'before',
               created_by_user: member,
               message: 'init')
 
-      Wiki::Commit.content!(
+      TagDescriptionOperation.update!(
-          page: wiki_page,
+        Locale.nipponese,
+          tag: wiki_page.tag,
           body: 'after',
-          created_user: member,
+          updated_by_user: member,
           message: 'edit',
-          base_revision_id: wiki_page.current_revision.id)
+          base_revision_id: current_description_version(wiki_page).id)
 
       get '/tags/versions', params: { id: wiki_tag.id }
 

backend/spec/requests/tag_wiki_history_integrity_spec.rb

@@ -1,6 +1,7 @@
 require 'rails_helper'
 
 RSpec.describe 'Tag and wiki history integrity', type: :request do
+  include WikiRecords
   let(:member_user) { create(:user, role: 'member') }
 
   def stub_current_user user
@@ -13,7 +14,7 @@ RSpec.describe 'Tag and wiki history integrity', type: :request do
   end
 
   def create_wiki_for_tag! tag:, body: 'wiki body', user: member_user
-    Wiki::Commit.create_content!(
+    seed_description(
         tag_name: primary_tag_name_for(tag, 'ja'),
         body:,
         created_by_user: user,
@@ -28,7 +29,7 @@ RSpec.describe 'Tag and wiki history integrity', type: :request do
     it 'renames the current Wiki resource without adding body history' do
       tag = create_tag!(name: 'patch_tag_wiki_before')
       wiki_page = create_wiki_for_tag!(tag:, body: 'wiki body before')
-      wiki_history = wiki_page.wiki_versions.map(&:attributes)
+      wiki_history = description_versions(wiki_page).map(&:attributes)
 
       expect {
         patch "/tags/#{ tag.id }", params: {
@@ -36,7 +37,7 @@ RSpec.describe 'Tag and wiki history integrity', type: :request do
         }
       }
           .to change(TagVersion, :count).by(2)
-          .and change(WikiVersion, :count).by(0)
+          .and change(TagDescriptionVersion, :count).by(0)
 
       expect(response).to have_http_status(:ok)
 
@@ -44,16 +45,16 @@ RSpec.describe 'Tag and wiki history integrity', type: :request do
       wiki_page.reload
 
       expect(primary_tag_name_for(tag, 'ja').name).to eq('patch_tag_wiki_after')
-      expect(wiki_page.title).to eq('patch_tag_wiki_after')
+      expect(wiki_page.tag.name('ja')).to eq('patch_tag_wiki_after')
 
-      expect(wiki_page.wiki_versions.reload.map(&:attributes)).to eq(wiki_history)
+      expect(description_versions(wiki_page).reload.map(&:attributes)).to eq(wiki_history)
     end
 
     it 'does not record wiki_version when only category changes' do
       tag = create_tag!(name: 'patch_tag_category_only')
       wiki_page = create_wiki_for_tag!(tag:, body: 'wiki body before')
 
-      before_wiki_versions = wiki_page.wiki_versions.count
+      before_wiki_versions = description_versions(wiki_page).count
 
       expect {
         patch "/tags/#{ tag.id }", params: {
@@ -69,7 +70,7 @@ RSpec.describe 'Tag and wiki history integrity', type: :request do
 
       expect(primary_tag_name_for(tag, 'ja').name).to eq('patch_tag_category_only')
       expect(tag.category).to eq('meme')
-      expect(wiki_page.wiki_versions.count).to eq(before_wiki_versions)
+      expect(description_versions(wiki_page).count).to eq(before_wiki_versions)
     end
   end
 
@@ -77,7 +78,7 @@ RSpec.describe 'Tag and wiki history integrity', type: :request do
     it 'renames the current Wiki resource without adding body history' do
       tag = create_tag!(name: 'put_tag_wiki_before')
       wiki_page = create_wiki_for_tag!(tag:, body: 'wiki body before')
-      wiki_history = wiki_page.wiki_versions.map(&:attributes)
+      wiki_history = description_versions(wiki_page).map(&:attributes)
 
       expect {
         put "/tags/#{ tag.id }", params: {
@@ -89,7 +90,7 @@ RSpec.describe 'Tag and wiki history integrity', type: :request do
         }
       }
           .to change(TagVersion, :count).by(2)
-          .and change(WikiVersion, :count).by(0)
+          .and change(TagDescriptionVersion, :count).by(0)
 
       expect(response).to have_http_status(:ok)
 
@@ -97,16 +98,16 @@ RSpec.describe 'Tag and wiki history integrity', type: :request do
       wiki_page.reload
 
       expect(primary_tag_name_for(tag, 'ja').name).to eq('put_tag_wiki_after')
-      expect(wiki_page.title).to eq('put_tag_wiki_after')
+      expect(wiki_page.tag.name('ja')).to eq('put_tag_wiki_after')
 
-      expect(wiki_page.wiki_versions.reload.map(&:attributes)).to eq(wiki_history)
+      expect(description_versions(wiki_page).reload.map(&:attributes)).to eq(wiki_history)
     end
 
     it 'does not record wiki_version when only category changes' do
       tag = create_tag!(name: 'put_tag_category_only')
       wiki_page = create_wiki_for_tag!(tag:, body: 'wiki body before')
 
-      before_wiki_versions = wiki_page.wiki_versions.count
+      before_wiki_versions = description_versions(wiki_page).count
 
       expect {
         put "/tags/#{ tag.id }", params: {
@@ -126,14 +127,14 @@ RSpec.describe 'Tag and wiki history integrity', type: :request do
 
       expect(primary_tag_name_for(tag, 'ja').name).to eq('put_tag_category_only')
       expect(tag.category).to eq('meme')
-      expect(wiki_page.wiki_versions.count).to eq(before_wiki_versions)
+      expect(description_versions(wiki_page).count).to eq(before_wiki_versions)
     end
 
     it 'does not record wiki_version when only aliases change' do
       tag = create_tag!(name: 'put_tag_alias_only')
       wiki_page = create_wiki_for_tag!(tag:, body: 'wiki body before')
 
-      before_wiki_versions = wiki_page.wiki_versions.count
+      before_wiki_versions = description_versions(wiki_page).count
 
       expect {
         put "/tags/#{ tag.id }", params: {
@@ -147,7 +148,7 @@ RSpec.describe 'Tag and wiki history integrity', type: :request do
           .to change(TagVersion, :count).by(2)
 
       expect(response).to have_http_status(:ok)
-      expect(wiki_page.reload.wiki_versions.count).to eq(before_wiki_versions)
+      expect(description_versions(wiki_page).count).to eq(before_wiki_versions)
     end
   end
 end

backend/spec/requests/tags_spec.rb

@@ -2,6 +2,7 @@ require 'cgi'
 require 'rails_helper'
 
 RSpec.describe 'Tags API', type: :request do
+  include WikiRecords
   let!(:tn) { create(:tag_name, name: 'spec_tag') }
   let!(:tag) { create(:tag, primary_tag_name: tn, category: :general) }
   let!(:alias_tn) { create(:tag_name, :alias, name: 'unko', tag:) }
@@ -38,6 +39,22 @@ RSpec.describe 'Tags API', type: :request do
   end
 
   describe 'GET /tags' do
+    it 'serialises descriptions and parents without loading legacy Wiki pages' do
+      TagDescription.create!(tag:, language_code: 'ja', body: '', version_no: 1)
+      TagDescription.create!(tag: tag2, language_code: 'ja', body: '', version_no: 1)
+      TagImplication.create!(tag:, parent_tag: tag2)
+      queries = []
+      subscriber = ->(*args) { queries << args.last.fetch(:sql) }
+      ActiveSupport::Notifications.subscribed(subscriber, 'sql.active_record') do
+        get '/tags', params: { name: 'spec_tag' }
+      end
+      expect(response).to have_http_status(:ok)
+      row = response_tags.sole
+      expect(row.fetch('has_wiki')).to be(true)
+      expect(row.fetch('parents').sole.fetch('has_wiki')).to be(true)
+      expect(queries.grep(/\bSELECT\b.*\bwiki_(pages|revisions|versions)\b/im)).to be_empty
+    end
+
     it 'includes legacy external JSON alongside an internal tag with the same id' do
       external = create(:external_tag, id: tag.id, name: 'spec_external', post_count: 3)
 
@@ -729,13 +746,13 @@ RSpec.describe 'Tags API', type: :request do
 
       it 'PATCH の名称変更で Wiki の本文履歴を追加しない' do
         wiki_page =
-            Wiki::Commit.create_content!(
+            seed_description(
                 tag_name: primary_tag_name_for(tag, 'ja'),
                 body: 'wiki body before',
                 created_by_user: member_user,
                 message: 'init')
 
-        wiki_history = wiki_page.wiki_versions.map(&:attributes)
+        wiki_history = description_versions(wiki_page).map(&:attributes)
 
         expect {
           patch "/tags/#{ tag.id }", params: {
@@ -743,23 +760,23 @@ RSpec.describe 'Tags API', type: :request do
           }
         }
             .to change(TagVersion, :count).by(2)
-            .and change(WikiVersion, :count).by(0)
+            .and change(TagDescriptionVersion, :count).by(0)
 
         expect(response).to have_http_status(:ok)
 
-        expect(wiki_page.reload.title).to eq('patch_wiki_renamed_tag')
+        expect(wiki_page.reload.tag.name('ja')).to eq('patch_wiki_renamed_tag')
-        expect(wiki_page.wiki_versions.reload.map(&:attributes)).to eq(wiki_history)
+        expect(description_versions(wiki_page).reload.map(&:attributes)).to eq(wiki_history)
       end
 
       it 'tag の category だけを変更しても wiki version は作成しない' do
         wiki_page =
-            Wiki::Commit.create_content!(
+            seed_description(
                 tag_name: primary_tag_name_for(tag, 'ja'),
                 body: 'wiki body before',
                 created_by_user: member_user,
                 message: 'init')
 
-        before_wiki_version_count = wiki_page.reload.wiki_versions.count
+        before_wiki_version_count = description_versions(wiki_page).count
 
         expect {
           patch "/tags/#{ tag.id }", params: {
@@ -768,7 +785,7 @@ RSpec.describe 'Tags API', type: :request do
         }.to change(TagVersion, :count).by(2)
 
         expect(response).to have_http_status(:ok)
-        expect(wiki_page.reload.wiki_versions.count).to eq(before_wiki_version_count)
+        expect(description_versions(wiki_page).count).to eq(before_wiki_version_count)
       end
 
       it 'full update で旧名 alias が残った tag を PATCH で旧名へ戻せる' do
@@ -799,7 +816,7 @@ RSpec.describe 'Tags API', type: :request do
 
       it '別 tag の正規名には変更できない' do
         wiki_page =
-            Wiki::Commit.create_content!(
+            seed_description(
                 tag_name: primary_tag_name_for(tag, 'ja'),
                 body: 'patch collision wiki',
                 created_by_user: member_user,
@@ -815,7 +832,7 @@ RSpec.describe 'Tags API', type: :request do
         expect(primary_tag_name_for(tag.reload, 'ja').name).to eq('spec_tag')
         expect(TagName.where(tag_id: tag.id, language_code: 'ja', primary_flg: false).pluck(:name))
             .to contain_exactly('unko')
-        expect(wiki_page.reload.tag_name).to eq(primary_tag_name_for(tag, 'ja'))
+        expect(wiki_page.reload.tag.tag_name('ja')).to eq(primary_tag_name_for(tag, 'ja'))
       end
 
       it 'system tag の name は変更できない' do
@@ -1193,7 +1210,7 @@ RSpec.describe 'Tags API', type: :request do
         expect(old_name_alias).to have_attributes(
             tag_id: tag.id, language_code: 'ja', primary_flg: false)
 
-        expect(alias_tn.reload.tag_id).to be_nil
+        expect(TagName.exists?(alias_tn.id)).to be(false)
 
         expect(TagName.where(tag_id: tag.parents.select(:id),
                              language_code: 'ja', primary_flg: true).pluck(:name))
@@ -1378,20 +1395,17 @@ RSpec.describe 'Tags API', type: :request do
 
       it 'Wiki を持つ Tag の名称変更で本文履歴を追加しない' do
         wiki_page =
-            Wiki::Commit.create_content!(
+            seed_description(
                 tag_name: primary_tag_name_for(tag, 'ja'),
                 body: 'wiki body before',
                 created_by_user: member_user,
                 message: 'init')
 
-        Wiki::Commit.content!(
+        TagDescriptionOperation.update!(
-          page: wiki_page,
+            Locale.nipponese, tag: wiki_page.tag, body: 'wiki body before',
-          body: 'wiki body before',
+            updated_by_user: member_user, message: 'init')
-          created_user: member_user,
-          message: 'init'
-        )
 
-        wiki_history = wiki_page.wiki_versions.map(&:attributes)
+        wiki_history = description_versions(wiki_page).map(&:attributes)
 
         expect {
           put "/tags/#{ tag.id }", params: {
@@ -1403,22 +1417,22 @@ RSpec.describe 'Tags API', type: :request do
           }
         }
             .to change(TagVersion, :count).by(2)
-            .and change(WikiVersion, :count).by(0)
+            .and change(TagDescriptionVersion, :count).by(0)
 
         expect(response).to have_http_status(:ok)
 
-        expect(wiki_page.reload.title).to eq('put_wiki_version_tag')
+        expect(wiki_page.reload.tag.name('ja')).to eq('put_wiki_version_tag')
-        expect(wiki_page.wiki_versions.reload.map(&:attributes)).to eq(wiki_history)
+        expect(description_versions(wiki_page).reload.map(&:attributes)).to eq(wiki_history)
       end
 
       it 'wiki を持つ tag を旧 alias へ戻しても wiki を新しい正本名へ移す' do
         wiki_page =
-            Wiki::Commit.create_content!(
+            seed_description(
                 tag_name: primary_tag_name_for(tag, 'ja'),
                 body: 'wiki body before',
                 created_by_user: member_user,
                 message: 'init')
-        wiki_history = wiki_page.wiki_versions.map(&:attributes)
+        wiki_history = description_versions(wiki_page).map(&:attributes)
 
         expect {
           put "/tags/#{ tag.id }", params: {
@@ -1438,20 +1452,19 @@ RSpec.describe 'Tags API', type: :request do
           }
         }
             .to change(TagVersion, :count).by(3)
-            .and change(WikiVersion, :count).by(0)
+            .and change(TagDescriptionVersion, :count).by(0)
 
         expect(response).to have_http_status(:ok)
 
         tag.reload
 
-        expect(wiki_page.reload.tag_name).to eq(primary_tag_name_for(tag, 'ja'))
+        expect(wiki_page.reload.tag.tag_name('ja')).to eq(primary_tag_name_for(tag, 'ja'))
-        expect(TagName.find_by!(language_code: 'ja', name: 'put_wiki_roundtrip_b').wiki_page)
+        expect(wiki_page.reload.tag_id).to eq(tag.id)
-            .to be_nil
         expect(TagName.find_by!(language_code: 'ja', name: 'put_wiki_roundtrip_b'))
             .to have_attributes(tag_id: tag.id, primary_flg: false)
 
-        expect(wiki_page.title).to eq('spec_tag')
+        expect(wiki_page.tag.name('ja')).to eq('spec_tag')
-        expect(wiki_page.wiki_versions.reload.map(&:attributes)).to eq(wiki_history)
+        expect(description_versions(wiki_page).reload.map(&:attributes)).to eq(wiki_history)
       end
 
       it '別名を他 tag から奪った場合、奪はれた側の tag version も作成する' do
@@ -1504,7 +1517,7 @@ RSpec.describe 'Tags API', type: :request do
             name: 'put_alias_collision_name',
             tag: old_owner)
         wiki_page =
-            Wiki::Commit.create_content!(
+            seed_description(
                 tag_name: primary_tag_name_for(tag, 'ja'),
                 body: 'put collision wiki',
                 created_by_user: member_user,
@@ -1538,7 +1551,7 @@ RSpec.describe 'Tags API', type: :request do
         expect(old_owner_versions.last.event_type).to eq('update')
         expect(version_alias_names(old_owner_versions.last, 'ja'))
             .not_to include('put_alias_collision_name')
-        expect(wiki_page.reload.tag_name).to eq(primary_tag_name_for(tag, 'ja'))
+        expect(wiki_page.reload.tag.tag_name('ja')).to eq(primary_tag_name_for(tag, 'ja'))
       end
 
       it 'parent_tags に指定すると循環する tag は 422 にする' do
@@ -1563,13 +1576,13 @@ RSpec.describe 'Tags API', type: :request do
 
       it 'Tag の名称変更で Wiki の本文履歴を追加しない' do
         wiki_page =
-            Wiki::Commit.create_content!(
+            seed_description(
                 tag_name: primary_tag_name_for(tag, 'ja'),
                 body: 'wiki body before',
                 created_by_user: member_user,
                 message: 'init')
 
-        wiki_history = wiki_page.wiki_versions.map(&:attributes)
+        wiki_history = description_versions(wiki_page).map(&:attributes)
 
         expect {
           put "/tags/#{ tag.id }", params: {
@@ -1581,12 +1594,12 @@ RSpec.describe 'Tags API', type: :request do
           }
         }
             .to change(TagVersion, :count).by(2)
-            .and change(WikiVersion, :count).by(0)
+            .and change(TagDescriptionVersion, :count).by(0)
 
         expect(response).to have_http_status(:ok)
 
-        expect(wiki_page.reload.title).to eq('put_wiki_renamed_tag')
+        expect(wiki_page.reload.tag.name('ja')).to eq('put_wiki_renamed_tag')
-        expect(wiki_page.wiki_versions.reload.map(&:attributes)).to eq(wiki_history)
+        expect(description_versions(wiki_page).reload.map(&:attributes)).to eq(wiki_history)
       end
     end
   end

backend/spec/requests/wiki_conflict_spec.rb

@@ -1,6 +1,7 @@
 require 'rails_helper'
 
