#55

**本番 DB のバックアップをかならずすること**

Reviewed-on: #420
Co-authored-by: miteruzo <miteruzo@naver.com>

AGENTS.md

@@ -124,7 +124,7 @@ npm run preview
 - For arrays, never put whitespace or a line break immediately before `]`.
 - Keep the first element on the same line as `[` by default.
 - If an array would exceed the line limit, break after `[` and indent
-  elements by 4 spaces.
+  elements 4 spaces deeper than the statement's base indentation.
 
 ### Ruby delimiter and wrapping rules
 
@@ -140,6 +140,32 @@ npm run preview
   99 文字を超えるなら block 形式へ切り替へるか、message 定数化などで縮める。
 - Ruby の method chain や call argument を折り返す際、call-site の `)` を
   block close のやうに独立させない。
+- Ruby では、行末の `\` を用途を問はず一切使用しない。
+- Ruby では、文字列連結、logger message、method call、条件式、SQL 断片、
+  正規表現その他すべての式で、行末バックスラッシュによる継続を禁止する。
+- Ruby の block body は、その基準位置から 2 空白深くする。
+- Ruby の wrapped expression、method argument、array element、hash pair などの
+  continuation indentation は、その statement の基準位置から 4 空白深くする。
+- Ruby の continuation indentation を、行頭からの絶対空白数として扱はない。
+- Ruby では、暗黙的に継続可能な構文を優先し、method call、array、Hash 及び
+  括弧内ではバックスラッシュなしで改行する。
+- Ruby では、行長制限を守るために行末バックスラッシュを導入してはならない。
+- Ruby で行末バックスラッシュが必要に見える場合は、括弧内で自然に改行する、
+  一つの文字列補間へまとめる、中間変数へ分ける、`format` を使ふ、heredoc を
+  使ふ、array 又は Hash を組み立ててから処理する、条件式全体を括弧で囲む、
+  method へ抽出する、のいづれかへ書き換へる。
+- Ruby では、一つの文字列を、改行をまたいだ隣接文字列 literal として記述しない。
+- Ruby では、method argument 内でも、複数の文字列 literal を区切りなしで縦に
+  並べない。
+- RSpec の `describe`、`context`、`it` 等の description が長い場合は、意味を
+  保ったまま一行へ収まる文言へ短縮する。
+- 文字列を短縮できない場合は、用途に応じて `format`、heredoc 又は中間変数を
+  検討する。
+- ただし RSpec description では、原則として簡潔な一行の文字列を使ふ。
+- formatter 又は自動修正にも、Ruby の行末バックスラッシュを生成させない。
+- 新規 code だけでなく、今回触れる Ruby code にも行末バックスラッシュを残さない。
+- 例へば class body 内の array は、class body の 2 空白を基準に、更に 4 空白
+  深くするため、結果として行頭から 6 空白になる。
 
 Bad:
 
@@ -191,6 +217,63 @@ end
 
 Bad:
 
+```rb
+Rails.logger.info(
+    "post_import_metadata_fetch_failure "\
+    "#{ payload.to_json }")
+```
+
+Good:
+
+```rb
+payload = {
+    error: e.class.name,
+    message: e.message }
+
+Rails.logger.info(
+    "post_import_metadata_fetch_failure #{ payload.to_json }")
+```
+
+Bad:
+
+```rb
+message = "first "\
+          "second"
+```
+
+Good:
+
+```rb
+message = format(
+    '%<first>s %<second>s',
+    first: 'first',
+    second: 'second')
+```
+
+Bad:
+
+```rb
+result = first_value + \
+         second_value
+```
+
+Bad:
+
+```rb
+it(
+    'returns 409 when stale changes '
+    'do not conflict'
+) do
+```
+
+Good:
+
+```rb
+it 'returns mergeable 409 for stale non-conflicting changes' do
+```
+
+Bad:
+
 ```rb
 records.each {
   do_work(_1) }
@@ -225,20 +308,37 @@ records.each {
   formatting as the local reference shape: component and callback bodies use
   2-space block indentation, single-line bodies do not gain unnecessary
   braces, wrapped expressions use 4-space continuation indentation, multi-
-  stage ternaries use explicit parentheses, and only complete leading runs
+  stage ternaries use explicit parentheses, and TypeScript / TSX indentation
-  of 8 spaces are compressed to tabs.
+  and alignment whitespace compress every complete run of 8 spaces to tabs.
-- In TypeScript and TSX only, tabs are for leading 8-column compression only.
 - A tab does not represent one indentation level.
-- Do not replace 2-space or 4-space indentation with tabs.
+- In TypeScript and TSX, first determine visible indentation using 2-space
-- First determine visible indentation using 2-space block indentation and
+  block indentation and 4-space continuation indentation, then compress every
-  4-space continuation indentation, then compress only complete leading runs
+  complete run of 8 spaces used for indentation or column alignment to tabs.
-  of 8 spaces into tabs.
+- In TypeScript and TSX, 8-space compression is mandatory, not optional.
-- Tabs are only for leading indentation, never for spaces after non-space
+- In TypeScript and TSX, this applies both to leading indentation and to
-  text.
+  alignment whitespace after non-space text, such as aligned inline type
-- Keep residual leading 2, 4, or 6 spaces after any tab compression.
+  columns.
+- In TypeScript and TSX, keep residual 2, 4, or 6 spaces after each tab
+  compression.
+- In TypeScript and TSX, do not treat a tab as one logical indentation level.
+- In TypeScript and TSX, do not alter string literals, template-literal
+  contents, regular expressions, or user-facing text merely to apply tab
+  compression.
 - Examples: 2 columns = 2 spaces, 4 columns = 4 spaces, 6 columns = 6
   spaces, 8 columns = 1 tab, 10 columns = 1 tab + 2 spaces, 12 columns = 1
-  tab + 4 spaces, 16 columns = 2 tabs.
+  tab + 4 spaces, 14 columns = 1 tab + 6 spaces, 16 columns = 2 tabs.
+- When TypeScript or TSX code already uses column alignment, apply the same
+  8-space compression rule to that alignment whitespace.
+- Example:
+
+```ts
+type Props = {
+    row:	      PostImportRow
+    displayNumber?:   number
+    onEdit?:	  () => void
+    onRetry?:	  () => void
+    onToggleSkip?:    (checked: boolean) => void }
+```
 - TypeScript and TSX imports may stay on one line if they remain within the
   line limit; do not expand short type-only imports mechanically.
 - Keep runtime value imports and type imports in separate declarations.
@@ -474,8 +574,32 @@ and layout reuse, follow `frontend/AGENTS.md`.
   wording and placement before implementing it.
 - Do not invent replacement copy when removing unrequested wording.
 - Do not create, modify, or run tests unless the user explicitly asks for
-  test work. When the user asks for tests, keep working and rerun them until
+  test work. When the user asks for tests, keep working within the permitted
-  they pass or the remaining failure is clearly blocked.
+  test-file scope and rerun them until they pass or the remaining failure is
+  clearly blocked.
+- Test-only work includes adding, updating, deleting, reorganising, or fixing
+  SyntaxError in tests. During test-only work, do not modify production code.
+- During test-only work, do not change production constants, behaviour, API
+  contracts, validation, routes, authentication, permissions, UI, copy,
+  dependencies, limits, thresholds, defaults, migrations, schema, or
+  environment settings to satisfy tests.
+- Do not make production code match failing tests, mock assumptions, fixtures,
+  snapshots, old expectations, or stale setup. This includes changing
+  production constants merely because a test expects a different value.
+- If test work reveals a production bug, spec mismatch, or missing behaviour,
+  stop without modifying production code and report: the failing test or
+  discovered issue, the related production file, the actual behaviour, the
+  expected behaviour, and why a production change appears necessary.
+- Modify production code for test failures only when the user explicitly asks
+  for that production change. Do not expand a test task into a production task
+  on your own authority.
+- If the user explicitly asks for both production implementation and test
+  updates, implement production code to the confirmed specification first,
+  then add or update tests to verify that specification. Never roll production
+  behaviour back to satisfy old tests.
+- If it is unclear whether the test or the production implementation is stale,
+  or a test cannot be corrected without changing production code, ask the user
+  instead of guessing.
 
 ## Backend rules
 
@@ -529,6 +653,11 @@ and layout reuse, follow `frontend/AGENTS.md`.
 - Mobile UI must be checked as a first-class layout. Avoid wide fixed content,
   make dense controls wrap or scroll intentionally, and keep tag/filter
   controls usable without horizontal page overflow.
+- Frontend のスマホ／PC表示境界は原則 `md` とする。
+- button stack、footer action、dialogue action は `md` 未満で縦並び、
+  `md` 以上で横並びとする。
+- 同じ画面内で `sm` と `md` を混在させて中間 layout を作らない。
+- 明確に別の responsive 要件がある component だけを例外とする。
 - For mobile horizontal scrollers, make the scroll direction and item sizing
   explicit, and ensure chip text remains readable in both light and dark modes.
 - In TypeScript and TSX, prefer direct comparison operators such as `===` and
@@ -593,10 +722,10 @@ and layout reuse, follow `frontend/AGENTS.md`.
   beginning of a line.
 - The TSX-specific self-review must confirm JSX closing markers and closing
   parentheses keep the surrounding compact style.
-- The TypeScript/TSX self-review must confirm leading block indentation uses
+- The TypeScript/TSX self-review must confirm block indentation uses 2 spaces
-  2 spaces per level, wrapped continuations use the repository's 4-space
+  per level, wrapped continuations use the repository's 4-space continuation
-  continuation alignment, and complete leading runs of 8 spaces may be
+  alignment, and every complete run of 8 spaces used for indentation or
-  compressed to tabs.
+  alignment has been compressed to tabs.
 - Prefer `const` arrow functions for TypeScript/TSX component and helper declarations.
 - Put two blank lines before and after top-level `const` function
   declarations, unless imports, exports, or file boundaries make that awkward.
@@ -609,9 +738,18 @@ and layout reuse, follow `frontend/AGENTS.md`.
 - Indent the block body 2 spaces deeper than the keyword and opening brace.
 - Put the closing `}` on its own line at the same indentation as the keyword.
 - Do not write `try {`, `catch {`, or `finally {`.
-- In TypeScript and TSX, convert every complete leading run of 8 spaces to a
+- In TypeScript and TSX, convert every complete run of 8 spaces used for
-  tab character.
+  indentation or alignment to a tab character.
-- A leading tab is exactly equivalent to 8 leading spaces.
+- In TypeScript and TSX, a tab is exactly equivalent to 8 columns, whether it
+  appears at the beginning of a line or in alignment whitespace after
+  non-space text.
+- In TSX, JSX nesting uses 2-space block indentation and wrapped JSX
+  attributes use 4-space continuation indentation; after visible columns are
+  determined, compress every complete run of 8 spaces in the resulting
+  indentation or alignment to tabs.
+- In TSX, do not leave JSX subtree indentation at 8, 10, 12, 14, or 16
+  columns as spaces alone; convert each complete run of 8 spaces to tabs and
+  keep only the residual 2, 4, or 6 spaces.
 - In TypeScript and TSX function declarations, including `const` arrow
   function declarations, classify the parameter list before placing the closing
   `)`.
@@ -1254,9 +1392,9 @@ to `.ts` and `.tsx`:
 7. JSX `>` and `/>` stay with the final prop unless nearby code proves
    otherwise.
 8. JSX closing parentheses keep the compact local style.
-9. Leading block indentation uses 2 spaces per level, wrapped continuations
+9. Block indentation uses 2 spaces per level, wrapped continuations use the
-   use the repository's 4-space continuation alignment, and complete leading
+   repository's 4-space continuation alignment, and every complete run of 8
-   runs of 8 spaces may be compressed to tabs.
+   spaces used for indentation or alignment has been compressed to tabs.
 10. No line has trailing whitespace.
 
 Preferred:

backend/app/controllers/application_controller.rb

@@ -85,4 +85,13 @@ class ApplicationController < ActionController::API
                    base_errors: },
            status:
   end
+
+  def normalise_json value
+    return nil if value.nil?
+    return JSON.parse(value) if value.is_a?(String)
+
+    value
+  end
+
+  def resolve_locale! = Locale.find_by(code: params[:locale]) || Locale.nipponese
 end

backend/app/controllers/materials_controller.rb

@@ -72,6 +72,7 @@ class MaterialsController < ApplicationController
     return head :unauthorized unless current_user
     return head :forbidden unless current_user.gte_member?
 
+    locale = resolve_locale!
     tag_name_raw = params[:tag].to_s.strip
     file = params[:file]
     file_sha256 = MaterialFileSha256.from_upload(file)
@@ -89,7 +90,7 @@ class MaterialsController < ApplicationController
 
     begin
       Material.transaction do
-        tag = resolve_material_tag!(tag_name_raw)
+        tag = resolve_material_tag!(locale, tag_name_raw)
         material = Material.new(tag:, url:,
                                 created_by_user: current_user,
                                 updated_by_user: current_user)
@@ -132,12 +133,14 @@ class MaterialsController < ApplicationController
     block = MaterialImportBlockMatcher.match_for_sha256(file_sha256)
     return render_material_import_block(block) if block
 
+    locale = resolve_locale!
+
     uploaded_blob = build_uploaded_material_blob!(file, file_sha256)
 
     begin
       Material.transaction do
         MaterialVersionRecorder.ensure_snapshot!(material, created_by_user: current_user)
-        tag = resolve_material_tag!(tag_name_raw)
+        tag = resolve_material_tag!(locale, tag_name_raw)
         material.assign_attributes(tag:, url:, updated_by_user: current_user)
         if uploaded_blob
           material.file.attach(uploaded_blob)
@@ -236,10 +239,8 @@ class MaterialsController < ApplicationController
     nil
   end
 
-  def resolve_material_tag! tag_name_raw
+  def resolve_material_tag! locale, tag_name_raw
-    tag_name = TagName.find_undiscard_or_create_by!(name: tag_name_raw)
+    Tag.find_or_create_by_tag_name!(locale, tag_name_raw, category: :material)
-    tag = tag_name.tag
-    tag || Tag.create!(tag_name:, category: :material)
   end
 
   def material_index_needs_tag_name? filters

backend/app/controllers/nico_tags_controller.rb

@@ -15,30 +15,35 @@ class NicoTagsController < ApplicationController
     limit = 1 if limit < 1
 
     post_tag_max_sql =
-        PostTag
+        PostExternalTag
-        .select('tag_id, MAX(created_at) AS max_created_at')
+        .select('external_tag_id, MAX(created_at) AS max_created_at')
-        .group('tag_id')
+        .group('external_tag_id')
         .to_sql
 
-    q = Tag.nico_tags
+    q =
-           .joins(:tag_name)
+        ExternalTag
-           .joins("LEFT JOIN (#{ post_tag_max_sql }) post_tag_max " \
+        .joins("LEFT JOIN (#{ post_tag_max_sql }) post_tag_max " \
-                  'ON post_tag_max.tag_id = tags.id')
+               'ON post_tag_max.external_tag_id = external_tags.id')
-           .includes(:tag_name, tag_name: :wiki_page, linked_tags: { tag_name: :wiki_page })
+        .includes(linked_tags: { tag_name: :wiki_page })
-    q = q.where('tag_names.name LIKE ?', "%#{ name }%") if name
+    if name
+      q = q.where(('external_tags.name LIKE ? ' +
+                   "OR CONCAT(external_tags.platform, ':', external_tags.name) LIKE ?"),
+                  "%#{ name }%", "%#{ name }")
+    end
+
     if linked_tag
       linked_tag_ids =
-        Tag
+          Tag
-        .joins(:tag_name)
+          .joins(:tag_name)
-        .where('tag_names.name LIKE ?', "%#{ linked_tag }%")
+          .where('tag_names.name LIKE ?', "%#{ linked_tag }%")
-        .pluck(:id)
+          .pluck(:id)
       linked_nico_tag_ids = NicoTagRelation.where(tag_id: linked_tag_ids).pluck(:nico_tag_id)
       q = q.where(id: linked_nico_tag_ids)
     end
     if link_status.in?(['linked', 'unlinked'])
       exists_sql =
           'EXISTS (SELECT 1 FROM nico_tag_relations ' \
-          'WHERE nico_tag_relations.nico_tag_id = tags.id)'
+          'WHERE nico_tag_relations.nico_tag_id = external_tags.id)'
       q = link_status == 'linked' ? q.where(exists_sql) : q.where("NOT #{ exists_sql }")
     end
 
@@ -46,51 +51,58 @@ class NicoTagsController < ApplicationController
     sort_sql =
         case order[0]
         when 'name'
-          'tag_names.name'
+          'external_tags.name'
         when 'updated_at'
           'post_tag_max.max_created_at'
         else
-          "tags.#{ order[0] }"
+          "external_tags.#{ order[0] }"
         end
-    tags = q.reselect('tags.*',
+    tags = q.reselect('external_tags.*',
                       Arel.sql('post_tag_max.max_created_at AS recent_post_tag_created_at'))
-            .order(Arel.sql("#{ sort_sql } #{ order[1] }, tags.id #{ order[1] }"))
+            .order(Arel.sql("#{ sort_sql } #{ order[1] }, external_tags.id #{ order[1] }"))
             .limit(limit)
             .offset((page - 1) * limit)
             .to_a
 
     render json: { tags: tags.map { |tag|
-      TagRepr.base(tag).merge(
+      external_tag_json(tag).merge(
           recent_post_tag_created_at: tag.recent_post_tag_created_at,
           linked_tags: tag.linked_tags.map { |lt| TagRepr.base(lt) })
     }, count: }
   end
 
+  def show
+    tag = ExternalTag.find(params[:id])
+
+    render json: external_tag_json(tag)
+  end
+
   def update
     return head :unauthorized unless current_user
     return head :forbidden unless current_user.gte_member?
 
+    locale = resolve_locale!
+
     id = params[:id].to_i
 
-    tag = Tag.find(id)
+    tag = ExternalTag.find(id)
-    return render_bad_request('ニコニコ・タグを指定してください．') unless tag.nico?
 
     linked_tag_names = params[:tags].to_s.split
     linked_tags = nil
 
     ApplicationRecord.transaction do
-      linked_tags = Tag.normalise_tags!(linked_tag_names, with_tagme: false,
+      linked_tags = Tag.normalise_tags!(locale, linked_tag_names,
-                                                          with_no_deerjikist: false)
+                                        with_tagme: false,
-      if linked_tags.any? { |t| t.nico? }
+                                        with_no_deerjikist: false)
-        raise Tag::NicoTagNormalisationError
-      end
 
       TagVersioning.record_tag_snapshots!(linked_tags, created_by_user: current_user)
 
       tag.linked_tags = linked_tags
       tag.save!
 
-      NicoTagVersionRecorder.record!(tag:, event_type: :update, created_by_user: current_user)
+      NicoTagVersionRecorder.record!(external_tag: tag,
+                                     event_type: :update,
+                                     created_by_user: current_user)
     end
 
     render json: tag.linked_tags.map { |t| TagRepr.base(t) }, status: :ok
@@ -102,6 +114,21 @@ class NicoTagsController < ApplicationController
 
   private
 
+  def external_tag_json tag
+    { id: tag.id,
+      name: "#{ tag.platform }:#{ tag.name }",
+      category: 'nico',
+      post_count: tag.post_count,
+      created_at: tag.created_at,
+      updated_at: tag.created_at,
+      deprecated_at: nil,
+      aliases: [],
+      parents: [],
+      has_wiki: false,
+      material_id: nil,
+      has_deerjikists: false }
+  end
+
   def render_nico_tag_form_record_invalid record
     if record.is_a?(TagName) || record.is_a?(Tag)
       render_validation_error fields: { tags: record.errors.full_messages.map { |message|

backend/app/controllers/post_imports_controller.rb

@@ -1,49 +0,0 @@
-class PostImportsController < ApplicationController
-  before_action :require_member!
-
-  def preview
-    rows = PostImportPreviewer.new.preview_rows(
-        rows: PostImportUrlListParser.parse(params[:source]))
-    render json: { rows: }
-  rescue ArgumentError => e
-    render_bad_request e.message
-  end
-
-  def validate
-    rows = normalised_import_rows allow_warning_fields: true
-    changed_row =
-        if params[:changed_row].to_s == 'all'
-          true
-        else
-          Integer(params[:changed_row], exception: false)
-        end
-    result =
-        PostImportPreviewer.new.preview_rows(rows:,
-                                             fetch_metadata: changed_row,
-                                             metadata_cache: { })
-    render json: { rows: result }
-  rescue ArgumentError => e
-    render_bad_request e.message
-  end
-
-  def create
-    result = PostImportRunner.new(actor: current_user,
-                                  rows: normalised_import_rows).run
-    render json: result, status: result[:created].positive? ? :created : :ok
-  rescue ArgumentError => e
-    render_bad_request e.message
-  end
-
-  private
-
-  def require_member!
-    return head :unauthorized unless current_user
-    return if current_user.gte_member?
-
-    head :forbidden
-  end
-
-  def normalised_import_rows allow_warning_fields: false
-    PostImportRowNormaliser.normalise!(params[:rows], allow_warning_fields:)
-  end
-end

backend/app/controllers/post_versions_controller.rb

@@ -1,7 +1,10 @@
 class PostVersionsController < ApplicationController
   def index
     post_id = params[:post].presence
-    tag_id = params[:tag].presence
+    tag_id = params[:tag].presence&.to_i
+    external_tag_id = params[:external_tag].presence&.to_i
+    return head :bad_request if tag_id && external_tag_id
+
     page = (params[:page].presence || 1).to_i
     limit = (params[:limit].presence || 20).to_i
 
@@ -10,12 +13,6 @@ class PostVersionsController < ApplicationController
 
     offset = (page - 1) * limit
 
-    tag_name =
-        if tag_id
-          TagName.joins(:tag).find_by(tag: { id: tag_id })
-        end
-    return render json: { versions: [], count: 0 } if tag_id && tag_name.blank?
-
     q = PostVersion.joins(<<~SQL.squish)
           LEFT JOIN
             post_versions prev
@@ -23,17 +20,23 @@ class PostVersionsController < ApplicationController
               prev.post_id = post_versions.post_id
               AND prev.version_no = post_versions.version_no - 1
         SQL
-        .select('post_versions.*', 'prev.title AS prev_title', 'prev.url AS prev_url',
+        .select('post_versions.*',
-                'prev.thumbnail_base AS prev_thumbnail_base', 'prev.tags AS prev_tags',
+                'prev.title AS prev_title',
+                'prev.url AS prev_url',
+                'prev.thumbnail_base AS prev_thumbnail_base',
+                'prev.tags_json AS prev_tags_json',
                 'prev.video_ms AS prev_video_ms',
                 'prev.original_created_from AS prev_original_created_from',
                 'prev.original_created_before AS prev_original_created_before')
     q = q.where('post_versions.post_id = ?', post_id) if post_id
-    if tag_name
+    if external_tag_id || (tag_id && !(Tag.exists?(id: tag_id)))
-      escaped = ActiveRecord::Base.sanitize_sql_like(tag_name.name)
+      q = q.where('JSON_CONTAINS(post_versions.tags_json,' +
-      q = q.where(("CONCAT(' ', post_versions.tags, ' ') LIKE :kw " +
+                  "JSON_OBJECT('external_tag_id', #{ external_tag_id || tag_id })) " +
-                   "OR CONCAT(' ', prev.tags, ' ') LIKE :kw"),
+                  'OR JSON_CONTAINS(prev.tags_json,' +
-                  kw: "% #{ escaped } %")
+                  "JSON_OBJECT('external_tag_id', #{ external_tag_id || tag_id }))")
+    elsif tag_id
+      q = q.where("JSON_CONTAINS(post_versions.tags_json, JSON_OBJECT('tag_id', #{ tag_id })) " +
+                  "OR JSON_CONTAINS(prev.tags_json, JSON_OBJECT('tag_id', #{ tag_id }))")
     end
 
     count = q.except(:select, :order, :limit, :offset).count
@@ -48,77 +51,91 @@ class PostVersionsController < ApplicationController
   private
 
   def serialise_versions rows
+    rows = rows.to_a
     user_ids = rows.map(&:created_by_user_id).compact.uniq
     users_by_id = User.where(id: user_ids).pluck(:id, :name).to_h
+    snapshots = rows.flat_map { |row|
+      [normalise_json(row.tags_json),
+       normalise_json(row.attributes['prev_tags_json']) || []]
+    }
+    external_tag_names = external_tag_names_for(snapshots)
 
     rows.map do |row|
-      cur_tags = split_tags(row.tags)
+      cur_tags = snapshot_tag_literals(normalise_json(row.tags_json), external_tag_names)
-      prev_tags = split_tags(row.attributes['prev_tags'])
+      prev_tags = snapshot_tag_literals(
+          normalise_json(row.attributes['prev_tags_json']) || [], external_tag_names)
 
-      {
+      { post_id: row.post_id,
-        post_id: row.post_id,
         version_no: row.version_no,
         event_type: row.event_type,
-        title: {
+        title: { current: row.title, prev: row.attributes['prev_title'] },
-          current: row.title,
+        url: { current: row.url, prev: row.attributes['prev_url'] },
-          prev: row.attributes['prev_title']
+        thumbnail: { current: nil, prev: nil },
-        },
+        thumbnail_base: { current: row.thumbnail_base,
-        url: {
+                          prev: row.attributes['prev_thumbnail_base'] },
-          current: row.url,
+        video_ms: { current: row.video_ms, prev: row.attributes['prev_video_ms'] },
-          prev: row.attributes['prev_url']
-        },
-        thumbnail: {
-          current: nil,
-          prev: nil
-        },
-        thumbnail_base: {
-          current: row.thumbnail_base,
-          prev: row.attributes['prev_thumbnail_base']
-        },
-        video_ms: {
-          current: row.video_ms,
-          prev: row.attributes['prev_video_ms']
-        },
         tags: build_version_tags(cur_tags, prev_tags),
         original_created_from: {
-          current: row.original_created_from&.iso8601,
+            current: row.original_created_from&.iso8601,
-          prev: row.attributes['prev_original_created_from']&.iso8601
+            prev: row.attributes['prev_original_created_from']&.iso8601 },
-        },
         original_created_before: {
-          current: row.original_created_before&.iso8601,
+            current: row.original_created_before&.iso8601,
-          prev: row.attributes['prev_original_created_before']&.iso8601
+            prev: row.attributes['prev_original_created_before']&.iso8601 },
-        },
         created_at: row.created_at.iso8601,
         created_by_user:
-          if row.created_by_user_id
+            if row.created_by_user_id
-            {
+              { id: row.created_by_user_id,
-              id: row.created_by_user_id,
+                name: users_by_id[row.created_by_user_id] }
-              name: users_by_id[row.created_by_user_id]
+            end }
-            }
-          end
-      }
     end
   end
 
-  def build_version_tags(cur_tags, prev_tags)
+  def external_tag_names_for snapshots
+    ids = snapshots.flatten.filter_map { _1['external_tag_id'] }.uniq
+    names = ExternalTag.where(id: ids).pluck(:id, :platform, :name).to_h { |id, platform, name|
+      [id, "#{ platform }:#{ name }"]
+    }
+    missing_ids = ids - names.keys
+
+    NicoTagVersion
+        .where(tag_id: missing_ids)
+        .order(:tag_id, version_no: :desc)
+        .pluck(:tag_id, :name)
+        .each { |id, name| names[id] ||= name }
+
+    names
+  end
+
+  def snapshot_tag_literals snapshots, external_tag_names
+    snapshots
+        .filter_map { |snapshot|
+          if snapshot.key?('tag_id')
+            [tag_category_order(snapshot['category']),
+             Post.tag_snapshot_literal(snapshot)]
+          elsif external_tag_names[snapshot['external_tag_id']]
+            [6, external_tag_names[snapshot['external_tag_id']]]
+          end
+        }
+        .sort_by { |order, name| [order, name.downcase] }
+        .map(&:second)
+  end
+
+  def tag_category_order category
+    ['deerjikist', 'meme', 'character', 'general', 'material', 'meta'].index(category) || 6
+  end
+
+  def build_version_tags cur_tags, prev_tags
     (cur_tags | prev_tags).map do |name|
       type =
-        if cur_tags.include?(name) && prev_tags.include?(name)
+          if cur_tags.include?(name) && prev_tags.include?(name)
-          'context'
+            'context'
-        elsif cur_tags.include?(name)
+          elsif cur_tags.include?(name)
-          'added'
+            'added'
-        else
+          else
-          'removed'
+            'removed'
-        end
+          end
 
-      {
+      { name:, type: }
-        name:,
-        type:
-      }
     end
   end
-
-  def split_tags(tags)
-    tags.to_s.split(/\s+/).reject(&:blank?)