 RSpec.describe 'Wiki conflict handling', type: :request do
+  include WikiRecords
   let!(:user) { create_member_user! }
 
   def auth_headers user
@@ -9,34 +10,33 @@ RSpec.describe 'Wiki conflict handling', type: :request do
 
   it 'returns 409 when base_revision_id is stale' do
     page =
-        Wiki::Commit.create_content!(
+        seed_description(
-            tag_name: create(:tag_name, name: 'wiki_conflict_request'),
+            tag_name: create(:tag, primary_name: 'wiki_conflict_request').tag_name('ja'),
             body: 'first',
             created_by_user: user,
             message: 'init')
 
-    stale_id = page.current_revision.id
+    stale_id = current_description_version(page).id
 
-    Wiki::Commit.content!(
+    TagDescriptionOperation.update!(
-        page:,
+        Locale.nipponese,
+        tag: page.tag,
         body: 'second',
-        created_user: user,
+        updated_by_user: user,
         message: 'other edit',
         base_revision_id: stale_id)
 
     put "/wiki/#{ page.id }",
-        params: {
+        params: { title: 'wiki_conflict_request',
-          title: 'wiki_conflict_request',
+                  body: 'third',
-          body: 'third',
+                  message: 'stale',
-          message: 'stale',
+                  base_revision_id: stale_id },
-          base_revision_id: stale_id,
-        },
         headers: auth_headers(user)
 
     expect(response).to have_http_status(:conflict)
 
     page.reload
     expect(page.body).to eq('second')
-    expect(page.current_revision.message).to eq('other edit')
+    expect(current_description_version(page)).to have_attributes(body: 'second', version_no: 2)
   end
 end

backend/spec/requests/wiki_creation_freeze_spec.rb

@@ -0,0 +1,47 @@
+require 'rails_helper'
+
+RSpec.describe 'Wiki creation freeze', type: :request do
+  include TagGroupRecords
+  include WikiRecords
+
+  let!(:user) { create_member_user! }
+  let(:headers) { { 'X-Transfer-Code' => user.inheritance_code } }
+
+
+  context 'existing description write protection' do
+    let!(:tag) { create(:tag, primary_name: 'protected_description') }
+    let!(:page) do
+      seed_description(tag_name: tag.tag_name('ja'), body: 'before', created_by_user: user)
+    end
+
+    [nil, :guest, :banned].each do |role|
+      it "rejects #{ role || 'anonymous' } without changing either history" do
+        actor = role && create(:user, role == :banned ? :member : role)
+        actor.update!(banned_at: Time.current) if role == :banned
+        request_headers = actor ? { 'X-Transfer-Code' => actor.inheritance_code } : { }
+        before_state = group_state
+        put "/wiki/#{ page.id }", params: { title: tag.name('ja'), body: 'after' },
+            headers: request_headers
+        expect(response).to have_http_status(role ? :forbidden : :unauthorized)
+        expect(group_state).to eq(before_state)
+      end
+    end
+
+    it 'rejects banned IPs without writes' do
+      IpAddress.create!(ip_address: IPAddr.new('127.0.0.1').hton, banned_at: Time.current)
+      before_state = group_state
+      put "/wiki/#{ page.id }", params: { title: tag.name('ja'), body: 'after' }, headers: headers
+      expect(response).to have_http_status(:forbidden)
+      expect(group_state).to eq(before_state)
+    end
+
+    ['', "\r\n\r\n"].each do |body|
+      it "rejects invalid description body #{ body.inspect } atomically" do
+        before_state = group_state
+        put "/wiki/#{ page.id }", params: { title: tag.name('ja'), body: }, headers: headers
+        expect(response).to have_http_status(:unprocessable_entity)
+        expect(group_state).to eq(before_state)
+      end
+    end
+  end
+end

backend/spec/requests/wiki_history_integrity_spec.rb

@@ -1,198 +0,0 @@
-require 'cgi'
-require 'rails_helper'
-
-RSpec.describe 'Wiki history integrity', type: :request do
-  let!(:user) { create_member_user! }
-
-  def auth_headers user
-    { 'X-Transfer-Code' => user.inheritance_code }
-  end
-
-  def create_wiki_page title:, body: 'body', message: 'init', user: self.user
-    Wiki::Commit.create_content!(
-        tag_name: create(:tag_name, name: title),
-        body:,
-        created_by_user: user,
-        message:)
-  end
-
-  describe 'POST /wiki' do
-    it 'creates wiki_page, wiki_revision, and wiki_version atomically' do
-      expect {
-        post '/wiki',
-             params: {
-               title: 'Help:wiki_history_create_atomic',
-               body: "a\nb\nc",
-               message: 'initial commit',
-             },
-             headers: auth_headers(user)
-      }
-          .to change(WikiPage, :count).by(1)
-          .and change(WikiRevision, :count).by(1)
-          .and change(WikiVersion, :count).by(1)
-
-      expect(response).to have_http_status(:created)
-
-      page = WikiPage.find(json.fetch('id'))
-      revision = page.current_revision
-      version = page.wiki_versions.order(:version_no).last
-
-      expect(page.title).to eq('Help:wiki_history_create_atomic')
-      expect(page.body).to eq("a\nb\nc")
-
-      expect(revision).to be_content
-      expect(revision.message).to eq('initial commit')
-      expect(revision.lines_count).to eq(3)
-
-      expect(version).to have_attributes(
-        version_no: 1,
-        event_type: 'create',
-        title: 'Help:wiki_history_create_atomic',
-        body: "a\nb\nc",
-        reason: 'initial commit',
-        created_by_user_id: user.id
-      )
-    end
-
-    it 'returns 422 and creates nothing when normalised body is blank' do
-      expect {
-        post '/wiki',
-             params: {
-               title: 'Help:wiki_history_blank_body',
-               body: "\r\n\r\n",
-               message: 'blank',
-             },
-             headers: auth_headers(user)
-      }
-          .not_to change(WikiPage, :count)
-
-      expect(response).to have_http_status(:unprocessable_entity)
-      expect(WikiPage.joins(:tag_name)
-          .where(tag_names: { name: 'Help:wiki_history_blank_body' })).not_to exist
-    end
-
-    it 'returns 422 and creates no partial page when title already exists' do
-      create_wiki_page(title: 'Help:wiki_history_duplicate_title', body: 'first')
-
-      expect {
-        post '/wiki',
-             params: {
-               title: 'Help:wiki_history_duplicate_title',
-               body: 'second',
-               message: 'duplicate',
-             },
-             headers: auth_headers(user)
-      }
-          .not_to change(WikiPage, :count)
-
-      expect(response).to have_http_status(:unprocessable_entity)
-      expect(WikiPage.joins(:tag_name)
-          .where(tag_names: { name: 'Help:wiki_history_duplicate_title' }).count).to eq(1)
-    end
-  end
-
-  describe 'PUT /wiki/:id' do
-    it 'updates body and records wiki_revision and wiki_version' do
-      page = create_wiki_page(title: 'wiki_history_update_body', body: 'before')
-      current_id = page.current_revision.id
-
-      expect {
-        put "/wiki/#{ page.id }",
-            params: {
-              title: 'wiki_history_update_body',
-              body: 'after',
-              message: 'edit body',
-              base_revision_id: current_id,
-            },
-            headers: auth_headers(user)
-      }
-          .to change(WikiRevision, :count).by(1)
-          .and change(WikiVersion, :count).by(1)
-
-      expect(response).to have_http_status(:ok)
-
-      page.reload
-      version = page.wiki_versions.order(:version_no).last
-
-      expect(page.title).to eq('wiki_history_update_body')
-      expect(page.body).to eq('after')
-
-      expect(version).to have_attributes(
-        event_type: 'update',
-        title: 'wiki_history_update_body',
-        body: 'after',
-        reason: 'edit body',
-        created_by_user_id: user.id
-      )
-    end
-
-    it 'renames title and records wiki_version with new title' do
-      page = create_wiki_page(title: 'wiki_history_rename_before', body: 'before')
-      current_id = page.current_revision.id
-
-      expect {
-        put "/wiki/#{ page.id }",
-            params: {
-              title: 'wiki_history_rename_after',
-              body: 'after',
-              message: 'rename',
-              base_revision_id: current_id,
-            },
-            headers: auth_headers(user)
-      }
-          .to change(WikiRevision, :count).by(1)
-          .and change(WikiVersion, :count).by(1)
-
-      expect(response).to have_http_status(:ok)
-
-      page.reload
-      version = page.wiki_versions.order(:version_no).last
-
-      expect(page.title).to eq('wiki_history_rename_after')
-      expect(page.body).to eq('after')
-
-      expect(version).to have_attributes(
-        event_type: 'update',
-        title: 'wiki_history_rename_after',
-        body: 'after',
-        reason: 'rename',
-        created_by_user_id: user.id
-      )
-    end
-
-    it 'does not change title, body, revision, or version on stale base_revision_id' do
-      page = create_wiki_page(title: 'wiki_history_conflict_page', body: 'first')
-      stale_id = page.current_revision.id
-
-      Wiki::Commit.content!(
-          page:,
-          body: 'second',
-          created_user: user,
-          message: 'other edit',
-          base_revision_id: stale_id)
-
-      page.reload
-      current_title = page.title
-      current_body = page.body
-      revision_count = page.wiki_revisions.count
-      version_count = page.wiki_versions.count
-
-      put "/wiki/#{ page.id }",
-          params: {
-            title: 'wiki_history_conflict_renamed',
-            body: 'third',
-            message: 'stale edit',
-            base_revision_id: stale_id,
-          },
-          headers: auth_headers(user)
-
-      expect(response).to have_http_status(:conflict)
-
-      page.reload
-      expect(page.title).to eq(current_title)
-      expect(page.body).to eq(current_body)
-      expect(page.wiki_revisions.count).to eq(revision_count)
-      expect(page.wiki_versions.count).to eq(version_count)
-    end
-  end
-end

backend/spec/requests/wiki_index_order_spec.rb

@@ -0,0 +1,42 @@
+require 'rails_helper'
+
+RSpec.describe 'Wiki resource ordering', type: :request do
+  include TagGroupRecords
+  let(:user) { create_member_user! }
+
+  it 'selects the latest twenty across both resources before applying the global limit' do
+    start = Time.utc(2026, 1, 1)
+    descriptions = 24.times.map do |index|
+      tag = create(:tag, primary_name: "rank_#{ index }")
+      TagDescription.create!(tag:, language_code: 'ja', body: 'current', version_no: 1,
+                             updated_at: start + index.hours)
+    end
+    groups = [24, 25].map do |hour|
+      group = TagGroup.find(seed_group(name: "rank_group_#{ hour }"))
+      group.update_columns(updated_at: start + hour.hours)
+      group
+    end
+
+    get '/wiki', params: { title: 'rank' }
+
+    expect(response).to have_http_status(:ok)
+    expected = groups.reverse.map { ['tag_group', _1.id] } +
+        descriptions.last(18).reverse.map { ['tag_description', _1.id] }
+    expect(json.map { [_1.fetch('resource_type'), _1.fetch('id')] }).to eq(expected)
+  end
+
+  it 'breaks timestamp ties by resource kind and ID while retaining legacy overlaps' do
+    time = Time.utc(2026, 1, 1)
+    tag = create(:tag, primary_name: 'tied')
+    description = TagDescription.create!(tag:, language_code: 'ja', body: 'current',
+                           version_no: 1, updated_at: time)
+    group = TagGroup.find(seed_group(name: 'tied', id: description.id))
+    group.update_columns(updated_at: time)
+
+    2.times do
+      get '/wiki', params: { title: 'tied' }
+      expect(json.map { [_1.fetch('resource_type'), _1.fetch('id')] })
+          .to eq([['tag_description', description.id], ['tag_group', description.id]])
+    end
+  end
+end

backend/spec/requests/wiki_locale_spec.rb

@@ -0,0 +1,158 @@
+require 'rails_helper'
+
+RSpec.describe 'Wiki and native API locale contracts', type: :request do
+  include WikiRecords
+  include TagGroupRecords
+  include_context 'Ainu locale contract'
+
+  let!(:user) { create_member_user! }
+  let!(:tag) { create(:tag, primary_name: 'japanese_title') }
+  let!(:ainu_name) { add_ainu_name(tag, 'ainu_title') }
+  let(:headers) { { 'X-Transfer-Code' => user.inheritance_code } }
+  let!(:japanese) do
+    TagDescriptionOperation.create!(
+        Locale.nipponese, tag:, body: 'Japanese body', created_by_user: user)
+  end
+  let!(:ainu) do
+    TagDescriptionOperation.create!(
+        ainu_locale, tag:, body: 'Ainu body', created_by_user: user)
+  end
+
+  ['/wiki', '/wiki/search'].each do |path|
+    it "filters #{ path } by the selected language" do
+      get path, params: { locale: 'ain' }
+      expect(response).to have_http_status(:ok)
+      expect(json.map { _1.fetch('id') }).to eq([ainu.id])
+      expect(json.sole).to include('title' => 'ainu_title', 'body' => 'Ainu body')
+
+      get path, params: { locale: 'ain', title: 'japanese' }
+      expect(response).to have_http_status(:ok)
+      expect(json).to eq([])
+    end
+  end
+
+  it 'uses the existing default locale when no locale is specified' do
+    get '/wiki'
+    expect(response).to have_http_status(:ok)
+    expect(json.map { _1.fetch('id') }).to eq([japanese.id])
+  end
+
+  it 'resolves titles and aliases only in the selected language in both APIs' do
+    ['/wiki/title/japanese_title', '/tags/name/japanese_title/description'].each do |path|
+      get path, params: { locale: 'ain' }
+      expect(response).to have_http_status(:not_found)
+    end
+    ['/wiki/title/ainu_title', '/tags/name/ainu_title/description'].each do |path|
+      get path, params: { locale: 'ain' }
+      expect(response).to have_http_status(:ok)
+      expect(json.fetch('body')).to eq('Ainu body')
+    end
+    get '/wiki/title/ainu_title/exists', params: { locale: 'ain' }
+    expect(response).to have_http_status(:no_content)
+    get '/wiki/title/japanese_title/exists', params: { locale: 'ain' }
+    expect(response).to have_http_status(:not_found)
+  end
+
+  it 'does not disclose another language through ID, existence, diff or history' do
+    revision = current_description_version(japanese)
+    ["/wiki/#{ japanese.id }", "/wiki/#{ japanese.id }/exists",
+     "/wiki/#{ japanese.id }/diff"].each do |path|
+      get path, params: { locale: 'ain', from: revision.id }
+      expect(response).to have_http_status(:not_found)
+      expect(response.body).not_to include('Japanese body')
+    end
+    get '/wiki/changes', params: { locale: 'ain', id: japanese.id }
+    expect(response).to have_http_status(:ok)
+    expect(json).to eq([])
+    get '/wiki/changes', params: { locale: 'ain' }
+    expect(json.map { _1.fetch('revision_id') })
+        .to eq([current_description_version(ainu).id])
+  end
+
+  it 'does not update a description addressed through another language ID' do
+    snapshot = [japanese.attributes, ainu.attributes, ainu_name.attributes]
+    expect do
+      put "/wiki/#{ japanese.id }", params: {
+          locale: 'ain', title: 'renamed', body: 'wrong target' }, headers: headers
+    end.not_to change(TagDescriptionVersion, :count)
+    expect(response).to have_http_status(:not_found)
+    expect([japanese.reload.attributes, ainu.reload.attributes, ainu_name.reload.attributes])
+        .to eq(snapshot)
+  end
+
+  [:wiki, :native].each do |api|
+    it "creates the selected language through #{ api } without changing Japanese history" do
+      other = create(:tag, primary_name: 'other_japanese')
+      add_ainu_name(other, 'other_ainu')
+      original = TagDescriptionOperation.create!(
+          Locale.nipponese, tag: other, body: 'original', created_by_user: user)
+      snapshot = original.attributes
+      expect do
+        if api == :wiki
+          post '/wiki', params: { locale: 'ain', title: 'other_ainu', body: 'created' },
+               headers: headers
+        else
+          put "/tags/#{ other.id }/description", params: { locale: 'ain', body: 'created' },
+              headers: headers
+        end
+      end.to change(TagDescription, :count).by(1)
+          .and change(TagDescriptionVersion, :count).by(1)
+      expect(response).to have_http_status(:created)
+      created = TagDescription.find_by!(tag: other, language_code: 'ain')
+      expect(created).to have_attributes(body: 'created', version_no: 1)
+      expect(current_description_version(created)).to have_attributes(language_code: 'ain')
+      expect(original.reload.attributes).to eq(snapshot)
+    end
+  end
+
+  it 'shares selected-language edits and revision identity across both APIs' do
+    snapshot = japanese.attributes
+    first = current_description_version(ainu)
+    put "/tags/#{ tag.id }/description", params: { locale: 'ain', body: 'native edit' },
+        headers: headers
+    expect(response).to have_http_status(:ok)
+    second = current_description_version(ainu)
+    expect(second).to have_attributes(language_code: 'ain', version_no: 2)
+    expect(second.id).not_to eq(first.id)
+    get "/wiki/#{ ainu.id }", params: { locale: 'ain' }
+    expect(json).to include('body' => 'native edit', 'revision_id' => second.id)
+
+    put "/wiki/#{ ainu.id }", params: {
+        locale: 'ain', title: 'ainu_title', body: 'facade edit',
+        base_revision_id: second.id }, headers: headers
+    expect(response).to have_http_status(:ok)
+    get "/tags/#{ tag.id }/description", params: { locale: 'ain' }
+    expect(json).to include('body' => 'facade edit', 'language_code' => 'ain', 'version_no' => 3)
+    expect(japanese.reload.attributes).to eq(snapshot)
+  end
+
+  it 'rejects a stale selected-language revision without a partial title or body edit' do
+    stale = current_description_version(ainu)
+    TagDescriptionOperation.update!(
+        ainu_locale, tag:, body: 'current', updated_by_user: user)
+    snapshot = [ainu.reload.attributes, ainu_name.attributes, japanese.attributes]
+    expect do
+      put "/wiki/#{ ainu.id }", params: {
+          locale: 'ain', title: 'conflicting_name', body: 'current',
+          base_revision_id: stale.id }, headers: headers
+    end.to change(TagDescriptionVersion, :count).by(0).and change(TagVersion, :count).by(0)
+    expect(response).to have_http_status(:conflict)
+    expect([ainu.reload.attributes, ainu_name.reload.attributes, japanese.reload.attributes])
+        .to eq(snapshot)
+  end
+
+  it 'scopes historical show and diff to the selected description' do
+    first = current_description_version(ainu)
+    TagDescriptionOperation.update!(
+        ainu_locale, tag:, body: 'later', updated_by_user: user)
+    get "/wiki/#{ ainu.id }", params: { locale: 'ain', version: first.id }
+    expect(response).to have_http_status(:ok)
+    expect(json).to include('body' => 'Ainu body', 'revision_id' => first.id)
+    get "/wiki/#{ ainu.id }/diff", params: { locale: 'ain', from: first.id }
+    expect(response).to have_http_status(:ok)
+    expect(json.fetch('newer_revision_id')).to eq(current_description_version(ainu).id)
+    get "/wiki/#{ ainu.id }/diff", params: {
+        locale: 'ain', from: current_description_version(japanese).id }
+    expect(response).to have_http_status(:not_found)
+  end
+end

backend/spec/requests/wiki_spec.rb

@@ -4,6 +4,7 @@ require 'securerandom'
 
 
 RSpec.describe 'Wiki API', type: :request do
+  include WikiRecords
   def auth_headers(user)
     { 'X-Transfer-Code' => user.inheritance_code }
   end
@@ -18,7 +19,7 @@ RSpec.describe 'Wiki API', type: :request do
         deprecated_at: Time.zone.local(2026, 6, 1))
   end
   let!(:page) do
-    Wiki::Commit.create_content!(
+    seed_description(
         tag_name: tn,
         body: 'init',
         created_by_user: user,
@@ -108,94 +109,14 @@ RSpec.describe 'Wiki API', type: :request do
       end
     end
 
-    context 'when success' do
+    ['Help:TestPage', 'ヘルプ:ホーム'].each do |title|
-      it 'creates wiki_page and first content revision' do
+      it "rejects frozen creation of #{ title } without history writes" do
         expect do
-          post endpoint, params: { title: 'Help:TestPage', body: "a\nb\nc", message: 'init' },
+          post endpoint, params: { title:, body: 'initial' }, headers: auth_headers(member)
-                         headers: auth_headers(member)
+        end.to change(TagDescription, :count).by(0)
-        end
+            .and change(TagDescriptionVersion, :count).by(0)
-            .to change(WikiPage, :count).by(1)
-            .and change(WikiRevision, :count).by(1)
-            .and change(WikiVersion, :count).by(1)
 
-        expect(response).to have_http_status(:created)
+        expect(response.status).to be_between(400, 499)
-
-        page_id = json.fetch('id')
-        expect(json.fetch('title')).to eq('Help:TestPage')
-
-        created_page = WikiPage.find(page_id)
-        version = created_page.wiki_versions.order(:version_no).last
-
-        expect(version).to have_attributes(
-          version_no: 1,
-          event_type: 'create',
-          title: 'Help:TestPage',
-          body: "a\nb\nc",
-          created_by_user_id: member.id
-        )
-
-        rev = created_page.current_revision
-        expect(rev).to be_present
-        expect(rev).to be_content
-        expect(rev.message).to eq('init')
-
-        expect(created_page.body).to eq("a\nb\nc")
-
-        expect(rev.lines_count).to eq(3)
-        expect(rev.wiki_revision_lines.order(:position).pluck(:position)).to eq([0, 1, 2])
-        expect(rev.wiki_lines.pluck(:body)).to match_array(['a', 'b', 'c'])
-      end
-
-      it 'reuses existing WikiLine rows by sha256' do
-        # 先に同じ行を作っておく
-        WikiLine.create!(sha256: Digest::SHA256.hexdigest('a'), body: 'a', created_at: Time.current, updated_at: Time.current)
-
-        post endpoint,
-             params: { title: 'Help:Reuse', body: "a\na" },
-             headers: auth_headers(member)
-
-        page = WikiPage.find(JSON.parse(response.body).fetch('id'))
-        rev = page.current_revision
-        expect(rev.lines_count).to eq(2)
-
-        # "a" の WikiLine が増殖しない（1行のはず）
-        expect(WikiLine.where(body: 'a').count).to eq(1)
-      end
-
-      it 'deduplicates duplicated new lines before upsert' do
-        duplicated = 'duplicated_line_for_wiki_line_upsert_spec'
-
-        post endpoint,
-             params: { title: 'Help:DuplicateNewLine', body: "#{ duplicated }\n#{ duplicated }" },
-             headers: auth_headers(member)
-
-        expect(response).to have_http_status(:created)
-
-        page = WikiPage.find(json.fetch('id'))
-        rev = page.current_revision
-
-        expect(rev.lines_count).to eq(2)
-        expect(WikiLine.where(body: duplicated).count).to eq(1)
-        expect(rev.wiki_revision_lines.count).to eq(2)
-        expect(rev.wiki_revision_lines.pluck(:wiki_line_id).uniq.size).to eq(1)
-      end
-
-      it 'normalises CRLF and strips trailing newlines' do
-        post endpoint,
-             params: { title: 'Help:NormalisedBody',
-                       body: "a\r\nb\r\n\r\n", message: 'normalise' },
-             headers: auth_headers(member)
-
-        expect(response).to have_http_status(:created)
-
-        page = WikiPage.find(json.fetch('id'))
-        rev = page.current_revision
-        version = page.wiki_versions.order(:version_no).last
-
-        expect(page.body).to eq("a\nb")
-        expect(version.body).to eq("a\nb")
-        expect(rev.lines_count).to eq(2)
-        expect(rev.wiki_lines.order('wiki_revision_lines.position').map(&:body)).to eq(['a', 'b'])
       end
     end
   end
@@ -208,10 +129,10 @@ RSpec.describe 'Wiki API', type: :request do
       { 'X-Transfer-Code' => user.inheritance_code }
     end
 
-    let!(:test_tag_name) { create(:tag_name, name: 'TestPage') }
+    let!(:test_tag_name) { create(:tag, primary_name: 'TestPage').tag_name('ja') }
 
     let!(:page) do
-      Wiki::Commit.create_content!(
+      seed_description(
           tag_name: test_tag_name,
           body: "a\nb",
           created_by_user: member,
@@ -245,33 +166,30 @@ RSpec.describe 'Wiki API', type: :request do
 
     context 'when success' do
       it 'creates new revision and returns 200' do
-        current_id = page.wiki_revisions.maximum(:id)
+        current_id = description_versions(page).maximum(:id)
 
         expect do
           put "/wiki/#{page.id}",
-              params: { title: 'TestPage', body: "x\ny", message: 'edit', base_revision_id: current_id },
+              params: { title: 'TestPage', body: "x\ny", message: 'edit',
+                        base_revision_id: current_id },
               headers: auth_headers(member)
         end
-            .to change(WikiRevision, :count).by(1)
+            .to change(TagDescriptionVersion, :count).by(1)
-            .and change(WikiVersion, :count).by(1)
 
-        version = page.wiki_versions.order(:version_no).last
+
+        version = description_versions(page).order(:version_no).last
 
         expect(version).to have_attributes(
           event_type: 'update',
-          title: 'TestPage',
           body: "x\ny",
-          created_by_user_id: member.id
+          created_by_user_id: member.id)
-        )
 
         expect(response).to have_http_status(:ok)
 
         page.reload
-        rev = page.current_revision
+        rev = current_description_version(page)
-        expect(rev).to be_content
-        expect(rev.message).to eq('edit')
         expect(page.body).to eq("x\ny")
-        expect(rev.base_revision_id).to eq(current_id)
+        expect(rev.version_no).to eq(2)
       end
 
       it 'wiki body だけを変更しても tag version は作成しない' do
@@ -284,13 +202,13 @@ RSpec.describe 'Wiki API', type: :request do
             created_by_user: member)
 
         linked_page =
-            Wiki::Commit.create_content!(
+            seed_description(
                 tag_name: linked_tag_name,
                 body: 'before',
                 created_by_user: member,
                 message: 'init')
 
-        current_id = linked_page.current_revision.id
+        current_id = current_description_version(linked_page).id
         before_count = linked_tag.reload.tag_versions.count
 
         expect {
@@ -303,8 +221,8 @@ RSpec.describe 'Wiki API', type: :request do
               },
               headers: auth_headers(member)
         }
-            .to change(WikiRevision, :count).by(1)
+            .to change(TagDescriptionVersion, :count).by(1)
-            .and change(WikiVersion, :count).by(1)
+
 
         expect(response).to have_http_status(:ok)
         expect(linked_tag.reload.tag_versions.count).to eq(before_count)
@@ -314,10 +232,12 @@ RSpec.describe 'Wiki API', type: :request do
     context 'when conflict' do
       it 'returns 409 when base_revision_id mismatches' do
         # 先に別ユーザ（同じ member でもOK）が 1 回更新して先頭を進める
-        Wiki::Commit.content!(page: page, body: "zzz", created_user: member, message: 'other edit')
+        TagDescriptionOperation.update!(
+            Locale.nipponese, tag: page.tag, body: 'zzz',
+            updated_by_user: member, message: 'other edit')
         page.reload
 
-        stale_id = page.wiki_revisions.order(:id).first.id # わざと古い id
+        stale_id = description_versions(page).order(:id).first.id # わざと古い id
         put "/wiki/#{page.id}",
             params: { title: 'TestPage', body: 'x', base_revision_id: stale_id },
             headers: auth_headers(member)
@@ -358,13 +278,14 @@ RSpec.describe 'Wiki API', type: :request do
 
   describe 'GET /wiki/search' do
     before do
-      Wiki::Commit.create_content!(
+      search_tag = create(:tag, primary_name: 'spec_wiki_title_2')
-          tag_name: create(:tag_name, name: 'spec_wiki_title_2'),
+      seed_description(
+          tag_name: search_tag.tag_name('ja'),
           body: 'search body 2',
           created_by_user: user,
           message: 'init')
 
-      Wiki::Commit.create_content!(
+      seed_description(
           tag_name: create(:tag_name, name: 'unrelated_title'),
           body: 'unrelated body',
           created_by_user: user,
@@ -395,13 +316,15 @@ RSpec.describe 'Wiki API', type: :request do
 
   describe 'GET /wiki/changes' do
     let!(:rev1) do
-      Wiki::Commit.content!(page: page, body: "a\nb", created_user: user, message: 'r1')
+      TagDescriptionOperation.update!(
-      page.current_revision
+          Locale.nipponese, tag: page.tag, body: "a\nb", updated_by_user: user, message: 'r1')
+      current_description_version(page)
     end
 
     let!(:rev2) do
-      Wiki::Commit.content!(page: page, body: "a\nc", created_user: user, message: 'r2')
+      TagDescriptionOperation.update!(
-      page.current_revision
+          Locale.nipponese, tag: page.tag, body: "a\nc", updated_by_user: user, message: 'r2')
+      current_description_version(page)
     end
 
     it 'returns latest revisions (optionally filtered by page id)' do
@@ -435,12 +358,9 @@ RSpec.describe 'Wiki API', type: :request do
     it 'returns empty array when page has no revisions and filtered by id' do
       # 別ページを作って revision 無し
       tn2 = create(:tag_name, name: 'spec_no_rev')
-      # 異常データ: revision 無し WikiPage を直接作る
+      # 異常データ: Version のない TagDescription を直接作る
-      p2 = WikiPage.create!(
+      p2 = TagDescription.create!(
-          tag_name: tn2,
+          tag: tn2.tag, language_code: 'ja', body: 'init', version_no: 1)
-          body: 'init',
-          created_user: user,
-          updated_user: user)
 
       get "/wiki/changes?id=#{p2.id}"
       expect(response).to have_http_status(:ok)
@@ -476,13 +396,15 @@ RSpec.describe 'Wiki API', type: :request do
 
   describe 'GET /wiki/:id/diff' do
     let!(:rev_a) do
-      Wiki::Commit.content!(page: page, body: "a\nb\nc", created_user: user, message: 'A')
+      TagDescriptionOperation.update!(
-      page.current_revision
+          Locale.nipponese, tag: page.tag, body: "a\nb\nc", updated_by_user: user, message: 'A')
+      current_description_version(page)
     end
 
     let!(:rev_b) do
-      Wiki::Commit.content!(page: page, body: "a\nx\nc", created_user: user, message: 'B')
+      TagDescriptionOperation.update!(
-      page.current_revision
+          Locale.nipponese, tag: page.tag, body: "a\nx\nc", updated_by_user: user, message: 'B')
+      current_description_version(page)
     end
 
     it 'returns diff json between revisions' do
@@ -508,44 +430,23 @@ RSpec.describe 'Wiki API', type: :request do
 
       expect(response).to have_http_status(:ok)
       expect(json['older_revision_id']).to eq(rev_a.id)
-      expect(json['newer_revision_id']).to eq(page.current_revision.id)
+      expect(json['newer_revision_id']).to eq(current_description_version(page).id)
     end
   end
 
-  describe 'Wiki::Commit.redirect!' do
-    it 'raises because redirect revisions are deprecated' do
-      target_tag_name = create(:tag_name, name: 'redirect_deprecated_target')
-      target =
-          Wiki::Commit.create_content!(
-              tag_name: target_tag_name,
-              body: 'target',
-              created_by_user: user,
-              message: 'init')
-
-      expect {
-        Wiki::Commit.redirect!(
-          page: page,
-          redirect_page: target,
-          created_user: user,
-          message: 'redirect',
-          base_revision_id: page.current_revision.id
-        )
-      }.to raise_error(RuntimeError, '廃止しました．')
-    end
-  end
 
   it 'wiki title を変更すると対応する tag の version を作成する' do
     linked_tag_name = create(:tag_name, name: 'wiki_linked_tag_for_version')
     linked_tag = create(:tag, primary_tag_name: linked_tag_name, category: :general)
 
     linked_page =
-        Wiki::Commit.create_content!(
+        seed_description(
             tag_name: linked_tag_name,
             body: 'before',
             created_by_user: user,
             message: 'init')
 
-    current_id = linked_page.current_revision.id
+    current_id = current_description_version(linked_page).id
 
     expect {
       put "/wiki/#{ linked_page.id }",
@@ -557,8 +458,7 @@ RSpec.describe 'Wiki API', type: :request do
           },
           headers: auth_headers(user)
     }
-        .to change(WikiRevision, :count).by(1)
+        .to change(TagDescriptionVersion, :count).by(1)
-        .and change(WikiVersion, :count).by(1)
         .and change { linked_tag.reload.tag_versions.count }.by(2)
 
     expect(response).to have_http_status(:ok)

backend/spec/requests/wiki_title_collision_spec.rb

@@ -1,6 +1,7 @@
 require 'rails_helper'
 
 RSpec.describe 'Wiki title collision', type: :request do
+  include WikiRecords
   let!(:user) { create_member_user! }
 
   def auth_headers user
@@ -8,7 +9,7 @@ RSpec.describe 'Wiki title collision', type: :request do
   end
 
   def create_wiki_page title:, body:
-    Wiki::Commit.create_content!(
+    seed_description(
         tag_name: create(:tag_name, name: title),
         body:,
         created_by_user: user,
@@ -19,9 +20,9 @@ RSpec.describe 'Wiki title collision', type: :request do
     source = create_wiki_page(title: 'wiki_collision_source', body: 'source body')
     create_wiki_page(title: 'wiki_collision_target', body: 'target body')
 
-    source_revision_count = source.wiki_revisions.count
+    source_revision_count = description_versions(source).count
-    source_version_count = source.wiki_versions.count
+    source_version_count = description_versions(source).count
-    old_title = source.title
+    old_title = source.tag.reload.name('ja')
     old_body = source.body
 
     put "/wiki/#{ source.id }",
@@ -29,7 +30,7 @@ RSpec.describe 'Wiki title collision', type: :request do
           title: 'wiki_collision_target',
           body: 'new body',
           message: 'rename collision',
-          base_revision_id: source.current_revision.id,
+          base_revision_id: current_description_version(source).id,
         },
         headers: auth_headers(user)
 
@@ -37,26 +38,23 @@ RSpec.describe 'Wiki title collision', type: :request do
 
     source.reload
 
-    expect(source.title).to eq(old_title)
+    expect(source.tag.reload.name('ja')).to eq(old_title)
     expect(source.body).to eq(old_body)
-    expect(source.wiki_revisions.count).to eq(source_revision_count)
+    expect(description_versions(source).count).to eq(source_revision_count)
-    expect(source.wiki_versions.count).to eq(source_version_count)
+    expect(description_versions(source).count).to eq(source_version_count)
   end
 
-  it 'returns 422 when creating wiki with existing title' do
+  it 'rejects frozen creation with an existing title without adding history' do
     create_wiki_page(title: 'Help:wiki_collision_create', body: 'already exists')
 
-    expect {
+    expect do
       post '/wiki',
-           params: {
+           params: { title: 'Help:wiki_collision_create', body: 'new body',
-             title: 'Help:wiki_collision_create',
+                     message: 'duplicate create' },
-             body: 'new body',
-             message: 'duplicate create',
-           },
            headers: auth_headers(user)
-    }
+    end.to change(TagDescription, :count).by(0)
-        .not_to change(WikiPage, :count)
+        .and change(TagDescriptionVersion, :count).by(0)
 