-  end
 end

backend/app/controllers/posts_controller.rb

@@ -1,5 +1,6 @@
 class PostsController < ApplicationController
   Event = Struct.new(:post, :tag, :user, :change_type, :timestamp, keyword_init: true)
+  MAX_BULK_REQUEST_BYTES = 40 * 1024 * 1024
 
   class VideoMsParseError < ArgumentError
     ;
@@ -35,8 +36,8 @@ class PostsController < ApplicationController
     offset = (page - 1) * limit
 
     pt_max_sql =
-        PostTag
+        PostVersion
-        .select('post_id, MAX(updated_at) AS max_updated_at')
+        .select('post_id, MAX(created_at) AS max_updated_at')
         .group('post_id')
         .to_sql
 
@@ -48,10 +49,9 @@ class PostsController < ApplicationController
         filtered_posts
         .joins("LEFT JOIN (#{ pt_max_sql }) pt_max ON pt_max.post_id = posts.id")
         .reselect('posts.*', Arel.sql("#{ updated_at_all_sql } AS updated_at_all"))
-        .preload(:uploaded_user, :parents, :children,
+        .preload(:external_tags, :uploaded_user, :parents, :children,
-                 active_post_tags: [:sections,
+                 post_tags: [:sections, { tag: [:deerjikists, :materials,
-                                    { tag: [:deerjikists, :materials,
+                                                { tag_name: :wiki_page }] }])
-                                            { tag_name: :wiki_page }] }])
         .with_attached_thumbnail
 
     q = q.where('posts.url LIKE ?', "%#{ url }%") if url
@@ -102,25 +102,96 @@ class PostsController < ApplicationController
   end
 
   def random
-    post = filtered_posts.preload(:uploaded_user, :parents, :children,
+    post =
-                                  active_post_tags: [:sections,
+        filtered_posts
-                                                     { tag: [:deerjikists, :materials,
+        .preload(:uploaded_user, :parents, :children,
-                                                             { tag_name: :wiki_page }] }])
+                 post_tags: [:sections, { tag: [:deerjikists, :materials,
-                         .with_attached_thumbnail
+                                                { tag_name: :wiki_page }] }])
-                         .order('RAND()')
+        .with_attached_thumbnail
-                         .first
+        .order('RAND()')
+        .first
     return head :not_found unless post
 
     render json: PostRepr.base(post, current_user)
   end
 
+  def metadata
+    return head :unauthorized unless current_user
+    return head :forbidden unless current_user.gte_member?
+    return render_bad_request('URL は必須です．') if params[:url].blank?
+
+    normal_url = PostUrlNormaliser.normalise(params[:url].to_s)
+    return render_validation_error(fields: { url: ['URL が不正です．'] }) if normal_url.blank?
+
+    Preview::UrlSafety.validate(normal_url)
+    existing_post = Post.with_attached_thumbnail.find_by(url: normal_url)
+    if existing_post.present?
+      return render json: {
+          url: normal_url,
+          title: nil,
+          thumbnail_base: nil,
+          tags: nil,
+          display_tags: [],
+          original_created_from: nil,
+          original_created_before: nil,
+          duration: nil,
+          video_ms: nil,
+          field_warnings: { },
+          base_warnings: [],
+          existing_post_id: existing_post.id,
+          existing_post: compact_post(existing_post.id) }
+    end
+
+    metadata = PostMetadataFetcher.fetch(normal_url)
+    field_warnings = { }
+    field_warnings[:title] = ['タイトルを取得できませんでした．'] if metadata[:title].blank?
+    if metadata[:thumbnail_base].blank?
+      field_warnings[:thumbnail_base] = ['サムネールを取得できませんでした．']
+    end
+
+    render json: {
+        url: normal_url,
+        title: metadata[:title],
+        thumbnail_base: metadata[:thumbnail_base],
+        tags: metadata[:tags],
+        display_tags: metadata[:display_tags],
+        original_created_from: metadata[:original_created_from],
+        original_created_before: metadata[:original_created_before],
+        duration: metadata[:duration],
+        video_ms: metadata[:video_ms],
+        field_warnings: field_warnings,
+        base_warnings: [],
+        existing_post_id: nil,
+        existing_post: nil }
+  rescue ArgumentError => e
+    render_bad_request e.message
+  rescue Preview::UrlSafety::UnsafeUrl => e
+    render_validation_error fields: { url: [e.message] }
+  rescue Preview::HttpFetcher::FetchFailed,
+         Preview::HttpFetcher::FetchTimeout,
+         Preview::HttpFetcher::ResponseTooLarge
+    render json: {
+        url: normal_url,
+        title: nil,
+        thumbnail_base: nil,
+        tags: nil,
+        display_tags: [],
+        original_created_from: nil,
+        original_created_before: nil,
+        duration: nil,
+        video_ms: nil,
+        field_warnings: { url: ['自動取得に失敗しました．'] },
+        base_warnings: [],
+        existing_post_id: nil,
+        existing_post: nil }
+  end
+
   def show
     post =
         Post
         .includes(:uploaded_user, :parents, :children,
-                  active_post_tags: [:sections,
+                  post_tags: [:sections, { tag: [:deerjikists, :materials,
-                                     { tag: [:deerjikists, :materials,
+                                                 { tag_name: :wiki_page }] }])
-                                             { tag_name: :wiki_page }] }])
         .with_attached_thumbnail
         .find_by(id: params[:id])
     return head :not_found unless post
@@ -142,17 +213,43 @@ class PostsController < ApplicationController
     return head :unauthorized unless current_user
     return head :forbidden unless current_user.gte_member?
 
+    locale = resolve_locale!
+
+    preflight = PostCreatePreflight.new(
+        attributes: post_create_attributes,
+        thumbnail: params[:thumbnail],
+        host: request.base_url).run(locale)
+    return render json: dry_run_json(preflight) if bool?(:dry)
+    if preflight[:existing_post_id].present?
+      post = Post.new(url: preflight[:url])
+      post.errors.add :url, :taken
+      return render_post_form_record_invalid post
+    end
+
     post = PostCreator.new(actor: current_user,
-                           attributes: { title: params[:title], url: params[:url],
+                           attributes: post_create_attributes.merge(
-                                         thumbnail: params[:thumbnail], tags: params[:tags],
+                               preflight.slice(
-                                         original_created_from: params[:original_created_from],
+                                   :url,
-                                         original_created_before: params[:original_created_before],
+                                   :title,
-                                         parent_post_ids: parse_parent_post_ids,
+                                   :thumbnail_base,
-                                         video_ms: params[:video_ms],
+                                   :tags,
-                                         duration: params[:duration] }).create!
+                                   :parent_post_ids,
+                                   :original_created_from,
+                                   :original_created_before,
+                                   :duration,
+                                   :video_ms,
+                                   :direct_tag_specs,
+                                   :default_tag_specs,
+                                   :snapshot_tag_specs,
+                                   :post_tag_specs,
+                                   :tag_sections,
+                                   :normalised_parent_post_ids).symbolize_keys).merge(
+                               thumbnail: params[:thumbnail])).create!(locale)
 
     post.reload
     render json: PostRepr.base(post), status: :created
+  rescue PostCreatePreflight::ValidationFailed => e
+    render_validation_error fields: e.fields, base: e.base_errors
   rescue Tag::NicoTagNormalisationError
     render_validation_error fields: { tags: 'ニコニコ・タグは直接指定できません．' }
   rescue Tag::DeprecatedTagNormalisationError
@@ -161,6 +258,8 @@ class PostsController < ApplicationController
     render_validation_error fields: { tags: ['タグ区間の記法が不正です．'] }
   rescue PostCreator::VideoMsParseError
     render_validation_error fields: { video_ms: ['動画時間の記法が不正です．'] }
+  rescue Post::RemoteThumbnailFetchFailed
+    render_validation_error fields: { thumbnail_base: ['サムネイル画像の取得に失敗しました．'] }
   rescue MiniMagick::Error
     render_validation_error fields: { thumbnail: ['サムネイル画像の変換に失敗しました．'] }
   rescue ArgumentError => e
@@ -169,6 +268,30 @@ class PostsController < ApplicationController
     render_post_form_record_invalid e.record
   end
 
+  def bulk
+    return head :unauthorized unless current_user
+    return head :forbidden unless current_user.gte_member?
+    return head :unsupported_media_type unless request.content_mime_type == Mime[:multipart_form]
+    return head :payload_too_large if request.content_length.to_i > MAX_BULK_REQUEST_BYTES
+
+    locale = resolve_locale!
+
+    posts = parse_bulk_posts_manifest
+    thumbnails = parse_bulk_thumbnails(posts.length)
+
+    result = PostBulkCreator.new(
+        actor: current_user,
+        posts:,
+        thumbnails:,
+        host: request.base_url).run(locale)
+
+    render json: result
+  rescue JSON::ParserError
+    render_bad_request 'posts manifest の JSON が不正です．'
+  rescue ArgumentError => e
+    render_validation_error base: [e.message]
+  end
+
   def viewed
     return head :unauthorized unless current_user
 
@@ -194,6 +317,7 @@ class PostsController < ApplicationController
     base_version_no = parse_base_version_no
     return render_bad_request('base_version_no は必須です．') if !(force) && !(base_version_no)
 
+    locale = Locale.find_by(code: params[:locale].presence) || Locale.nipponese
     title = params[:title].presence
     tag_names = params[:tags].to_s.split
     original_created_from = params[:original_created_from]
@@ -215,7 +339,8 @@ class PostsController < ApplicationController
         base_snapshot = post_snapshot_from_version(base_version)
         current_snapshot = post_snapshot_from_record(post)
       end
-      incoming_snapshot = post_incoming_snapshot(title:,
+      incoming_snapshot = post_incoming_snapshot(locale:,
+                                                 title:,
                                                  original_created_from:,
                                                  original_created_before:,
                                                  tag_names:,
@@ -244,7 +369,7 @@ class PostsController < ApplicationController
             end
           end
 
-      apply_post_snapshot!(post, snapshot_to_apply)
+      apply_post_snapshot!(locale, post, snapshot_to_apply)
     end
 
     return render json: conflict_json, status: :conflict if conflict_json
@@ -267,50 +392,6 @@ class PostsController < ApplicationController
     render_post_form_record_invalid e.record
   end
 
-  def changes
-    id = params[:id].presence
-    tag_id = params[:tag].presence
-    page = (params[:page].presence || 1).to_i
-    limit = (params[:limit].presence || 20).to_i
-
-    page = 1 if page < 1
-    limit = 1 if limit < 1
-
-    offset = (page - 1) * limit
-
-    pts = PostTag.with_discarded
-    pts = pts.where(post_id: id) if id.present?
-    pts = pts.where(tag_id:) if tag_id.present?
-    pts = pts.includes(:post, :created_user, :deleted_user,
-                       tag: [:deerjikists, :materials, { tag_name: :wiki_page }])
-
-    events = []
-    pts.each do |pt|
-      tag = TagRepr.base(pt.tag)
-      post = pt.post
-
-      events << Event.new(
-          post:,
-          tag:,
-          user: pt.created_user && { id: pt.created_user.id, name: pt.created_user.name },
-          change_type: 'add',
-          timestamp: pt.created_at)
-
-      if pt.discarded_at
-        events << Event.new(
-            post:,
-            tag:,
-            user: pt.deleted_user && { id: pt.deleted_user.id, name: pt.deleted_user.name },
-            change_type: 'remove',
-            timestamp: pt.discarded_at)
-      end
-    end
-    events.sort_by!(&:timestamp)
-    events.reverse!
-
-    render json: { changes: (events.slice(offset, limit) || []).as_json, count: events.size }
-  end
-
   private
 
   def filtered_posts
@@ -356,8 +437,20 @@ class PostsController < ApplicationController
     end
   end
 
-  def tagged_post_ids_for(name) =
+  def tagged_post_ids_for(name)
-      Post.joins(tags: :tag_name).where(tag_names: { name: }).select(:id)
+    posts_by_internal_tags =
+        Post
+        .joins(tags: :tag_name)
+        .where(tag_names: { name: })
+        .select(:id)
+
+    posts_by_external_tags =
+        Post
+        .joins(:external_tags)
+        .where("CONCAT(external_tags.platform, ':', external_tags.name) = ?", name)
+
+    (posts_by_internal_tags + posts_by_external_tags).uniq(&:id)
+  end
 
   def sync_post_tags! post, desired_tags, sections
     desired_tags.each do |t|
@@ -385,13 +478,13 @@ class PostsController < ApplicationController
       end
     end
 
-    PostTag.where(post_id: post.id, tag_id: to_remove.to_a).kept.find_each do |pt|
+    PostTag.where(post_id: post.id, tag_id: to_remove.to_a).find_each do |pt|
-      pt.discard_by!(current_user)
+      pt.destroy!
     end
   end
 
   def build_tag_tree_for post
-    post_tags = post.active_post_tags.reject { |post_tag| post_tag.tag.deprecated? }
+    post_tags = post.post_tags.reject { |post_tag| post_tag.tag.deprecated? }
     tags = post_tags.map(&:tag)
     tag_ids = tags.map(&:id)
 
@@ -435,7 +528,10 @@ class PostsController < ApplicationController
       memo[tag_id] = TagRepr.inline(tag).merge(children:, sections:)
     end
 
-    root_ids.filter_map { |id| build_node.call(id, []) }
+    internal_tags = root_ids.filter_map { |id| build_node.call(id, []) }
+    external_tags =
+        post.external_tags.map { ExternalTagRepr.inline(_1).merge(children: [], sections: []) }
+    internal_tags + external_tags
   end
 
   def sibling_posts_by_parent parent_post_ids
@@ -463,6 +559,79 @@ class PostsController < ApplicationController
     }.uniq
   end
 
+  def post_create_attributes
+    { title: params[:title],
+      url: params[:url],
+      thumbnail_base: params[:thumbnail_base],
+      tags: params[:tags],
+      original_created_from: params[:original_created_from],
+      original_created_before: params[:original_created_before],
+      parent_post_ids: parse_parent_post_ids,
+      video_ms: params[:video_ms],
+      duration: params[:duration] }
+  end
+
+  def parse_bulk_posts_manifest
+    manifest = params[:posts]
+    raise ArgumentError, 'posts は必須です．' if manifest.blank?
+    raise ArgumentError, 'posts は JSON 文字列で指定してください．' unless manifest.is_a?(String)
+
+    posts = JSON.parse(manifest)
+    raise ArgumentError, 'posts は配列で指定してください．' unless posts.is_a?(Array)
+    raise ArgumentError, '投稿件数は 1 件以上必要です．' if posts.empty?
+    raise ArgumentError, '投稿件数が多すぎます．' if posts.length > 100
+    raise ArgumentError, 'posts 要素の形式が不正です．' unless posts.all? { _1.is_a?(Hash) }
+
+    posts
+  end
+
+  def parse_bulk_thumbnails post_count
+    thumbnails = { }
+    raw = params[:thumbnails]
+    return thumbnails if raw.blank?
+    raise ArgumentError, 'thumbnail key が不正です．' unless raw.respond_to?(:to_unsafe_h)
+
+    raw.to_unsafe_h.each do |key, value|
+      raise ArgumentError, 'thumbnail key が不正です．' unless key.to_s.match?(/\A\d+\z/)
+
+      index = Integer(key, 10)
+      raise ArgumentError, 'thumbnail index が範囲外です．' if index.negative? || index >= post_count
+      raise ArgumentError, 'thumbnail index が重複しています．' if thumbnails.key?(index)
+      unless value.is_a?(ActionDispatch::Http::UploadedFile)
+        raise ArgumentError, 'thumbnail upload が不正です．'
+      end
+
+      thumbnails[index] = value
+    end
+
+    thumbnails
+  end
+
+  def compact_post post_id
+    return nil if post_id.blank?
+
+    post = Post.with_attached_thumbnail.find_by(id: post_id)
+    PostCompactRepr.base(post, host: request.base_url)
+  end
+
+  def dry_run_json preflight
+    preflight.slice(
+        :url,
+        :title,
+        :thumbnail_base,
+        :tags,
+        :display_tags,
+        :parent_post_ids,
+        :original_created_from,
+        :original_created_before,
+        :duration,
+        :video_ms,
+        :field_warnings,
+        :base_warnings,
+        :existing_post_id,
+        :existing_post)
+  end
+
   def sync_parent_posts! post, parent_post_ids
     if parent_post_ids.include?(post.id)
       post.errors.add :parent_post_ids, '自分自身を親投稿にはできません．'
@@ -509,7 +678,10 @@ class PostsController < ApplicationController
   end
 
   def editable_tag_names_from_version version
-    version.tags.to_s.split.reject { |name| name.downcase.start_with?('nico:') }.sort
+    version.tags_json
+        .select { _1.key?('tag_id') }
+        .map { Post.tag_snapshot_literal(_1) }
+        .sort
   end
 
   def post_snapshot_from_record post
@@ -524,9 +696,7 @@ class PostsController < ApplicationController
   def editable_tag_names_from_post post
     post
         .post_tags
-        .kept
         .joins(tag: :tag_name)
-        .merge(Tag.not_nico)
         .merge(Tag.where(deprecated_at: nil))
         .includes(:sections, tag: :tag_name)
         .order('tag_names.name')
@@ -540,11 +710,14 @@ class PostsController < ApplicationController
     end
   end
 
-  def post_incoming_snapshot title:, original_created_from:, original_created_before:,
+  def post_incoming_snapshot locale:, title:, original_created_from:, original_created_before:,
                              tag_names:, video_ms_param:, duration_param:, parent_post_ids:
-    Tag.normalise_tags!(tag_names, with_tagme: false, deny_deprecated: true,
+    validate_original_created_values!(original_created_from, original_created_before)
-                                        with_sections: true) =>
+
-        { tags:, sections: }
+    Tag.normalise_tags!(locale, tag_names,
+                        with_tagme: false,
+                        deny_deprecated: true,
+                        with_sections: true) => { tags:, sections: }
 
     tags = Tag.expand_parent_tags(tags).reject(&:deprecated?)
     video_ms = normalise_video_ms(tags, video_ms_param:, duration_param:)
@@ -579,6 +752,23 @@ class PostsController < ApplicationController
     value.to_s
   end
 
+  def validate_original_created_values! original_created_from, original_created_before
+    candidate = Post.new(
+        url: 'https://example.invalid/original-created-validation',
+        original_created_from:,
+        original_created_before:)
+    candidate.valid?
+    fields = [:original_created_from, :original_created_before, :original_created_at]
+    relevant_errors = candidate.errors.select { fields.include?(_1.attribute) }
+    return if relevant_errors.empty?
+
+    invalid_post = Post.new
+    relevant_errors.each { |error|
+      invalid_post.errors.add(error.attribute, error.message)
+    }
+    raise ActiveRecord::RecordInvalid, invalid_post
+  end
+
   def section_literal section
     "[#{ Post.ms_to_time(section[0]) }-#{ section[1] ? Post.ms_to_time(section[1]) : '' }]"
   end
@@ -662,7 +852,7 @@ class PostsController < ApplicationController
     (added_by_current & removed_by_me).present? || (removed_by_current & added_by_me).present?
   end
 
-  def apply_post_snapshot! post, snapshot
+  def apply_post_snapshot! locale, post, snapshot
     PostVersionRecorder.ensure_snapshot!(post, created_by_user: current_user)
 
     post.update!(title: snapshot[:title],
@@ -670,15 +860,12 @@ class PostsController < ApplicationController
                  original_created_from: snapshot[:original_created_from],
                  original_created_before: snapshot[:original_created_before])
 
-    Tag.normalise_tags!(snapshot[:tag_names], with_tagme: false,
+    Tag.normalise_tags!(locale, snapshot[:tag_names],
-                                               deny_deprecated: true,
+                        with_tagme: false,
-                                               with_sections: true) =>
+                        deny_deprecated: true,
-        { tags: editable_tags, sections: }
+                        with_sections: true) => { tags:, sections: }
-    TagVersioning.record_tag_snapshots!(editable_tags, created_by_user: current_user)
+    TagVersioning.record_tag_snapshots!(tags, created_by_user: current_user)
 
-    readonly_tags = post.tags.nico.to_a
-
-    tags = readonly_tags + editable_tags
     tags = Tag.expand_parent_tags(tags).reject(&:deprecated?)
 
     post.video_ms = tags.any? { _1.id == Tag.video.id } ? snapshot[:video_ms] : nil

backend/app/controllers/preview_controller.rb

@@ -18,32 +18,9 @@ class PreviewController < ApplicationController
   def thumbnail
     return render_bad_request('URL は必須です．') if params[:url].blank?
 
-    image = MiniMagick::Image.read(Preview::ThumbnailFetcher.fetch(params[:url]))
+    attachment =
-    image.auto_orient
+        Post.resized_thumbnail_attachment(
-    image.resize '180x180>'
+            StringIO.new(Preview::ThumbnailFetcher.fetch(params[:url])))
-    image.format 'png'
-    width, height = image.dimensions
-    raise Preview::ThumbnailFetcher::GenerationFailed, 'サムネール画像の変換に失敗しました．' if width > 180 || height > 180
-
-    send_data image.to_blob, type: 'image/png', disposition: 'inline'
-  rescue Preview::UrlSafety::UnsafeUrl => e
-    render_bad_request(e.message)
-  rescue Preview::HttpFetcher::FetchTimeout => e
-    render_preview_error(e.message, :gateway_timeout)
-  rescue Preview::HttpFetcher::ResponseTooLarge => e
-    render_preview_error(e.message, :payload_too_large)
-  rescue Preview::HttpFetcher::FetchFailed => e
-    render_preview_error(e.message, :bad_gateway)
-  rescue Preview::ThumbnailFetcher::GenerationFailed, MiniMagick::Error => e
-    render_unprocessable_entity(e.message)
-  end
-
-  def image
-    return render_bad_request('URL は必須です．') if params[:url].blank?
-
-    attachment = Post.resized_thumbnail_attachment(
-        StringIO.new(Preview::ThumbnailFetcher.fetch_image_response(params[:url]).body))
-    attachment[:io].rewind
     send_data attachment[:io].read,
               type: attachment[:content_type],
               disposition: 'inline'

backend/app/controllers/tag_children_controller.rb

@@ -10,7 +10,6 @@ class TagChildrenController < ApplicationController
 
     parent = Tag.find(parent_id)
     child = Tag.find(child_id)
-    return render_bad_request('ニコニコ・タグの階層は変更できません．') if parent.nico? || child.nico?
 
     ApplicationRecord.transaction do
       TagVersioning.ensure_snapshot!(child, created_by_user: current_user)
@@ -33,7 +32,6 @@ class TagChildrenController < ApplicationController
 
     parent = Tag.find(parent_id)
     child = Tag.find(child_id)
-    return render_bad_request('ニコニコ・タグの階層は変更できません．') if parent.nico? || child.nico?
 
     ApplicationRecord.transaction do
       TagVersioning.ensure_snapshot!(child, created_by_user: current_user)

backend/app/controllers/tags_controller.rb

@@ -34,49 +34,155 @@ class TagsController < ApplicationController
 
     offset = (page - 1) * limit
 
-    q =
+    tags =
         if post_id.present?
-          Tag.joins(:posts, :tag_name)
+          Tag.joins(:posts, :tag_name).where(posts: { id: post_id })
         else
           Tag.joins(:tag_name)
         end
-        .includes(:tag_name, :materials, tag_name: :wiki_page)
-    q = q.where(posts: { id: post_id }) if post_id.present?
 
-    q = q.where('tag_names.name LIKE ?', "%#{ name }%") if name
+    external_tags =
-    q = q.where(category:) if category
+        if post_id.present?
-    q = q.where('tags.post_count >= ?', post_count_between[0]) if post_count_between[0]
+          ExternalTag.joins(:posts).where(posts: { id: post_id })
-    q = q.where('tags.post_count <= ?', post_count_between[1]) if post_count_between[1]
+        else
-    q = q.where('tags.created_at >= ?', created_between[0]) if created_between[0]
+          ExternalTag.all
-    q = q.where('tags.created_at <= ?', created_between[1]) if created_between[1]
+        end
-    q = q.where('tags.updated_at >= ?', updated_between[0]) if updated_between[0]
+
-    q = q.where('tags.updated_at <= ?', updated_between[1]) if updated_between[1]
+    if name
-    if deprecated_given
+      tags = tags.where('tag_names.name LIKE ?', "%#{ name }%")
-      q = deprecated ? q.where.not(deprecated_at: nil) : q.where(deprecated_at: nil)
+      external_tags =
+          external_tags.where("CONCAT(external_tags.platform, ':', external_tags.name) LIKE ?",
+                              "%#{ name }%")
     end
 
+    if category == 'nico'
+      tags = tags.none
+    elsif category
+      tags = tags.where(category:)
+      external_tags = external_tags.none
+    end
+
+    if post_count_between[0]
+      tags = tags.where('tags.post_count >= ?', post_count_between[0])
+      external_tags = external_tags.where('external_tags.post_count >= ?', post_count_between[0])
+    end
+
+    if post_count_between[1]
+      tags = tags.where('tags.post_count <= ?', post_count_between[1])
+      external_tags = external_tags.where('external_tags.post_count <= ?', post_count_between[1])
+    end
+
+    if created_between[0]
+      tags = tags.where('tags.created_at >= ?', created_between[0])
+      external_tags = external_tags.where('external_tags.created_at >= ?', created_between[0])
+    end
+
+    if created_between[1]
+      tags = tags.where('tags.created_at <= ?', created_between[1])
+      external_tags = external_tags.where('external_tags.created_at <= ?', created_between[1])
+    end
+
+    if updated_between[0]
+      tags = tags.where('tags.updated_at >= ?', updated_between[0])
+      external_tags = external_tags.where('external_tags.created_at >= ?', updated_between[0])
+    end
+
+    if updated_between[1]
+      tags = tags.where('tags.updated_at <= ?', updated_between[1])
+      external_tags = external_tags.where('external_tags.created_at <= ?', updated_between[1])
+    end
+
+    if deprecated_given
+      if deprecated
+        tags = tags.where.not(deprecated_at: nil)
+        external_tags = external_tags.none
+      else
+        tags = tags.where(deprecated_at: nil)
+      end
+    end
+
+    tag_sql = tags.select("'tag' AS source",
+                          'tags.id',
+                          'tag_names.name',
+                          'tags.category',
+                          'tags.post_count',
+                          'tags.created_at',
+                          'tags.updated_at',
+                          'tags.deprecated_at').to_sql
+
+    external_tag_sql = external_tags.select(
+        "'external_tag' AS source",
+        'external_tags.id',
+        "CONCAT(external_tags.platform, ':', external_tags.name) AS name",
+        "'nico' AS category",
+        'external_tags.post_count',
+        'external_tags.created_at',
+        'external_tags.created_at AS updated_at',
+        'NULL AS deprecated_at').to_sql
+
+    union_sql = "#{ tag_sql } UNION ALL #{ external_tag_sql }"
+
     sort_sql =
-        case order[0]
+        if order[0] == 'category'
-        when 'name'
+          'CASE category ' +
-          'tag_names.name'
-        when 'category'
-          'CASE tags.category ' +
           "WHEN 'deerjikist' THEN 0 " +
           "WHEN 'meme' THEN 1 " +
           "WHEN 'character' THEN 2 " +
           "WHEN 'general' THEN 3 " +
           "WHEN 'material' THEN 4 " +
           "WHEN 'meta' THEN 5 " +
-          "WHEN 'nico' THEN 6 END"
+          "WHEN 'nico' THEN 6 " +
+          'END'
         else
-          "tags.#{ order[0] }"
+          order[0]
         end
-    tags = q.order(Arel.sql("#{ sort_sql } #{ order[1] }, tags.id #{ order[1] }"))
-            .limit(limit)
-            .offset(offset)
-            .to_a
 
-    render json: { tags: TagRepr.many(tags), count: q.size }
+    connection = ApplicationRecord.connection
+
+    count = connection.select_value(<<~SQL)
+      SELECT
+        COUNT(0)
+      FROM
+        (#{ union_sql }) legacy_tags
+    SQL
+
+    rows = connection.select_all(<<~SQL).to_a
+      SELECT
+        source
+      , id
+      FROM
+        (#{ union_sql }) legacy_tags
+      ORDER BY
+        #{ sort_sql } #{ order[1] }
+      , id #{ order[1] }
+      , source #{ order[1] }
+      LIMIT
+        #{ limit }
+      OFFSET
+        #{ offset }
+    SQL
+
+    tag_ids = rows.filter { _1['source'] == 'tag' }.map { _1['id'] }
+    external_tag_ids = rows.filter { _1['source'] == 'external_tag' }.map { _1['id'] }
+
+    tags_by_id =
+        Tag
+        .joins(:tag_name)
+        .includes(:tag_name, :materials, tag_name: :wiki_page)
+        .where(id: tag_ids)
+        .index_by(&:id)
+    external_tags_by_id =
+        ExternalTag
+        .where(id: external_tag_ids)
+        .index_by(&:id)
+
+    render json: { tags: rows.map { |row|
+      if row['source'] == 'tag'
+        TagRepr.base(tags_by_id.fetch(row['id']))
+      else
+        external_tag_json(external_tags_by_id.fetch(row['id']))
+      end
+    }, count: }
   end
 
   def with_depth
@@ -100,13 +206,14 @@ class TagsController < ApplicationController
 
   def autocomplete
     q = params[:q].to_s.strip.sub(/\Anot:/i, '')
+    prefix = "#{ ActiveRecord::Base.sanitize_sql_like(q) }%"
 
     with_nico = bool?(:nico, default: true)
     present_only = bool?(:present, default: true)
 
     alias_rows =
         TagName
-        .where('name LIKE ?', "#{ q }%")
+        .where('name LIKE ?', prefix)
         .where.not(canonical_id: nil)
         .pluck(:canonical_id, :name)
 
@@ -118,54 +225,77 @@ class TagsController < ApplicationController
       matched_alias_by_tag_name_id[canonical_id] ||= alias_name
     end
 
-    base = Tag.joins(:tag_name)
+    base =
-              .includes(:tag_name, :materials, tag_name: :wiki_page)
+        Tag
-              .where(deprecated_at: nil)
+        .joins(:tag_name)
+        .includes(:tag_name, :materials, tag_name: :wiki_page)
+        .where(deprecated_at: nil)
     base = base.where('tags.post_count > 0') if present_only
 
-    canonical_hit =
+    canonical_hit = base.where('tag_names.name LIKE ?', prefix)
-        base
-        .where(((with_nico ? '(tags.category = ? AND tag_names.name LIKE ?) OR ' : '') +
-                'tag_names.name LIKE ?'),
-               *(with_nico ? ['nico', "nico:#{ q }%"] : []), "#{ q }%")
 
-    tags =
+    internal_tags = canonical_hit.or(base.where(tag_name_id: canonical_ids.uniq))
-        if canonical_ids.present?
-          canonical_hit.or(base.where(tag_name_id: canonical_ids.uniq))
-        else
-          canonical_hit
-        end
 
-    tags = tags.order(Arel.sql('post_count DESC, tag_names.name')).limit(20).to_a
+    internal_rows =
+        internal_tags
+        .order(Arel.sql('tags.post_count DESC, tag_names.name'))
+        .limit(20)
+        .map { |tag|
+          TagRepr.base(tag).merge(matched_alias: matched_alias_by_tag_name_id[tag.tag_name_id])
+        }
 
-    render json: tags.map { |tag|
+    return render json: internal_rows unless with_nico
-      TagRepr.base(tag).merge(matched_alias: matched_alias_by_tag_name_id[tag.tag_name_id])
+
-    }
+    external_base = ExternalTag.all
+    external_base = external_base.where('post_count > 0') if present_only
+
+    external_rows =
+        external_base
+        .where("CONCAT(platform, ':', name) LIKE ? OR name LIKE ?", prefix, prefix)
+        .order(post_count: :desc, name: :asc)
+        .limit(20)
+        .map { external_tag_json(_1) }
+
+    rows =
+        (internal_rows + external_rows)
+        .sort_by { |row| [-row['post_count'], row['name']] }
+        .first(20)
+
+    render json: rows
   end
 
   def show
-    tag = Tag.joins(:tag_name)
+    tag =
-             .includes(:tag_name, :materials, tag_name: :wiki_page)
+        Tag
-             .find_by(id: params[:id])
+        .joins(:tag_name)
-    if tag
+        .includes(:tag_name, :materials, tag_name: :wiki_page)
-      render json: TagRepr.base(tag)
+        .find_by(id: params[:id])
-    else
+    return render json: TagRepr.base(tag) if tag
-      head :not_found
+
-    end
+    external_tag = ExternalTag.find_by(id: params[:id])
+    return render json: ExternalTagRepr.base(external_tag) if external_tag
+
+    head :not_found
   end
 
   def show_by_name
     name = params[:name].to_s.strip
     return render_bad_request('name は必須です．') if name.blank?
 
-    tag = Tag.joins(:tag_name)
+    tag =
-             .includes(:tag_name, :materials, tag_name: :wiki_page)
+        Tag
-             .find_by(tag_names: { name: })
+        .joins(:tag_name)
-    if tag
+        .includes(:tag_name, :materials, tag_name: :wiki_page)
-      render json: TagRepr.base(tag)
+        .find_by(tag_names: { name: })
-    else
+    return render json: TagRepr.base(tag) if tag
-      head :not_found
+
-    end
+    platform, external_name = name.split(':', 2)
+    return head :not_found unless external_name
+
+    external_tag = ExternalTag.find_by(platform:, name: external_name)
+    return head :not_found unless external_tag
+
+    render json: ExternalTagRepr.base(external_tag)
   end
 
   def deerjikists
@@ -200,14 +330,45 @@ class TagsController < ApplicationController
              .find_by(id: params[:id])
     return head :not_found unless tag
 
+    rows = normalise_deerjikist_rows(tag)
+    return if performed?
+
     ApplicationRecord.transaction do
-      tag.deerjikists = []
+      tag.lock!
-      params[:_json].each.with_index do |item, i|
+
-        platform = item[:platform]
+      requested_keys = rows.map { |row| [row[:platform], row[:code]] }.uniq
-        code = normalise_deerjikist_code(platform, item[:code])
+      row_indexes_by_key = rows_by_key(rows)
-        deerjikist = Deerjikist.find_or_initialize_by(platform:, code:)
+      locked_deerjikists = lock_deerjikists_for_tag_update(tag.id, requested_keys)
-        deerjikist.tag = tag
+      current_deerjikists = locked_deerjikists.filter { |deerjikist|
-        render_deerjikist_form_record_invalid(deerjikist, i) unless deerjikist.save
+        deerjikist.tag_id == tag.id
+      }
+      requested_deerjikists = locked_deerjikists.filter { |deerjikist|
+        row_indexes_by_key.key?([deerjikist.platform, deerjikist.code])
+      }
+
+      render_deerjikist_conflicts(requested_deerjikists, row_indexes_by_key, tag)
+      raise ActiveRecord::Rollback if performed?
+
+      requested_keys_set = requested_keys.to_set
+      current_deerjikists.each do |deerjikist|
+        key = [deerjikist.platform, deerjikist.code]
+        deerjikist.destroy! unless requested_keys_set.include?(key)
+      end
+
+      existing_keys = requested_deerjikists.to_h { |deerjikist|
+        [[deerjikist.platform, deerjikist.code], true]
+      }
+      requested_keys.each do |platform, code|
+        next if existing_keys[[platform, code]]
+
+        deerjikist = Deerjikist.new(platform:, code:, tag:)
+        row_index = row_indexes_by_key[[platform, code]].first
+        begin
+          render_deerjikist_form_record_invalid(deerjikist, row_index) unless deerjikist.save
+        rescue ActiveRecord::RecordNotUnique
+          conflicts = lock_deerjikists_for_tag_update(tag.id, [[platform, code]])
+          render_deerjikist_conflicts(conflicts, row_indexes_by_key, tag)
+        end
         raise ActiveRecord::Rollback if performed?
       end
     end
@@ -245,17 +406,15 @@ class TagsController < ApplicationController
     return render_unprocessable_entity('カテゴリは必須です．', field: :category) if category.blank?
     return render_unprocessable_entity '廃止状態は必須です．', field: :deprecated unless params.key?(:deprecated)
 
-    return unless validate_tag_rename(tag, name)
+    locale = resolve_locale!
+
+    return unless validate_tag_rename(locale, tag, name)
 
     alias_names = params[:aliases].to_s.split.uniq
     parent_names = params[:parent_tags].to_s.split.uniq
     deprecated = bool?(:deprecated)
 
-    if tag.nico? && deprecated
+    if category == 'nico'
-      return render_unprocessable_entity 'ニコタグは廃止できません．', field: :deprecated
-    end
-
-    if tag.nico? || category == 'nico'
       return render_unprocessable_entity 'ニコタグは変更できません．', field: :category
     end
 
@@ -277,7 +436,7 @@ class TagsController < ApplicationController
       alias_names.delete(name)
 
       update_aliases!(tag, alias_names)
-      update_parent_tags!(tag, parent_names)
+      update_parent_tags!(locale, tag, parent_names)
 
       tag.reload
 
@@ -296,6 +455,8 @@ class TagsController < ApplicationController
     return head :unauthorized unless current_user
     return head :forbidden unless current_user.gte_member?
 
+    locale = resolve_locale!
+
     name = params[:name].presence
     category = params[:category].presence
     deprecated_given = params.key?(:deprecated)
@@ -303,13 +464,9 @@ class TagsController < ApplicationController
 
     tag = Tag.find(params[:id])
 
-    if tag.nico? && deprecated_given && deprecated
+    return unless validate_tag_rename(locale, tag, name)
-      return render_unprocessable_entity 'ニコタグは廃止できません．', field: :deprecated
-    end
 
-    return unless validate_tag_rename(tag, name)
+    if category.present? && category == 'nico'
-
-    if tag.nico? || (category.present? && category == 'nico')
       return render_unprocessable_entity 'ニコタグは変更できません．', field: :category
     end
 
@@ -516,11 +673,6 @@ class TagsController < ApplicationController
   end
 
   def record_tag_version! tag, event_type:, created_by_user:, name_changed: false, wiki_page: nil
-    if tag.nico?
-      NicoTagVersionRecorder.record!(tag:, event_type:, created_by_user:)
-      return
-    end
-
     TagVersionRecorder.record!(tag:, event_type:, created_by_user:)
 
     return unless name_changed
@@ -534,7 +686,7 @@ class TagsController < ApplicationController
         created_by_user:)
   end
 
-  def validate_tag_rename tag, name
+  def validate_tag_rename locale, tag, name
     return true if name.blank? || name == tag.name
 
     if tag.in?([Tag.tagme, Tag.bot, Tag.no_deerjikist, Tag.video, Tag.niconico])
@@ -542,9 +694,8 @@ class TagsController < ApplicationController
       return false
     end
 
-    target_tag_name = TagName.with_discarded.find_by(name:)
+    target_tag_name = TagName.find_by(language_code: locale.language_code, name:)
-    return true if target_tag_name.nil?
+    return true unless target_tag_name&.primary_flg
-    return true if target_tag_name.canonical_id?
 
     render_unprocessable_entity 'その名前は既に使はれてゐます．', field: :name
     false
@@ -554,17 +705,14 @@ class TagsController < ApplicationController
     return if name == tag.name
 
     current_tag_name = tag.tag_name
-    target_tag_name = TagName.with_discarded.find_by(name:)
+    target_tag_name = TagName.find_by(name:)
 
     if target_tag_name.nil?
       current_tag_name.update!(name:)
       return
     end
 
-    promote_tag_alias!(
+    promote_tag_alias!(tag, current_tag_name:, promoted_tag_name: target_tag_name)
-        tag,
-        current_tag_name:,
-        promoted_tag_name: target_tag_name)
   end
 
   def promote_tag_alias! tag, current_tag_name:, promoted_tag_name:
@@ -574,11 +722,9 @@ class TagsController < ApplicationController
       TagVersioning.ensure_snapshot!(old_owner_tag, created_by_user: current_user)
     end
 
-    promoted_tag_name.undiscard! if promoted_tag_name.discarded?
     promoted_tag_name.update!(canonical: nil)
 
-    TagName.with_discarded
+    TagName.where(canonical_id: current_tag_name.id)
-           .where(canonical_id: current_tag_name.id)
            .where.not(id: promoted_tag_name.id)
            .find_each do |alias_tag_name|
       alias_tag_name.update!(canonical: promoted_tag_name)
@@ -609,7 +755,7 @@ class TagsController < ApplicationController
     end
 
     alias_names.each do |alias_name|
-      alias_tag_name = TagName.find_undiscard_or_create_by!(name: alias_name)
+      alias_tag_name = TagName.find_or_create_by!(name: alias_name)
       affected_tags << alias_tag_name.canonical&.tag
     end
 
@@ -624,7 +770,7 @@ class TagsController < ApplicationController
     end
 
     alias_names.each do |alias_name|
-      alias_tag_name = TagName.find_undiscard_or_create_by!(name: alias_name)
+      alias_tag_name = TagName.find_or_create_by!(name: alias_name)
       alias_tag_name.update!(canonical: tag.tag_name)
     end
 
@@ -633,10 +779,10 @@ class TagsController < ApplicationController
     end
   end
 
-  def update_parent_tags! tag, parent_names
+  def update_parent_tags! locale, tag, parent_names
-    parent_tags = Tag.normalise_tags!(parent_names, with_tagme: false,
+    parent_tags = Tag.normalise_tags!(locale, parent_names,
-                                                    with_no_deerjikist: false,
+                                      with_tagme: false,
-                                                    deny_nico: true)
+                                      with_no_deerjikist: false)
 
     old_parent_tags = tag.parents.to_a
 
@@ -653,6 +799,7 @@ class TagsController < ApplicationController
   end
 
   def normalise_deerjikist_code platform, code
+    code = code.to_s
     return code if platform != 'youtube' || code[0] != '@'
 
     url = "https://www.youtube.com/#{ code }"
@@ -669,6 +816,82 @@ class TagsController < ApplicationController
     nil
   end
 
+  def normalise_deerjikist_rows tag
+    rows = []
+
+    params[:_json].each.with_index do |item, index|
+      platform = item[:platform]
+      unless Deerjikist.platforms.key?(platform)
+        render_deerjikist_platform_invalid(index)
+        return rows
+      end
+
+      code = normalise_deerjikist_code(platform, item[:code])
+      deerjikist = Deerjikist.new(platform:, code:, tag:)
+      unless deerjikist.valid?
+        render_deerjikist_form_record_invalid(deerjikist, index)
+        return rows
+      end
+
+      rows << { index:, platform:, code: }
+    end
+
+    rows
+  end
+
+  def lock_deerjikists_for_tag_update tag_id, keys
+    clauses = ['tag_id = ?']
+    values = [tag_id]
+
+    keys.each do |platform, code|
+      clauses << '(platform = ? AND code = ?)'
+      values << platform << code
+    end
+
+    Deerjikist
+      .where(clauses.join(' OR '), *values)
+      .order(:platform, :code)
+      .lock
+      .to_a
+  end
+
+  def render_deerjikist_conflicts deerjikists, row_indexes_by_key, tag
+    conflicts = deerjikists.filter { |deerjikist| deerjikist.tag_id != tag.id }
+    return if conflicts.empty?
+
+    tag_names_by_id = Tag
+                      .joins(:tag_name)
+                      .where(id: conflicts.map(&:tag_id).uniq)
+                      .pluck('tags.id', 'tag_names.name')
+                      .to_h
+    fields = { }
+
+    conflicts.each do |deerjikist|
+      message = "この情報は既に「#{ tag_names_by_id[deerjikist.tag_id] }」に紐づいてゐます．"
+      row_indexes_by_key[[deerjikist.platform, deerjikist.code]].each do |index|
+        field = :"deerjikists.#{ index }.code"
+        fields[field] ||= []
+        fields[field] << message
+      end
+    end
+
+    render_validation_error fields:
+  end
+
+  def render_deerjikist_platform_invalid index
+    render_validation_error fields: {
+      :"deerjikists.#{ index }.platform" => ['値が不正です．'],
+    }
+  end
+
+  def rows_by_key rows
+    rows.each_with_object({ }) do |row, result|
+      key = [row[:platform], row[:code]]
+      result[key] ||= []
+      result[key] << row[:index]
+    end
+  end
+
   def render_deerjikist_form_record_invalid deerjikist, index
     fields = { }
 
@@ -687,4 +910,20 @@ class TagsController < ApplicationController
 
     render_validation_error fields:
   end
+
+  def external_tag_json tag
+    { 'id' => tag.id,
+      'name' => "#{ tag.platform }:#{ tag.name }",
+      'category' => 'nico',
+      'deprecated_at' => nil,
+      'created_at' => tag.created_at,
+      'updated_at' => tag.created_at,
+      'post_count' => tag.post_count,
+      'matched_alias' => nil,
+      'aliases' => [],
+      'parents' => [],
+      'has_wiki' => false,
+      'material_id' => nil,
+      'has_deerjikists' => false }
+  end
 end

backend/app/controllers/wiki_pages_controller.rb

@@ -94,7 +94,7 @@ 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?
 
-    tag_name = TagName.find_undiscard_or_create_by!(name: title)
+    tag_name = TagName.find_or_create_by!(name: title)
 
     page =
         Wiki::Commit.create_content!(

backend/app/models/external_tag.rb

@@ -0,0 +1,20 @@
+class ExternalTag < ApplicationRecord
+  enum :platform, nico: 'nico'
+  validates :platform, presence: true, inclusion: { in: ExternalTag.platforms.keys }
+
+  has_many :post_external_tags, dependent: :delete_all
+  has_many :posts, through: :post_external_tags
+
+  has_many :nico_tag_versions, foreign_key: :tag_id, inverse_of: :external_tag
+
+  has_many :nico_tag_relations,
+           foreign_key: :nico_tag_id,
+           inverse_of: :nico_tag,
+           dependent: :destroy
+
+  has_many :linked_tags, through: :nico_tag_relations, source: :tag
+
+  def snapshot_linked_tag_names
+    linked_tags.joins(:tag_name).order('tag_names.name').pluck('tag_names.name')
+  end
+end

backend/app/models/language.rb

@@ -0,0 +1,3 @@
+class Language < ApplicationRecord
+  has_many :languages, class_name: 'Locale', foreign_key: :language_code
+end

backend/app/models/locale.rb

@@ -0,0 +1,24 @@
+class Locale < ApplicationRecord
+  after_create_commit :generate_tag_names!
+
+  belongs_to :language, foreign_key: :language_code, primary_key: :code
+  belongs_to :script, foreign_key: :script_code, primary_key: :code
+
+  def self.nipponese = Locale.find('ja')
+
+  private
+
+  def generate_tag_names!
+    tag_ids = TagName.where(language_code:, primary_flg: true).pluck(:tag_id)
+    Tag.where.not(id: tag_ids).find_each do
+      TagName.create!(tag_id: _1.id,
+                      language_code:,
+                      name: TagName.generate_name(self, _1, _1.name),
+                      script_code:,
+                      primary_flg: true,
+                      # TODO: 公証実装したら書く．
+                      # auto_generated: true,
+                      canonical_id: nil)
+    end
+  end
+end

backend/app/models/nico_tag_relation.rb

@@ -1,24 +1,10 @@
 class NicoTagRelation < ApplicationRecord
-  belongs_to :nico_tag, class_name: 'Tag'
+  belongs_to :nico_tag,
-  belongs_to :tag, class_name: 'Tag'
+             class_name: 'ExternalTag',
+             foreign_key: :nico_tag_id,
+             inverse_of: :nico_tag_relations
+  belongs_to :tag, class_name: 'Tag', foreign_key: :tag_id
 
   validates :nico_tag_id, presence: true
   validates :tag_id, presence: true
-
-  validate :nico_tag_must_be_nico
-  validate :tag_mustnt_be_nico
-
-  private
-
-  def nico_tag_must_be_nico
-    if nico_tag && nico_tag.category != 'nico'
-      errors.add :nico_tag_id, 'タグのカテゴリがニコニコである必要があります．'
-    end
-  end
-
-  def tag_mustnt_be_nico
-    if tag && tag.category == 'nico'
-      errors.add :tag_id, '連携先タグのカテゴリはニコニコであってはなりません．'
-    end
-  end
 end

backend/app/models/nico_tag_version.rb

@@ -1,7 +1,7 @@
 class NicoTagVersion < ApplicationRecord
   include VersionRecord
 
-  belongs_to :tag
+  belongs_to :external_tag, foreign_key: :tag_id, inverse_of: :nico_tag_versions
 
   validates :name, presence: true
 end

backend/app/models/post.rb

@@ -1,7 +1,9 @@
 class Post < ApplicationRecord
   require 'date'
   require 'mini_magick'
+  require 'nokogiri'
   require 'stringio'
+  require 'timeout'
 
   class RemoteThumbnailFetchFailed < StandardError; end
 
@@ -11,44 +13,69 @@ class Post < ApplicationRecord
   ORIGINAL_CREATED_ORDER_MESSAGE = 'オリジナルの作成日時の順番がをかしぃです．'.freeze
   ORIGINAL_CREATED_MINIMUM_RANGE_MESSAGE =
       'オリジナルの作成日時の範囲は1分以上必要です．'.freeze
-
+  REMOTE_SVG_CONTENT_TYPE = 'image/svg+xml'.freeze
-  def self.resized_thumbnail_attachment(upload)
+  MAX_SVG_DIMENSION = 4_096
+  MAX_SVG_PIXELS = 16_777_216
+  THUMBNAIL_PROCESS_TIMEOUT = 5.seconds
+  def self.resized_thumbnail_attachment(upload, content_type: nil)
     upload.rewind
-    image = MiniMagick::Image.read(upload.read)
+    bytes = upload.read
-    image.resize '180x180^'
+    blob = Timeout.timeout(THUMBNAIL_PROCESS_TIMEOUT) do
-    image.gravity 'Center'
+      image = image_for_thumbnail_upload(bytes, content_type:)
-    image.extent '180x180'
+      image.auto_orient
-    image.format 'jpg'
+      image.resize '180x180'
+      image.format 'jpg'
+      image.to_blob
+    end
 
-    { io: StringIO.new(image.to_blob),
+    { io: StringIO.new(blob),
       filename: 'resized_thumbnail.jpg',
       content_type: 'image/jpeg' }
+  rescue Timeout::Error
+    raise MiniMagick::Error, 'サムネイル画像の変換に失敗しました．'
   ensure
     upload.rewind
   end
 
+  def self.remote_thumbnail_attachment(raw_url)
+    response = Preview::ThumbnailFetcher.fetch_image_response(raw_url)
+    resized_thumbnail_attachment(
+        StringIO.new(response.body),
+        content_type: response.content_type)
+  rescue Preview::UrlSafety::UnsafeUrl,
+         Preview::ThumbnailFetcher::GenerationFailed,
+         Preview::HttpFetcher::FetchFailed,
+         Preview::HttpFetcher::FetchTimeout,
+         Preview::HttpFetcher::ResponseTooLarge,
+         Timeout::Error,
+         MiniMagick::Error => e
+    raise RemoteThumbnailFetchFailed, e.message
+  end
+
   belongs_to :uploaded_user, class_name: 'User', optional: true
 
   has_many :post_tags, dependent: :destroy, inverse_of: :post
-  has_many :active_post_tags, -> { kept }, class_name: 'PostTag', inverse_of: :post
+  has_many :tags, through: :post_tags
-  has_many :post_tags_with_discarded, -> { with_discarded }, class_name: 'PostTag'
-  has_many :tags, through: :active_post_tags
   has_many :active_tags, -> { where(tags: { deprecated_at: nil }) },
-           through: :active_post_tags, source: :tag
+           through: :post_tags,
+           source: :tag
 
   has_many :user_post_views, dependent: :delete_all
   has_many :post_similarities, dependent: :delete_all
   has_many :post_versions
+
   has_many :gekanator_guessed_games,
            class_name: 'GekanatorGame',
            foreign_key: :guessed_post_id,
            dependent: :delete_all,
            inverse_of: :guessed_post
+
   has_many :gekanator_correct_games,
            class_name: 'GekanatorGame',
            foreign_key: :correct_post_id,
            dependent: :delete_all,
            inverse_of: :correct_post
+
   has_many :gekanator_question_examples, dependent: :delete_all
 
   has_many :parent_post_implications,
@@ -65,6 +92,9 @@ class Post < ApplicationRecord
            inverse_of: :parent_post
   has_many :children, through: :child_post_implications, source: :post
 
+  has_many :post_external_tags, dependent: :destroy
+  has_many :external_tags, through: :post_external_tags
+
   has_one_attached :thumbnail
 
   attribute :version_no, :integer, default: 1
@@ -98,7 +128,6 @@ class Post < ApplicationRecord
 
   def snapshot_tag_names
     post_tags
-        .kept
         .joins(tag: :tag_name)
         .includes(:sections, tag: :tag_name)
         .order('tag_names.name')
@@ -112,8 +141,46 @@ class Post < ApplicationRecord
     end
   end
 
+  def self.tag_snapshot_literal tag
+    sections = tag.fetch('sections', []).map do |sec|
+      begin_ms = sec.fetch('begin_ms')
+      end_ms = sec['end_ms']
+
+      "[#{ Post.ms_to_time(begin_ms) }-#{ end_ms ? Post.ms_to_time(end_ms) : '' }]"
+    end
+
+    "#{ tag.fetch('name') }#{ sections.join }"
+  end
+
+  def snapshot_tags_json
+    tag_snapshots =
+        post_tags
+            .joins(tag: :tag_name)
+            .includes(:sections, tag: :tag_name)
+            .order('tags.id')
+            .map { |pt|
+          { 'tag_id' => pt.tag.id,
+            'version_no' => pt.tag.version_no,
+            'name' => pt.tag.name,
+            'category' => pt.tag.category,
+            'sections' => pt.sections.sort_by(&:begin_ms).map {
+                            { 'begin_ms' => _1.begin_ms, 'end_ms' => _1.end_ms }
+                          } }
+        }
+
+    external_tag_snapshots =
+        post_external_tags.order(:external_tag_id).map {
+          { 'external_tag_id' => _1.external_tag_id }
+        }
+
+    tag_snapshots + external_tag_snapshots
+  end
+
   def self.section_literal section
-    "[#{ Post.ms_to_time(section.begin_ms) }-#{ section.end_ms ? Post.ms_to_time(section.end_ms) : '' }]"
+    end_ms =
+        section.end_ms ? Post.ms_to_time(section.end_ms) : ''
+
+    "[#{ Post.ms_to_time(section.begin_ms) }-#{ end_ms }]"
   end
 
   def self.ms_to_time ms
@@ -157,17 +224,7 @@ class Post < ApplicationRecord
   end
 
   def attach_thumbnail_from_url! raw_url
-    response = Preview::ThumbnailFetcher.fetch_image_response(raw_url)
+    thumbnail.attach(self.class.remote_thumbnail_attachment(raw_url))
-    thumbnail.attach(
-        self.class.resized_thumbnail_attachment(
-            StringIO.new(response.body)))
-  rescue Preview::UrlSafety::UnsafeUrl,
-         Preview::ThumbnailFetcher::GenerationFailed,
-         Preview::HttpFetcher::FetchFailed,
-         Preview::HttpFetcher::FetchTimeout,
-         Preview::HttpFetcher::ResponseTooLarge,
-         MiniMagick::Error => e
-    raise RemoteThumbnailFetchFailed, e.message
   end
 
   private
@@ -209,6 +266,179 @@ class Post < ApplicationRecord
     self.url = PostUrlNormaliser.normalise(url) || url.strip
   end
 
+  def self.image_for_thumbnail_upload(bytes, content_type: nil)
+    if svg_content_type?(content_type) || svg_document_bytes?(bytes)
+      return decode_svg_thumbnail(bytes)
+    end
+
+    raise MiniMagick::Error, 'サムネイル画像の形式が不正です．' unless raster_thumbnail_bytes?(bytes)
+
+    decode_raster_thumbnail(bytes)
+  end
+
+  def self.raster_thumbnail_bytes?(bytes)
+    raster_thumbnail_format(bytes).present?