-    expect(response).to have_http_status(:unprocessable_entity)
+    expect(response.status).to be_between(400, 499)
   end
 end

backend/spec/requests/wiki_unmigrated_contract_spec.rb

@@ -1,115 +1,25 @@
 require 'rails_helper'
 
-RSpec.describe 'Unmigrated Wiki compatibility', type: :request do
+RSpec.describe 'Removed standalone Wiki resources', type: :request do
-  let!(:user) { create_member_user! }
+  include TagGroupRecords
-  let!(:tag_name) { create(:tag_name, name: 'Help_contract') }
+  let(:user) { create_member_user! }
-  let!(:page) do
-    Wiki::Commit.create_content!(tag_name:, body: 'before', created_by_user: user)
-  end
-  let!(:first_revision) { page.current_revision }
-  let!(:last_revision) do
-    Wiki::Commit.content!(page:, body: 'after', created_user: user,
-                          message: 'legacy edit', base_revision_id: first_revision.id)
-  end
 
-  before { expect(TagDescription.exists?(id: page.id)).to be(false) }
+  ['Help:old', 'ヘルプ:旧ページ'].each do |title|
-
+    it "does not resolve #{ title } as a Wiki resource" do
-  it 'keeps a Tag-linked legacy page in the legacy domain when its title changes' do
+      path = "/wiki/title/#{ CGI.escapeURIComponent(title) }"
-    create(:tag, primary_tag_name: tag_name)
+      without_group_legacy_reads { get path }
-
+      expect(response).to have_http_status(:not_found)
-    expect do
+      get "#{ path }/exists"
-      put "/wiki/#{ page.id }",
-          params: { title: 'legacy_tag_renamed', body: 'changed legacy body',
-                    message: 'legacy rename', base_revision_id: last_revision.id },
-          headers: { 'X-Transfer-Code' => user.inheritance_code }
-    end.to change(WikiRevision, :count).by(1)
-        .and change(WikiVersion, :count).by(1)
-        .and change(TagDescription, :count).by(0)
-        .and change(TagDescriptionVersion, :count).by(0)
-
-    expect(response).to have_http_status(:ok)
-    expect(page.reload).to have_attributes(body: 'changed legacy body')
-    expect(page.title).to eq('legacy_tag_renamed')
-    expect(page.current_revision).to have_attributes(message: 'legacy rename')
-  end
-
-  it 'shows legacy current and historical content by ID' do
-    get "/wiki/#{ page.id }"
-    expect(response).to have_http_status(:ok)
-    expect(json).to include('body' => 'after', 'revision_id' => last_revision.id,
-                           'pred' => first_revision.id, 'succ' => nil)
-    get "/wiki/#{ page.id }", params: { version: first_revision.id }
-    expect(response).to have_http_status(:ok)
-    expect(json).to include('body' => 'before', 'revision_id' => first_revision.id,
-                           'pred' => nil, 'succ' => last_revision.id)
-  end
-
-  it 'shows legacy current and historical content by title' do
-    get "/wiki/title/#{ tag_name.name }"
-    expect(response).to have_http_status(:ok)
-    expect(json).to include('body' => 'after', 'revision_id' => last_revision.id)
-    get "/wiki/title/#{ tag_name.name }", params: { version: first_revision.id }
-    expect(response).to have_http_status(:ok)
-    expect(json).to include('body' => 'before', 'revision_id' => first_revision.id)
-  end
-
-  it 'recognises legacy IDs' do
-    get "/wiki/#{ page.id }/exists"
-    expect(response).to have_http_status(:no_content)
-  end
-
-  it 'recognises legacy titles' do
-    get "/wiki/title/#{ tag_name.name }/exists"
-    expect(response).to have_http_status(:no_content)
-  end
-
-  it 'diffs legacy revisions with explicit and current target' do
-    [last_revision.id, nil].each do |to|
-      get "/wiki/#{ page.id }/diff", params: { from: first_revision.id, to: }
-      expect(response).to have_http_status(:ok)
-      expect(json).to include(
-          'wiki_page_id' => page.id, 'title' => tag_name.name,
-          'older_revision_id' => first_revision.id, 'newer_revision_id' => last_revision.id,
-          'diff' => [{ 'type' => 'removed', 'content' => 'before' },
-                     { 'type' => 'added', 'content' => 'after' }])
-    end
-  end
-
-  describe 'revision resource scope' do
-    let!(:other_page) do
-      Wiki::Commit.create_content!(
-          tag_name: create(:tag_name, name: 'Help_other_contract'),
-          body: 'other page history', created_by_user: user)
-    end
-    let(:other_revision) { other_page.current_revision }
-
-    it 'returns 404 when show specifies another page revision' do
-      get "/wiki/#{ page.id }", params: { version: other_revision.id }
       expect(response).to have_http_status(:not_found)
     end
 
-    it 'returns 404 when diff from belongs to another page' do
+    it "rejects standalone creation of #{ title } without writes" do
-      get "/wiki/#{ page.id }/diff",
+      user
-          params: { from: other_revision.id, to: last_revision.id }
+      before_state = group_state
-      expect(response).to have_http_status(:not_found)
+      post '/wiki', params: { title:, body: 'body' },
+           headers: { 'X-Transfer-Code' => user.inheritance_code }
+      expect(response).to have_http_status(:unprocessable_entity)
+      expect(group_state).to eq(before_state)
     end
-
-    it 'returns 404 when diff to belongs to another page' do
-      get "/wiki/#{ page.id }/diff",
-          params: { from: first_revision.id, to: other_revision.id }
-      expect(response).to have_http_status(:not_found)
-    end
-  end
-
-  it 'retains legacy history metadata and ordering' do
-    get '/wiki/changes', params: { id: page.id }
-    expect(response).to have_http_status(:ok)
-    expect(json.map { |row| row.fetch('revision_id') }).to eq(
-        [last_revision.id, first_revision.id])
-    expect(json.first).to include(
-        'pred' => first_revision.id, 'succ' => nil, 'kind' => 'content',
-        'message' => 'legacy edit', 'timestamp' => last_revision.created_at.iso8601(3),
-        'wiki_page' => { 'id' => page.id, 'title' => tag_name.name, 'deprecated_at' => nil },
-        'user' => { 'id' => user.id, 'name' => user.name })
   end
 end

backend/spec/services/shared_resource_id_allocator_mysql_spec.rb

@@ -0,0 +1,156 @@
+require 'rails_helper'
+require 'timeout'
+
+RSpec.describe 'Shared resource IDs across MySQL connections', type: :model do
+  self.use_transactional_tests = false
+
+  before do
+    expect(Rails.env.test?).to be(true)
+    expect(ApplicationRecord.connection.adapter_name).to match(/mysql/i)
+    expect(ApplicationRecord.connection_pool.size).to be >= 3
+    @prefix = "shared_ids_#{ SecureRandom.hex(8) }"
+    @tag = create(:tag, primary_name: "#{ @prefix }_owner")
+    @group = TagGroup.create!(name: "#{ @prefix }_owner", version_no: 1)
+    @tag_ids = Queue.new
+    @threads = []
+    @release = Queue.new
+  end
+
+  after do
+    @release << true if @release
+    begin
+      Array(@threads).each do |thread|
+        raise 'Shared ID worker did not finish' unless thread.join(15)
+      end
+    ensure
+      TagDescriptionVersion.where(tag_id: @tag.id).delete_all if @tag
+      if @group
+        TagGroupVersion.where(tag_group_id: @group.id).delete_all
+        @group.delete
+      end
+      if @prefix
+        ExternalTag.where(name: "#{ @prefix }_external").delete_all
+        TagGroup.where(name: "#{ @prefix }_group").delete_all
+      end
+      TagDescription.where(tag_id: @tag.id).delete_all if @tag
+      ids = []
+      ids << @tag_ids.pop until @tag_ids.empty? if @tag_ids
+      ids << @tag.id if @tag
+      TagName.where(tag_id: ids).delete_all
+      Tag.where(id: ids).delete_all
+    end
+  end
+
+  def await_queue queue
+    Timeout.timeout(15) { queue.pop }
+  end
+
+  def worker &block
+    Thread.new do
+      Thread.current.report_on_exception = false
+      ApplicationRecord.connection_pool.with_connection(&block)
+    end.tap { @threads << _1 }
+  end
+
+  def create_resource kind
+    case kind
+    when :tag
+      Tag.create!(category: :general).tap { @tag_ids << _1.id }
+    when :external
+      ExternalTag.create!(platform: :nico, name: "#{ @prefix }_external")
+    when :description
+      TagDescription.create!(tag: @tag, language_code: 'ja', body: '', version_no: 1)
+    when :description_version
+      TagDescriptionVersion.create!(
+          tag_id: @tag.id, language_code: 'ja', body: 'body', version_no: 1,
+          event_type: 'create', created_at: Time.current)
+    when :group_version
+      TagGroupVersion.create!(
+          tag_group: @group, name: @group.name, version_no: 1, event_type: 'create',
+          members: [], placements: [], created_at: Time.current)
+    when :group
+      TagGroup.create!(name: "#{ @prefix }_group", version_no: 1)
+    end
+  end
+
+  def hold_creation kind, rollback: false
+    ready = Queue.new
+    thread = worker do |connection|
+      id = nil
+      connection.transaction do
+        lock_name = nil
+        subscriber = lambda do |*args|
+          match = args.last.fetch(:sql).match(/GET_LOCK\('([^']+)'/)
+          lock_name = match[1] if match
+        end
+        ActiveSupport::Notifications.subscribed(subscriber, 'sql.active_record') do
+          id = create_resource(kind).id
+        end
+        ready << [id, connection.select_value('SELECT CONNECTION_ID()').to_i, lock_name]
+        await_queue(@release)
+        raise ActiveRecord::Rollback if rollback
+      end
+      id
+    end
+    [thread, await_queue(ready)]
+  end
+
+  def result thread
+    raise 'Shared ID worker did not finish' unless thread.join(15)
+    thread.value
+  end
+
+  { tags: [:external, :tag], wiki: [:description, :group],
+    wiki_history: [:description_version, :group_version] }.each do |space, kinds|
+    [false, true].each do |rollback|
+      it "serialises #{ space } inserts through #{ rollback ? 'rollback' : 'commit' }" do
+        tables = SharedResourceIdAllocator::SPACES.fetch(space.to_s)
+        maxima = tables.map do |table|
+          ApplicationRecord.connection.select_value("SELECT MAX(id) FROM #{ table }").to_i
+        end
+        first, (first_id, connection_id, lock_name) = hold_creation(kinds.first, rollback:)
+        expect(first_id).to be > maxima.max
+        connection = ApplicationRecord.connection
+        quoted_lock = connection.quote(lock_name)
+        expect(connection.select_value("SELECT IS_USED_LOCK(#{ quoted_lock })").to_i)
+            .to eq(connection_id)
+
+        started = Queue.new
+        second = worker do |other|
+          started << other.select_value('SELECT CONNECTION_ID()').to_i
+          create_resource(kinds.last).id
+        end
+        expect(await_queue(started)).not_to eq(connection_id)
+        @release << true
+        expect(result(first)).to eq(first_id)
+        expect(result(second)).to be > first_id
+        expect(connection.select_value("SELECT IS_FREE_LOCK(#{ quoted_lock })").to_i).to eq(1)
+      end
+    end
+  end
+
+  it 'allows the other ID space to commit while the first space remains locked' do
+    first, (_id, connection_id, lock_name) = hold_creation(:external)
+    second = worker { create_resource(:group).id }
+    expect(result(second)).to be_positive
+    connection = ApplicationRecord.connection
+    quoted_lock = connection.quote(lock_name)
+    expect(connection.select_value("SELECT IS_USED_LOCK(#{ quoted_lock })").to_i)
+        .to eq(connection_id)
+    @release << true
+    result(first)
+  end
+
+  it 'raises on a real lock acquisition failure without inserting a record' do
+    first, (_id, _connection_id, lock_name) = hold_creation(:external, rollback: true)
+    stub_const('SharedResourceIdAllocator::LOCK_TIMEOUT', 0)
+    expect { create_resource(:external) }.to raise_error(ActiveRecord::LockWaitTimeout)
+    expect(ExternalTag.where(name: "#{ @prefix }_external")).not_to exist
+    @release << true
+    result(first)
+    connection = ApplicationRecord.connection
+    quoted_lock = connection.quote(lock_name)
+    expect(connection.select_value("SELECT IS_FREE_LOCK(#{ quoted_lock })").to_i)
+        .to eq(1)
+  end
+end

backend/spec/services/shared_resource_id_allocator_spec.rb

@@ -0,0 +1,193 @@
+require 'rails_helper'
+
+RSpec.describe SharedResourceIdAllocator do
+  let(:tag) { create(:tag) }
+
+  def resource table, id: nil, number: 1
+    case table
+    when 'tags'
+      Tag.new(id:, category: :general)
+    when 'external_tags'
+      ExternalTag.new(id:, platform: :nico, name: "external #{ number }")
+    when 'tag_descriptions'
+      TagDescription.new(id:, tag:, language_code: 'ja', body: 'body', version_no: number)
+    when 'tag_groups'
+      TagGroup.new(id:, name: "group #{ number }", version_no: number)
+    when 'tag_description_versions'
+      TagDescriptionVersion.new(
+          id:, tag_id: tag.id, language_code: 'ja', body: 'body', version_no: number,
+          event_type: 'create', created_at: Time.current)
+    when 'tag_group_versions'
+      TagGroupVersion.new(
+          id:, tag_group_id: group.id, name: group.name, version_no: number,
+          event_type: 'create', members: [], placements: [], created_at: Time.current)
+    end
+  end
+
+  let(:group) { TagGroup.create!(name: 'history owner', version_no: 1) }
+
+  described_class::SPACES.each do |space, tables|
+    tables.permutation.each do |first_table, second_table|
+      it "keeps deleted #{ first_table } IDs reserved for #{ second_table }" do
+        first = resource(first_table)
+        first.save!
+        used_id = first.id
+        first.class.where(id: first.id).delete_all
+        second = resource(second_table)
+        second.save!
+        expect(second.id).to be > used_id
+      end
+
+      it "advances #{ space } after an explicit INSERT in #{ first_table }" do
+        first = resource(first_table)
+        first.save!
+        high = first.id + 100
+        explicit = resource(first_table, id: high, number: 2)
+        first.class.where(id: first.id).delete_all
+        explicit.save!
+        explicit.class.where(id: explicit.id).delete_all
+        second = resource(second_table)
+        second.save!
+        expect(second.id).to be > high
+      end
+    end
+
+    it "allows explicit overlapping Id.s in #{ space }" do
+      first = resource(tables.first)
+      first.save!
+
+      second = resource(tables.last, id: first.id)
+      second.save!
+
+      expect(second.id).to eq(first.id)
+      expect(first.reload.id).to eq(first.id)
+    end
+
+    it "preserves historical #{ space } overlaps without repairing them" do
+      first = resource(tables.first)
+      first.save!
+      second = resource(tables.last)
+      second.save!
+      second.class.where(id: second.id).update_all(id: first.id)
+      second = second.class.find(first.id)
+      snapshots = [first.reload.attributes, second.reload.attributes]
+      next_record = resource(tables.last, number: 2)
+      next_record.save!
+      expect(next_record.id).to be > first.id
+      expect(first.reload.attributes).to eq(snapshots.first)
+      expect(second.reload.attributes).to eq(snapshots.last)
+    end
+  end
+
+  it 'reserves a Tag ID referenced only by remaining description history' do
+    high = [Tag.maximum(:id).to_i, ExternalTag.maximum(:id).to_i].max + 1000
+    TagDescriptionVersion.create!(
+        tag_id: high, language_code: 'ja', version_no: 1, body: 'history',
+        event_type: 'create', created_at: Time.current)
+    expect(create(:tag).id).to be > high
+    expect(create(:external_tag).id).to be > high
+  end
+
+  it 'reserves a group ID referenced only by remaining group history' do
+    high = [TagGroup.maximum(:id).to_i, TagDescription.maximum(:id).to_i].max + 1000
+    version = resource('tag_group_versions')
+    version.save!
+    TagGroupVersion.where(id: version.id).update_all(tag_group_id: high)
+    expect(TagGroup.create!(name: 'replacement', version_no: 1).id).to be > high
+  end
+end
+
+RSpec.describe SharedResourceIdAllocator, 'lock lifecycle' do
+  let(:record) { build(:external_tag) }
+  let(:connection) { double('connection') }
+  let(:transaction) { double('transaction', open?: true) }
+  let(:callbacks) { { } }
+  let(:sql) { [] }
+
+  before do
+    config = double('config', database: 'test_shared_ids')
+    allow(connection).to receive_message_chain(:pool, :db_config).and_return(config)
+    allow(connection).to receive(:quote) { "'#{ _1 }'" }
+    allow(connection).to receive(:quote_column_name) { "`#{ _1 }`" }
+    allow(connection).to receive(:execute) { sql << _1 }
+    allow(connection).to receive(:select_all) do |statement|
+      tables = described_class::SPACES.values.flatten.select do |table|
+        statement.include?("'#{ table }'")
+      end
+      tables.map { { 'TABLE_NAME' => _1, 'ENGINE' => 'InnoDB', 'AUTO_INCREMENT' => 9 } }
+    end
+    allow(connection).to receive(:quote_table_name) { "`#{ _1 }`" }
+    allow(connection).to receive(:select_value) do |statement|
+      sql << statement
+      if statement.include?('GET_LOCK') || statement.include?('RELEASE_LOCK')
+        1
+      elsif statement.include?('`tags`')
+        8
+      else
+        3
+      end
+    end
+    allow(ExternalTag).to receive(:connection).and_return(connection)
+    allow(ExternalTag).to receive(:current_transaction).and_return(transaction)
+    allow(ExternalTag).to receive(:uncached).and_yield
+    [:after_commit, :after_rollback].each do |event|
+      allow(transaction).to receive(event) { |&callback| callbacks[event] = callback }
+    end
+  end
+
+  [:after_commit, :after_rollback].each do |event|
+    it "holds the shared lock until #{ event }" do
+      described_class.assign!(record)
+      expect(record.id).to eq(9)
+      expect(sql.grep(/RELEASE_LOCK/)).to be_empty
+      callbacks.fetch(event).call
+      expect(sql.grep(/RELEASE_LOCK/).size).to eq(1)
+    end
+  end
+
+  it 'does not silently proceed after an acquisition timeout' do
+    allow(connection).to receive(:select_value).and_return(0)
+    expect { described_class.assign!(record) }.to raise_error(ActiveRecord::LockWaitTimeout)
+    expect(record.id).to be_nil
+    expect(callbacks).to be_empty
+  end
+
+  it 'releases a successfully acquired lock when allocation fails and rolls back' do
+    allow(connection).to receive(:select_all).and_raise('query failed')
+    expect { described_class.assign!(record) }.to raise_error(RuntimeError, 'query failed')
+    callbacks.fetch(:after_rollback).call
+    expect(sql.grep(/RELEASE_LOCK/).size).to eq(1)
+  end
+
+  it 'accepts an explicit ID above the reserved position' do
+    record.id = 50
+    described_class.assign!(record)
+    expect(record.id).to eq(50)
+    expect(sql.grep(/FOR UPDATE/)).to be_empty
+    callbacks.fetch(:after_commit).call
+  end
+
+  it 'uses the same named lock within each space and different locks between spaces' do
+    locks = [Tag, ExternalTag, TagDescription, TagGroup, TagDescriptionVersion, TagGroupVersion].map do |model|
+      allow(model).to receive(:connection).and_return(connection)
+      allow(model).to receive(:current_transaction).and_return(transaction)
+      allow(model).to receive(:uncached).and_yield
+      record = model.new(id: 50)
+      described_class.assign!(record)
+      statement = sql.grep(/GET_LOCK/).last
+      callbacks.fetch(:after_commit).call
+      statement
+    end
+    expect(locks[0]).to eq(locks[1])
+    expect(locks[2]).to eq(locks[3])
+    expect(locks[4]).to eq(locks[5])
+    expect([locks[0], locks[2], locks[4]].uniq.size).to eq(3)
+  end
+
+  it 'reports lock release failures' do
+    described_class.assign!(record)
+    allow(connection).to receive(:select_value).with(/RELEASE_LOCK/).and_return(nil)
+    expect { callbacks.fetch(:after_commit).call }
+        .to raise_error(ActiveRecord::ActiveRecordError, /lock release failed/)
+  end
+end