+  end
+
+  def self.remote_thumbnail_image_bytes?(bytes, content_type: nil)
+    return true if svg_content_type?(content_type) || svg_document_bytes?(bytes)
+
+    raster_thumbnail_bytes?(bytes)
+  end
+
+  def self.svg_content_type?(content_type)
+    content_type.to_s.split(';', 2).first.to_s.downcase.strip == REMOTE_SVG_CONTENT_TYPE
+  end
+
+  def self.svg_document_bytes?(bytes)
+    document = Nokogiri::XML(
+        bytes,
+        nil,
+        nil,
+        Nokogiri::XML::ParseOptions::STRICT |
+        Nokogiri::XML::ParseOptions::NONET)
+    document.root&.name == 'svg'
+  rescue Nokogiri::XML::SyntaxError
+    false
+  end
+
+  def self.decode_raster_thumbnail(bytes)
+    MiniMagick::Image.read(bytes)
+  end
+
+  def self.decode_svg_thumbnail(bytes)
+    MiniMagick::Image.read(sanitised_svg_bytes(bytes))
+  end
+
+  def self.raster_thumbnail_format(bytes)
+    binary = bytes.to_s.b
+    return 'jpeg' if binary.start_with?("\xFF\xD8\xFF".b)
+    return 'png' if binary.start_with?("\x89PNG\r\n\x1A\n".b)
+    return 'gif' if binary.start_with?('GIF87a'.b) || binary.start_with?('GIF89a'.b)
+    return 'webp' if binary.bytesize >= 12 &&
+                     binary.start_with?('RIFF'.b) &&
+                     binary.byteslice(8, 4) == 'WEBP'
+
+    nil
+  end
+
+  def self.sanitised_svg_bytes(bytes)
+    parse_options =
+        Nokogiri::XML::ParseOptions::STRICT |
+        Nokogiri::XML::ParseOptions::NONET
+    document = Nokogiri::XML(
+        bytes,
+        nil,
+        nil,
+        parse_options)
+    root = document.root
+    raise MiniMagick::Error, 'SVG が不正です．' if root == nil || root.name != 'svg'
+    raise MiniMagick::Error, 'SVG が不正です．' if document.internal_subset != nil
+    raise MiniMagick::Error, 'SVG が不正です．' if svg_uses_disallowed_features?(document)
+
+    width, height = svg_dimensions(root)
+    raise MiniMagick::Error, 'SVG が大きすぎます．' if width == nil || height == nil
+    if width > MAX_SVG_DIMENSION || height > MAX_SVG_DIMENSION || width * height > MAX_SVG_PIXELS
+      raise MiniMagick::Error, 'SVG が大きすぎます．'
+    end
+
+    document.to_xml
+  rescue Nokogiri::XML::SyntaxError
+    raise MiniMagick::Error, 'SVG が不正です．'
+  end
+
+  def self.svg_uses_disallowed_features?(document)
+    document.traverse.any? do |node|
+      next false unless node.element?
+
+      name = node.name.to_s.downcase
+      next true if name == 'script' || name == 'foreignobject'
+      next style_contains_disallowed_urls?(node.text.to_s) if name == 'style'
+
+      node.attribute_nodes.any? do |attribute|
+        attribute_name = attribute.name.to_s.downcase
+        attribute_value = attribute.value.to_s
+        attribute_name.start_with?('on') ||
+            external_svg_reference?(attribute_name, attribute_value)
+      end
+    end
+  end
+
+  def self.external_svg_reference?(attribute_name, attribute_value)
+    if ['href', 'xlink:href', 'src'].include?(attribute_name)
+      return external_svg_url?(attribute_value)
+    end
+    return style_contains_disallowed_urls?(attribute_value) if attribute_name == 'style'
+    return svg_url_function_disallowed?(attribute_value) if attribute_value.match?(/url\s*\(/i)
+
+    false
+  end
+
+  def self.external_svg_url?(value)
+    stripped = value.to_s.strip
+    return false if stripped.blank? || stripped.start_with?('#')
+
+    true
+  end
+
+  def self.style_contains_disallowed_urls?(value)
+    text = value.to_s
+    text.match?(/@import/i) || svg_url_function_disallowed?(text)
+  end
+
+  def self.svg_url_function_disallowed?(value)
+    value.to_s.scan(/url\s*\(([^)]*)\)/i).flatten.any? do |entry|
+      reference =
+          entry.to_s.strip
+               .delete_prefix("'")
+               .delete_prefix('"')
+               .delete_suffix("'")
+               .delete_suffix('"')
+      reference.present? && !(reference.start_with?('#'))
+    end
+  end
+
+  def self.svg_dimensions(root)
+    width = svg_length_to_pixels(root['width'])
+    height = svg_length_to_pixels(root['height'])
+    return [width, height] if width && height
+
+    view_box = root['viewBox'].to_s.strip.split(/\s+/).map { Float(_1) rescue nil }
+    return [nil, nil] if view_box.length != 4 || view_box.any?(&:nil?)
+    return [nil, nil] unless view_box[2].finite? && view_box[2].positive?
+    return [nil, nil] unless view_box[3].finite? && view_box[3].positive?
+
+    [view_box[2], view_box[3]]
+  end
+
+  def self.svg_length_to_pixels(value)
+    return nil if value.blank?
+
+    matched = /\A([0-9]+(?:\.[0-9]+)?)(px)?\z/i.match(value.to_s.strip)
+    return nil if matched == nil
+
+    pixels = Float(matched[1])
+    return nil unless pixels.finite? && pixels.positive?
+
+    pixels
+  rescue ArgumentError
+    nil
+  end
+
+  private_class_method :image_for_thumbnail_upload,
+                       :svg_content_type?,
+                       :decode_raster_thumbnail,
+                       :decode_svg_thumbnail,
+                       :raster_thumbnail_format,
+                       :sanitised_svg_bytes,
+                       :svg_uses_disallowed_features?,
+                       :external_svg_reference?,
+                       :external_svg_url?,
+                       :style_contains_disallowed_urls?,
+                       :svg_url_function_disallowed?,
+                       :svg_dimensions,
+                       :svg_length_to_pixels
+
   def parse_original_created_value field
     raw_value = public_send("#{ field }_before_type_cast")
     value = public_send(field)
@@ -252,7 +482,12 @@ class Post < ApplicationRecord
 
     match =
         value.match(
-            /\A(\d{4})-(\d{2})-(\d{2})T(\d{2}):(\d{2})(?::(\d{2})(?:\.(\d+))?)?(Z|[+-]\d{2}:?\d{2})?\z/)
+            /
+              \A(\d{4})-(\d{2})-(\d{2})T(\d{2}):(\d{2})
+              (?::(\d{2})(?:\.(\d+))?)?
+              (Z|[+-]\d{2}:?\d{2})?
+              \z
+            /x)
     return nil if match.nil?
 
     year = match[1].to_i

backend/app/models/post_external_tag.rb

@@ -0,0 +1,4 @@
+class PostExternalTag < ApplicationRecord
+  belongs_to :post
+  belongs_to :external_tag, counter_cache: :post_count
+end

backend/app/models/post_tag.rb

@@ -1,14 +1,7 @@
 class PostTag < ApplicationRecord
-  include Discard::Model
-
-  before_destroy do
-    raise ActiveRecord::ReadOnlyRecord, '消さないでください．'
-  end
-
   belongs_to :post
   belongs_to :tag, counter_cache: :post_count
   belongs_to :created_user, class_name: 'User', optional: true
-  belongs_to :deleted_user, class_name: 'User', optional: true
 
   has_many :sections, -> { order(:begin_ms) }, class_name: 'PostTagSection',
                                                foreign_key: [:post_id, :tag_id],
@@ -18,18 +11,5 @@ class PostTag < ApplicationRecord
 
   validates :post_id, presence: true
   validates :tag_id, presence: true
-  validates :post_id, uniqueness: {
+  validates :post_id, uniqueness: { scope: :tag_id }
-      scope: :tag_id,
-      conditions: -> { where(discarded_at: nil) } }
-
-  def discard_by! deleted_user
-    return self if discarded?
-
-    transaction do
-      update!(discarded_at: Time.current, deleted_user:)
-      Tag.where(id: tag_id).update_all('post_count = GREATEST(post_count - 1, 0)')
-    end
-
-    self
-  end
 end

backend/app/models/post_tag_section.rb

@@ -4,10 +4,10 @@ class PostTagSection < ApplicationRecord
   belongs_to :post
   belongs_to :tag
 
-  belongs_to :post_tag, -> { kept }, foreign_key: [:post_id, :tag_id],
+  belongs_to :post_tag, foreign_key: [:post_id, :tag_id],
-                                     primary_key: [:post_id, :tag_id],
+                        primary_key: [:post_id, :tag_id],
-                                     inverse_of: :sections,
+                        inverse_of: :sections,
-                                     optional: true
+                        optional: true
 
   validates :post_id, presence: true
   validates :tag_id, presence: true

backend/app/models/script.rb

@@ -0,0 +1,3 @@
+class Script < ApplicationRecord
+  ;
+end

backend/app/models/tag.rb

@@ -2,8 +2,6 @@ require 'set'
 
 
 class Tag < ApplicationRecord
-  include MyDiscard
-
   class NicoTagNormalisationError < ArgumentError
     ;
   end
@@ -28,15 +26,12 @@ class Tag < ApplicationRecord
   end
 
   has_many :post_tags, inverse_of: :tag
-  has_many :active_post_tags, -> { kept }, class_name: 'PostTag', inverse_of: :tag
+  has_many :posts, through: :post_tags
-  has_many :post_tags_with_discarded, -> { with_discarded }, class_name: 'PostTag'
-  has_many :posts, through: :active_post_tags
-
-  has_many :nico_tag_relations, foreign_key: :nico_tag_id, dependent: :destroy
-  has_many :linked_tags, through: :nico_tag_relations, source: :tag
 
   has_many :reversed_nico_tag_relations,
-           class_name: 'NicoTagRelation', foreign_key: :tag_id, dependent: :destroy
+           class_name: 'NicoTagRelation',
+           foreign_key: :tag_id,
+           dependent: :destroy
   has_many :linked_nico_tags, through: :reversed_nico_tag_relations, source: :nico_tag
 
   has_many :tag_implications, foreign_key: :parent_tag_id, dependent: :destroy
@@ -54,8 +49,8 @@ class Tag < ApplicationRecord
   has_many :materials
 
   has_many :tag_versions
-  has_many :nico_tag_versions
 
+  has_many :tag_names
   belongs_to :tag_name
   delegate :wiki_page, to: :tag_name
 
@@ -69,17 +64,13 @@ class Tag < ApplicationRecord
                   character:   'character',
                   general:     'general',
                   material:    'material',
-                  nico:        'nico',
                   meta:        'meta'
 
   validates :category, presence: true, inclusion: { in: Tag.categories.keys }
 
-  validate :nico_tag_name_must_start_with_nico
+  validate :tag_name_mustnt_start_with_nico
   validate :tag_name_must_be_canonical
   validate :category_must_be_deerjikist_with_deerjikists
-  validate :nico_tags_cannot_be_deprecated
-
-  scope :nico_tags, -> { nico }
 
   CATEGORY_PREFIXES = {
       'general:'    => :general,
@@ -105,19 +96,20 @@ class Tag < ApplicationRecord
 
   def has_deerjikists = deerjikists.loaded? ? deerjikists.any? : deerjikists.exists?
 
-  def self.tagme = find_or_create_by_tag_name!('タグ希望', category: :meta)
+  def self.tagme = find_or_create_by_tag_name!(Locale.nipponese, 'タグ希望', category: :meta)
-  def self.bot = find_or_create_by_tag_name!('bot操作', category: :meta)
+  def self.bot = find_or_create_by_tag_name!(Locale.nipponese, 'bot操作', category: :meta)
-  def self.no_deerjikist = find_or_create_by_tag_name!('ニジラー情報不詳', category: :meta)
+  def self.no_deerjikist =
-  def self.video = find_or_create_by_tag_name!('動画', category: :meta)
+      find_or_create_by_tag_name!(Locale.nipponese, 'ニジラー情報不詳', category: :meta)
-  def self.niconico = find_or_create_by_tag_name!('ニコニコ', category: :meta)
+  def self.video = find_or_create_by_tag_name!(Locale.nipponese, '動画', category: :meta)
-  def self.youtube = find_or_create_by_tag_name!('YouTube', category: :meta)
+  def self.niconico = find_or_create_by_tag_name!(Locale.nipponese, 'ニコニコ', category: :meta)
+  def self.youtube = find_or_create_by_tag_name!(Locale.nipponese, 'YouTube', category: :meta)
 
-  def self.normalise_tags! tag_names, with_tagme: true,
+  def self.normalise_tags! locale, tag_names,
-                                      with_no_deerjikist: true,
+                           with_tagme: true,
-                                      deny_nico: true,
+                           with_no_deerjikist: true,
-                                      deny_deprecated: false,
+                           deny_deprecated: false,
-                                      with_sections: false
+                           with_sections: false
-    if deny_nico && tag_names.any? { |n| n.downcase.start_with?('nico:') }
+    if tag_names.any? { |n| n.downcase.start_with?('nico:') }
       raise NicoTagNormalisationError
     end
 
@@ -143,9 +135,9 @@ class Tag < ApplicationRecord
         raise SectionLiteralParseError.new(raw_name, raw_name)
       end
 
-      name = TagName.canonicalise(name).first
+      name = TagName.canonicalise(locale, name).first
 
-      find_or_create_by_tag_name!(name, category: (cat || :general)).tap do |tag|
+      find_or_create_by_tag_name!(locale, name, category: (cat || :general)).tap do |tag|
         if deny_deprecated && tag.deprecated?
           raise DeprecatedTagNormalisationError, [tag.name]
         end
@@ -233,13 +225,22 @@ class Tag < ApplicationRecord
     [left_end_ms, right_end_ms].max
   end
 
-  def self.find_or_create_by_tag_name! name, category:
+  def self.find_or_create_by_tag_name! locale, name, category:
-    tn = TagName.find_undiscard_or_create_by!(name: name.to_s.strip)
+    language_code = locale.language_code
-    tn = tn.canonical if tn.canonical_id?
+    name = name.to_s.strip
 
-    Tag.find_undiscard_or_create_by!(tag_name_id: tn.id) do |t|
+    tn = TagName.find_or_create_by!(language_code:, name:) do
-      t.category = category
+      _1.script_code = locale.script_code
+      _1.primary_flg = true
     end
+
+    tag = tn.tag
+    return tag if tag
+
+    tag = Tag.create!(tag_name: tn, category:)
+    tn.update!(tag:)
+
+    tag
   rescue ActiveRecord::RecordNotUnique
     retry
   end
@@ -259,11 +260,11 @@ class Tag < ApplicationRecord
 
         TagVersioning.ensure_snapshot!(source_tag, created_by_user:)
 
-        source_tag.post_tags.kept.find_each do |source_pt|
+        source_tag.post_tags.find_each do |source_pt|
           post_id = source_pt.post_id
           affected_post_ids << post_id
-          source_pt.discard_by!(created_by_user)
+          source_pt.destroy!
-          unless PostTag.kept.exists?(post_id:, tag: target_tag)
+          unless PostTag.exists?(post_id:, tag: target_tag)
             PostTag.create!(post_id:, tag: target_tag)
           end
         end
@@ -275,14 +276,12 @@ class Tag < ApplicationRecord
         end
 
         TagVersioning.record!(source_tag, event_type: :discard, created_by_user:)
-        source_tag.discard!
+        source_tag.tag_names.update_all(tag_id: source_tag.id, primary_key: false,
+                                        updated_at: Time.current)
+        source_tag.destroy!
 
-        if source_tag.nico?
+        source_tag_name.update_columns(canonical_id: target_tag.tag_name_id,
-          source_tag_name.discard!
+                                       updated_at: Time.current)
-        else
-          source_tag_name.update_columns(canonical_id: target_tag.tag_name_id,
-                                         updated_at: Time.current)
-        end
 
         TagVersioning.record!(target_tag, event_type: :update, created_by_user:)
       end
@@ -293,13 +292,13 @@ class Tag < ApplicationRecord
       end
 
       # 投稿件数を再集計
-      target_tag.update_columns(post_count: PostTag.kept.where(tag: target_tag).count)
+      target_tag.update_columns(post_count: PostTag.where(tag: target_tag).count)
     end
 
     target_tag.reload
   end
 
-  def snapshot_aliases = tag_name.aliases.kept.order(:name).pluck(:name)
+  def snapshot_aliases = tag_name.aliases.order(:name).pluck(:name)
 
   def snapshot_parent_tag_ids = parents.order(:id).pluck(:id)
 
@@ -309,11 +308,9 @@ class Tag < ApplicationRecord
 
   private
 
-  def nico_tag_name_must_start_with_nico
+  def tag_name_mustnt_start_with_nico
-    n = name.to_s
+    if name.to_s.downcase.start_with?('nico:')
-    if ((nico? && !(n.downcase.start_with?('nico:'))) || 
+      errors.add :name, 'タグの命名規則に反してゐます．'
-        (!(nico?) && n.downcase.start_with?('nico:')))
-      errors.add :name, 'ニコニコ・タグの命名規則に反してゐます．'
     end
   end
 
@@ -354,10 +351,4 @@ class Tag < ApplicationRecord
 
     total_s * 1_000 + match[:ms].to_s.ljust(3, '0')[0, 3].to_i
   end
-
-  def nico_tags_cannot_be_deprecated
-    if nico? && deprecated_at.present?
-      errors.add :deprecated_at, 'ニコタグは廃止できません．'
-    end
-  end
 end

backend/app/models/tag_name.rb

@@ -1,45 +1,55 @@
 class TagName < ApplicationRecord
-  include MyDiscard
+  belongs_to :language, foreign_key: :language_code, primary_key: :code
-
+  belongs_to :tag, optional: true
-  has_one :tag
   has_one :wiki_page
 
-  belongs_to :canonical, class_name: 'TagName', optional: true
+  validates :name, presence: true,
-  has_many :aliases, class_name: 'TagName', foreign_key: :canonical_id
+                   length: { maximum: 255 },
+                   uniqueness: { scope: :language_code }
 
-  validates :name, presence: true, length: { maximum: 255 }, uniqueness: true
-
-  validate :canonical_must_be_canonical
   validate :alias_name_must_not_have_prefix
-  validate :canonical_must_not_be_present_with_tag_or_wiki_page
+  validate :alias_must_not_have_wiki_page
   validate :name_must_be_sanitised
 
-  def self.canonicalise names
+  def primary? = primary_flg
+
+  def canonical = TagName.find_by(language:, tag:, primary_flg: true)
+  def aliases = TagName.where(language:, tag:, primary_flg: false)
+
+  def self.canonicalise locale, names
     names = Array(names).map { |n| n.to_s.strip }.reject(&:blank?)
     return [] if names.blank?
 
-    tns = TagName.includes(:canonical).where(name: names).index_by(&:name)
+    tns = TagName.where(language_code: locale.language_code, name: names).index_by(&:name)
 
-    names.map { |name| tns[name]&.canonical&.name || name }.uniq
+    names.map { |name|
+      if tns[name].primary_flg
+        name
+      else
+        TagName.find_by(language_code: locale.language_code,
+                        tag_id: tns[name].tag_id,
+                        primary_flg: true).name
+      end
+    }.uniq
+  end
+
+  def self.generate_name locale, tag, name
+    # TODO: 言語ごとの自動命名ロジック完成したら書く．
+
+    "Tag_##{ tag.id }"
   end
 
   private
 
-  def canonical_must_be_canonical
-    if canonical&.canonical_id?
-      errors.add :canonical, 'canonical は実体を示す必要があります．'
-    end
-  end
-
   def alias_name_must_not_have_prefix
-    if canonical_id? && name.to_s.include?(':')
+    if !(primary?) && name.to_s.include?(':')
       errors.add :name, 'エーリアス名にプレフィクスを含むことはできません．'
     end
   end
 
-  def canonical_must_not_be_present_with_tag_or_wiki_page
+  def alias_must_not_have_wiki_page
-    if canonical_id? && (tag || wiki_page)
+    if !(primary?) && wiki_page
-      errors.add :canonical, 'タグもしくは Wiki の参照がある名前はエーリアスになれません．'
+      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
 

backend/app/models/tag_name_sanitisation_rule.rb

@@ -10,35 +10,43 @@ class TagNameSanitisationRule < ApplicationRecord
   validate :source_pattern_must_be_regexp
 
   class << self
-    def sanitise(name) =
+    def sanitise(name)
-        rules.reduce(name.dup) { |name, (pattern, replacement)| name.gsub(pattern, replacement) }
+      rules.reduce(name.dup) { |name, (pattern, replacement)| name.gsub(pattern, replacement) }
+    end
 
     def apply!
-      TagName.find_each do |tn|
+      Language.find_each do |language|
-        name = sanitise(tn.name)
+        TagName.where(language:).find_each do |tn|
-        next if name == tn.name
+          name = sanitise(tn.name)
+          next if name == tn.name
 
-        TagName.transaction do
+          TagName.transaction do
-          existing_tn = TagName.find_by(name:)
+            existing_tn = TagName.find_by(language:, name:)
-          if existing_tn
+            if existing_tn
-            existing_tn = existing_tn.canonical || existing_tn
+              unless existing_tn.primary_flg
-            next if existing_tn.id == tn.id
+                existing_tn = TagName.find_by!(language:,
+                                               tag_id: existing_tn.tag_id,
+                                               primary_flg: true)
+              end
+              next if existing_tn.id == tn.id
 
-            existing_tag = Tag.find_by(tag_name_id: existing_tn.id)
+              existing_tag = existing_tn.tag
-            source_tag = Tag.find_by(tag_name_id: tn.id)
+              source_tag = tn.tag
 
-            if existing_tag
+              if existing_tag
-              Tag.merge_tags!(existing_tag, source_tag) if tn.tag
+                Tag.merge_tags!(existing_tag, source_tag) if tn.tag
-            elsif source_tag
+              elsif source_tag
-              source_tag.update_columns(tag_name_id: existing_tn.id, 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
-            tn.discard!
 
-            next
+            # TagName 側の自動サニタイズを回避
+            tn.update_columns(name:, updated_at: Time.current)
           end
-
-          # TagName 側の自動サニタイズを回避
-          tn.update_columns(name:, updated_at: Time.current)
         end
       end
     end

backend/app/representations/external_tag_repr.rb

@@ -0,0 +1,20 @@
+module ExternalTagRepr
+  module_function
+
+  def base tag
+    { 'id' => tag.id,
+      'name' => "#{ tag.platform }:#{ tag.name }",
+      'category' => 'nico',
+      'post_count' => tag.post_count,
+      'created_at' => tag.created_at,
+      'updated_at' => tag.created_at,
+      'deprecated_at' => nil,
+      'aliases' => [],
+      'parents' => [],
+      'has_wiki' => false,
+      'material_id' => nil,
+      'has_deerjikists' => false }
+  end
+
+  def inline(tag) = base(tag)
+end

backend/app/representations/post_compact_repr.rb

@@ -0,0 +1,19 @@
+# frozen_string_literal: true
+
+
+module PostCompactRepr
+  module_function
+
+  def base post, host: nil
+    return nil if post.nil?
+
+    PostRepr
+        .common(post, host:)
+        .slice(
+            'id',
+            'title',
+            'url',
+            'thumbnail',
+            'thumbnail_base')
+  end
+end

backend/app/representations/post_repr.rb

@@ -17,8 +17,13 @@ module PostRepr
 
   module_function
 
-  def base post, current_user = nil
+  def base post, current_user = nil, host: nil
-    json = common(post)
+    json =
+        if host.present?
+          common(post, host:)
+        else
+          common(post)
+        end
     json['tags'] = tag_json(post)
     json['uploaded_user'] = post.uploaded_user && UserRepr.base(post.uploaded_user)
     json['viewed'] = current_user ? current_user.viewed?(post) : false
@@ -26,50 +31,98 @@ module PostRepr
   end
 
   def detail post, current_user = nil, parent_posts: [], child_posts: [],
-             sibling_posts: { }, related: []
+             sibling_posts: { }, related: [], host: nil
-    base(post, current_user).merge(
+    if host.present?
-        'parent_posts' => cards(parent_posts),
+      base(post, current_user, host:).merge(
-        'child_posts' => cards(child_posts),
+          'parent_posts' => cards(parent_posts, host:),
-        'sibling_posts' => sibling_posts.transform_keys(&:to_s).transform_values { |posts|
+          'child_posts' => cards(child_posts, host:),
-          cards(posts)
+          'sibling_posts' => sibling_posts.transform_keys(&:to_s).transform_values { |posts|
-        },
+            cards(posts, host:)
-        'related' => cards(related))
+          },
+          'related' => cards(related, host:))
+    else
+      base(post, current_user).merge(
+          'parent_posts' => cards(parent_posts),
+          'child_posts' => cards(child_posts),
+          'sibling_posts' => sibling_posts.transform_keys(&:to_s).transform_values { |posts|
+            cards(posts)
+          },
+          'related' => cards(related))
+    end
   end
 
-  def card post
+  def card post, host: nil
-    common(post).merge('parent_posts' => [], 'child_posts' => [])
+    if host.present?
+      common(post, host:).merge('parent_posts' => [], 'child_posts' => [])
+    else
+      common(post).merge('parent_posts' => [], 'child_posts' => [])
+    end
   end
 
-  def cards posts
+  def cards posts, host: nil
-    posts.map { |post| card(post) }
+    if host.present?
+      posts.map { |post| card(post, host:) }
+    else
+      posts.map { |post| card(post) }
+    end
   end
 
-  def many posts, current_user = nil
+  def many posts, current_user = nil, host: nil
-    posts.map { |p| base(p, current_user) }
+    if host.present?
+      posts.map { |p| base(p, current_user, host:) }
+    else
+      posts.map { |p| base(p, current_user) }
+    end
   end
 
-  def common post
+  def common post, host: nil
     BASE_FIELDS.to_h { |field| [field.to_s, post.public_send(field)] }
-               .merge('thumbnail' => thumbnail_url(post))
+               .merge(
+                   'thumbnail' =>
+                       if host.present?
+                         thumbnail_url(post, host:)
+                       else
+                         thumbnail_url(post)
+                       end)
   end
 
   def tag_json post
-    post
+    internal_tags =
-        .active_post_tags
+        post
+        .post_tags
         .reject { _1.tag.deprecated? }
         .sort_by { _1.tag.name }
         .map { |post_tag|
-      TagRepr.inline(post_tag.tag).merge(
+          TagRepr.inline(post_tag.tag).merge(
-          'children' => [],
+              'children' => [],
-          'sections' => post_tag.sections.as_json(only: [:begin_ms, :end_ms]))
+              'sections' => post_tag.sections.as_json(only: [:begin_ms, :end_ms]))
-    }
+        }
+
+    external_tags =
+        post
+        .external_tags
+        .sort_by { _1.name }
+        .map { ExternalTagRepr.base(_1).merge('children' => [], 'sections' => []) }
+
+    internal_tags + external_tags
   end
 
-  def thumbnail_url post
+  def thumbnail_url post, host: nil
     return nil unless post.thumbnail.attached?
 
-    Rails.application.routes.url_helpers.rails_blob_url(post.thumbnail, only_path: false)
+    options = { only_path: false }
-  rescue
+    options[:host] = host if host.present?
+
+    Rails.application.routes.url_helpers.rails_storage_proxy_url(post.thumbnail, **options)
+  rescue ActionController::UrlGenerationError, ArgumentError, URI::InvalidURIError => e
+    payload = {
+        post_id: post.id,
+        attachment_id: post.thumbnail.attachment&.id,
+        blob_id: post.thumbnail.blob&.id,
+        error_class: e.class,
+        message: e.message }
+
+    Rails.logger.warn("PostRepr.thumbnail_url failed #{ payload.to_json }")
     nil
   end
 end

backend/app/services/nico_tag_version_recorder.rb

@@ -1,19 +1,22 @@
 class NicoTagVersionRecorder < VersionRecorder
-  def self.record! tag:, event_type:, created_by_user:
+  def self.record! external_tag:, event_type:, created_by_user:
-    new(tag:, event_type:, created_by_user:).record!
+    new(external_tag:, event_type:, created_by_user:).record!
   end
 
-  def initialize tag:, event_type:, created_by_user:
+  def initialize external_tag:, event_type:, created_by_user:
-    super(record: tag, event_type:, created_by_user:)
+    super(record: external_tag, event_type:, created_by_user:)
   end
 
   private
 
   def version_class = NicoTagVersion
   def version_association = :nico_tag_versions
-  def record_key = :tag
+  def record_key = :external_tag
 
   def snapshot_attributes
-    { name: @record.name, linked_tags: @record.snapshot_linked_tag_names.join(' ') }
+    { name: "#{ @record.platform }:#{ @record.name }",
+      linked_tags: @record.snapshot_linked_tag_names.join(' ') }
   end
+
+  def tracks_version_no_on_record? = false
 end

backend/app/services/post_bulk_creator.rb

@@ -0,0 +1,202 @@
+class PostBulkCreator
+  def initialize actor:, posts:, thumbnails:, host: nil
+    @actor_id = actor.id
+    @posts = posts
+    @thumbnails = thumbnails
+    @host = host
+  end
+
+  def run locale
+    results = Array.new(@posts.length)
+    mutex = Mutex.new
+    next_index = 0
+
+    workers = Array.new(2) do
+      Thread.new do
+        Rails.application.executor.wrap do
+          ActiveRecord::Base.connection_pool.with_connection do
+            actor = User.find(@actor_id)
+            loop do
+              index = nil
+              begin
+                index = mutex.synchronize do
+                  current = next_index
+                  next_index += 1
+                  current
+                end
+                break if index >= @posts.length
+
+                attributes = @posts[index]
+                results[index] = create_row(locale, actor, attributes, index)
+              rescue StandardError => e
+                Rails.logger.error(
+                    "post_bulk_creator_worker_failure #{ { error: e.class.name,
+                                                          message: e.message,
+                                                          index: }.to_json }")
+                results[index] = {
+                    status: 'failed',
+                    recoverable: false,
+                    errors: { base: ['登録中にエラーが発生しました．'] },
+                    base_errors: [] }
+              end
+            end
+          end
+        end
+      end
+    end
+    workers.each(&:join)
+
+    results.each_index do |index|
+      next if results[index].present?
+
+      results[index] = {
+          status: 'failed',
+          recoverable: false,
+          errors: { base: ['登録中にエラーが発生しました．'] },
+          base_errors: [] }
+    end
+
+    { results: }
+  end
+
+  private
+
+  def create_row locale, actor, attributes, index
+    preflight =
+        PostCreatePreflight.new(
+            attributes: attributes,
+            thumbnail: thumbnail_for(index, attributes),
+            host: @host).run
+    if preflight[:existing_post_id].present?
+      return {
+          status: 'skipped',
+          existing_post_id: preflight[:existing_post_id],
+          existing_post: preflight[:existing_post] }
+    end
+
+    post = PostCreator.new(
+        actor: actor,
+        attributes: normalised_attributes(attributes, preflight, index)).create!(locale)
+    result = {
+        status: 'created',
+        post: { id: post.id } }
+    result[:field_warnings] = preflight[:field_warnings] if preflight[:field_warnings].present?
+    result[:base_warnings] = preflight[:base_warnings] if preflight[:base_warnings].present?
+    result
+  rescue PostCreatePreflight::ValidationFailed => e
+    {
+        status: 'failed',
+        recoverable: true,
+        errors: e.fields,
+        base_errors: e.base_errors }
+  rescue ActiveRecord::RecordInvalid => e
+    existing_post = existing_post_for_race(attributes, e.record)
+    if existing_post.present?
+      return {
+          status: 'skipped',
+          existing_post_id: existing_post[:id],
+          existing_post: existing_post }
+    end
+
+    {
+        status: 'failed',
+        recoverable: true,
+        errors: e.record.errors.to_hash,
+        base_errors: e.record.errors[:base] }
+  rescue ActiveRecord::RecordNotUnique => e
+    if e.message.include?('index_posts_on_url')
+      existing_post = existing_post_for_race(attributes)
+      return {
+          status: 'skipped',
+          existing_post_id: existing_post[:id],
+          existing_post: existing_post } if existing_post.present?
+    end
+
+    Rails.logger.error(
+        "post_bulk_creator_record_not_unique #{ { error: e.class.name,
+                                                 message: e.message }.to_json }")
+    {
+        status: 'failed',
+        recoverable: false,
+        errors: { base: ['登録中にエラーが発生しました．'] },
+        base_errors: [] }
+  rescue Tag::NicoTagNormalisationError
+    {
+        status: 'failed',
+        recoverable: true,
+        errors: { tags: ['ニコニコ・タグは直接指定できません．'] },
+        base_errors: [] }
+  rescue Tag::DeprecatedTagNormalisationError
+    {
+        status: 'failed',
+        recoverable: true,
+        errors: { tags: ['廃止済みタグは付与できません．'] },
+        base_errors: [] }
+  rescue PostCreator::VideoMsParseError
+    {
+        status: 'failed',
+        recoverable: true,
+        errors: { video_ms: ['動画時間の記法が不正です．'] },
+        base_errors: [] }
+  rescue Post::RemoteThumbnailFetchFailed
+    {
+        status: 'failed',
+        recoverable: true,
+        errors: { thumbnail_base: ['サムネイル画像の取得に失敗しました．'] },
+        base_errors: [] }
+  rescue ArgumentError => e
+    {
+        status: 'failed',
+        recoverable: true,
+        errors: { base: [e.message] },
+        base_errors: [] }
+  rescue StandardError => e
+    Rails.logger.error(
+        "post_bulk_creator_failure #{ { error: e.class.name,
+                                        message: e.message }.to_json }")
+    {
+        status: 'failed',
+        recoverable: false,
+        errors: { base: ['登録中にエラーが発生しました．'] },
+        base_errors: [] }
+  end
+
+  def normalised_attributes attributes, preflight, index
+    {
+        url: preflight[:url],
+        title: preflight[:title],
+        thumbnail_base: preflight[:thumbnail_base],
+        thumbnail: thumbnail_for(index, attributes),
+        tags: preflight[:tags],
+        parent_post_ids: preflight[:parent_post_ids],
+        original_created_from: preflight[:original_created_from],
+        original_created_before: preflight[:original_created_before],
+        duration: preflight[:duration],
+        video_ms: preflight[:video_ms],
+        direct_tag_specs: preflight[:direct_tag_specs],
+        default_tag_specs: preflight[:default_tag_specs],
+        snapshot_tag_specs: preflight[:snapshot_tag_specs],
+        post_tag_specs: preflight[:post_tag_specs],
+        tag_sections: preflight[:tag_sections],
+        normalised_parent_post_ids: preflight[:normalised_parent_post_ids] }
+  end
+
+  def thumbnail_for index, attributes
+    return nil if attributes['thumbnail_base'].present? || attributes[:thumbnail_base].present?
+
+    @thumbnails[index]
+  end
+
+  def existing_post_for_race attributes, record = nil
+    return nil if record.present? && !(record.errors.of_kind?(:url, :taken))
+
+    normal_url = PostUrlNormaliser.normalise(attributes['url'] || attributes[:url])
+    return nil if normal_url.blank?
+
+    compact_existing_post(Post.with_attached_thumbnail.find_by(url: normal_url))
+  end
+
+  def compact_existing_post post
+    PostCompactRepr.base(post, host: @host)
+  end
+end

backend/app/services/post_create_plan.rb

@@ -0,0 +1,274 @@
+class PostCreatePlan
+  VIDEO_TAG_NAME = '動画'.freeze
+  TAGME_TAG_NAME = 'タグ希望'.freeze
+  NO_DEERJIKIST_TAG_NAME = 'ニジラー情報不詳'.freeze
+
+  def initialize attributes:
+    @attributes = attributes.symbolize_keys
+    @existing_tags_by_name = nil
+  end
+
+  def build! locale
+    direct_tag_specs, tag_sections = parse_direct_tag_specs(locale)
+    default_tag_specs = build_default_tag_specs(direct_tag_specs)
+    snapshot_tag_specs = merge_tag_specs(direct_tag_specs + default_tag_specs)
+    preload_existing_tags_by_name!(snapshot_tag_specs.map { _1[:name] })
+    validate_new_tag_specs!(snapshot_tag_specs)
+    post_tag_specs = expand_parent_tag_specs(locale, snapshot_tag_specs)
+    video_ms = normalise_video_ms(snapshot_tag_specs)
+    validate_video_sections!(video_ms, tag_sections)
+    parent_post_ids = normalise_parent_post_ids
+    validate_parent_post_ids!(parent_post_ids)
+
+    { url: @attributes[:url],
+      title: @attributes[:title].to_s,
+      thumbnail_base: @attributes[:thumbnail_base].presence,
+      original_created_from: @attributes[:original_created_from].presence,
+      original_created_before: @attributes[:original_created_before].presence,
+      tags: serialised_tags(direct_tag_specs, tag_sections),
+      display_tags: display_tags(direct_tag_specs, tag_sections),
+      duration: @attributes[:duration].to_s,
+      video_ms: video_ms,
+      parent_post_ids: parent_post_ids.join(' '),
+      direct_tag_specs: direct_tag_specs,
+      default_tag_specs: default_tag_specs,
+      snapshot_tag_specs: snapshot_tag_specs,
+      post_tag_specs: post_tag_specs,
+      tag_sections: tag_sections,
+      normalised_parent_post_ids: parent_post_ids }
+  end
+
+  private
+
+  def tag_names = @attributes[:tags].to_s.split
+
+  def parse_direct_tag_specs locale
+    tag_sections = { }
+    direct_tag_specs = []
+
+    tag_names.each do |raw_name|
+      tag_name, category, sections = parse_raw_tag_name(locale, raw_name)
+      existing_tag = existing_tags_by_name(locale)[tag_name]
+      raise Tag::DeprecatedTagNormalisationError, [existing_tag.name] if existing_tag&.deprecated?
+
+      direct_tag_specs << {
+          name: tag_name,
+          category: (category || existing_tag&.category || 'general').to_sym }
+      if sections.present?
+        tag_sections[tag_name] ||= []
+        tag_sections[tag_name].concat(sections)
+        tag_sections[tag_name] = Tag.merge_section_ranges(tag_sections[tag_name])
+        tag_sections.delete(tag_name) if tag_sections[tag_name] == [[0, nil]]
+      end
+    end
+
+    [merge_tag_specs(direct_tag_specs), tag_sections]
+  end
+
+  def parse_raw_tag_name locale, raw_name
+    name = raw_name.to_s
+    prefix, category =
+        Tag::CATEGORY_PREFIXES.find {
+          name.downcase.start_with?(_1[0])
+        } || ['', nil]
+    name = name.sub(/\A#{ prefix }/i, '')
+
+    sections = []
+    while match = name.match(/\A(\S*?)\[([^\[\]\s]*)-([^\[\]\s]*)\](\S*)\z/)
+      name = "#{ match[1] }#{ match[4] }"
+      next if match[2].empty? && match[3].empty?
+
+      sections << Tag.normalise_section_range!(
+          begin_raw: match[2],
+          end_raw: match[3],
+          tag_name: name)
+    end
+    if name.include?('[') || name.include?(']')
+      raise Tag::SectionLiteralParseError.new(raw_name, raw_name)
+    end
+
+    [resolved_tag_name(locale, name), category&.to_sym, sections]
+  end
+
+  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 << {
+          name: TAGME_TAG_NAME,
+          category: :meta }
+    end
+    if direct_tag_specs.none? { deerjikist_tag_spec?(locale, _1) }
+      default_tag_specs << {
+          name: NO_DEERJIKIST_TAG_NAME,
+          category: :meta }
+    end
+
+    default_tag_specs
+  end
+
+  def validate_new_tag_specs! specs
+    Array(specs).each do |spec|
+      next if existing_tags_by_name.key?(spec[:name])
+
+      validate_new_tag_spec!(spec)
+    end
+  end
+
+  def validate_new_tag_spec! spec
+    tag_name = TagName.new(name: spec[:name])
+    tag = Tag.new(category: spec[:category], tag_name:)
+    return if tag_name.valid? && tag.valid?
+
+    post = Post.new
+    tag_name.errors[:name].each do |message|
+      post.errors.add :tags, "#{ spec[:name] }: #{ message }"
+    end
+    tag.errors.each do |error|
+      next if error.attribute == :tag_name
+
+      post.errors.add :tags, "#{ spec[:name] }: #{ error.message }"
+    end
+    raise ActiveRecord::RecordInvalid, post
+  end
+
+  def expand_parent_tag_specs locale, snapshot_tag_specs
+    existing_snapshot_tags = snapshot_tag_specs.filter_map do
+      existing_tags_by_name(locale)[_1[:name]]
+    end
+    expanded_parent_specs =
+        Tag.expand_parent_tags(existing_snapshot_tags)
+           .reject(&:deprecated?)
+           .map { |tag|
+             { name: tag.name,
+               category: tag.category.to_sym }
+        }
+    merge_tag_specs(snapshot_tag_specs + expanded_parent_specs)
+  end
+
+  def merge_tag_specs specs
+    specs.each_with_object({ }) { |spec, merged|
+      merged[spec[:name]] =
+          if merged.key?(spec[:name]) && merged[spec[:name]][:category] != :general
+            merged[spec[:name]]
+          else
+            {
+                name: spec[:name],
+                category: spec[:category] }
+          end
+    }.values.sort_by { _1[:name] }
+  end
+
+  def existing_tags_by_name locale
+    @existing_tags_by_name ||= begin
+      names = tag_names.map { canonical_tag_name_without_sections(locale, _1) }.uniq
+      Tag.joins(:tag_name).where(tag_names: { name: names }).index_by(&:name)
+    end
+  end
+
+  def preload_existing_tags_by_name! locale, names
+    wanted_names = Array(names).map { _1.to_s }.reject(&:blank?).uniq
+    missing_names = wanted_names - existing_tags_by_name(locale).keys
+    return if missing_names.empty?
+
+    existing_tags_by_name(locale).merge!(
+        Tag.joins(:tag_name)
+           .where(tag_names: { name: missing_names })
+           .index_by(&:name))
+  end
+
+  def canonical_tag_name_without_sections locale, raw_name
+    name, = parse_raw_tag_name(locale, raw_name)
+    name
+  end
+
+  def deerjikist_tag_spec? locale, spec
+    return true if spec[:category] == :deerjikist
+
+    existing_tags_by_name(locale)[spec[:name]]&.deerjikist?
+  end
+
+  def normalise_parent_post_ids
+    Array(@attributes[:parent_post_ids]).flat_map { _1.to_s.split }.map { |token|
+      id = Integer(token, exception: false)
+      raise ArgumentError, "親投稿 Id. が不正です: #{ token }" if id.nil? || id <= 0
+
+      id
+    }.uniq.sort
+  end
+
+  def validate_parent_post_ids! ids
+    missing = ids - Post.where(id: ids).pluck(:id)
+    raise ArgumentError, "存在しない親投稿 Id. があります: #{ missing.join(' ') }" if missing.present?
+  end
+
+  def serialised_tags direct_tag_specs, tag_sections
+    direct_tag_specs.map { |spec|
+      "#{ spec[:name] }#{ tag_sections[spec[:name]].to_a.map { section_literal(_1) }.join }"
+    }.sort.join(' ')
+  end
+
+  def display_tags direct_tag_specs, tag_sections
+    direct_tag_specs.map { |spec|
+      {
+          name: spec[:name],
+          category: spec[:category].to_s,
+          section_literals: tag_sections[spec[:name]].to_a.map { section_literal(_1) } }
+    }.sort_by { _1[:name] }
+  end
+
+  def section_literal range
+    begin_ms, end_ms = range
+    "[#{ Post.ms_to_time(begin_ms) }-#{ end_ms ? Post.ms_to_time(end_ms) : '' }]"
+  end
+
+  def normalise_video_ms snapshot_tag_specs
+    return nil unless snapshot_tag_specs.any? { _1[:name] == VIDEO_TAG_NAME }
+
+    video_ms = @attributes[:video_ms]
+    if video_ms.present?
+      value = Integer(video_ms, exception: false)
+      raise PostCreator::VideoMsParseError unless value&.positive?
+
+      return value
+    end
+
+    duration = @attributes[:duration]
+    return nil if duration.blank?
+
+    value = Tag.time_to_ms!(duration.to_s, tag_name: '動画時間')
+    raise PostCreator::VideoMsParseError unless value.positive?
+
+    value
+  rescue Tag::SectionLiteralParseError
+    raise PostCreator::VideoMsParseError
+  end
+
+  def validate_video_sections! video_ms, tag_sections
+    return unless video_ms
+
+    tag_sections.each_value do |ranges|
+      ranges.each do |begin_ms, end_ms|
+        if begin_ms >= video_ms
+          post = Post.new
+          post.errors.add :video_ms, 'タグ区間の開始が動画時間以上です．'
+          raise ActiveRecord::RecordInvalid, post
+        end
+        if end_ms && end_ms > video_ms
+          post = Post.new
+          post.errors.add :video_ms, 'タグ区間の終端が動画時間を超えてゐます．'
+          raise ActiveRecord::RecordInvalid, post
+        end
+      end
+    end
+  end
+
+  def resolved_tag_name locale, name
+    tag_name = TagName.find_by!(language_code: locale.language_code, name:)
+    unless tag_name.primary_flg
+      tag_name = TagName.find_by!(language_code: locale.language_code,
+                                  tag_id: tag_name.tag_id,
+                                  primary_flg: true)
+    end
+    tag_name.name
+  end
+end

backend/app/services/post_create_preflight.rb

@@ -0,0 +1,141 @@
+class PostCreatePreflight
+  class ValidationFailed < StandardError
+    attr_reader :fields, :base_errors
+
+    def initialize fields: { }, base_errors: []
+      super('入力内容を確認してください．')
+      @fields = fields
+      @base_errors = base_errors
+    end
+  end
+
+  def initialize attributes:, thumbnail: nil, host: nil
+    @attributes = attributes.symbolize_keys
+    @thumbnail = thumbnail
+    @host = host
+  end
+
+  def run
+    preview = PostImportPreviewer.new.preview_rows(
+        rows: [preview_row],
+        fetch_metadata: false).first
+    if preview[:existing_post_id].present?
+      return {
+          url: preview[:url],
+          title: preview[:attributes]['title'],
+          thumbnail_base: preview[:attributes]['thumbnail_base'],
+          tags: preview[:attributes]['tags'],
+          parent_post_ids: preview[:attributes]['parent_post_ids'],
+          original_created_from: preview[:attributes]['original_created_from'],
+          original_created_before: preview[:attributes]['original_created_before'],
+          duration: preview[:attributes]['duration'],
+          video_ms: preview[:attributes]['video_ms'],
+          display_tags: preview[:display_tags] || [],
+          field_warnings: final_field_warnings(preview[:field_warnings] || { }),
+          base_warnings: preview[:base_warnings],
+          existing_post_id: preview[:existing_post_id],
+          existing_post: existing_post_compact(preview[:existing_post_id]) }
+    end
+
+    if preview[:validation_errors].present?
+      raise ValidationFailed.new(fields: preview[:validation_errors])
+    end
+
+    validate_thumbnail_upload!
+
+    plan = PostCreatePlan.new(
+        attributes: {
+            url: preview[:url],
+            title: preview[:attributes]['title'],
+            thumbnail_base: preview[:attributes]['thumbnail_base'],
+            tags: preview[:attributes]['tags'],
+            parent_post_ids: preview[:attributes]['parent_post_ids'],
+            original_created_from: preview[:attributes]['original_created_from'],
+            original_created_before: preview[:attributes]['original_created_before'],
+            duration: preview[:attributes]['duration'],
+            video_ms: preview[:attributes]['video_ms'] }).build!
+
+    {
+        url: plan[:url],
+        title: plan[:title],
+        thumbnail_base: plan[:thumbnail_base],
+        tags: plan[:tags],
+        parent_post_ids: plan[:parent_post_ids],
+        original_created_from: plan[:original_created_from],
+        original_created_before: plan[:original_created_before],
+        duration: plan[:duration],
+        video_ms: plan[:video_ms],
+        display_tags: plan[:display_tags],
+        direct_tag_specs: plan[:direct_tag_specs],
+        default_tag_specs: plan[:default_tag_specs],
+        snapshot_tag_specs: plan[:snapshot_tag_specs],
+        post_tag_specs: plan[:post_tag_specs],
+        tag_sections: plan[:tag_sections],
+        normalised_parent_post_ids: plan[:normalised_parent_post_ids],
+        field_warnings: final_field_warnings(preview[:field_warnings] || { }),
+        base_warnings: preview[:base_warnings],
+        existing_post_id: preview[:existing_post_id],
+        existing_post: existing_post_compact(preview[:existing_post_id]) }
+  end
+
+  private
+
+  def preview_row
+    {
+        source_row: 1,
+        url: @attributes[:url].to_s,
+        attributes: {
+            'title' => @attributes[:title].to_s,
+            'thumbnail_base' => @attributes[:thumbnail_base].to_s,
+            'original_created_from' => @attributes[:original_created_from].to_s,
+            'original_created_before' => @attributes[:original_created_before].to_s,
+            'duration' => @attributes[:duration].to_s,
+            'video_ms' => @attributes[:video_ms],
+            'tags' => @attributes[:tags].to_s,
+            'parent_post_ids' => parent_post_ids_text },
+        provenance: {
+            'url' => 'manual',
+            'title' => 'manual',
+            'thumbnail_base' => 'manual',
+            'original_created_from' => 'manual',
+            'original_created_before' => 'manual',
+            'duration' => 'manual',
+            'video_ms' => 'manual',
+            'tags' => 'manual',
+            'parent_post_ids' => 'manual' },
+        tag_sources: {
+            'automatic' => '',
+            'manual' => @attributes[:tags].to_s } }
+  end
+
+  def parent_post_ids_text
+    Array(@attributes[:parent_post_ids]).flat_map { _1.to_s.split }.join(' ')
+  end
+
+  def validate_thumbnail_upload!
+    return if @attributes[:thumbnail_base].present?
+    return if @thumbnail.blank?
+
+    PostThumbnailUploadValidator.validate!(@thumbnail)
+  rescue PostThumbnailUploadValidator::InvalidUpload => e
+    raise ValidationFailed.new(fields: { thumbnail: [e.message] })
+  end
+
+  def existing_post_compact post_id
+    return nil if post_id.blank?
+
+    post = Post.with_attached_thumbnail.find_by(id: post_id)
+    PostCompactRepr.base(post, host: @host)
+  end
+
+  def final_field_warnings field_warnings
+    thumbnail_warnings = (field_warnings['thumbnail_base'] || []).reject { _1 == 'サムネールなし' }
+    if @attributes[:thumbnail_base].blank? && @thumbnail.blank?
+      thumbnail_warnings = (thumbnail_warnings + ['サムネールなし']).uniq
+    end
+
+    next_warnings = field_warnings.except('thumbnail_base')
+    next_warnings['thumbnail_base'] = thumbnail_warnings if thumbnail_warnings.present?
+    next_warnings
+  end
+end

backend/app/services/post_creator.rb

@@ -9,104 +9,125 @@ class PostCreator
     @field_warnings = { }
   end
 
-  def create!
+  def create! locale
+    thumbnail_attachment = prepare_thumbnail_attachment
     post = Post.new(title: @attributes[:title].presence,
                     url: @attributes[:url],
                     thumbnail_base: @attributes[:thumbnail_base].presence,
                     uploaded_user: @actor,
                     original_created_from: @attributes[:original_created_from].presence,
                     original_created_before: @attributes[:original_created_before].presence)
-    attach_thumbnail!(post)
 
     ApplicationRecord.transaction do
       post.save!
-      Tag.normalise_tags!(tag_names, deny_deprecated: true, with_sections: true) =>
+      post.thumbnail.attach(thumbnail_attachment) if thumbnail_attachment.present?
-          { tags:, sections: }
+      snapshot_tags = planned_snapshot_tags(locale)
-      TagVersioning.record_tag_snapshots!(tags, created_by_user: @actor)
+      post_tags = planned_post_tags(locale)
-      tags = Tag.expand_parent_tags(tags).reject(&:deprecated?)
+      sections = planned_sections(locale)
-      post.video_ms = normalise_video_ms(tags)
+      TagVersioning.record_tag_snapshots!(snapshot_tags, created_by_user: @actor)
-      validate_video_sections!(post.video_ms, sections)
+      post.video_ms = planned_video_ms(locale)
       post.save!
-      sync_post_tags!(post, tags, sections)
+      sync_post_tags!(post, post_tags, sections)
-      sync_parent_posts!(post, parent_post_ids)
+      sync_parent_posts!(post, planned_parent_post_ids(locale))
       PostVersionRecorder.record!(post:, event_type: :create, created_by_user: @actor)
     end
     post
+  rescue StandardError
+    post&.thumbnail&.purge if post&.thumbnail&.attached?
+    raise
   end
 
   private
 
-  def attach_thumbnail! post
+  def prepare_thumbnail_attachment
-    thumbnail = @attributes[:thumbnail]
+    PostThumbnailAttachmentBuilder.build(
-    if thumbnail.present?
+        thumbnail: @attributes[:thumbnail],
-      post.thumbnail.attach(Post.resized_thumbnail_attachment(thumbnail))
+        thumbnail_base: @attributes[:thumbnail_base].presence)
-      return
-    end
-
-    thumbnail_base = post.thumbnail_base
-    return if thumbnail_base.blank?