backend/spec/services/wiki/commit_integrity_spec.rb

@@ -1,173 +0,0 @@
-require 'digest'
-require 'rails_helper'
-
-RSpec.describe Wiki::Commit do
-  let(:user) { create_member_user! }
-
-  def create_page title:, body: 'initial body'
-    described_class.create_content!(
-        tag_name: create(:tag_name, name: title),
-        body:,
-        created_by_user: user,
-        message: 'init')
-  end
-
-  describe '.create_content!' do
-    it 'creates page, revision, and version with normalised body' do
-      expect {
-        described_class.create_content!(
-            tag_name: create(:tag_name, name: 'commit_integrity_create'),
-            body: "a\r\nb\r\n\r\n",
-            created_by_user: user,
-            message: 'init')
-      }
-          .to change(WikiPage, :count).by(1)
-          .and change(WikiRevision, :count).by(1)
-          .and change(WikiVersion, :count).by(1)
-
-      page = WikiPage.joins(:tag_name).find_by!(tag_names: { name: 'commit_integrity_create' })
-      revision = page.current_revision
-      version = page.wiki_versions.order(:version_no).last
-
-      expect(page.body).to eq("a\nb")
-      expect(revision.lines_count).to eq(2)
-      expect(version.body).to eq("a\nb")
-      expect(version.reason).to eq('init')
-    end
-
-    it 'rejects body that becomes blank after normalisation' do
-      tag_name = create(:tag_name, name: 'commit_integrity_blank')
-
-      expect {
-        described_class.create_content!(
-            tag_name:,
-            body: "\r\n\r\n",
-            created_by_user: user,
-            message: 'blank')
-      }
-          .to raise_error(ActiveRecord::RecordInvalid)
-
-      expect(WikiPage.where(tag_name:)).not_to exist
-    end
-  end
-
-  describe '.content!' do
-    it 'updates page body, revision, and version' do
-      page = create_page(title: 'commit_integrity_update', body: 'before')
-      current_id = page.current_revision.id
-
-      expect {
-        described_class.content!(
-            page:,
-            body: 'after',
-            created_user: user,
-            message: 'edit',
-            base_revision_id: current_id)
-      }
-          .to change(WikiRevision, :count).by(1)
-          .and change(WikiVersion, :count).by(1)
-
-      page.reload
-      version = page.wiki_versions.order(:version_no).last
-
-      expect(page.body).to eq('after')
-      expect(version.body).to eq('after')
-      expect(version.reason).to eq('edit')
-    end
-
-    it 'does not record tag_version on body-only wiki update' do
-      tag_name = create(:tag_name, name: 'commit_integrity_linked_tag')
-      tag = create(:tag, primary_tag_name: tag_name, category: :general)
-
-      page =
-          described_class.create_content!(
-              tag_name:,
-              body: 'before',
-              created_by_user: user,
-              message: 'init')
-
-      TagVersionRecorder.record!(
-          tag:,
-          event_type: :create,
-          created_by_user: user)
-
-      before_count = tag.reload.tag_versions.count
-
-      described_class.content!(
-          page:,
-          body: 'after',
-          created_user: user,
-          message: 'edit',
-          base_revision_id: page.current_revision.id)
-
-      expect(tag.reload.tag_versions.count).to eq(before_count)
-    end
-
-    it 'raises conflict and leaves page, revision, and version unchanged' do
-      page = create_page(title: 'commit_integrity_conflict', body: 'first')
-      stale_id = page.current_revision.id
-
-      described_class.content!(
-          page:,
-          body: 'second',
-          created_user: user,
-          message: 'second',
-          base_revision_id: stale_id)
-
-      page.reload
-      before_body = page.body
-      before_revision_count = page.wiki_revisions.count
-      before_version_count = page.wiki_versions.count
-
-      expect {
-        described_class.content!(
-            page:,
-            body: 'third',
-            created_user: user,
-            message: 'stale',
-            base_revision_id: stale_id)
-      }
-          .to raise_error(Wiki::Commit::Conflict)
-
-      page.reload
-      expect(page.body).to eq(before_body)
-      expect(page.wiki_revisions.count).to eq(before_revision_count)
-      expect(page.wiki_versions.count).to eq(before_version_count)
-    end
-
-    it 'deduplicates duplicated missing wiki lines' do
-      page = create_page(title: 'commit_integrity_dedup', body: 'before')
-      duplicated = 'commit_integrity_duplicate_line'
-
-      described_class.content!(
-          page:,
-          body: "#{ duplicated }\n#{ duplicated }",
-          created_user: user,
-          message: 'dedup',
-          base_revision_id: page.current_revision.id)
-
-      revision = page.reload.current_revision
-
-      expect(WikiLine.where(body: duplicated).count).to eq(1)
-      expect(revision.wiki_revision_lines.count).to eq(2)
-      expect(revision.wiki_revision_lines.pluck(:wiki_line_id).uniq.size).to eq(1)
-    end
-  end
-
-  describe '.redirect!' do
-    it 'raises because redirect revisions are deprecated' do
-      page = create_page(title: 'commit_integrity_redirect_source', body: 'source')
-      target = create_page(title: 'commit_integrity_redirect_target', body: 'target')
-
-      expect {
-        described_class.redirect!(
-            page:,
-            redirect_page: target,
-            created_user: user,
-            message: 'redirect',
-            base_revision_id: page.current_revision.id)
-      }
-          .to raise_error(RuntimeError, '廃止しました．')
-    end
-  end
-end

backend/spec/services/wiki/commit_spec.rb

@@ -1,150 +0,0 @@
-require 'rails_helper'
-
-RSpec.describe Wiki::Commit do
-  let(:user) { create_member_user! }
-
-  def create_page(title: 'commit_spec_page', body: 'initial body')
-    tag_name = create(:tag_name, name: title)
-
-    Wiki::Commit.create_content!(
-        tag_name:,
-        body:,
-        created_by_user: user,
-        message: 'init')
-  end
-
-  describe '.content!' do
-    it 'stores normalised body in wiki_pages and wiki_versions' do
-      page = create_page(title: 'commit_normalised_page')
-
-      described_class.content!(
-        page:,
-        body: "a\r\nb\r\n\r\n",
-        created_user: user,
-        message: 'init'
-      )
-
-      page.reload
-      version = page.wiki_versions.order(:version_no).last
-
-      expect(page.body).to eq("a\nb")
-      expect(version.body).to eq("a\nb")
-      expect(page.current_revision.lines_count).to eq(2)
-    end
-
-    it 'deduplicates duplicated missing wiki lines before upsert' do
-      page = create_page(title: 'commit_duplicate_line_page')
-      duplicated = 'commit_duplicate_line'
-
-      described_class.content!(
-        page:,
-        body: "#{ duplicated }\n#{ duplicated }",
-        created_user: user,
-        message: 'init'
-      )
-
-      page.reload
-
-      expect(WikiLine.where(body: duplicated).count).to eq(1)
-      expect(page.current_revision.lines_count).to eq(2)
-      expect(page.current_revision.wiki_revision_lines.count).to eq(2)
-    end
-
-    it 'raises conflict when base_revision_id is stale' do
-      page = create_page(title: 'commit_conflict_page')
-
-      first = described_class.content!(
-        page:,
-        body: 'first',
-        created_user: user,
-        message: 'first'
-      )
-
-      described_class.content!(
-        page:,
-        body: 'second',
-        created_user: user,
-        message: 'second',
-        base_revision_id: first.id
-      )
-
-      expect {
-        described_class.content!(
-          page:,
-          body: 'third',
-          created_user: user,
-          message: 'third',
-          base_revision_id: first.id
-        )
-      }.to raise_error(Wiki::Commit::Conflict)
-    end
-
-    it 'does not record tag version when corresponding tag has no versions' do
-      tag_name = create(:tag_name, name: 'commit_linked_tag_without_versions')
-      tag = create(:tag, primary_tag_name: tag_name, category: :general)
-
-      page =
-          described_class.create_content!(
-              tag_name:,
-              body: 'before',
-              created_by_user: user,
-              message: 'init')
-
-      expect(tag.reload.tag_versions.count).to eq(0)
-
-      current_revision_id = page.current_revision.id
-
-      expect {
-        described_class.content!(
-            page:,
-            body: 'after',
-            created_user: user,
-            message: 'edit',
-            base_revision_id: current_revision_id)
-      }.to change(WikiVersion, :count).by(1)
-
-      expect(tag.reload.tag_versions.count).to eq(0)
-    end
-
-    it 'does not record tag version when corresponding tag has no versions' do
-      tag_name = create(:tag_name, name: 'commit_linked_tag_without_versions')
-      tag = create(:tag, primary_tag_name: tag_name, category: :general)
-
-      page =
-          described_class.create_content!(
-              tag_name:,
-              body: 'before',
-              created_by_user: user,
-              message: 'init')
-
-      current_revision_id = page.current_revision.id
-
-      expect {
-        described_class.content!(
-            page:,
-            body: 'after',
-            created_user: user,
-            message: 'edit',
-            base_revision_id: current_revision_id)
-      }.to change(WikiVersion, :count).by(1)
-
-      expect(tag.reload.tag_versions.count).to eq(0)
-    end
-  end
-
-  describe '.redirect!' do
-    it 'raises because redirect revisions are deprecated' do
-      page = create_page(title: 'commit_redirect_source')
-      target = create_page(title: 'commit_redirect_target')
-
-      expect {
-        described_class.redirect!(
-          page:,
-          redirect_page: target,
-          created_user: user,
-          message: 'redirect'
-        )
-      }.to raise_error(RuntimeError, '廃止しました．')
-    end
-  end
-end

backend/spec/services/wiki_version_recorder_spec.rb

@@ -1,99 +0,0 @@
-require 'rails_helper'
-
-RSpec.describe WikiVersionRecorder do
-  let(:user) { create_member_user! }
-
-  def create_page title:, body: 'body'
-    Wiki::Commit.create_content!(
-        tag_name: create(:tag_name, name: title),
-        body:,
-        created_by_user: user,
-        message: 'init')
-  end
-
-  describe '.record!' do
-    it 'records title, body, reason, user, and version number' do
-      page = create_page(title: 'wiki_version_recorder_basic', body: 'body')
-
-      expect {
-        described_class.record!(
-            page:,
-            event_type: :update,
-            reason: 'manual reason',
-            created_by_user: user)
-      }
-          .to change { page.reload.wiki_versions.count }.by(1)
-
-      version = page.wiki_versions.order(:version_no).last
-
-      expect(version).to have_attributes(
-        version_no: 2,
-        event_type: 'update',
-        title: 'wiki_version_recorder_basic',
-        body: 'body',
-        reason: 'manual reason',
-        created_by_user_id: user.id
-      )
-    end
-
-    it 'does not create duplicated update version for identical snapshot' do
-      page = create_page(title: 'wiki_version_recorder_duplicate', body: 'body')
-
-      described_class.record!(
-          page:,
-          event_type: :update,
-          reason: nil,
-          created_by_user: user)
-
-      before_count = page.reload.wiki_versions.count
-
-      described_class.record!(
-          page:,
-          event_type: :update,
-          reason: nil,
-          created_by_user: user)
-
-      expect(page.reload.wiki_versions.count).to eq(before_count)
-    end
-
-    it 'creates update version when title changes' do
-      page = create_page(title: 'wiki_version_recorder_title_before', body: 'body')
-      page.tag_name.update!(name: 'wiki_version_recorder_title_after')
-
-      expect {
-        described_class.record!(
-            page:,
-            event_type: :update,
-            reason: 'rename',
-            created_by_user: user)
-      }
-          .to change { page.reload.wiki_versions.count }.by(1)
-
-      version = page.wiki_versions.order(:version_no).last
-
-      expect(version.title).to eq('wiki_version_recorder_title_after')
-      expect(version.body).to eq('body')
-      expect(version.reason).to eq('rename')
-    end
-
-    it 'creates update version when body changes' do
-      page = create_page(title: 'wiki_version_recorder_body', body: 'before')
-      page.update!(body: 'after')
-
-      expect {
-        described_class.record!(
-            page:,
-            event_type: :update,
-            reason: 'body',
-            created_by_user: user)
-      }
-          .to change { page.reload.wiki_versions.count }.by(1)
-
-      version = page.wiki_versions.order(:version_no).last
-
-      expect(version.title).to eq('wiki_version_recorder_body')
-      expect(version.body).to eq('after')
-      expect(version.reason).to eq('body')
-    end
-  end
-end

backend/spec/support/ainu_locale_contract.rb

@@ -0,0 +1,22 @@
+RSpec.shared_context 'Ainu locale contract' do
+  let(:ainu_locale) { instance_double(Locale, language_code: 'ain', script_code: 'Jpan') }
+
+  before do
+    # Only the foreign-key reference is seeded; no Locale or enum is enabled.
+    Language.connection.execute(<<~SQL)
+      INSERT IGNORE INTO languages (code, name, created_at)
+      VALUES ('ain', 'Ainu', CURRENT_TIMESTAMP)
+    SQL
+    allow(Locale).to receive(:find_by).and_call_original
+    allow(Locale).to receive(:find_by).with(code: 'ain').and_return(ainu_locale)
+  end
+
+  def add_ainu_name tag, name
+    TagName.insert_all!([{
+        tag_id: tag.id, language_code: 'ain', script_code: 'Jpan', name:,
+        primary_flg: true, auto_generated: false,
+        created_at: Time.current, updated_at: Time.current }])
+    tag.tag_names.reset
+    TagName.find_by!(tag_id: tag.id, language_code: 'ain', name:)
+  end
+end