-
-    post.attach_thumbnail_from_url!(thumbnail_base)
-  rescue Post::RemoteThumbnailFetchFailed => e
-    @field_warnings[:thumbnail_base] = [e.message]
   end
 
-  def tag_names = @attributes[:tags].to_s.split
+  def planned_snapshot_tags(locale) = planned_create_attributes(locale)[:snapshot_tags]
 
-  def parent_post_ids
+  def planned_post_tags(locale) = planned_create_attributes(locale)[:post_tags]
-    Array(@attributes[:parent_post_ids]).flat_map { _1.to_s.split }.map { |token|
-      id = Integer(token, exception: false)
-      raise ArgumentError, "親投稿 Id. が不正です: #{ token }" if id.nil? || id <= 0
 
-      id
+  def planned_sections(locale) = planned_create_attributes(locale)[:tag_sections]
-    }.uniq
+
+  def planned_parent_post_ids locale
+    planned_create_attributes(locale)[:normalised_parent_post_ids]
   end
 
-  def normalise_video_ms tags
+  def planned_video_ms locale
-    return nil unless tags.any? { _1.id == Tag.video.id }
+    planned_create_attributes(locale)[:video_ms]
-
-    video_ms = @attributes[:video_ms]
-    if video_ms.present?
-      value = Integer(video_ms, exception: false)
-      raise VideoMsParseError unless value&.positive?
-
-      return value
-    end
-    duration = @attributes[:duration]
-    return nil if duration.blank?
-
-    value = Tag.time_to_ms!(duration.to_s, tag_name: '動画時間')
-    raise VideoMsParseError unless value.positive?
-
-    value
-  rescue Tag::SectionLiteralParseError
-    raise VideoMsParseError
   end
 
-  def validate_video_sections! video_ms, sections
+  def planned_create_attributes locale
-    return unless video_ms
+    @planned_create_attributes ||= begin
-
+      if @attributes.key?(:snapshot_tag_specs)
-    sections.each_value do |ranges|
+        snapshot_tags = materialise_tags(locale, @attributes[:snapshot_tag_specs] || [])
-      ranges.each do |begin_ms, end_ms|
+        post_tags = materialise_tags(locale, @attributes[:post_tag_specs] || [])
-        post = Post.new
+        {
-        if begin_ms >= video_ms
+            snapshot_tags: snapshot_tags,
-          post.errors.add :video_ms, 'タグ区間の開始が動画時間以上です．'
+            post_tags: post_tags,
-          raise ActiveRecord::RecordInvalid, post
+            tag_sections: materialise_sections(
-        end
+                @attributes[:tag_sections] || { },
-        if end_ms && end_ms > video_ms
+                snapshot_tags,
-          post.errors.add :video_ms, 'タグ区間の終端が動画時間を超えてゐます．'
+                post_tags),
-          raise ActiveRecord::RecordInvalid, post
+            normalised_parent_post_ids: @attributes[:normalised_parent_post_ids] || [],
-        end
+            video_ms: @attributes[:video_ms] }
+      else
+        build_materialised_plan
       end
     end
   end
 
+  def build_materialised_plan
+    plan = PostCreatePlan.new(attributes: @attributes).build!
+    snapshot_tags = materialise_tags(plan[:snapshot_tag_specs] || [])
+    post_tags = materialise_tags(plan[:post_tag_specs] || [])
+    {
+        snapshot_tags: snapshot_tags,
+        post_tags: post_tags,
+        tag_sections: materialise_sections(
+            plan[:tag_sections] || { },
+            snapshot_tags,
+            post_tags),
+        normalised_parent_post_ids: plan[:normalised_parent_post_ids] || [],
+        video_ms: plan[:video_ms] }
+  end
+
+  def materialise_tags locale, specs
+    Array(specs).each_with_object({ }) do |spec, tags|
+      name = spec[:name] || spec['name']
+      category = spec[:category] || spec['category']
+      next if name.blank? || category.blank?
+
+      tag = Tag.find_or_create_by_tag_name!(locale, name, category:)
+      tag.update!(category:) if tag.category.to_sym != category.to_sym
+      tags[name] ||= tag
+    end.values
+  end
+
+  def materialise_sections sections_by_name, snapshot_tags, post_tags
+    tags_by_name = post_tags.index_by(&:name)
+    snapshot_tags.each do |tag|
+      tags_by_name[tag.name] ||= tag
+    end
+
+    sections_by_name.each_with_object({ }) do |(tag_name, ranges), sections|
+      tag = tags_by_name[tag_name.to_s]
+      next if tag.nil?
+
+      sections[tag.id] = Array(ranges).map { |range| [range[0], range[1]] }
+    end
+  end
+
   def sync_post_tags! post, desired_tags, sections
     desired_ids = desired_tags.map(&:id).to_set
     current_ids = post.tags.pluck(:id).to_set
+
     Tag.where(id: desired_ids - current_ids).find_each do |tag|
       PostTag.create_or_find_by!(post:, tag:, created_user: @actor)
     end
+
     PostTagSection.where(post_id: post.id).destroy_all
     sections.each do |tag_id, ranges|
       ranges.each do |begin_ms, end_ms|
@@ -116,10 +137,9 @@ class PostCreator
                                end_ms:)
       end
     end
+
     PostTag.where(post_id: post.id,
-                  tag_id: (current_ids - desired_ids).to_a).kept.find_each do |post_tag|
+                  tag_id: (current_ids - desired_ids).to_a).destroy_all
-      post_tag.discard_by!(@actor)
-    end
   end
 
   def sync_parent_posts! post, ids

backend/app/services/post_import_previewer.rb

@@ -3,13 +3,14 @@ require 'timeout'
 
 class PostImportPreviewer
   FIELDS = [
-    'title',
+      'title',
-    'thumbnail_base',
+      'thumbnail_base',
-    'original_created_from',
+      'original_created_from',
-    'original_created_before',
+      'original_created_before',
-    'duration',
+      'video_ms',
-    'tags',
+      'duration',
-    'parent_post_ids'].freeze
+      'tags',
+      'parent_post_ids'].freeze
   FETCH_WARNING_FIELDS = ['url', 'title', 'thumbnail_base'].freeze
   TITLE_FETCH_WARNING = 'タイトルを取得できませんでした．'.freeze
   THUMBNAIL_FETCH_WARNING = 'サムネールを取得できませんでした．'.freeze
@@ -125,7 +126,6 @@ class PostImportPreviewer
     validate_basic_data(attributes, validation_errors)
     validate_preview_tags(merged_tags(tag_sources, provenance['tags']),
                           validation_errors,
-                          field_warnings,
                           known_tags)
     validate_parents(attributes['parent_post_ids'], validation_errors, existing_parent_ids)
     attributes.delete('url')
@@ -162,6 +162,8 @@ class PostImportPreviewer
       normalised =
           if field == 'duration'
             normalise_duration_attribute(value)
+          elsif field == 'video_ms'
+            value.nil? ? '' : value.to_s
           else
             value.to_s
           end
@@ -194,7 +196,7 @@ class PostImportPreviewer
 
   def clear_automatic_values! attributes, provenance, tag_sources
     ['title', 'thumbnail_base', 'original_created_from',
-     'original_created_before', 'duration'].each do |field|
+     'original_created_before', 'video_ms', 'duration'].each do |field|
       attributes[field] = '' if provenance[field] == 'automatic'
     end
     tag_sources['automatic'] = ''
@@ -223,15 +225,15 @@ class PostImportPreviewer
     end
     { data:, warnings:, validation_errors: { } }
   rescue Preview::UrlSafety::UnsafeUrl => e
+    payload = { error: e.class.name, message: e.message }
     Rails.logger.info(
-        "post_import_metadata_fetch_unsafe_url "\
+        "post_import_metadata_fetch_unsafe_url #{ payload.to_json }")
-        "#{ { error: e.class.name, message: e.message }.to_json }")
     { data: { }, warnings: { }, validation_errors: { url: [e.message] } }
   rescue Preview::HttpFetcher::FetchFailed,
          Preview::HttpFetcher::ResponseTooLarge => e
+    payload = { error: e.class.name, message: e.message }
     Rails.logger.info(
-        "post_import_metadata_fetch_failure "\
+        "post_import_metadata_fetch_failure #{ payload.to_json }")
-        "#{ { error: e.class.name, message: e.message }.to_json }")
     { data: { }, warnings: { 'url' => [METADATA_FETCH_WARNING] }, validation_errors: { } }
   end
 
@@ -252,7 +254,15 @@ class PostImportPreviewer
   def sanitise_metadata_url value
     return nil unless value.is_a?(String)
 
-    PostUrlNormaliser.normalise(value)
+    stripped = value.strip
+    return nil if stripped.blank?
+
+    uri = URI.parse(stripped)
+    return nil unless uri.is_a?(URI::HTTP) && uri.host.present?
+
+    stripped
+  rescue URI::InvalidURIError
+    nil
   end
 
   def sanitise_metadata_time value
@@ -325,14 +335,14 @@ class PostImportPreviewer
   def safe_fetch_metadata url
     fetch_metadata(url)
   rescue Preview::UrlSafety::UnsafeUrl => e
+    payload = { error: e.class.name, message: e.message }
     Rails.logger.info(
-        "post_import_metadata_fetch_unsafe_url "\
+        "post_import_metadata_fetch_unsafe_url #{ payload.to_json }")
-        "#{ { error: e.class.name, message: e.message }.to_json }")
     { data: { }, warnings: { }, validation_errors: { url: [e.message] } }
   rescue StandardError => e
+    payload = { error: e.class.name, message: e.message }
     Rails.logger.error(
-        "post_import_metadata_fetch_unexpected_failure "\
+        "post_import_metadata_fetch_unexpected_failure #{ payload.to_json }")
-        "#{ { error: e.class.name, message: e.message }.to_json }")
     { data: { }, warnings: { 'url' => [METADATA_FETCH_WARNING] }, validation_errors: { } }
   end
 
@@ -439,7 +449,7 @@ class PostImportPreviewer
     []
   end
 
-  def validate_preview_tags raw, errors, field_warnings, known_tags
+  def validate_preview_tags raw, errors, known_tags
     names = raw.to_s.split
     return if names.empty?
     if names.any? { _1.downcase.start_with?('nico:') }
@@ -451,11 +461,6 @@ class PostImportPreviewer
     existing = parsed.filter_map { known_tags[_1] }
     deprecated = existing.select(&:deprecated?).map(&:name)
     errors[:tags] = ["廃止済みタグがあります: #{ deprecated.join(' ') }"] if deprecated.present?
-    known = existing.reject(&:deprecated?).map(&:name)
-    new_tags = parsed.uniq - known
-    if new_tags.present?
-      add_field_warning!(field_warnings, 'tags', "新規タグを作成します: #{ new_tags.join(' ') }")
-    end
   rescue Tag::SectionLiteralParseError
     errors[:tags] = ['タグ区間の記法が不正です．']
   end
@@ -466,7 +471,7 @@ class PostImportPreviewer
                     thumbnail_base: attributes['thumbnail_base'].presence,
                     original_created_from: attributes['original_created_from'].presence,
                     original_created_before: attributes['original_created_before'].presence,
-                    video_ms: parse_duration(attributes['duration'], errors))
+                    video_ms: parse_video_ms(attributes, errors))
     post.valid?
     post.errors.each do |error|
       next if error.attribute == :url && error.type == :taken
@@ -475,7 +480,21 @@ class PostImportPreviewer
     end
   end
 
-  def parse_duration value, errors
+  def parse_video_ms attributes, errors
+    return nil unless attributes['tags'].to_s.split.include?('動画')
+
+    video_ms = attributes['video_ms']
+    if video_ms.present?
+      value = Integer(video_ms, exception: false)
+      if value&.positive?
+        return value
+      end
+
+      errors[:video_ms] = ['動画時間の記法が不正です．']
+      return nil
+    end
+
+    value = attributes['duration']
     return nil if value.blank?
 
     Tag.time_to_ms!(value.to_s, tag_name: '動画時間')

backend/app/services/post_import_row_normaliser.rb

@@ -1,190 +0,0 @@
-class PostImportRowNormaliser
-  ORIGINS = ['automatic', 'manual'].freeze
-  STRING_FIELDS = [
-    'title',
-    'thumbnail_base',
-    'original_created_from',
-    'original_created_before',
-    'duration',
-    'tags',
-    'parent_post_ids'].freeze
-  FLEXIBLE_FIELDS = ['video_ms'].freeze
-  ATTRIBUTE_FIELDS = (STRING_FIELDS + FLEXIBLE_FIELDS).freeze
-
-  def self.normalise! rows, allow_warning_fields: false
-    raise ArgumentError, '取込行の形式が不正です．' unless rows.is_a?(Array)
-    raise ArgumentError, '取込件数が多すぎます．' if rows.length > PostImportUrlListParser::MAX_ROWS
-
-    normalised_rows = rows.map { normalise_row!(_1, allow_warning_fields:) }
-    source_rows = normalised_rows.map { _1['source_row'] }
-    raise ArgumentError, '元行番号が重複しています．' if source_rows.uniq.length != source_rows.length
-    if normalised_rows.sum { row_bytesize(_1) } > PostImportUrlListParser::MAX_BYTES
-      raise ArgumentError, '取込データが大きすぎます．'
-    end
-
-    normalised_rows
-  end
-
-  def self.normalise_row! row, allow_warning_fields:
-    unless row.is_a?(Hash) || row.is_a?(ActionController::Parameters)
-      raise ArgumentError, '取込行の形式が不正です．'
-    end
-
-    parameters =
-        row.is_a?(ActionController::Parameters) ? row : ActionController::Parameters.new(row)
-    permitted = parameters.permit(*permitted_keys(allow_warning_fields))
-    normalised = permitted.to_h.deep_transform_keys { _1.to_s.underscore }
-
-    normalised['source_row'] = normalise_source_row!(normalised['source_row'])
-    normalise_url!(normalised['url'])
-    normalise_metadata_url!(normalised['metadata_url'])
-    normalise_attributes!(normalised.fetch('attributes', { }))
-    normalise_provenance!(normalised.fetch('provenance', { }))
-    normalise_tag_sources!(normalised['tag_sources'])
-    normalise_warning_values!(normalised, allow_warning_fields:)
-    if row_bytesize(normalised) > PostImportUrlListParser::MAX_BYTES
-      raise ArgumentError, '取込行が大きすぎます．'
-    end
-
-    normalised
-  end
-
-  def self.permitted_keys allow_warning_fields
-    keys = [
-      :source_row,
-      :sourceRow,
-      :url,
-      :metadata_url,
-      :metadataUrl,
-      { attributes: {} },
-      { provenance: {} },
-      { tag_sources: {} },
-      { tagSources: {} }]
-    return keys unless allow_warning_fields
-
-    keys + [
-      { field_warnings: {} },
-      { fieldWarnings: {} },
-      { base_warnings: [] },
-      { baseWarnings: [] }]
-  end
-  private_class_method :permitted_keys
-
-  def self.normalise_source_row! value
-    source_row = Integer(value, exception: false)
-    raise ArgumentError, '元行番号が不正です．' if source_row.nil? || source_row <= 0
-
-    source_row
-  end
-  private_class_method :normalise_source_row!
-
-  def self.normalise_url! value
-    unless value.is_a?(String)
-      raise ArgumentError, 'URL の形式が不正です．'
-    end
-    if value.bytesize > PostImportUrlListParser::MAX_URL_BYTES
-      raise ArgumentError, 'URL が長すぎます．'
-    end
-  end
-  private_class_method :normalise_url!
-
-  def self.normalise_metadata_url! value
-    raise ArgumentError, 'metadata_url の形式が不正です．' unless value.nil? || value.is_a?(String)
-    if value.to_s.bytesize > PostImportUrlListParser::MAX_URL_BYTES
-      raise ArgumentError, 'metadata_url が長すぎます．'
-    end
-  end
-  private_class_method :normalise_metadata_url!
-
-  def self.normalise_attributes! attributes
-    raise ArgumentError, 'attributes の形式が不正です．' unless attributes.is_a?(Hash)
-    raise ArgumentError, '取込項目が不正です．' unless (attributes.keys - ATTRIBUTE_FIELDS).empty?
-
-    attributes.each do |key, value|
-      case key
-      when *STRING_FIELDS
-        raise ArgumentError, '取込項目の型が不正です．' unless value.nil? || value.is_a?(String)
-      when *FLEXIBLE_FIELDS
-        unless value.nil? || value.is_a?(String) || value.is_a?(Numeric)
-          raise ArgumentError, '取込項目の型が不正です．'
-        end
-      end
-      if value.to_s.bytesize > PostImportUrlListParser::MAX_URL_BYTES
-        raise ArgumentError, '取込項目が大きすぎます．'
-      end
-    end
-  end
-  private_class_method :normalise_attributes!
-
-  def self.normalise_provenance! provenance
-    unless provenance.is_a?(Hash)
-      raise ArgumentError, 'provenance の形式が不正です．'
-    end
-
-    allowed = ATTRIBUTE_FIELDS + ['url']
-    unless (provenance.keys - allowed).empty?
-      raise ArgumentError, '値の由来が不正です．'
-    end
-    unless provenance.values.all? { ORIGINS.include?(_1) }
-      raise ArgumentError, '値の由来が不正です．'
-    end
-  end
-  private_class_method :normalise_provenance!
-
-  def self.normalise_tag_sources! tag_sources
-    return if tag_sources.nil?
-
-    unless tag_sources.is_a?(Hash)
-      raise ArgumentError, 'タグ由来の形式が不正です．'
-    end
-    unless (tag_sources.keys - ORIGINS).empty?
-      raise ArgumentError, 'タグ由来の形式が不正です．'
-    end
-    unless tag_sources.values.all? { _1.is_a?(String) }
-      raise ArgumentError, 'タグ由来の形式が不正です．'
-    end
-    if tag_sources.values.any? { _1.bytesize > PostImportUrlListParser::MAX_URL_BYTES }
-      raise ArgumentError, 'タグ由来が大きすぎます．'
-    end
-    if tag_sources.values.sum(&:bytesize) > PostImportUrlListParser::MAX_URL_BYTES
-      raise ArgumentError, 'タグ由来が大きすぎます．'
-    end
-  end
-  private_class_method :normalise_tag_sources!
-
-  def self.normalise_warning_values! normalised, allow_warning_fields:
-    return unless allow_warning_fields
-
-    field_warnings = normalised['field_warnings']
-    unless field_warnings.nil? || field_warnings.is_a?(Hash)
-      raise ArgumentError, '警告の形式が不正です．'
-    end
-    field_warnings&.each do |key, values|
-      unless ATTRIBUTE_FIELDS.include?(key) || key == 'url'
-        raise ArgumentError, '警告の形式が不正です．'
-      end
-      unless values.is_a?(Array) && values.all? { _1.is_a?(String) }
-        raise ArgumentError, '警告の形式が不正です．'
-      end
-      if values.any? { _1.bytesize > PostImportUrlListParser::MAX_URL_BYTES }
-        raise ArgumentError, '警告が大きすぎます．'
-      end
-    end
-
-    base_warnings = normalised['base_warnings']
-    return if base_warnings.nil?
-
-    unless base_warnings.is_a?(Array) && base_warnings.all? { _1.is_a?(String) }
-      raise ArgumentError, '警告の形式が不正です．'
-    end
-    if base_warnings.any? { _1.bytesize > PostImportUrlListParser::MAX_URL_BYTES }
-      raise ArgumentError, '警告が大きすぎます．'
-    end
-  end
-  private_class_method :normalise_warning_values!
-
-  def self.row_bytesize row
-    row.to_json.bytesize
-  end
-  private_class_method :row_bytesize
-end

backend/app/services/post_import_runner.rb

@@ -1,109 +0,0 @@
-class PostImportRunner
-  def initialize actor:, rows:
-    @actor = actor
-    @rows = rows
-  end
-
-  def run
-    normalised_rows = PostImportRowNormaliser.normalise!(@rows)
-    previews = PostImportPreviewer.new.preview_rows(rows: normalised_rows,
-                                                    fetch_metadata: false)
-    preview_map = previews.index_by { _1[:source_row] }
-
-    results = normalised_rows.map do |row|
-      run_row(row, preview_map.fetch(row['source_row']))
-    end
-
-    { created: results.count { _1[:status] == 'created' },
-      skipped: results.count { _1[:status] == 'skipped' },
-      failed: results.count { _1[:status] == 'failed' },
-      rows: results }
-  end
-
-  private
-
-  def run_row row, preview
-    attributes = row.fetch('attributes', { }).transform_keys { _1.to_s.underscore }
-    return { source_row: row['source_row'],
-             status: 'failed',
-             errors: preview[:validation_errors],
-             recoverable: true } if preview[:validation_errors].present?
-    if preview[:skip_reason] == 'existing'
-      return { source_row: row['source_row'],
-               status: 'skipped',
-               existing_post_id: preview[:existing_post_id] }
-    end
-
-    attributes['tags'] = preview[:attributes]['tags']
-    attributes['url'] = row['url']
-    creator = PostCreator.new(actor: @actor, attributes:)
-    post = creator.create!
-    result = { source_row: row['source_row'], status: 'created', post: PostRepr.base(post) }
-    if creator.field_warnings.present?
-      result[:field_warnings] = creator.field_warnings
-    end
-    result
-  rescue ActiveRecord::RecordInvalid => e
-    existing_post = existing_post_for_race(row, e.record)
-    if existing_post
-      return { source_row: row['source_row'],
-               status: 'skipped',
-               existing_post_id: existing_post.id }
-    end
-
-    { source_row: row['source_row'],
-      status: 'failed',
-      errors: e.record.errors.to_hash,
-      recoverable: true }
-  rescue ActiveRecord::RecordNotUnique => e
-    raise unless url_record_not_unique?(e)
-
-    existing_post = existing_post_for_race(row)
-    raise unless existing_post
-
-    { source_row: row['source_row'],
-      status: 'skipped',
-      existing_post_id: existing_post.id }
-  rescue Tag::NicoTagNormalisationError
-    { source_row: row['source_row'],
-      status: 'failed',
-      errors: { tags: ['ニコニコ・タグは直接指定できません．'] },
-      recoverable: true }
-  rescue Tag::DeprecatedTagNormalisationError
-    { source_row: row['source_row'],
-      status: 'failed',
-      errors: { tags: ['廃止済みタグは付与できません．'] },
-      recoverable: true }
-  rescue PostCreator::VideoMsParseError
-    { source_row: row['source_row'],
-      status: 'failed',
-      errors: { duration: ['動画時間の記法が不正です．'] },
-      recoverable: true }
-  rescue ArgumentError
-    { source_row: row['source_row'],
-      status: 'failed',
-      errors: { base: ['入力値が不正です．'] },
-      recoverable: true }
-  rescue StandardError => e
-    Rails.logger.error("post_import_runner_failure #{ { error: e.class.name,
-                                                        message: e.message }.to_json }")
-    { source_row: row['source_row'],
-      status: 'failed',
-      errors: { base: ['登録中にエラーが発生しました．'] } }
-  end
-
-  def existing_post_for_race row, record = nil
-    if record && !(record.errors.of_kind?(:url, :taken))
-      return nil
-    end
-
-    normal_url = PostUrlNormaliser.normalise(row['url'])
-    return nil if normal_url.blank?
-
-    Post.find_by(url: normal_url)
-  end
-
-  def url_record_not_unique? error
-    error.message.include?('index_posts_on_url')
-  end
-end

backend/app/services/post_import_url_list_parser.rb

@@ -1,25 +0,0 @@
-class PostImportUrlListParser
-  MAX_ROWS = 100
-  MAX_BYTES = 1.megabyte
-  MAX_URL_BYTES = 20.kilobytes
-
-  def self.parse source
-    raw = source.to_s
-    raise ArgumentError, '入力が大きすぎます．' if raw.bytesize > MAX_BYTES
-
-    rows = raw.split(/\r\n|\n|\r/).each_with_index.filter_map { |line, index|
-      url = line.strip
-      next if url.blank?
-
-      if url.bytesize > MAX_URL_BYTES
-        raise ArgumentError, "#{ index + 1 } 行目: URL が長すぎます．"
-      end
-
-      { source_row: index + 1, url: }
-    }
-    raise ArgumentError, 'URL を入力してください．' if rows.empty?
-    raise ArgumentError, "取込件数は #{ MAX_ROWS } 件までです．" if rows.length > MAX_ROWS
-
-    rows
-  end
-end

backend/app/services/post_metadata_fetcher.rb

@@ -3,10 +3,9 @@ require 'date'
 
 class PostMetadataFetcher
   TIMESTAMP_PATTERN =
-      Regexp.new(
+      /\A(\d{4})-(\d{2})-(\d{2})T(\d{2})
-          '\A(\d{4})-(\d{2})-(\d{2})T(\d{2})' \
+        (?::(\d{2})(?::(\d{2})(?:\.(\d+))?)?)?
-          '(?::(\d{2})(?::(\d{2})(?:\.(\d+))?)?)?' \
+        (Z|[+-]\d{2}:?\d{2})?\z/x
-          '(Z|[+-]\d{2}:?\d{2})?\z')
 
   def self.fetch raw_url
     uri, = Preview::UrlSafety.validate(raw_url)
@@ -32,6 +31,7 @@ class PostMetadataFetcher
       original_created_from: serialise_time(created_range&.first),
       original_created_before: serialise_time(created_range&.last),
       duration: serialise_duration(duration),
+      display_tags: display_tags(platform_tags),
       tags: platform_tags.join(' ') }
   end
 
@@ -42,6 +42,24 @@ class PostMetadataFetcher
     []
   end
 
+  def self.display_tags names
+    return [] if names.blank?
+
+    existing_tags =
+        Tag
+        .joins(:tag_name)
+        .where(tag_names: { name: names })
+        .index_by(&:name)
+
+    names.map { |name|
+      tag = existing_tags[name]
+      {
+          name: name,
+          category: (tag&.category || 'meta'),
+          section_literals: [] }
+    }
+  end
+
   def self.original_created_range value
     return nil if value.blank?
 
@@ -168,6 +186,7 @@ class PostMetadataFetcher
   end
 
   private_class_method :platform_tags,
+                       :display_tags,
                        :original_created_range,
                        :parse_timestamp_range,
                        :parse_nanoseconds,

backend/app/services/post_thumbnail_attachment_builder.rb

@@ -0,0 +1,11 @@
+class PostThumbnailAttachmentBuilder
+  def self.build thumbnail:, thumbnail_base:
+    if thumbnail_base.present?
+      return Post.remote_thumbnail_attachment(thumbnail_base)
+    end
+
+    return nil if thumbnail.blank?
+
+    Post.resized_thumbnail_attachment(thumbnail)
+  end
+end

backend/app/services/post_thumbnail_upload_validator.rb

@@ -0,0 +1,34 @@
+class PostThumbnailUploadValidator
+  MAX_THUMBNAIL_BYTES = 20 * 1024 * 1024
+  ALLOWED_CONTENT_TYPES = Preview::ThumbnailFetcher::RASTER_IMAGE_CONTENT_TYPES.freeze
+
+  class InvalidUpload < StandardError; end
+
+  def self.validate! thumbnail
+    return if thumbnail.blank?