backend/spec/support/tag_group_records.rb

@@ -0,0 +1,194 @@
+require 'cgi'
+
+# SQL fixtures use the migration contract without inventing application models.
+# Include explicitly; these helpers must not affect unrelated examples.
+module TagGroupRecords
+  GROUP_TABLES = [
+      'tag_groups', 'tag_group_tags', 'tag_group_groups',
+      'tag_group_placements', 'tag_group_versions'].freeze
+  WRITE_TABLES = GROUP_TABLES + [
+      'tag_names', 'tag_description_versions',
+      'tag_descriptions']
+
+  def group_connection = ApplicationRecord.connection
+
+  def group_rows table, conditions = { }
+    clauses = conditions.map do |column, value|
+      "#{ group_connection.quote_column_name(column) } = #{ group_connection.quote(value) }"
+    end
+    sql = "SELECT * FROM #{ group_connection.quote_table_name(table) }"
+    sql += " WHERE #{ clauses.join(' AND ') }" if clauses.any?
+    group_connection.select_all(sql).to_a.sort_by { |row| row.values.map(&:to_s) }
+  end
+
+  def insert_group_row table, attributes
+    columns = attributes.keys.map { group_connection.quote_column_name(_1) }.join(', ')
+    values = attributes.values.map { group_connection.quote(_1) }.join(', ')
+    group_connection.insert(
+        "INSERT INTO #{ group_connection.quote_table_name(table) } (#{ columns }) " +
+        "VALUES (#{ values })")
+  end
+
+  def group_state
+    WRITE_TABLES.to_h { |table| [table, group_rows(table)] }
+  end
+
+  def expect_noop_group_update group_id:
+    before_state = group_state
+    group = TagGroup.find(group_id)
+    version_id = TagGroupVersion.find_by!(
+        tag_group_id: group_id, version_no: group.version_no).id
+    writes = []
+    tables = Regexp.union(WRITE_TABLES)
+    subscriber = lambda do |*args|
+      sql = args.last.fetch(:sql)
+      if sql.match?(/\A\s*(?:INSERT INTO|UPDATE|DELETE FROM)\s+`?(?:#{ tables })`?\s/i)
+        writes << sql
+      end
+    end
+
+    aggregate_failures 'no-op current state, history and SQL writes' do
+      ActiveSupport::Notifications.subscribed(subscriber, 'sql.active_record') { yield }
+      expect(response).to have_http_status(:ok)
+      after_state = group_state
+      before_state.each do |table, rows|
+        expect(after_state.fetch(table)).to eq(rows), "No-op changed #{ table }"
+      end
+      expect(TagGroupVersion.find_by!(
+          tag_group_id: group_id, version_no: group.reload.version_no).id).to eq(version_id)
+      expect(writes).to be_empty
+    end
+  end
+
+  def expect_atomic_group_write table
+    before_state = group_state
+    failure = Class.new(StandardError)
+    injected = false
+    subscriber = lambda do |*args|
+      sql = args.last.fetch(:sql)
+      next unless sql.match?(/\A\s*(?:INSERT INTO|UPDATE)\s+`?#{ table }`?\s/i)
+
+      injected = true
+      raise failure, 'injected after SQL write'
+    end
+    begin
+      ActiveSupport::Notifications.subscribed(subscriber, 'sql.active_record') { yield }
+    rescue failure
+      # Inspect the database after the operation's transaction unwinds.
+    end
+    aggregate_failures do
+      expect(injected).to be(true), "No INSERT/UPDATE reached #{ table }"
+      expect(group_state).to eq(before_state)
+    end
+  end
+
+  def group_version group_id, number
+    row = group_rows('tag_group_versions', tag_group_id: group_id, version_no: number).sole
+    row.merge('members' => JSON.parse(row.fetch('members')),
+              'placements' => JSON.parse(row.fetch('placements')))
+  end
+
+  def group_tag name
+    tag = create(:tag, primary_name: name)
+    TagVersioning.ensure_snapshot!(tag, created_by_user: user)
+    tag.reload
+  end
+
+  def create_markdown_group name, body, locale: Locale.nipponese
+    parsed = TagGroupMarkdownParser.parse(locale, body:)
+    TagGroupOperation.create!(
+        locale, name:, actor: user, **parsed.slice(:description, :members, :placements))
+  end
+
+  def group_markdown group, locale: Locale.nipponese
+    TagGroupMarkdownRenderer.render(TagGroupRepr.one(locale, group.reload))
+  end
+
+  def seed_group name:, placements: [], members: [], description: nil, id: nil
+    now = Time.current.change(usec: 0)
+    attributes = {
+        name:, description:, version_no: 1,
+        created_by_user_id: user.id, updated_by_user_id: user.id,
+        created_at: now, updated_at: now }
+    attributes[:id] = id if id
+    group_id = insert_group_row('tag_groups', attributes)
+    insert_group_row('tag_group_versions', {
+        tag_group_id: group_id, version_no: 1, event_type: 'create',
+        name:, description:, members: members.to_json, placements: placements.to_json,
+        created_by_user_id: user.id, created_at: now })
+    members.each do |member|
+      tag_member = member.key?('tag_id')
+      table = tag_member ? 'tag_group_tags' : 'tag_group_groups'
+      key = tag_member ? :tag_id : :child_tag_group_id
+      value = member.fetch(tag_member ? 'tag_id' : 'tag_group_id')
+      insert_group_row(table, {
+          tag_group_id: group_id, key => value,
+          created_by_user_id: user.id, created_at: now })
+    end
+    position = 0
+    append = lambda do |nodes, parent|
+      nodes.each do |node|
+        position += 1
+        own_position = position
+        insert_group_row('tag_group_placements', {
+            tag_group_id: group_id, position:, parent_position: parent,
+            section_name: node['section_name'], description: node['description'],
+            tag_id: node['tag_id'], child_tag_group_id: node['tag_group_id'],
+            created_by_user_id: user.id, updated_by_user_id: user.id,
+            created_at: now, updated_at: now })
+        append.call(node.fetch('children'), own_position)
+      end
+    end
+    append.call(placements, nil)
+    group_id
+  end
+
+  def without_group_legacy_reads
+    queries = []
+    subscriber = lambda do |*args|
+      sql = args.last.fetch(:sql)
+      if (sql.match?(/\bSELECT\b/i) &&
+          sql.match?(/\bwiki_(pages|revisions|versions|lines|revision_lines)\b/i))
+        queries << sql
+      end
+    end
+    ActiveSupport::Notifications.subscribed(subscriber, 'sql.active_record') { yield }
+    expect(queries).to be_empty
+  end
+
+  def group_title_path name
+    "/wiki/title/#{ CGI.escapeURIComponent("タググループ:#{ name }") }"
+  end
+
+  def expect_group_snapshot group_id, number:, placements:, members:, description: nil
+    current = group_rows('tag_groups', id: group_id).sole
+    version = group_version(group_id, number)
+    expect(current).to include('version_no' => number, 'description' => description),
+                       @group_migration_messages&.join("\n")
+    expect(version).to include(
+        'name' => current.fetch('name'), 'description' => description,
+        'version_no' => number, 'placements' => placements)
+    expect(version.fetch('members')).to match_array(members)
+    expect(group_rows('tag_group_tags', tag_group_id: group_id).map { _1.fetch('tag_id') })
+        .to match_array(members.filter_map { _1['tag_id'] })
+    children = group_rows('tag_group_groups', tag_group_id: group_id)
+    expect(children.map { _1.fetch('child_tag_group_id') })
+        .to match_array(members.filter_map { _1['tag_group_id'] })
+
+    rows = group_rows('tag_group_placements', tag_group_id: group_id)
+    tree = lambda do |parent|
+      rows.select { _1['parent_position'] == parent }.sort_by { _1.fetch('position') }
+          .map do |row|
+        node = if row['tag_id']
+          { 'tag_id' => row.fetch('tag_id') }
+        elsif row['child_tag_group_id']
+          { 'tag_group_id' => row.fetch('child_tag_group_id') }
+        else
+          { 'section_name' => row.fetch('section_name'), 'description' => row['description'] }
+        end
+        node.merge('children' => tree.call(row.fetch('position')))
+      end
+    end
+    expect(tree.call(nil)).to eq(placements)
+  end
+end

backend/spec/support/wiki_records.rb

@@ -0,0 +1,14 @@
+module WikiRecords
+  def seed_description(tag_name:, body:, created_by_user:, message: nil, locale: Locale.nipponese)
+    TagDescriptionOperation.create!(locale, tag: tag_name.tag, body:, created_by_user:, message:)
+  end
+
+  def description_versions(description)
+    TagDescriptionVersion.where(
+        tag_id: description.tag_id, language_code: description.language_code)
+  end
+
+  def current_description_version(description)
+    description_versions(description).find_by!(version_no: description.reload.version_no)
+  end
+end

backend/spec/tasks/nico_export_spec.rb

@@ -18,8 +18,8 @@ RSpec.describe 'nico:export' do
   before do
     task.reenable
 
-    allow(ENV).to receive(:fetch).with('MYSQL_USER').and_return('mysql-user')
+    allow(ENV).to receive(:fetch).with('NIZIKA_NICO_MYSQL_USER').and_return('mysql-user')
-    allow(ENV).to receive(:fetch).with('MYSQL_PASS').and_return('mysql-pass')
+    allow(ENV).to receive(:fetch).with('NIZIKA_NICO_MYSQL_PASS').and_return('mysql-pass')
     allow(ENV).to receive(:fetch).with('NIZIKA_NICO_PATH').and_return('/srv/nizika-nico')
   end
 
@@ -33,8 +33,8 @@ RSpec.describe 'nico:export' do
       expect(Open3).to receive(:capture3) do |env, *args, **kwargs|
         expect(env).to eq(
           {
-            'MYSQL_USER' => 'mysql-user',
+            'NIZIKA_NICO_MYSQL_USER' => 'mysql-user',
-            'MYSQL_PASS' => 'mysql-pass',
+            'NIZIKA_NICO_MYSQL_PASS' => 'mysql-pass',
           },
         )
 

frontend/.gitignore

@@ -22,3 +22,5 @@ dist-ssr
 *.njsproj
 *.sln
 *.sw?
+
+/help

frontend/package-lock.json

@@ -38,6 +38,7 @@
         "remark-gfm": "^4.0.1",
         "tailwind-merge": "^3.3.0",
         "unist-util-visit-parents": "^6.0.1",
+        "yaml": "^2.9.1",
         "zustand": "^5.0.8"
       },
       "devDependencies": {
@@ -2060,9 +2061,6 @@
         "arm"
       ],
       "dev": true,
-      "libc": [
-        "glibc"
-      ],
       "license": "MIT",
       "optional": true,
       "os": [
@@ -2077,9 +2075,6 @@
         "arm"
       ],
       "dev": true,
-      "libc": [
-        "musl"
-      ],
       "license": "MIT",
       "optional": true,
       "os": [
@@ -2094,9 +2089,6 @@
         "arm64"
       ],
       "dev": true,
-      "libc": [
-        "glibc"
-      ],
       "license": "MIT",
       "optional": true,
       "os": [
@@ -2111,9 +2103,6 @@
         "arm64"
       ],
       "dev": true,
-      "libc": [
-        "musl"
-      ],
       "license": "MIT",
       "optional": true,
       "os": [
@@ -2128,9 +2117,6 @@
         "loong64"
       ],
       "dev": true,
-      "libc": [
-        "glibc"
-      ],
       "license": "MIT",
       "optional": true,
       "os": [
@@ -2145,9 +2131,6 @@
         "loong64"
       ],
       "dev": true,
-      "libc": [
-        "musl"
-      ],
       "license": "MIT",
       "optional": true,
       "os": [
@@ -2162,9 +2145,6 @@
         "ppc64"
       ],
       "dev": true,
-      "libc": [
-        "glibc"
-      ],
       "license": "MIT",
       "optional": true,
       "os": [
@@ -2179,9 +2159,6 @@
         "ppc64"
       ],
       "dev": true,
-      "libc": [
-        "musl"
-      ],
       "license": "MIT",
       "optional": true,
       "os": [
@@ -2196,9 +2173,6 @@
         "riscv64"
       ],
       "dev": true,
-      "libc": [
-        "glibc"
-      ],
       "license": "MIT",
       "optional": true,
       "os": [
@@ -2213,9 +2187,6 @@
         "riscv64"
       ],
       "dev": true,
-      "libc": [
-        "musl"
-      ],
       "license": "MIT",
       "optional": true,
       "os": [
@@ -2230,9 +2201,6 @@
         "s390x"
       ],
       "dev": true,
-      "libc": [
-        "glibc"
-      ],
       "license": "MIT",
       "optional": true,
       "os": [
@@ -2247,9 +2215,6 @@
         "x64"
       ],
       "dev": true,
-      "libc": [
-        "glibc"
-      ],
       "license": "MIT",
       "optional": true,
       "os": [
@@ -2264,9 +2229,6 @@
         "x64"
       ],
       "dev": true,
-      "libc": [
-        "musl"
-      ],
       "license": "MIT",
       "optional": true,
       "os": [
@@ -9114,10 +9076,9 @@
       "license": "ISC"
     },
     "node_modules/yaml": {
-      "version": "2.8.3",
+      "version": "2.9.1",
-      "resolved": "https://registry.npmjs.org/yaml/-/yaml-2.8.3.tgz",
+      "resolved": "https://registry.npmjs.org/yaml/-/yaml-2.9.1.tgz",
-      "integrity": "sha512-AvbaCLOO2Otw/lW5bmh9d/WEdcDFdQp2Z2ZUH3pX9U2ihyUY0nvLv7J6TrWowklRGPYbB/IuIMfYgxaCPg5Bpg==",
+      "integrity": "sha512-3NxN8+78OdzbT7C/WjGsyfPAtJaN3FNDsWxv7Y7mcDsT/oOmgW8BpyQQFFBnvZE3j9Y2Sdz1ULFLezL7Eb2yFw==",
-      "dev": true,
       "license": "ISC",
       "bin": {
         "yaml": "bin.mjs"

frontend/package.json

@@ -42,6 +42,7 @@
     "remark-gfm": "^4.0.1",
     "tailwind-merge": "^3.3.0",
     "unist-util-visit-parents": "^6.0.1",
+    "yaml": "^2.9.1",
     "zustand": "^5.0.8"
   },
   "devDependencies": {

frontend/scripts/help-assets.test.ts

@@ -0,0 +1,112 @@
+import { mkdir, mkdtemp, rm, writeFile } from 'node:fs/promises'
+import { tmpdir } from 'node:os'
+import path from 'node:path'
+import { afterAll, afterEach, beforeEach, describe, expect, it, vi } from 'vitest'
+
+import { generateHelpAssets } from './help-assets'
+
+import type { ArticleMeta, HelpChange, HelpSearchEntry, HelpTitleIndex } from '@/lib/help'
+
+vi.hoisted (() => {
+  vi.stubGlobal ('Uint8Array', Object.getPrototypeOf (new TextEncoder ().encode ('')).constructor)
+})
+afterAll (() => vi.unstubAllGlobals ())
+
+
+const readAsset = <T,> (modules: Map<string, string>, name: string): T => {
+  const source = modules.get (`virtual:help/${ name }`)!
+  const argument = source.slice ('export default JSON.parse('.length, -1)
+  return JSON.parse (JSON.parse (argument))
+}
+
+
+describe ('Build-time Help assets', () => {
+  let root: string
+
+  beforeEach (async () => {
+    root = await mkdtemp (path.join (tmpdir (), 'btrc-help-assets-'))
+  })
+
+  afterEach (async () => {
+    await rm (root, { recursive: true, force: true })
+  })
+
+  const writeArticle = async (
+      identifier: string,
+      editions: Record<string, string>,
+      current = '2026-10-02.10',
+  ) => {
+    const articleRoot = path.join (root, identifier)
+    const editionRoot = path.join (articleRoot, 'editions', 'ja')
+    await mkdir (editionRoot, { recursive: true })
+    await writeFile (path.join (articleRoot, 'article.yml'), [
+	`identifier: ${ identifier }`, 'canonical_language: ja', 'title: stale YAML title',
+	'languages:', '  ja:', `    current_edition: ${ current }`].join ('\n'))
+    await Promise.all (Object.entries (editions).map (([edition, source]) =>
+	writeFile (path.join (editionRoot, `${ edition }.mdx`), source)))
+  }
+
+  it ('generates current search and ordered published history from each edition H1', async () => {
+    await writeArticle ('guide', {
+	'2026-10-01': '# 旧ホーム\n\n過去本文',
+	'2026-10-02': '# ホーム\n\n最初の同日版',
+	'2026-10-02.2': '# ホーム\n\n第二版',
+	'2026-10-02.3': '# ホーム\n\n第三版',
+	'2026-10-02.10': '\uFEFF# 最新ホーム\r\n\r\n現在本文\r\n# 別見出し',
+	'2026-10-02.11': '# 未公開\n\n検索に含めない' })
+    const { modules } = await generateHelpAssets (root)
+    const articles = readAsset<Record<string, ArticleMeta>> (modules, 'articles')
+    expect (articles.guide.languages.ja).toEqual ({
+	currentEdition: '2026-10-02.10', publishedEditions: [
+	    '2026-10-01', '2026-10-02', '2026-10-02.2', '2026-10-02.3', '2026-10-02.10'] })
+    expect (readAsset<Record<string, HelpSearchEntry[]>> (modules, 'search').ja).toEqual ([{
+	identifier: 'guide', edition: '2026-10-02.10', title: '最新ホーム',
+	body: '\r\n現在本文\r\n# 別見出し' }])
+    const changes = readAsset<Record<string, HelpChange[]>> (modules, 'changes').ja
+    expect (changes.map (row => [row.edition, row.title, row.pred, row.change, row.date]))
+	.toEqual ([
+	    ['2026-10-02.10', '最新ホーム', '2026-10-02.3', 'update', '2026-10-02'],
+	    ['2026-10-02.3', 'ホーム', '2026-10-02.2', 'update', '2026-10-02'],
+	    ['2026-10-02.2', 'ホーム', '2026-10-02', 'update', '2026-10-02'],
+	    ['2026-10-02', 'ホーム', '2026-10-01', 'update', '2026-10-02'],
+	    ['2026-10-01', '旧ホーム', null, 'new', '2026-10-01']])
+    const titles = readAsset<Record<string, HelpTitleIndex>> (modules, 'titles').ja
+    expect (titles).toEqual ({ '旧ホーム': ['guide'], 'ホーム': ['guide'],
+	'最新ホーム': ['guide'] })
+    expect (modules.get ('virtual:help/loaders')).not.toContain ('2026-10-02.11')
+    expect (modules.get ('virtual:help/loaders')).toContain ('2026-10-02.10.mdx?raw')
+    expect (modules.get ('virtual:help/search')).not.toContain ('import(')
+  })
+
+  it ('retains ambiguous title identifiers and normalises width and case', async () => {
+    await writeArticle ('alpha', { '2026-10-02': '# ＨＯＭＥ\n本文' }, '2026-10-02')
+    await writeArticle ('beta', { '2026-10-02': '# Home\n本文' }, '2026-10-02')
+    const { modules } = await generateHelpAssets (root)
+    expect (readAsset<Record<string, HelpTitleIndex>> (modules, 'titles').ja.home)
+	.toEqual (['alpha', 'beta'])
+    expect (readAsset<Record<string, HelpChange[]>> (modules, 'changes').ja
+	.map (row => row.identifier)).toEqual (['alpha', 'beta'])
+  })
+
+  it ('rejects missing current files during generation', async () => {
+    await writeArticle ('guide', { '2026-10-02': '# ホーム' })
+    await expect (generateHelpAssets (root)).rejects.toThrow ('Missing current Help edition')
+  })
+
+  it.each (['本文\n# 遅い見出し', '#   \n本文']) (
+      'rejects missing leading H1 at build time: %s', async source => {
+	await writeArticle ('guide', { '2026-10-02.10': source })
+	await expect (generateHelpAssets (root)).rejects.toThrow ('Missing leading Help H1')
+      })
+
+  it ('rejects absent canonical metadata instead of generating incomplete assets', async () => {
+    await writeArticle ('guide', { '2026-10-02.10': '# ホーム' })
+    await writeFile (path.join (root, 'guide', 'article.yml'),
+	'identifier: guide\nlanguages:\n  ja:\n    current_edition: 2026-10-02.10')
+    await expect (generateHelpAssets (root)).rejects.toThrow ('Invalid Help metadata')
+  })
+
+  it ('rejects an empty Help checkout', async () => {
+    await expect (generateHelpAssets (root)).rejects.toThrow ('No Help articles found')
+  })
+})

frontend/scripts/help-assets.ts

@@ -0,0 +1,192 @@
+import { readFile, readdir } from 'node:fs/promises'
+import path from 'node:path'
+import { normalizePath as normalisePath } from 'vite'
+import { parse as parseYAML } from 'yaml'
+
+import type { Plugin } from 'vite'
+
+type Language = { currentEdition: string; publishedEditions: string[] }
+type Article = {
+    identifier: string
+    canonicalLanguage: string
+    languages: Record<string, Language> }
+type Text = { title: string; body: string }
+type SearchEntry = Text & { identifier: string; edition: string }
+type Change = {
+    identifier: string
+    edition: string
+    title: string
+    pred: string | null
+    change: 'new' | 'update'
+    date: string }
+type RawArticle = {
+    identifier: string
+    canonical_language: string
+    languages: Record<string, { current_edition: string }> }
+
+const prefix = 'virtual:help/'
+
+
+const compareEditions = (a: string, b: string): number => {
+  const [dateA, revisionA = '1'] = a.split ('.')
+  const [dateB, revisionB = '1'] = b.split ('.')
+  return dateA.localeCompare (dateB) || Number (revisionA) - Number (revisionB)
+}
+
+
+const validateEdition = (edition: string): void => {
+  const [date, revision = '1'] = edition.split ('.')
+  if (!(/^\d{4}-\d{2}-\d{2}(?:\.[1-9]\d*)?$/.test (edition))
+      || new Date (date).toISOString ().slice (0, 10) !== date
+      || !(Number.isSafeInteger (Number (revision))))
+    throw new Error (`Invalid Help edition: ${ edition }`)
+}
+
+
+export const generateHelpAssets = async (
+    root: string,
+): Promise<{ modules: Map<string, string>; files: string[] }> => {
+  const modules = new Map<string, string> ()
+  const files: string[] = [root]
+  const articles: Record<string, Article> = Object.create (null)
+  const search: Record<string, SearchEntry[]> = Object.create (null)
+  const changes: Record<string, Change[]> = Object.create (null)
+  const titles: Record<string, Record<string, string[]>> = Object.create (null)
+  const components: string[] = []
+  const sources: string[] = []
+  const texts: string[] = []
+  const directories = (await readdir (root, { withFileTypes: true }))
+      .filter (entry => entry.isDirectory () && !(entry.name.startsWith ('.')))
+      .sort ((a, b) => a.name.localeCompare (b.name))
+
+  for (const directory of directories)
+  {
+    const articlePath = path.join (root, directory.name, 'article.yml')
+    files.push (articlePath)
+    const raw = parseYAML (await readFile (articlePath, 'utf8')) as RawArticle | null
+    if (raw == null || raw.identifier !== directory.name
+	|| typeof raw.canonical_language !== 'string'
+	|| raw.languages == null || typeof raw.languages !== 'object'
+	|| !(Object.hasOwn (raw.languages, raw.canonical_language)))
+      throw new Error (`Invalid Help metadata: ${ articlePath }`)
+
+    const article: Article = {
+	identifier: raw.identifier,
+	canonicalLanguage: raw.canonical_language,
+	languages: Object.create (null) }
+    articles[raw.identifier] = article
+
+    for (const [language, metadata] of Object.entries (raw.languages))
+    {
+      if (!(/^[a-zA-Z0-9-]+$/.test (language))
+	  || typeof metadata?.current_edition !== 'string')
+	throw new Error (`Invalid Help language: ${ articlePath }/${ language }`)
+
+      const currentEdition = metadata.current_edition
+      validateEdition (currentEdition)
+      const editionRoot = path.join (root, directory.name, 'editions', language)
+      files.push (editionRoot)
+      const editions = (await readdir (editionRoot)).filter (name => name.endsWith ('.mdx'))
+	  .map (name => name.slice (0, -4))
+      editions.forEach (validateEdition)
+      if (!(editions.includes (currentEdition)))
+	throw new Error (`Missing current Help edition: ${ editionRoot }/${ currentEdition }`)
+
+      const publishedEditions = editions
+	  .filter (edition => compareEditions (edition, currentEdition) <= 0)
+	  .sort (compareEditions)
+      article.languages[language] = { currentEdition, publishedEditions }
+      search[language] ??= []
+      changes[language] ??= []
+      titles[language] ??= Object.create (null)
+
+      for (const [index, edition] of publishedEditions.entries ())
+      {
+	const sourcePath = path.join (editionRoot, `${ edition }.mdx`)
+	files.push (sourcePath)
+	const mdx = (await readFile (sourcePath, 'utf8')).replace (/^\uFEFF/, '')
+	const heading = mdx.match (/^# +([^\r\n]+)(?:\r?\n|$)/)
+	if (heading == null || !(heading[1].trim ()))
+	  throw new Error (`Missing leading Help H1: ${ sourcePath }`)
+
+	const text = { title: heading[1].trim (), body: mdx.slice (heading[0].length) }
+	const key = JSON.stringify (`${ raw.identifier }/${ language }/${ edition }`)
+	const textId = `${ prefix }text/${ raw.identifier }/${ language }/${ edition }`
+	const componentId = JSON.stringify (normalisePath (sourcePath))
+	const sourceId = JSON.stringify (normalisePath (sourcePath) + '?raw')
+	modules.set (textId, `export default ${ JSON.stringify (text) }`)
+	texts.push (`${ key }: () => import(${ JSON.stringify (textId) })`)
+	components.push (`${ key }: () => import(${ componentId })`)
+	sources.push (`${ key }: () => import(${ sourceId })`)
+
+	if (edition === currentEdition)
+	  search[language].push ({ identifier: raw.identifier, edition, ...text })
+	changes[language].push ({ identifier: raw.identifier, edition, title: text.title,
+	    pred: publishedEditions[index - 1] ?? null,
+	    change: index === 0 ? 'new' : 'update', date: edition.split ('.')[0] })
+	const title = text.title.trim ().normalize ('NFKC').toLowerCase ()
+	const identifiers = titles[language][title] ??= []
+	if (!(identifiers.includes (raw.identifier)))
+	  identifiers.push (raw.identifier)
+      }
+    }
+  }
+
+  if (Object.keys (articles).length === 0)
+    throw new Error (`No Help articles found: ${ root }`)
+
+  Object.values (changes).forEach (rows => rows.sort ((a, b) =>
+      compareEditions (b.edition, a.edition) || a.identifier.localeCompare (b.identifier)))
+  for (const [name, data] of Object.entries ({ articles, search, changes, titles }))
+  {
+    modules.set (`${ prefix }${ name }`,
+	`export default JSON.parse(${ JSON.stringify (JSON.stringify (data)) })`)
+  }
+  modules.set (`${ prefix }loaders`, [
+      `export const components = { ${ components.join (',\n') } };`,
+      `export const sources = { ${ sources.join (',\n') } };`,
+      `export const texts = { ${ texts.join (',\n') } };`].join ('\n'))
+  return { modules, files }
+}
+
+
+export const helpAssets = (): Plugin => {
+  const state: { root: string; data?: ReturnType<typeof generateHelpAssets> } = { root: '' }
+  const data = () => state.data ??= generateHelpAssets (state.root)
+
+  return {
+      name: 'help-assets',
+      configResolved (config) {
+	state.root = path.resolve (config.root, 'help')
+      },
+      async buildStart () {
+	state.data = generateHelpAssets (state.root)
+	const generated = await data ()
+	generated.files.forEach (file => this.addWatchFile (file))
+      },
+      resolveId (id) {
+	return id.startsWith (prefix) ? `\0${ id }` : null
+      },
+      async load (id) {
+	if (!(id.startsWith (`\0${ prefix }`)))
+	  return null
+	const source = (await data ()).modules.get (id.slice (1))
+	if (source == null)
+	  throw new Error (`Unknown Help asset: ${ id.slice (1) }`)
+	return source
+      },
+      configureServer (server) {
+	server.watcher.add (state.root)
+	server.watcher.on ('all', (_event, file) => {
+	  if (!(file.startsWith (state.root + path.sep)) || !(/\.(mdx|yml)$/.test (file)))
+	    return
+	  state.data = undefined
+	  for (const module of server.moduleGraph.idToModuleMap.values ())
+	  {
+	    if (module.id?.startsWith (`\0${ prefix }`))
+	      server.moduleGraph.invalidateModule (module)
+	  }
+	  server.ws.send ({ type: 'full-reload' })
+	})
+      } }
+}

frontend/src/App.tsx

@@ -15,7 +15,6 @@ import { Toaster } from '@/components/ui/toaster'
 import { apiPost, isApiError } from '@/lib/api'
 import { applyClientAnimationMode,
 	 applyClientAppearance,
-	 type ClientAnimationMode,
 	 fetchUserThemeSlots,
 	 fetchUserSettings,
 	 getClientThemeMode,
@@ -25,7 +24,6 @@ import { applyClientAnimationMode,
 	 seedClientThemeMode } from '@/lib/settings'
 import { useClientBehaviourSettings } from '@/lib/useClientBehaviourSettings'
 import { UnsavedChangesGuardProvider } from '@/lib/useUnsavedChangesGuard'
-
 import { KeyboardShortcutsProvider } from '@/lib/useKeyboardShortcuts'
 import DeerjikistDetailPage from '@/pages/deerjikists/DeerjikistDetailPage'
 import MaterialBasePage from '@/pages/materials/MaterialBasePage'
@@ -34,12 +32,15 @@ import MaterialHistoryPage from '@/pages/materials/MaterialHistoryPage'
 import MaterialListPage from '@/pages/materials/MaterialListPage'
 import MaterialNewPage from '@/pages/materials/MaterialNewPage'
 import MaterialSyncSuppressionsPage from '@/pages/materials/MaterialSyncSuppressionsPage'
-// import MaterialSearchPage from '@/pages/materials/MaterialSearchPage'
 import MorePage from '@/pages/MorePage'
 import GekanatorPage from '@/pages/GekanatorPage'
 import NicoTagListPage from '@/pages/tags/NicoTagListPage'
 import NotFound from '@/pages/NotFound'
 import TOSPage from '@/pages/TOSPage.mdx'
+import HelpDetailPage from '@/pages/help/HelpDetailPage'
+import HelpChangesPage from '@/pages/help/HelpChangesPage'
+import HelpDiffPage from '@/pages/help/HelpDiffPage'
+import HelpListPage from '@/pages/help/HelpListPage'
 import PostDetailPage from '@/pages/posts/PostDetailPage'
 import PostHistoryPage from '@/pages/posts/PostHistoryPage'
 import PostNewPage from '@/pages/posts/PostNewPage'
@@ -60,90 +61,62 @@ import WikiSearchPage from '@/pages/wiki/WikiSearchPage'
 
 import type { Dispatch, FC, SetStateAction } from 'react'
 
+import type { ClientAnimationMode } from '@/lib/settings'
 import type { User } from '@/types'
 
 
 const RouteTransitionWrapper = ({ animationMode, user, setUser }: {
-    animationMode: ClientAnimationMode
+    animationMode:  ClientAnimationMode
-    user:     User | null
+    user:           User | null
-    setUser:  Dispatch<SetStateAction<User | null>> }) => {
+    setUser:        Dispatch<SetStateAction<User | null>> }) => {
   const location = useLocation ()
 
+  const routes = (
+      <Routes location={location}>
+	<Route path="/" element={<Navigate to="/posts" replace/>}/>
+	<Route path="/posts" element={<PostListPage/>}/>
+	<Route path="/posts/new" element={<PostNewPage user={user}/>}/>
+	<Route path="/posts/search" element={<PostSearchPage/>}/>
+	<Route path="/posts/:id" element={<PostDetailRoute user={user}/>}/>
+	<Route path="/posts/changes" element={<PostHistoryPage/>}/>
+	<Route path="/tags" element={<TagListPage/>}/>
+	<Route path="/tags/:id" element={<TagDetailPage/>}/>
+	<Route path="/tags/:id/deerjikists" element={<DeerjikistDetailPage/>}/>
+	<Route path="/tags/nico" element={<NicoTagListPage user={user}/>}/>
+	<Route path="/nico/tags" element={<NicoTagListPage user={user}/>}/>
+	<Route path="/tags/changes" element={<TagHistoryPage/>}/>
+	<Route path="/theatres/:id" element={<TheatreDetailPage user={user}/>}/>
+	<Route path="/materials" element={<MaterialBasePage/>}>
+	  <Route index element={<MaterialListPage/>}/>
+	  <Route path="changes" element={<MaterialHistoryPage/>}/>
+	  <Route path="new" element={<MaterialNewPage/>}/>
+	  <Route path="suppressions" element={<MaterialSyncSuppressionsPage/>}/>
+	  <Route path=":id" element ={<MaterialDetailPage/>}/>
+	</Route>
+	<Route path="/wiki" element={<WikiSearchPage/>}/>
+	<Route path="/wiki/:title" element={<WikiDetailPage/>}/>
+	<Route path="/wiki/new" element={<WikiNewPage user={user}/>}/>
+	<Route path="/wiki/:id/edit" element={<WikiEditPage user={user}/>}/>
+	<Route path="/wiki/:id/diff" element={<WikiDiffPage/>}/>
+	<Route path="/wiki/changes" element={<WikiHistoryPage/>}/>
+	<Route path="/help" element={<HelpListPage/>}/>
+	<Route path="/help/changes" element={<HelpChangesPage/>}/>
+	<Route path="/help/:identifier/diff" element={<HelpDiffPage/>}/>
+	<Route path="/help/:identifier" element={<HelpDetailPage/>}/>
+	<Route path="/users/settings" element={<SettingPage user={user} setUser={setUser}/>}/>
+	<Route path="/settings" element={<Navigate to="/users/settings" replace/>}/>
+	<Route path="/tos" element={<TOSPage/>}/>
+	<Route path="/gekanator" element={<GekanatorPage user={user}/>}/>
+	<Route path="/more" element={<MorePage/>}/>
+	<Route path="*" element={<NotFound/>}/>
+      </Routes>)
+
   if (animationMode === 'off')
-    {
+    return routes
-      return (
-	  <Routes location={location}>
-	    <Route path="/" element={<Navigate to="/posts" replace/>}/>
-	    <Route path="/posts" element={<PostListPage/>}/>
-	    <Route path="/posts/new" element={<PostNewPage user={user}/>}/>
-	    <Route path="/posts/search" element={<PostSearchPage/>}/>
-	    <Route path="/posts/:id" element={<PostDetailRoute user={user}/>}/>
-	    <Route path="/posts/changes" element={<PostHistoryPage/>}/>
-	    <Route path="/tags" element={<TagListPage/>}/>
-	    <Route path="/tags/:id" element={<TagDetailPage/>}/>
-	    <Route path="/tags/:id/deerjikists" element={<DeerjikistDetailPage/>}/>
-	    <Route path="/tags/nico" element={<NicoTagListPage user={user}/>}/>
-	    <Route path="/nico/tags" element={<NicoTagListPage user={user}/>}/>
-	    <Route path="/tags/changes" element={<TagHistoryPage/>}/>
-	    <Route path="/theatres/:id" element={<TheatreDetailPage user={user}/>}/>
-	    <Route path="/materials" element={<MaterialBasePage/>}>
-	      <Route index element={<MaterialListPage/>}/>
-	      <Route path="changes" element={<MaterialHistoryPage/>}/>
-	      <Route path="new" element={<MaterialNewPage/>}/>
-	      <Route path="suppressions" element={<MaterialSyncSuppressionsPage/>}/>
-	      <Route path=":id" element ={<MaterialDetailPage/>}/>
-	    </Route>
-	    <Route path="/wiki" element={<WikiSearchPage/>}/>
-	    <Route path="/wiki/:title" element={<WikiDetailPage/>}/>
-	    <Route path="/wiki/new" element={<WikiNewPage user={user}/>}/>
-	    <Route path="/wiki/:id/edit" element={<WikiEditPage user={user}/>}/>
-	    <Route path="/wiki/:id/diff" element={<WikiDiffPage/>}/>
-	    <Route path="/wiki/changes" element={<WikiHistoryPage/>}/>
-	    <Route path="/users/settings" element={<SettingPage user={user} setUser={setUser}/>}/>
-	    <Route path="/settings" element={<Navigate to="/users/settings" replace/>}/>
-	    <Route path="/tos" element={<TOSPage/>}/>
-	    <Route path="/gekanator" element={<GekanatorPage user={user}/>}/>
-	    <Route path="/more" element={<MorePage/>}/>
-	    <Route path="*" element={<NotFound/>}/>
-	  </Routes>)
-    }
 
   return (
       <AnimatePresence mode="wait">
-	<Routes location={location}>
+	{routes}
-	  <Route path="/" element={<Navigate to="/posts" replace/>}/>
-	  <Route path="/posts" element={<PostListPage/>}/>
-	  <Route path="/posts/new" element={<PostNewPage user={user}/>}/>
-	  <Route path="/posts/search" element={<PostSearchPage/>}/>
-	  <Route path="/posts/:id" element={<PostDetailRoute user={user}/>}/>
-	  <Route path="/posts/changes" element={<PostHistoryPage/>}/>
-	  <Route path="/tags" element={<TagListPage/>}/>
-	  <Route path="/tags/:id" element={<TagDetailPage/>}/>
-	  <Route path="/tags/:id/deerjikists" element={<DeerjikistDetailPage/>}/>
-	  <Route path="/tags/nico" element={<NicoTagListPage user={user}/>}/>
-	  <Route path="/nico/tags" element={<NicoTagListPage user={user}/>}/>
-	  <Route path="/tags/changes" element={<TagHistoryPage/>}/>
-	  <Route path="/theatres/:id" element={<TheatreDetailPage user={user}/>}/>
-	  <Route path="/materials" element={<MaterialBasePage/>}>
-	    <Route index element={<MaterialListPage/>}/>
-	    <Route path="changes" element={<MaterialHistoryPage/>}/>
-	    <Route path="new" element={<MaterialNewPage/>}/>
-	    <Route path="suppressions" element={<MaterialSyncSuppressionsPage/>}/>
-	    <Route path=":id" element ={<MaterialDetailPage/>}/>
-	  </Route>
-	  <Route path="/wiki" element={<WikiSearchPage/>}/>
-	  <Route path="/wiki/:title" element={<WikiDetailPage/>}/>
-	  <Route path="/wiki/new" element={<WikiNewPage user={user}/>}/>
-	  <Route path="/wiki/:id/edit" element={<WikiEditPage user={user}/>}/>
-	  <Route path="/wiki/:id/diff" element={<WikiDiffPage/>}/>
-	  <Route path="/wiki/changes" element={<WikiHistoryPage/>}/>
-	  <Route path="/users/settings" element={<SettingPage user={user} setUser={setUser}/>}/>
-	  <Route path="/settings" element={<Navigate to="/users/settings" replace/>}/>
-	  <Route path="/tos" element={<TOSPage/>}/>
-	  <Route path="/gekanator" element={<GekanatorPage user={user}/>}/>
-	  <Route path="/more" element={<MorePage/>}/>
-	  <Route path="*" element={<NotFound/>}/>
-	</Routes>
       </AnimatePresence>)
 }
 