+    unless thumbnail.is_a?(ActionDispatch::Http::UploadedFile)
+      raise InvalidUpload, 'thumbnail upload が不正です．'
+    end
+    raise InvalidUpload, 'thumbnail file size が大きすぎます．' if thumbnail.size > MAX_THUMBNAIL_BYTES
+    raise InvalidUpload, 'サムネイル画像の形式が不正です．' unless allowed_content_type?(thumbnail.content_type)
+    bytes = thumbnail.read
+    raise InvalidUpload, 'サムネイル画像の形式が不正です．' if Post.svg_document_bytes?(bytes)
+    unless Post.raster_thumbnail_bytes?(bytes)
+      raise InvalidUpload, 'サムネイル画像の形式が不正です．'
+    end
+
+    attachment = Post.resized_thumbnail_attachment(
+        StringIO.new(bytes),
+        content_type: thumbnail.content_type)
+    attachment[:io].close if attachment[:io].respond_to?(:close)
+  rescue MiniMagick::Error, Timeout::Error
+    raise InvalidUpload, 'サムネイル画像の変換に失敗しました．'
+  ensure
+    thumbnail&.rewind if thumbnail.respond_to?(:rewind)
+  end
+
+  def self.allowed_content_type? content_type
+    mime_type = content_type.to_s.split(';', 2).first.to_s.downcase.strip
+    ALLOWED_CONTENT_TYPES.include?(mime_type)
+  end
+end

backend/app/services/post_version_recorder.rb

@@ -25,6 +25,7 @@ class PostVersionRecorder < VersionRecorder
       thumbnail_base: @record.thumbnail_base,
       video_ms: @record.video_ms,
       tags: @record.snapshot_tag_names.join(' '),
+      tags_json: @record.snapshot_tags_json,
       parent_post_ids: @record.snapshot_parent_post_ids.join(' '),
       original_created_from: @record.original_created_from,
       original_created_before: @record.original_created_before }

backend/app/services/preview/thumbnail_fetcher.rb

@@ -1,7 +1,7 @@
 module Preview
   class ThumbnailFetcher
     class GenerationFailed < StandardError; end
-    ALLOWED_IMAGE_CONTENT_TYPES = [
+    RASTER_IMAGE_CONTENT_TYPES = [
       'image/jpeg', 'image/png', 'image/gif', 'image/webp'
     ].freeze
     HTML_MAX_BYTES = 1.megabyte
@@ -28,7 +28,9 @@ module Preview
     def self.fetch_image_response(raw_url)
       uri, = UrlSafety.validate(raw_url)
       response = HttpFetcher.fetch(uri.to_s)
-      unless allowed_image_content_type?(response.content_type)
+      unless Post.remote_thumbnail_image_bytes?(
+                 response.body,
+                 content_type: response.content_type)
         raise GenerationFailed, 'サムネール画像が見つかりませんでした．'
       end
 
@@ -51,7 +53,9 @@ module Preview
       return nil if url.blank?
 
       response = HttpFetcher.fetch(url)
-      return nil unless allowed_image_content_type?(response.content_type)
+      return nil unless Post.remote_thumbnail_image_bytes?(
+                            response.body,
+                            content_type: response.content_type)
 
       response.body
     rescue HttpFetcher::FetchTimeout
@@ -92,13 +96,7 @@ module Preview
       nil
     end
 
-    def self.allowed_image_content_type?(content_type)
-      mime_type = content_type.to_s.split(';', 2).first.downcase.strip
-      ALLOWED_IMAGE_CONTENT_TYPES.include?(mime_type)
-    end
-
     private_class_method :fetch_image_or_nil, :fetch_image!,
-                         :niconico_thumbnail_url,
+                         :niconico_thumbnail_url
-                         :allowed_image_content_type?
   end
 end

backend/app/services/tag_versioning.rb

@@ -1,32 +1,16 @@
 class TagVersioning
   def self.record! tag, event_type:, created_by_user:
-    if tag.nico?
+    TagVersionRecorder.record!(tag:, event_type:, created_by_user:)
-      NicoTagVersionRecorder.record!(tag:, event_type:, created_by_user:)
-    else
-      TagVersionRecorder.record!(tag:, event_type:, created_by_user:)
-    end
   end
 
   def self.ensure_snapshot! tag, created_by_user:
-    if tag.nico?
+    return if tag.tag_versions.exists?
-      return if tag.nico_tag_versions.exists?
 
-      NicoTagVersionRecorder.record!(tag:, event_type: :create, created_by_user:)
+    TagVersionRecorder.record!(tag:, event_type: :create, created_by_user:)
-    else
-      return if tag.tag_versions.exists?
-
-      TagVersionRecorder.record!(tag:, event_type: :create, created_by_user:)
-    end
   end
 
   def self.record_tag_snapshot! tag, created_by_user:
-    event_type =
+    event_type = tag.tag_versions.exists? ? :update : :create
-        if tag.nico?
-          tag.nico_tag_versions.exists? ? :update : :create
-        else
-          tag.tag_versions.exists? ? :update : :create
-        end
-
     record!(tag, event_type:, created_by_user:)
   end
 

backend/app/services/version_recorder.rb

@@ -47,10 +47,14 @@ class VersionRecorder
   end
 
   def update_record_version_no! version_no
+    return unless tracks_version_no_on_record?
+
     @record.update_columns(version_no:)
     @record.version_no = version_no
   end
 
+  def tracks_version_no_on_record? = true
+
   def validate_version_sequence! latest
     if !(latest) && @event_type != 'create'
       raise "#{ version_class.name } first event must be create"
@@ -60,7 +64,7 @@ class VersionRecorder
       raise "#{ version_class.name } create event already exists"
     end
 
-    return unless latest
+    return if !(latest) || !(tracks_version_no_on_record?)
 
     if @record.version_no != latest.version_no
       raise ("#{ record_class.name }##{ @record.id } version_no is #{ @record.version_no }, " +

backend/app/services/youtube/sync.rb

@@ -103,7 +103,7 @@ module Youtube
     end
 
     def sync_post_tags! post, desired_tag_ids, current_tag_ids: nil
-      current_tag_ids ||= PostTag.kept.where(post_id: post.id).pluck(:tag_id).to_set
+      current_tag_ids ||= PostTag.where(post_id: post.id).pluck(:tag_id).to_set
       desired_tag_ids = desired_tag_ids.compact.to_set
 
       to_add = desired_tag_ids - current_tag_ids
@@ -117,8 +117,8 @@ module Youtube
         end
       end
 
-      PostTag.where(post_id: post.id, tag_id: to_remove.to_a).kept.find_each do |pt|
+      PostTag.where(post_id: post.id, tag_id: to_remove.to_a).find_each do |pt|
-        pt.discard_by!(nil)
+        pt.destroy!
       end
     end
 

backend/config/environments/development.rb

@@ -1,4 +1,4 @@
-require "active_support/core_ext/integer/time"
+require 'active_support/core_ext/integer/time'
 
 Rails.application.configure do
   # Settings specified here will take precedence over those in config/application.rb.
@@ -17,8 +17,8 @@ Rails.application.configure do
 
   # Enable/disable Action Controller caching. By default Action Controller caching is disabled.
   # Run rails dev:cache to toggle Action Controller caching.
-  if Rails.root.join("tmp/caching-dev.txt").exist?
+  if Rails.root.join('tmp/caching-dev.txt').exist?
-    config.public_file_server.headers = { "cache-control" => "public, max-age=#{2.days.to_i}" }
+    config.public_file_server.headers = { 'cache-control' => "public, max-age=#{2.days.to_i}" }
   else
     config.action_controller.perform_caching = false
   end
@@ -36,7 +36,11 @@ Rails.application.configure do
   config.action_mailer.perform_caching = false
 
   # Set localhost to be used by links generated in mailer templates.
-  config.action_mailer.default_url_options = { host: "localhost", port: 3000 }
+  config.action_mailer.default_url_options = { host: 'localhost', port: 3000 }
+  Rails.application.routes.default_url_options.merge!(
+      host: 'localhost',
+      port: 3002,
+      protocol: 'http')
 
   # Print deprecation notices to the Rails logger.
   config.active_support.deprecation = :log

backend/config/routes.rb

@@ -1,5 +1,5 @@
 Rails.application.routes.draw do
-  resources :nico_tags, path: 'tags/nico', only: [:index, :update]
+  resources :nico_tags, path: 'tags/nico', only: [:index, :show, :update]
 
   scope 'tags/:parent_id/children', controller: :tag_children do
     post ':child_id', action: :create
@@ -31,13 +31,6 @@ Rails.application.routes.draw do
   scope :preview, controller: :preview do
     get :title
     get :thumbnail
-    get :image
-  end
-
-  scope 'posts/import', controller: :post_imports do
-    post :preview
-    post :validate
-    post '', action: :create
   end
 
   resources :wiki_pages, path: 'wiki', only: [:index, :show, :create, :update] do
@@ -59,8 +52,9 @@ Rails.application.routes.draw do
 
   resources :posts, only: [:index, :show, :create, :update] do
     collection do
+      get :metadata
+      post :bulk
       get :random
-      get :changes
       get :versions, to: 'post_versions#index'
     end
 

backend/db/migrate/20260727123600_add_tags_json_to_post_versions.rb

@@ -0,0 +1,299 @@
+class AddTagsJsonToPostVersions < ActiveRecord::Migration[8.0]
+  RESOLUTION_GRACE = 1.second
+  SECTION_LITERAL_PATTERN = /\[[^\[\]\s]*-[^\[\]\s]*\]\z/
+
+  class MigrationPostVersion < ActiveRecord::Base
+    self.table_name = 'post_versions'
+  end
+
+  class MigrationTag < ActiveRecord::Base
+    self.table_name = 'tags'
+  end
+
+  class MigrationTagName < ActiveRecord::Base
+    self.table_name = 'tag_names'
+  end
+
+  class MigrationTagVersion < ActiveRecord::Base
+    self.table_name = 'tag_versions'
+  end
+
+  class MigrationNicoTagVersion < ActiveRecord::Base
+    self.table_name = 'nico_tag_versions'
+  end
+
+  def up
+    add_column :post_versions, :tags_json, :json, after: :tags
+    MigrationPostVersion.reset_column_information
+
+    backfill_missing_initial_tag_versions!
+    intervals_by_name = build_intervals_by_name
+
+    say_with_time 'Backfilling post_versions.tags_json' do
+      MigrationPostVersion.where(tags_json: nil).find_each(batch_size: 500) do |version|
+        version.update_columns(tags_json: build_tags_json(version, intervals_by_name))
+      end
+    end
+
+    change_column_null :post_versions, :tags_json, false
+
+    schema = connection.quote(JSON.generate({
+        type: 'array',
+        items: { type: 'object',
+                 properties: { id: { type: 'integer', minimum: 1 },
+                               version_no: { type: 'integer', minimum: 1 },
+                               name: { type: 'string', minLength: 1 },
+                               category: { type: 'string', enum: ['deerjikist',
+                                                                  'meme',
+                                                                  'character',
+                                                                  'general',
+                                                                  'material',
+                                                                  'meta',
+                                                                  'nico'] },
+                               sections: { type: 'array',
+                                           items: { type: 'object',
+                                                    properties: { begin_ms: { type: 'integer',
+                                                                              minimum: 0 },
+                                                                  end_ms: { type: ['integer',
+                                                                                   'null'],
+                                                                            minimum: 0 } },
+                                                    required: ['begin_ms', 'end_ms'],
+                                                    additionalProperties: false } } },
+                 required: ['id', 'version_no', 'name', 'category', 'sections'],
+                 additionalProperties: false } }))
+
+    add_check_constraint :post_versions,
+                         "JSON_SCHEMA_VALID(#{ schema }, tags_json)",
+                         name: 'chk_post_versions_tags_json_schema'
+  end
+
+  def down
+    remove_check_constraint :post_versions, name: 'chk_post_versions_tags_json_schema'
+
+    remove_column :post_versions, :tags_json
+  end
+
+  private
+
+  def backfill_missing_initial_tag_versions!
+    say_with_time 'Backfilling missing initial tag versions' do
+      tag_rows = missing_initial_version_rows(MigrationTagVersion, nico: false)
+      nico_rows = missing_initial_version_rows(MigrationNicoTagVersion, nico: true)
+
+      MigrationTagVersion.insert_all!(tag_rows) if tag_rows.any?
+      MigrationNicoTagVersion.insert_all!(nico_rows) if nico_rows.any?
+
+      tag_rows.length + nico_rows.length
+    end
+  end
+
+  def missing_initial_version_rows version_class, nico:
+    first_versions =
+        version_class
+        .order(:tag_id, :version_no)
+        .to_a
+        .group_by(&:tag_id)
+        .transform_values(&:first)
+    rows = []
+
+    MigrationTag.find_each do |tag|
+      next if (tag.category == 'nico') != nico
+
+      first_version = first_versions[tag.id]
+      next unless first_version
+      next if valid_initial_version?(first_version)
+
+      assert_inferable_initial_version!(tag, first_version)
+      rows << initial_version_row(tag, first_version, nico:)
+    end
+
+    rows
+  end
+
+  def valid_initial_version? version
+    version.version_no == 1 && version.event_type == 'create'
+  end
+
+  def assert_inferable_initial_version! tag, version
+    inferable =
+        version.version_no == 2 &&
+        version.event_type == 'discard' &&
+        tag.created_at < version.created_at
+    return if inferable
+
+    details = [
+        "tag_id=#{ tag.id }",
+        "version_no=#{ version.version_no }",
+        "event_type=#{ version.event_type.inspect }",
+        "tag_created_at=#{ tag.created_at.iso8601(6) }",
+        "version_created_at=#{ version.created_at.iso8601(6) }"]
+
+    raise "Cannot infer initial tag version: #{ details.join(', ') }"
+  end
+
+  def initial_version_row tag, discard_version, nico:
+    row = {
+        tag_id: tag.id,
+        version_no: 1,
+        event_type: 'create',
+        name: discard_version.name,
+        created_at: tag.created_at,
+        created_by_user_id: nil }
+
+    if nico
+      return row.merge(linked_tags: discard_version.linked_tags)
+    end
+
+    row.merge(
+        category: discard_version.category,
+        aliases: discard_version.aliases,
+        parent_tag_ids: discard_version.parent_tag_ids,
+        deprecated_at: discard_version.deprecated_at)
+  end
+
+  def build_intervals_by_name
+    intervals_by_name = Hash.new { |hash, name| hash[name] = [] }
+    versions_by_kind = {
+        tag: versions_by_tag_id(MigrationTagVersion),
+        nico: versions_by_tag_id(MigrationNicoTagVersion) }
+    current_names = current_names_by_tag_id
+
+    MigrationTag.find_each do |tag|
+      nico = tag.category == 'nico'
+      kind = nico ? :nico : :tag
+      versions = versions_by_kind.fetch(kind).fetch(tag.id, [])
+
+      intervals_for(
+          tag,
+          versions,
+          current_name: current_names.fetch(tag.id),
+          nico:).each do |interval|
+        name = interval.delete(:name)
+        intervals_by_name[name] << interval
+      end
+    end
+
+    intervals_by_name
+  end
+
+  def versions_by_tag_id version_class
+    version_class
+        .order(:tag_id, :version_no)
+        .to_a
+        .group_by(&:tag_id)
+  end
+
+  def current_names_by_tag_id
+    MigrationTagName
+        .joins('INNER JOIN tags ON tags.tag_name_id = tag_names.id')
+        .pluck('tags.id', 'tag_names.name')
+        .to_h
+  end
+
+  def intervals_for tag, versions, current_name:, nico:
+    if versions.empty?
+      return [{
+          name: current_name,
+          tag_id: tag.id,
+          version_no: tag.version_no,
+          category: nico ? 'nico' : tag.category,
+          from: tag.created_at,
+          to: tag.discarded_at }]
+    end
+
+    versions.each_with_index.filter_map do |version, index|
+      next if version.event_type == 'discard'
+
+      {
+          name: version.name,
+          tag_id: tag.id,
+          version_no: version.version_no,
+          category: nico ? 'nico' : version.category,
+          from: version.created_at,
+          to: versions[index + 1]&.created_at || tag.discarded_at }
+    end
+  end
+
+  def build_tags_json version, intervals_by_name
+    entries = version.tags.to_s.split.map do |literal|
+      name = tag_name_from_literal(literal)
+      interval = resolve_tag!(intervals_by_name.fetch(name, []), name:, version:)
+
+      { 'id' => interval.fetch(:tag_id),
+        'version_no' => interval.fetch(:version_no),
+        'name' => name,
+        'category' => interval.fetch(:category),
+        'sections' => [] }
+    end
+
+    assert_unique_tag_ids!(version, entries)
+
+    entries.sort_by { |entry| entry.fetch('id') }
+  end
+
+  def tag_name_from_literal literal
+    name = literal.dup
+    name.sub!(SECTION_LITERAL_PATTERN, '') while name.match?(
+        SECTION_LITERAL_PATTERN)
+
+    if name.empty? || name.include?('[') || name.include?(']')
+      raise "Invalid legacy tag literal: #{ literal.inspect }"
+    end
+
+    name
+  end
+
+  def resolve_tag! intervals, name:, version:
+    time = version.created_at
+    candidates = intervals.select do |interval|
+      interval.fetch(:from) <= time &&
+        (interval[:to].nil? || time < interval.fetch(:to))
+    end
+
+    candidates = future_candidates(intervals, time) if candidates.empty?
+
+    return candidates.first if candidates.one?
+
+    candidate_versions = candidates.map do |candidate|
+      [candidate.fetch(:tag_id), candidate.fetch(:version_no)]
+    end
+    details = [
+        "post_version_id=#{ version.id }",
+        "post_id=#{ version.post_id }",
+        "name=#{ name.inspect }",
+        "created_at=#{ time.iso8601(6) }",
+        "candidates=#{ candidate_versions.inspect }"].join(', ')
+
+    raise "Could not resolve tag snapshot: #{ details }"
+  end
+
+  def future_candidates intervals, time
+    candidates = intervals.select do |interval|
+      interval.fetch(:from) > time &&
+        interval.fetch(:from) <= time + RESOLUTION_GRACE
+    end
+    return [] if candidates.empty?
+
+    nearest_from = candidates.map { |interval| interval.fetch(:from) }.min
+
+    candidates.select do |interval|
+      interval.fetch(:from) == nearest_from
+    end
+  end
+
+  def assert_unique_tag_ids! version, entries
+    duplicate_tag_ids =
+        entries
+        .map { |entry| entry.fetch('id') }
+        .tally
+        .select { |_tag_id, count| count > 1 }
+        .keys
+    return if duplicate_tag_ids.empty?
+
+    details = [
+        "post_version_id=#{ version.id }",
+        "duplicate_tag_ids=#{ duplicate_tag_ids.inspect }"].join(', ')
+
+    raise "Duplicate tag IDs: #{ details }"
+  end
+end

backend/db/migrate/20260921000000_delete_inactive_records_from_post_tags.rb

@@ -0,0 +1,53 @@
+class DeleteInactiveRecordsFromPostTags < ActiveRecord::Migration[8.0]
+  def up
+    execute <<~SQL
+      DELETE
+      FROM
+        post_tags
+      WHERE
+        discarded_at IS NOT NULL
+    SQL
+
+    remove_index :post_tags, [:tag_id, :discarded_at]
+    remove_index :post_tags, [:post_id, :discarded_at]
+    remove_index :post_tags, name: 'idx_post_tags_active_unique'
+    remove_index :post_tags, :discarded_at
+
+    remove_foreign_key :post_tags, column: :deleted_user_id
+    remove_index :post_tags, :deleted_user_id
+
+    remove_column :post_tags, :active_unique_key
+    remove_column :post_tags, :is_active
+    remove_column :post_tags, :discarded_at
+    remove_column :post_tags, :deleted_user_id
+    remove_column :post_tags, :updated_at
+
+    execute <<~SQL
+      ALTER TABLE
+        post_tags
+      MODIFY COLUMN
+        id BIGINT NOT NULL
+    SQL
+
+    execute <<~SQL
+      ALTER TABLE
+        post_tags
+      DROP PRIMARY KEY
+    SQL
+
+    remove_column :post_tags, :id
+
+    execute <<~SQL
+      ALTER TABLE
+        post_tags
+      ADD PRIMARY KEY
+        (post_id, tag_id)
+    SQL
+
+    remove_index :post_tags, :post_id
+  end
+
+  def down
+    raise ActiveRecord::IrreversibleMigration, '戻せません．'
+  end
+end

backend/db/migrate/20260921010000_add_foreign_key_on_post_id_and_tag_id_in_post_tag_sections.rb

@@ -0,0 +1,11 @@
+class AddForeignKeyOnPostIdAndTagIdInPostTagSections < ActiveRecord::Migration[8.0]
+  def change
+    remove_foreign_key :post_tag_sections, :posts, column: :post_id
+    remove_foreign_key :post_tag_sections, :tags, column: :tag_id
+
+    add_foreign_key :post_tag_sections, :post_tags,
+                    column: [:post_id, :tag_id],
+                    primary_key: [:post_id, :tag_id],
+                    on_delete: :cascade
+  end
+end

backend/db/migrate/20260921020000_delete_discarded_records_from_tags.rb

@@ -0,0 +1,46 @@
+class DeleteDiscardedRecordsFromTags < ActiveRecord::Migration[8.0]
+  def up
+    remove_foreign_key :tag_versions, :tags, column: :tag_id
+    remove_foreign_key :nico_tag_versions, :tags, column: :tag_id
+    remove_foreign_key :material_versions, :tags, column: :tag_id
+
+    execute <<~SQL
+      DELETE
+        ntr
+      FROM
+        nico_tag_relations ntr
+        INNER JOIN
+          tags t
+          ON
+            t.discarded_at IS NOT NULL
+            AND t.id IN (ntr.tag_id, ntr.nico_tag_id)
+    SQL
+
+    execute <<~SQL
+      DELETE
+        ti
+      FROM
+        tag_implications ti
+        INNER JOIN
+          tags t
+          ON
+            t.discarded_at IS NOT NULL
+            AND t.id IN (ti.tag_id, ti.parent_tag_id)
+    SQL
+
+    execute <<~SQL
+      DELETE
+      FROM
+        tags
+      WHERE
+        discarded_at IS NOT NULL
+    SQL
+
+    remove_index :tags, :discarded_at
+    remove_column :tags, :discarded_at
+  end
+
+  def down
+    raise ActiveRecord::IrreversibleMigration, '戻せません．'
+  end
+end

backend/db/migrate/20260921030000_delete_discarded_records_from_tag_names.rb

@@ -0,0 +1,18 @@
+class DeleteDiscardedRecordsFromTagNames < ActiveRecord::Migration[8.0]
+  def up
+    execute <<~SQL
+      DELETE
+      FROM
+        tag_names
+      WHERE
+        discarded_at IS NOT NULL
+    SQL
+
+    remove_index :tag_names, :discarded_at
+    remove_column :tag_names, :discarded_at
+  end
+
+  def down
+    raise ActiveRecord::IrreversibleMigration, '戻せません．'
+  end
+end

backend/db/migrate/20260921040000_create_external_tags.rb

@@ -0,0 +1,54 @@
+class CreateExternalTags < ActiveRecord::Migration[8.0]
+  def up
+    create_table :external_tags do |t|
+      t.string :platform, limit: 16, null: false
+      t.string :name, limit: 255, null: false
+      t.integer :post_count, null: false, default: 0
+      t.datetime :created_at, null: false
+
+      t.index [:platform, :name], unique: true
+    end
+
+    execute <<~SQL
+      INSERT INTO
+        external_tags(id, platform, name, post_count, created_at)
+      SELECT
+        t.id
+      , 'nico' AS platform
+      , SUBSTR(tn.name, 6) AS name
+      , t.post_count
+      , t.created_at
+      FROM
+        tags t
+        INNER JOIN
+          tag_names tn
+          ON
+            tn.id = t.tag_name_id
+            AND t.category = 'nico'
+    SQL
+
+    execute <<~SQL
+      INSERT INTO
+        external_tags(id, platform, name, post_count, created_at)
+      SELECT
+        ntv.tag_id
+      , 'nico' AS platform
+      , SUBSTR(ntv.name, 6) AS name
+      , 0 AS post_count
+      , ntv.created_at
+      FROM
+        nico_tag_versions ntv
+        LEFT JOIN
+          external_tags et
+          ON
+            et.id = ntv.tag_id
+      WHERE
+        ntv.version_no = 1
+        AND et.id IS NULL
+    SQL
+  end
+
+  def down
+    drop_table :external_tags
+  end
+end

backend/db/migrate/20260921050000_create_post_external_tags.rb

@@ -0,0 +1,29 @@
+class CreatePostExternalTags < ActiveRecord::Migration[8.0]
+  def up
+    create_table :post_external_tags, primary_key: [:post_id, :external_tag_id] do |t|
+      t.references :post, null: false, index: false, foreign_key: true
+      t.references :external_tag, null: false, foreign_key: true
+      t.datetime :created_at, null: false
+    end
+
+    execute <<~SQL
+      INSERT INTO
+        post_external_tags(post_id, external_tag_id, created_at)
+      SELECT
+        pt.post_id
+      , pt.tag_id AS external_tag_id
+      , pt.created_at
+      FROM
+        post_tags pt
+        INNER JOIN
+          tags t
+          ON
+            pt.tag_id = t.id
+            AND t.category = 'nico'
+    SQL
+  end
+
+  def down
+    drop_table :post_external_tags
+  end
+end

backend/db/migrate/20260921060000_change_foreign_key_on_nico_tag_relations.rb

@@ -0,0 +1,6 @@
+class ChangeForeignKeyOnNicoTagRelations < ActiveRecord::Migration[8.0]
+  def change
+    remove_foreign_key :nico_tag_relations, :tags, column: :nico_tag_id
+    add_foreign_key :nico_tag_relations, :external_tags, column: :nico_tag_id
+  end
+end

backend/db/migrate/20260921230000_migrate_external_tags.rb

@@ -0,0 +1,199 @@
+class MigrateExternalTags < ActiveRecord::Migration[8.0]
+  class MigrationPostVersion < ActiveRecord::Base
+    self.table_name = 'post_versions'
+  end
+
+  def up
+    x = connection.select_value(<<~SQL)
+      SELECT
+        COUNT(0)
+      FROM
+        post_tag_sections pts
+      INNER JOIN
+        tags t
+        ON
+          t.id = pts.tag_id
+      WHERE
+        t.category = 'nico'
+    SQL
+    if x > 0
+      raise "post_tag_sections に #{ x } 件のチンカスがあります!"
+    end
+
+    x = connection.select_value(<<~SQL)
+      SELECT
+        COUNT(0)
+      FROM
+        materials m
+        INNER JOIN
+          tags t
+          ON
+            t.id = m.tag_id
+      WHERE
+        t.category = 'nico'
+    SQL
+    if x > 0
+      raise "materials に #{ x } 件のチンカスがあります!"
+    end
+
+    x = connection.select_value(<<~SQL)
+      SELECT
+        COUNT(0)
+      FROM
+        tag_implications ti
+        INNER JOIN
+          tags t
+          ON
+            t.id = ti.tag_id
+            OR t.id = ti.parent_tag_id
+      WHERE
+        t.category = 'nico'
+    SQL
+    if x > 0
+      raise "tag_implications に #{ x } 件のチンカスがあります!"
+    end
+
+    execute <<~SQL
+      DELETE
+        ts
+      FROM
+        tag_similarities ts
+        INNER JOIN
+          tags t
+          ON
+            t.category = 'nico'
+            AND (t.id = ts.tag_id
+                 OR t.id = ts.target_tag_id)
+    SQL
+
+    execute <<~SQL
+      DELETE
+        tset
+      FROM
+        theatre_skip_event_tags tset
+        INNER JOIN
+          tags t
+          ON
+            t.category = 'nico'
+            AND t.id = tset.tag_id
+    SQL
+
+    remove_check_constraint :post_versions, name: 'chk_post_versions_tags_json_schema'
+
+    say_with_time 'Migrate post_versions.tags_json' do
+      count = 0
+
+      MigrationPostVersion.find_each(batch_size: 500) do |version|
+        tags = version.tags_json.map do |tag|
+          if tag.fetch('category') == 'nico'
+            { 'external_tag_id' => tag.fetch('id') }
+          else
+            { 'tag_id' => tag.fetch('id'),
+              'version_no' => tag.fetch('version_no'),
+              'name' => tag.fetch('name'),
+              'category' => tag.fetch('category'),
+              'sections' => tag.fetch('sections') }
+          end
+        end
+
+        version.update_columns(tags_json: tags)
+        count += 1
+      end
+
+      count
+    end
+
+    add_tags_json_constraint!