@@ -166,9 +139,9 @@ const RoutedApp: FC = () => {
       () => (
 	  animationMode === 'off'
 	  ? { duration: 0 }
-	  : animationMode === 'reduced'
+	  : (animationMode === 'reduced'
-	    ? { duration: .08, ease: 'linear' as const }
+	     ? { duration: .08, ease: 'linear' as const }
-	    : { duration: .2, ease: 'easeOut' as const }
+	     : { duration: .2, ease: 'easeOut' as const })
       ),
       [animationMode],
   )
@@ -285,10 +258,12 @@ const RoutedApp: FC = () => {
       </DialogueProvider>)
 }
 
+
 const router = createBrowserRouter ([{
     path: '*',
     element: <RoutedApp/> }])
 
+
 const App: FC = () => (
     <>
       <RouteBlockerOverlay/>
@@ -296,4 +271,5 @@ const App: FC = () => (
       <RouterProvider router={router}/>
     </>)
 
+
 export default App

frontend/src/components/TopNav.tsx

@@ -20,6 +20,7 @@ import type { FC, MouseEvent } from 'react'
 import type { Material, Menu, MenuVisibleItem, Tag, User } from '@/types'
 
 type Props = { user: User | null }
+type NavDensity = 'auto' | 'comfortable' | 'compact'
 
 
 export const menuOutline = (
@@ -40,6 +41,9 @@ export const menuOutline = (
 
   const materialFlg = /^\/materials\/\d+/.test (pathName)
 
+  const helpVsbl = /\/help\/((?!changes)[^\/?]+)/.test (pathName)
+  const helpIdentifier = pathName.split ('/')[2] ?? ''
+
   return [
       { name: '広場', to: '/posts', subMenu: [
 	  { name: '一覧', to: '/posts' },
@@ -71,7 +75,7 @@ export const menuOutline = (
 	    visible: materialFlg && Boolean (material?.tag) },
 	  { name: '履歴', to: `/materials/changes?material_id=${ material?.id }`,
 	    visible: materialFlg }] },
-      { name: 'Wiki', to: '/wiki/ヘルプ:ホーム', base: '/wiki', subMenu: [
+      { name: 'Wiki', to: '/wiki', subMenu: [
 	  { name: '検索', to: '/wiki' },
 	  { name: '新規', to: '/wiki/new', visible: editable },
 	  { name: '全体履歴', to: '/wiki/changes' },
@@ -82,6 +86,13 @@ export const menuOutline = (
 	  { name: '履歴', to: `/wiki/changes?id=${ wikiId }`, visible: wikiPageFlg },
 	  { name: '編輯', to: `/wiki/${ wikiId || wikiTitle }/edit`,
 	    visible: wikiPageFlg && editable }] },
+      { name: 'ヘルプ', to: '/help/home', base: '/help', subMenu: [
+	  { name: '検索', to: '/help' },
+	  { name: '全体履歴', to: '/help/changes' },
+	  { component: <Separator/>, visible: helpVsbl },
+	  { name: '履歴',
+	    to: `/help/changes?identifier=${ helpIdentifier }`,
+	    visible: helpVsbl }] },
       { name: 'おたのしみ', visible: false, subMenu: [
 	  { name: '上映会 (β)', to: '/theatres/1' },
 	  { name: 'グカネータ (β)', to: '/gekanator' }] },
@@ -104,6 +115,8 @@ const TopNav: FC<Props> = ({ user }) => {
   const dirRef = useRef<(-1) | 1> (1)
   const itemsRef = useRef<(HTMLAnchorElement | null)[]> ([])
   const navRef = useRef<HTMLDivElement | null> (null)
+  const layoutRef = useRef<HTMLDivElement | null> (null)
+  const barRef = useRef<HTMLElement | null> (null)
 
   const measure = (idx: number) => {
     const nav = navRef.current
@@ -128,6 +141,8 @@ const TopNav: FC<Props> = ({ user }) => {
       width:    0,
       visible:  false })
   const [menuOpen, setMenuOpen] = useState (false)
+  const [desktop, setDesktop] = useState (false)
+  const [density, setDensity] = useState<NavDensity> ('auto')
   const [moreVsbl, setMoreVsbl] = useState (false)
   const [openItemIdx, setOpenItemIdx] = useState (-1)
   const [wikiId, setWikiId] = useState<number | null> (WikiIdBus.get ())
@@ -194,15 +209,81 @@ const TopNav: FC<Props> = ({ user }) => {
   const dir = dirRef.current
 
   useLayoutEffect (() => {
-    const raf = requestAnimationFrame (() => measure (moreVsbl ? -1 : activeIdx))
+    const layout = layoutRef.current
-    const onResize = () => requestAnimationFrame (() => measure (moreVsbl ? -1 : activeIdx))
+    const bar = barRef.current
+    const primary = bar?.querySelector<HTMLElement> ('.top-nav-primary')
+    if (layout == null || bar == null || primary == null)
+      return
 
-    addEventListener ('resize', onResize)
+    const userLink = bar.querySelector<HTMLElement> ('.top-nav-user-desktop')
-    return () => {
+    let raf = 0
-      cancelAnimationFrame (raf)
+    let active = true
-      removeEventListener ('resize', onResize)
+
+    const update = () => {
+      if (!(window.matchMedia ('(min-width: 768px)').matches))
+      {
+	setDesktop (false)
+	setDensity ('auto')
+	return
+      }
+
+      // Measure the same desktop elements while the mobile layout is active.
+      layout.setAttribute ('data-measuring', '')
+      const previousDensity = layout.getAttribute ('data-density') ?? 'auto'
+      const fittingDensity = (() => {
+	try
+	{
+	  for (const candidate of ['auto', 'comfortable', 'compact'] as const)
+	  {
+	    layout.setAttribute ('data-density', candidate)
+	    const style = getComputedStyle (bar)
+	    const required = primary.getBoundingClientRect ().width
+		+ (userLink?.getBoundingClientRect ().width ?? 0)
+		+ parseFloat (style.paddingLeft) + parseFloat (style.paddingRight)
+		+ (userLink == null ? 0 : parseFloat (style.columnGap))
+	    if (required <= bar.clientWidth)
+	      return candidate
+	  }
+	  return null
+	}
+	finally
+	{
+	  layout.setAttribute ('data-density', previousDensity)
+	  layout.removeAttribute ('data-measuring')
+	}
+      }) ()
+      setDensity (fittingDensity ?? 'compact')
+      setDesktop (fittingDensity != null)
+      if (fittingDensity != null)
+	measure (moreVsbl ? -1 : activeIdx)
     }
-  })
+
+    const schedule = () => {
+      if (!(active))
+	return
+      cancelAnimationFrame (raf)
+      raf = requestAnimationFrame (update)
+    }
+
+    const observer =
+	typeof ResizeObserver === 'undefined' ? null : new ResizeObserver (schedule)
+    observer?.observe (bar)
+    observer?.observe (primary)
+    if (userLink != null)
+      observer?.observe (userLink)
+    update ()
+    addEventListener ('resize', schedule)
+    document.fonts?.addEventListener ('loadingdone', schedule)
+    void document.fonts?.ready.then (schedule)
+
+    return () => {
+      active = false
+      cancelAnimationFrame (raf)
+      observer?.disconnect ()
+      removeEventListener ('resize', schedule)
+      document.fonts?.removeEventListener ('loadingdone', schedule)
+    }
+  }, [activeIdx, moreVsbl, desktop, density, user?.name])
 
   useEffect (() => {
     const unsubscribe = WikiIdBus.subscribe (setWikiId)
@@ -215,19 +296,22 @@ const TopNav: FC<Props> = ({ user }) => {
   }, [activeIdx, location])
 
   return (
-      <>
+      <div ref={layoutRef} className="top-nav-layout w-full min-w-0 shrink-0"
-	<nav className="top-nav-root px-3 flex justify-between items-center w-full">
+	  data-desktop={desktop} data-density={density}>
-	  <div className="flex items-center gap-2 h-12">
+	<nav ref={barRef}
+	    className="top-nav-root top-nav-bar flex justify-between items-center w-full">
+	  <div className="top-nav-primary flex shrink-0 items-center h-12">
 	    <PrefetchLink
 		to="/posts"
-		className="top-nav-brand-link mx-4 text-xl font-bold"
+		className="top-nav-brand-link shrink-0 whitespace-nowrap font-bold"
 		onClick={() => {
 		  scroll (0, 0)
 		}}>
 	      ぼざクリ タグ広場
 	    </PrefetchLink>
 
-	    <div ref={navRef} className="relative hidden md:flex h-12 items-center">
+	    <div ref={navRef}
+		className="top-nav-desktop-menu relative shrink-0 h-12 items-center">
 	      <div aria-hidden
 		   className={cn ('absolute inset-y-0 h-12',
 				  'top-nav-highlight',
@@ -239,6 +323,7 @@ const TopNav: FC<Props> = ({ user }) => {
 	      {visibleMenu.map ((item, i) => (
 		  <motion.div
 		      key={item.to}
+		      className="shrink-0 whitespace-nowrap"
 		      {...(animationsOff
 			   ? { }
 			   : { layoutId: `menu-${ item.name }` })}
@@ -252,7 +337,7 @@ const TopNav: FC<Props> = ({ user }) => {
 			ref={(el: (HTMLAnchorElement | null)) => {
 			  itemsRef.current[i] = el
 			}}
-			className={cn ('top-nav-menu-link relative z-10 flex h-full items-center px-5',
+			className={cn ('top-nav-menu-link relative z-10 flex h-full items-center',
 				       (i === openItemIdx) && 'font-bold')}>
 		      {item.name}
 		    </PrefetchLink>
@@ -267,7 +352,8 @@ const TopNav: FC<Props> = ({ user }) => {
 		    setMoreVsbl (true)
 		    measure (-1)
 		  }}
-		  className={cn ('top-nav-menu-link relative z-10 flex h-full items-center px-5',
+		  className={cn ('top-nav-menu-link relative z-10 flex h-full items-center',
+				 'shrink-0 whitespace-nowrap',
 				 (openItemIdx < 0 || moreVsbl) && 'font-bold')}>
 		その他 &raquo;
 	      </PrefetchLink>
@@ -278,7 +364,8 @@ const TopNav: FC<Props> = ({ user }) => {
 
 	  <button
 	     type="button"
-	     className="top-nav-mobile-toggle md:hidden ml-auto border-0 bg-transparent pr-4"
+	     className="top-nav-mobile-toggle shrink-0 whitespace-nowrap
+			ml-auto border-0 bg-transparent pr-4"
 	     onClick={() => {
 	       setMenuOpen (!(menuOpen))
 	     }}>
@@ -291,7 +378,8 @@ const TopNav: FC<Props> = ({ user }) => {
 	      key="submenu-shell"
 	      {...(animationsOff ? { }
 		   : { layout: true })}
-	      className="relative z-20 hidden md:block overflow-hidden top-nav-submenu"
+	      className="top-nav-desktop-submenu relative z-20 shrink-0
+			 overflow-hidden top-nav-submenu"
 	      animate={{ height: submenuHeight }}
 	      onMouseLeave={() => {
 		if (moreVsbl)
@@ -305,7 +393,8 @@ const TopNav: FC<Props> = ({ user }) => {
 	   ? (
 	      moreMenu.map ((item, i) => (
 		  <div key={i} className="relative h-[40px]">
-		    <div className="absolute inset-0 flex items-center px-3">
+		    <div className="absolute inset-0 flex items-center px-3
+				    overflow-x-auto whitespace-nowrap">
 		      <motion.div
 			  transition={topNavTransition}
 			  {...(animationsOff
@@ -315,7 +404,7 @@ const TopNav: FC<Props> = ({ user }) => {
 			       : { initial: { x: 40, y: -40, opacity: 0 },
 				   animate: { x: 0, y: 0, opacity: 1 },
 				   exit: { x: 40, y: -40, opacity: 0 } }))}
-			  className="z-10 h-full flex items-center px-3 font-bold w-28">
+			  className="z-10 h-full flex shrink-0 items-center px-3 font-bold w-28">
 			<h2>{item.name}</h2>
 		      </motion.div>
 		      {item.subMenu
@@ -363,7 +452,8 @@ const TopNav: FC<Props> = ({ user }) => {
 		  <div className="relative h-[40px]">
 		    {animationsOff
 		     ? (
-			 <div className="absolute inset-0 flex items-center px-3">
+			 <div className="absolute inset-0 flex items-center px-3
+					 overflow-x-auto whitespace-nowrap">
 			   {(visibleMenu[activeIdx]?.subMenu ?? [])
 			    .filter (item => item.visible ?? true)
 			    .map ((item, i) => (
@@ -392,7 +482,8 @@ const TopNav: FC<Props> = ({ user }) => {
 			       variants={{ enter: (d: -1 | 1) => ({ y: d * 24, opacity: 0 }),
 					   centre: { y: 0, opacity: 1 },
 					   exit: (d: -1 | 1) => ({ y: (-d) * 24, opacity: 0 }) }}
-			       className="absolute inset-0 flex items-center px-3"
+			       className="absolute inset-0 flex items-center px-3
+					  overflow-x-auto whitespace-nowrap"
 			       initial="enter"
 			       animate="centre"
 			       exit="exit"
@@ -432,7 +523,7 @@ const TopNav: FC<Props> = ({ user }) => {
 	 ? (
 	     menuOpen && (
 		 <div
-		     className={cn ('top-nav-root top-nav-mobile-menu flex flex-col md:hidden',
+		     className={cn ('top-nav-root top-nav-mobile-menu flex flex-col',
 				    'items-start')}>
 		   <Separator/>
 		   {visibleMenu.map ((item, i) => (
@@ -476,9 +567,6 @@ const TopNav: FC<Props> = ({ user }) => {
 		       </Fragment>))}
 		   <PrefetchLink
 		       to="/more"
-		       ref={(el: (HTMLAnchorElement | null)) => {
-			 itemsRef.current[visibleMenu.length] = el
-		       }}
 		       className={cn ('top-nav-mobile-row w-full min-h-[40px] flex items-center pl-8',
 				      ((openItemIdx < 0)
 				       && 'top-nav-mobile-active font-bold'))}>
@@ -492,7 +580,7 @@ const TopNav: FC<Props> = ({ user }) => {
 	       {menuOpen && (
 		   <motion.div
 		       key="spmenu"
-		       className={cn ('top-nav-root top-nav-mobile-menu flex flex-col md:hidden',
+		       className={cn ('top-nav-root top-nav-mobile-menu flex flex-col',
 				      'items-start')}
 		       variants={{ closed: { clipPath: 'inset(0 0 100% 0)',
 					     height:   0 },
@@ -558,9 +646,6 @@ const TopNav: FC<Props> = ({ user }) => {
 			 </Fragment>))}
 		     <PrefetchLink
 			 to="/more"
-			 ref={(el: (HTMLAnchorElement | null)) => {
-			   itemsRef.current[visibleMenu.length] = el
-			 }}
 			 className={cn ('top-nav-mobile-row w-full min-h-[40px] flex items-center pl-8',
 					((openItemIdx < 0)
 					 && 'top-nav-mobile-active font-bold'))}>
@@ -570,7 +655,7 @@ const TopNav: FC<Props> = ({ user }) => {
 		     <Separator/>
 		   </motion.div>)}
 	     </AnimatePresence>)}
-      </>)
+      </div>)
 }
 
 export default TopNav