+
+    tag_name_ids = connection.select_values(<<~SQL)
+      SELECT
+        tag_name_id
+      FROM
+        tags
+      WHERE
+        category = 'nico'
+    SQL
+
+    connection.transaction do
+      execute <<~SQL
+        DELETE
+          pt
+        FROM
+          post_tags pt
+          INNER JOIN
+            tags t
+            ON
+              t.category = 'nico'
+              AND t.id = pt.tag_id
+      SQL
+
+      execute <<~SQL
+        DELETE
+        FROM
+          tags
+        WHERE
+          category = 'nico'
+      SQL
+
+      unless tag_name_ids.empty?
+        execute <<~SQL
+          DELETE
+          FROM
+            tag_names
+          WHERE
+            id IN (#{ tag_name_ids.join(', ') })
+        SQL
+      end
+    end
+  end
+
+  def down
+    raise ActiveRecord::IrreversibleMigration, '戻せません．'
+  end
+
+  private
+
+  def add_tags_json_constraint!
+    schema = { type: 'array',
+               items: { oneOf: [internal_tag_schema, external_tag_schema] } }
+
+    quoted_schema = connection.quote(JSON.generate(schema))
+
+    add_check_constraint :post_versions,
+                         "JSON_SCHEMA_VALID(#{ quoted_schema }, tags_json)",
+                         name: 'chk_post_versions_tags_json_schema'
+  end
+
+  def internal_tag_schema
+    { type: 'object',
+      properties: { tag_id: { type: 'integer', minimum: 1 },
+                    version_no: { type: 'integer', minimum: 1 },
+                    name: { type: 'string', minLength: 1 },
+                    category: { type: 'string',
+                                enum: ['deerjikist',
+                                       'meme',
+                                       'character',
+                                       'general',
+                                       'material',
+                                       'meta'] },
+                    sections: sections_schema },
+      required: ['tag_id', 'version_no', 'sections'],
+      additionalProperties: false }
+  end
+
+  def external_tag_schema
+    { type: 'object',
+      properties: { external_tag_id: { type: 'integer', minimum: 1 } },
+      required: ['external_tag_id'],
+      additionalProperties: false }
+  end
+
+  def sections_schema
+    { type: 'array',
+      items: { type: 'object',
+               properties: { begin_ms: { type: 'integer', minimum: 0 },
+                             end_ms: { type: ['integer', 'null'], minimum: 0 } },
+               required: ['begin_ms', 'end_ms'],
+               additionalProperties: false } }
+  end
+end

backend/db/migrate/20260922000000_create_languages.rb

@@ -0,0 +1,20 @@
+class CreateLanguages < ActiveRecord::Migration[8.0]
+  def up
+    create_table :languages, id: { type: :string, limit: 16 }, primary_key: :code do |t|
+      t.string :name, null: false
+      t.datetime :deprecated_at, index: true
+      t.datetime :created_at, null: false
+    end
+
+    execute <<~SQL
+      INSERT INTO
+        languages(code, name, created_at)
+      VALUES
+        ('ja', '日本語', #{ connection.quote Time.current })
+    SQL
+  end
+
+  def down
+    drop_table :languages
+  end
+end

backend/db/migrate/20260922010000_create_scripts.rb

@@ -0,0 +1,20 @@
+class CreateScripts < ActiveRecord::Migration[8.0]
+  def up
+    create_table :scripts, id: { type: 'CHAR(4)' }, primary_key: :code do |t|
+      t.string :name, null: false
+      t.datetime :deprecated_at, index: true
+      t.datetime :created_at, null: false
+    end
+
+    execute <<~SQL
+      INSERT INTO
+        scripts(code, name, created_at)
+      VALUES
+        ('Jpan', '漢字および仮名文字', #{ connection.quote Time.current })
+    SQL
+  end
+
+  def down
+    drop_table :scripts
+  end
+end

backend/db/migrate/20260922020000_create_locales.rb

@@ -0,0 +1,25 @@
+class CreateLocales < ActiveRecord::Migration[8.0]
+  def up
+    create_table :locales, id: { type: :string, limit: 32 }, primary_key: :code do |t|
+      t.string :language_code, limit: 16, null: false, index: true
+      t.column :script_code, 'CHAR(4)', null: false
+      t.string :name, null: false
+      t.datetime :deprecated_at, index: true
+      t.datetime :created_at, null: false
+
+      t.foreign_key :languages, column: :language_code, primary_key: :code
+      t.foreign_key :scripts, column: :script_code, primary_key: :code
+    end
+
+    execute <<~SQL
+      INSERT INTO
+        locales(code, language_code, script_code, name, created_at)
+      VALUES
+        ('ja', 'ja', 'Jpan', '日本語', #{ connection.quote Time.current })
+    SQL
+  end
+
+  def down
+    drop_table :locales
+  end
+end

backend/db/migrate/20260922030000_add_columns_to_tag_names.rb

@@ -0,0 +1,59 @@
+class AddColumnsToTagNames < ActiveRecord::Migration[8.0]
+  def up
+    add_reference :tag_names, :tag, after: :id, foreign_key: true
+    add_column :tag_names, :language_code, :string,
+               limit: 16, null: false, after: :tag_id, default: 'ja'
+    add_column :tag_names, :script_code, 'CHAR(4)',
+               null: false, after: :name, default: 'Jpan'
+    add_column :tag_names, :primary_flg, :boolean,
+               null: false, after: :script_code, default: true
+
+    add_foreign_key :tag_names, :languages, column: :language_code, primary_key: :code
+    add_foreign_key :tag_names, :scripts, column: :script_code, primary_key: :code
+
+    remove_index :tag_names, :name
+    add_index :tag_names, [:language_code, :name], unique: true
+
+    change_column_default :tag_names, :language_code, from: 'ja', to: nil
+    change_column_default :tag_names, :script_code, from: 'Jpan', to: nil
+
+    execute <<~SQL
+      UPDATE
+        tag_names tn
+        LEFT JOIN
+          tags AS t
+          ON
+            t.tag_name_id = COALESCE(tn.canonical_id, tn.id)
+      SET
+        tn.tag_id = t.id
+      , tn.primary_flg = CASE
+                         WHEN tn.canonical_id IS NULL THEN
+                           1
+                         ELSE
+                           0
+                         END
+    SQL
+
+    change_column_default :tag_names, :primary_flg, from: true, to: nil
+
+    add_column :tag_names, :primary_tag_id, :bigint,
+               as: 'CASE WHEN primary_flg THEN tag_id ELSE NULL END'
+    add_index :tag_names, [:primary_tag_id, :language_code], unique: true
+  end
+
+  def down
+    remove_index :tag_names, [:primary_tag_id, :language_code]
+    remove_column :tag_names, :primary_tag_id
+
+    remove_foreign_key :tag_names, column: :language_code
+    remove_foreign_key :tag_names, column: :script_code
+
+    remove_index :tag_names, [:language_code, :name]
+    add_index :tag_names, :name, unique: true
+
+    remove_column :tag_names, :primary_flg
+    remove_column :tag_names, :script_code
+    remove_column :tag_names, :language_code
+    remove_reference :tag_names, :tag, foreign_key: true
+  end
+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_07_13_000000) do
+ActiveRecord::Schema[8.0].define(version: 2026_09_22_030000) 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
@@ -48,6 +48,14 @@ ActiveRecord::Schema[8.0].define(version: 2026_07_13_000000) do
     t.index ["tag_id"], name: "index_deerjikists_on_tag_id"
   end
 
+  create_table "external_tags", charset: "utf8mb4", collation: "utf8mb4_0900_ai_ci", force: :cascade do |t|
+    t.string "platform", limit: 16, null: false
+    t.string "name", null: false
+    t.integer "post_count", default: 0, null: false
+    t.datetime "created_at", null: false
+    t.index ["platform", "name"], name: "index_external_tags_on_platform_and_name", unique: true
+  end
+
   create_table "gekanator_ai_runs", charset: "utf8mb4", collation: "utf8mb4_0900_ai_ci", force: :cascade do |t|
     t.string "model", null: false
     t.integer "input_tokens", default: 0, null: false
@@ -130,6 +138,24 @@ ActiveRecord::Schema[8.0].define(version: 2026_07_13_000000) do
     t.index ["ip_address"], name: "index_ip_addresses_on_ip_address", unique: true
   end
 
+  create_table "languages", primary_key: "code", id: { type: :string, limit: 16 }, charset: "utf8mb4", collation: "utf8mb4_0900_ai_ci", force: :cascade do |t|
+    t.string "name", null: false
+    t.datetime "deprecated_at"
+    t.datetime "created_at", null: false
+    t.index ["deprecated_at"], name: "index_languages_on_deprecated_at"
+  end
+
+  create_table "locales", primary_key: "code", id: { type: :string, limit: 32 }, charset: "utf8mb4", collation: "utf8mb4_0900_ai_ci", force: :cascade do |t|
+    t.string "language_code", limit: 16, null: false
+    t.string "script_code", limit: 4, null: false
+    t.string "name", null: false
+    t.datetime "deprecated_at"
+    t.datetime "created_at", null: false
+    t.index ["deprecated_at"], name: "index_locales_on_deprecated_at"
+    t.index ["language_code"], name: "index_locales_on_language_code"
+    t.index ["script_code"], name: "fk_rails_0b74ce96a8"
+  end
+
   create_table "material_export_items", charset: "utf8mb4", collation: "utf8mb4_0900_ai_ci", force: :cascade do |t|
     t.bigint "material_id", null: false
     t.string "profile", default: "legacy_drive", null: false
@@ -281,6 +307,13 @@ ActiveRecord::Schema[8.0].define(version: 2026_07_13_000000) do
     t.check_constraint "`version_no` > 0", name: "nico_tag_versions_version_no_positive"
   end
 
+  create_table "post_external_tags", primary_key: ["post_id", "external_tag_id"], charset: "utf8mb4", collation: "utf8mb4_0900_ai_ci", force: :cascade do |t|
+    t.bigint "post_id", null: false
+    t.bigint "external_tag_id", null: false
+    t.datetime "created_at", null: false
+    t.index ["external_tag_id"], name: "index_post_external_tags_on_external_tag_id"
+  end
+
   create_table "post_implications", primary_key: ["post_id", "parent_post_id"], charset: "utf8mb4", collation: "utf8mb4_0900_ai_ci", force: :cascade do |t|
     t.bigint "post_id", null: false
     t.bigint "parent_post_id", null: false
@@ -311,23 +344,12 @@ ActiveRecord::Schema[8.0].define(version: 2026_07_13_000000) do
     t.check_constraint "`begin_ms` >= 0", name: "chk_post_tag_sections_begin_ms_natural"
   end
 
-  create_table "post_tags", charset: "utf8mb4", collation: "utf8mb4_0900_ai_ci", force: :cascade do |t|
+  create_table "post_tags", primary_key: ["post_id", "tag_id"], charset: "utf8mb4", collation: "utf8mb4_0900_ai_ci", force: :cascade do |t|
     t.bigint "post_id", null: false
     t.bigint "tag_id", null: false
     t.bigint "created_user_id"
-    t.bigint "deleted_user_id"
     t.datetime "created_at", null: false
-    t.datetime "updated_at", null: false
-    t.datetime "discarded_at"
-    t.virtual "is_active", type: :boolean, as: "(`discarded_at` is null)", stored: true
-    t.virtual "active_unique_key", type: :string, as: "(case when (`discarded_at` is null) then concat(`post_id`,_utf8mb4':',`tag_id`) else NULL end)", stored: true
-    t.index ["active_unique_key"], name: "idx_post_tags_active_unique", unique: true
     t.index ["created_user_id"], name: "index_post_tags_on_created_user_id"
-    t.index ["deleted_user_id"], name: "index_post_tags_on_deleted_user_id"
-    t.index ["discarded_at"], name: "index_post_tags_on_discarded_at"
-    t.index ["post_id", "discarded_at"], name: "index_post_tags_on_post_id_and_discarded_at"
-    t.index ["post_id"], name: "index_post_tags_on_post_id"
-    t.index ["tag_id", "discarded_at"], name: "index_post_tags_on_tag_id_and_discarded_at"
     t.index ["tag_id"], name: "index_post_tags_on_tag_id"
   end
 
@@ -349,6 +371,7 @@ ActiveRecord::Schema[8.0].define(version: 2026_07_13_000000) do
     t.string "url", limit: 768, null: false
     t.string "thumbnail_base", limit: 2000
     t.text "tags", null: false
+    t.json "tags_json", null: false
     t.text "parent_post_ids", null: false
     t.datetime "original_created_from"
     t.datetime "original_created_before"
@@ -362,6 +385,7 @@ ActiveRecord::Schema[8.0].define(version: 2026_07_13_000000) do
     t.check_constraint "(`video_ms` is null) or (`video_ms` > 0)", name: "chk_post_versions_video_ms_positive"
     t.check_constraint "`event_type` in (_utf8mb4'create',_utf8mb4'update',_utf8mb4'discard',_utf8mb4'restore')", name: "post_versions_event_type_valid"
     t.check_constraint "`version_no` > 0", name: "post_versions_version_no_positive"
+    t.check_constraint "json_schema_valid(_utf8mb4'{\"type\":\"array\",\"items\":{\"oneOf\":[{\"type\":\"object\",\"properties\":{\"tag_id\":{\"type\":\"integer\",\"minimum\":1},\"version_no\":{\"type\":\"integer\",\"minimum\":1},\"name\":{\"type\":\"string\",\"minLength\":1},\"category\":{\"type\":\"string\",\"enum\":[\"deerjikist\",\"meme\",\"character\",\"general\",\"material\",\"meta\"]},\"sections\":{\"type\":\"array\",\"items\":{\"type\":\"object\",\"properties\":{\"begin_ms\":{\"type\":\"integer\",\"minimum\":0},\"end_ms\":{\"type\":[\"integer\",\"null\"],\"minimum\":0}},\"required\":[\"begin_ms\",\"end_ms\"],\"additionalProperties\":false}}},\"required\":[\"tag_id\",\"version_no\",\"sections\"],\"additionalProperties\":false},{\"type\":\"object\",\"properties\":{\"external_tag_id\":{\"type\":\"integer\",\"minimum\":1}},\"required\":[\"external_tag_id\"],\"additionalProperties\":false}]}}',`tags_json`)", name: "chk_post_versions_tags_json_schema"
   end
 
   create_table "posts", charset: "utf8mb4", collation: "utf8mb4_0900_ai_ci", force: :cascade do |t|
@@ -382,6 +406,13 @@ ActiveRecord::Schema[8.0].define(version: 2026_07_13_000000) do
     t.check_constraint "`version_no` > 0", name: "chk_posts_version_no_positive"
   end
 
+  create_table "scripts", primary_key: "code", id: { type: :string, limit: 4 }, charset: "utf8mb4", collation: "utf8mb4_0900_ai_ci", force: :cascade do |t|
+    t.string "name", null: false
+    t.datetime "deprecated_at"
+    t.datetime "created_at", null: false
+    t.index ["deprecated_at"], name: "index_scripts_on_deprecated_at"
+  end
+
   create_table "settings", charset: "utf8mb4", collation: "utf8mb4_0900_ai_ci", force: :cascade do |t|
     t.bigint "user_id", null: false
     t.datetime "created_at", null: false
@@ -393,19 +424,6 @@ ActiveRecord::Schema[8.0].define(version: 2026_07_13_000000) do
     t.index ["user_id"], name: "index_settings_on_user_id", unique: true
   end
 
-  create_table "wiki_assets", charset: "utf8mb4", collation: "utf8mb4_0900_ai_ci", force: :cascade do |t|
-    t.bigint "wiki_page_id", null: false
-    t.integer "no", null: false
-    t.string "alt_text"
-    t.binary "sha256", limit: 32, null: false
-    t.bigint "created_by_user_id", null: false
-    t.datetime "created_at", null: false
-    t.datetime "updated_at", null: false
-    t.index ["created_by_user_id"], name: "index_wiki_assets_on_created_by_user_id"
-    t.index ["wiki_page_id", "no"], name: "index_wiki_assets_on_wiki_page_id_and_no", unique: true
-    t.index ["wiki_page_id", "sha256"], name: "index_wiki_assets_on_wiki_page_id_and_sha256", unique: true
-  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
@@ -427,14 +445,20 @@ ActiveRecord::Schema[8.0].define(version: 2026_07_13_000000) do
   end
 
   create_table "tag_names", charset: "utf8mb4", collation: "utf8mb4_0900_ai_ci", force: :cascade do |t|
+    t.bigint "tag_id"
+    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.bigint "canonical_id"
     t.datetime "created_at", null: false
     t.datetime "updated_at", null: false
-    t.datetime "discarded_at"
+    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 ["discarded_at"], name: "index_tag_names_on_discarded_at"
+    t.index ["language_code", "name"], name: "index_tag_names_on_language_code_and_name", unique: true
-    t.index ["name"], name: "index_tag_names_on_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"
+    t.index ["tag_id"], name: "index_tag_names_on_tag_id"
   end
 
   create_table "tag_similarities", primary_key: ["tag_id", "target_tag_id"], charset: "utf8mb4", collation: "utf8mb4_0900_ai_ci", force: :cascade do |t|
@@ -470,10 +494,8 @@ ActiveRecord::Schema[8.0].define(version: 2026_07_13_000000) do
     t.datetime "created_at", null: false
     t.datetime "updated_at", null: false
     t.integer "post_count", default: 0, null: false
-    t.datetime "discarded_at"
     t.integer "version_no", null: false
     t.index ["deprecated_at"], name: "index_tags_on_deprecated_at"
-    t.index ["discarded_at"], name: "index_tags_on_discarded_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"
@@ -614,6 +636,19 @@ ActiveRecord::Schema[8.0].define(version: 2026_07_13_000000) do
     t.index ["banned_at"], name: "index_users_on_banned_at"
   end
 
+  create_table "wiki_assets", charset: "utf8mb4", collation: "utf8mb4_0900_ai_ci", force: :cascade do |t|
+    t.bigint "wiki_page_id", null: false
+    t.integer "no", null: false
+    t.string "alt_text"
+    t.binary "sha256", limit: 32, null: false
+    t.bigint "created_by_user_id", null: false
+    t.datetime "created_at", null: false
+    t.datetime "updated_at", null: false
+    t.index ["created_by_user_id"], name: "index_wiki_assets_on_created_by_user_id"
+    t.index ["wiki_page_id", "no"], name: "index_wiki_assets_on_wiki_page_id_and_no", unique: true
+    t.index ["wiki_page_id", "sha256"], name: "index_wiki_assets_on_wiki_page_id_and_sha256", unique: true
+  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
@@ -699,6 +734,8 @@ ActiveRecord::Schema[8.0].define(version: 2026_07_13_000000) do
   add_foreign_key "gekanator_question_suggestions", "users"
   add_foreign_key "gekanator_questions", "gekanator_question_suggestions"
   add_foreign_key "gekanator_questions", "users", column: "created_by_id"
+  add_foreign_key "locales", "languages", column: "language_code", primary_key: "code"
+  add_foreign_key "locales", "scripts", column: "script_code", primary_key: "code"
   add_foreign_key "material_export_items", "materials"
   add_foreign_key "material_export_items", "users", column: "created_by_user_id"
   add_foreign_key "material_import_blocks", "users", column: "created_by_user_id"
@@ -707,37 +744,37 @@ ActiveRecord::Schema[8.0].define(version: 2026_07_13_000000) do
   add_foreign_key "material_sync_suppressions", "users", column: "created_by_user_id"
   add_foreign_key "material_versions", "materials"
   add_foreign_key "material_versions", "materials", column: "parent_id"
-  add_foreign_key "material_versions", "tags"
   add_foreign_key "material_versions", "users", column: "created_by_user_id"
   add_foreign_key "material_versions", "users", column: "updated_by_user_id"
   add_foreign_key "materials", "materials", column: "parent_id"
   add_foreign_key "materials", "tags"
   add_foreign_key "materials", "users", column: "created_by_user_id"
   add_foreign_key "materials", "users", column: "updated_by_user_id"
+  add_foreign_key "nico_tag_relations", "external_tags", column: "nico_tag_id"
   add_foreign_key "nico_tag_relations", "tags"
-  add_foreign_key "nico_tag_relations", "tags", column: "nico_tag_id"
-  add_foreign_key "nico_tag_versions", "tags"
   add_foreign_key "nico_tag_versions", "users", column: "created_by_user_id"
+  add_foreign_key "post_external_tags", "external_tags"
+  add_foreign_key "post_external_tags", "posts"
   add_foreign_key "post_implications", "posts"
   add_foreign_key "post_implications", "posts", column: "parent_post_id"
   add_foreign_key "post_similarities", "posts"
   add_foreign_key "post_similarities", "posts", column: "target_post_id"
-  add_foreign_key "post_tag_sections", "posts"
+  add_foreign_key "post_tag_sections", "post_tags", column: ["post_id", "tag_id"], primary_key: ["post_id", "tag_id"], on_delete: :cascade
-  add_foreign_key "post_tag_sections", "tags"
   add_foreign_key "post_tags", "posts"
   add_foreign_key "post_tags", "tags"
   add_foreign_key "post_tags", "users", column: "created_user_id"
-  add_foreign_key "post_tags", "users", column: "deleted_user_id"
   add_foreign_key "post_versions", "posts"
   add_foreign_key "post_versions", "users", column: "created_by_user_id"
   add_foreign_key "posts", "users", column: "uploaded_user_id"
   add_foreign_key "settings", "users"
   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", "tags"
   add_foreign_key "tag_versions", "users", column: "created_by_user_id"
   add_foreign_key "tags", "tag_names"
   add_foreign_key "theatre_comments", "theatres"

backend/lib/tasks/sync_nico.rake

@@ -16,7 +16,7 @@ namespace :nico do
     end
 
     def sync_post_tags! post, desired_tag_ids, current_tag_ids: nil
-      current_tag_ids ||= PostTag.kept.where(post_id: post.id).pluck(:tag_id).to_set
+      current_tag_ids ||= PostTag.where(post_id: post.id).pluck(:tag_id).to_set
       desired_tag_ids = desired_tag_ids.compact.to_set
 
       to_add = desired_tag_ids - current_tag_ids
@@ -30,9 +30,28 @@ namespace :nico do
         end
       end
 
-      PostTag.where(post_id: post.id, tag_id: to_remove.to_a).kept.find_each do |pt|
+      PostTag.where(post_id: post.id, tag_id: to_remove.to_a).find_each(&:destroy!)
-        pt.discard_by!(nil)
+    end
+
+    def sync_post_external_tags! post, desired_external_tag_ids, current_external_tag_ids: nil
+      current_external_tag_ids ||=
+          PostExternalTag.where(post_id: post.id).pluck(:external_tag_id).to_set
+      desired_external_tag_ids = desired_external_tag_ids.compact.to_set
+
+      to_add = desired_external_tag_ids - current_external_tag_ids
+      to_remove = current_external_tag_ids - desired_external_tag_ids
+
+      ExternalTag.where(id: to_add.to_a).find_each do |external_tag|
+        begin
+          PostExternalTag.create!(post:, external_tag:)
+        rescue ActiveRecord::RecordNotUnique
+          ;
+        end
       end
+
+      PostExternalTag
+          .where(post_id: post.id, external_tag_id: to_remove.to_a)
+          .find_each(&:destroy!)
     end
 
     mysql_user = ENV['MYSQL_USER']
@@ -111,58 +130,64 @@ namespace :nico do
         sync_post_tags!(post, [Tag.tagme.id, Tag.bot.id, Tag.niconico.id, Tag.video.id])
       end
 
-      tags = post.tags
       # 既存のタグ Id. 集合
-      kept_tag_ids = tags.pluck(:id).to_set
+      kept_tag_ids = post.tags.pluck(:id).to_set
-      # うち内部タグ Id. 集合
+
-      kept_non_nico_tag_ids = tags.not_nico.pluck(:id).to_set
+      # 既存の外部タグ Id. 集合
+      kept_external_tag_ids = post.external_tags.nico.pluck(:id).to_set
+
+      # 記載すべき外部タグ Id. のリスト
+      desired_external_tag_ids = []
 
-      # 記載すべき外部タグ Id. および連携される内部タグ Id. のリスト
-      desired_nico_tag_based_ids = []
       # 記載すべき内部タグ Id. のリスト
-      desired_non_nico_tag_ids = []
+      desired_tag_ids = kept_tag_ids.to_a
 
       datum['tags'].each do |raw|
-        name = TagNameSanitisationRule.sanitise("nico:#{ raw }")
+        name = TagNameSanitisationRule.sanitise("nico:#{ raw }").delete_prefix('nico:')
-        tag = Tag.find_or_create_by_tag_name!(name, category: :nico)
+        tag = ExternalTag.find_or_create_by!(platform: :nico, name:)
 
-        event_type = tag.nico_tag_versions.exists? ? :update : :create
+        unless tag.nico_tag_versions.exists?
-        NicoTagVersionRecorder.record!(tag:, event_type:, created_by_user: nil)
+          NicoTagVersionRecorder.record!(external_tag: tag,
+                                         event_type: :create,
+                                         created_by_user: nil)
+        end
 
-        desired_nico_tag_based_ids << tag.id
+        desired_external_tag_ids << tag.id
 
         # 新たに記載される外部タグと連携される内部タグを記載
-        unless tag.id.in?(kept_tag_ids)
+        # 連携タグは記載すれども消除せず．
-          linked_ids = tag.linked_tags.pluck(:id)
+        unless tag.id.in?(kept_external_tag_ids)
-          desired_non_nico_tag_ids.concat(linked_ids)
+          desired_tag_ids.concat(tag.linked_tags.pluck(:id))
-          desired_nico_tag_based_ids.concat(linked_ids)
         end
       end
 
       deerjikist = Deerjikist.find_by(platform: :nico, code: datum['user'])
       if deerjikist
-        desired_non_nico_tag_ids << deerjikist.tag_id
+        desired_tag_ids << deerjikist.tag_id
-        desired_nico_tag_based_ids << deerjikist.tag_id
+      elsif !(Tag.where(id: kept_tag_ids).where(category: :deerjikist).exists?)
-      elsif !(Tag.where(id: kept_non_nico_tag_ids).where(category: :deerjikist).exists?)
+        desired_tag_ids << Tag.no_deerjikist.id
-        desired_non_nico_tag_ids << Tag.no_deerjikist.id
-        desired_nico_tag_based_ids << Tag.no_deerjikist.id
       end
 
-      desired_nico_tag_based_ids.uniq!
+      desired_external_tag_ids.uniq!
+      desired_tag_ids.uniq!
 
-      desired_all_tag_ids = kept_non_nico_tag_ids.to_a + desired_nico_tag_based_ids
+      # 外部タグの記載に際しては “bot 操作” タグを記載しなぃ．
-      desired_non_nico_tag_ids.concat(kept_non_nico_tag_ids.to_a)
+      if kept_tag_ids != desired_tag_ids.to_set
-      desired_non_nico_tag_ids.uniq!
+        desired_tag_ids << Tag.bot.id
-      if kept_non_nico_tag_ids != desired_non_nico_tag_ids.to_set
+        desired_tag_ids.uniq!
-        desired_all_tag_ids << Tag.bot.id
       end
-      desired_all_tag_ids.uniq!
 
-      sync_post_tags!(post, desired_all_tag_ids, current_tag_ids: kept_tag_ids)
+      tags_changed =
+          kept_tag_ids != desired_tag_ids.to_set ||
+          kept_external_tag_ids != desired_external_tag_ids.to_set
+
+      sync_post_tags!(post, desired_tag_ids, current_tag_ids: kept_tag_ids)
+      sync_post_external_tags!(post, desired_external_tag_ids,
+                               current_external_tag_ids: kept_external_tag_ids)
 
       if post_created
         PostVersionRecorder.record!(post:, event_type: :create, created_by_user: nil)
-      elsif post_changed || kept_tag_ids != desired_all_tag_ids.to_set
+      elsif post_changed || tags_changed
         PostVersionRecorder.ensure_snapshot!(post, created_by_user: nil)
         PostVersionRecorder.record!(post:, event_type: :update, created_by_user: nil)
       end

backend/spec/db/delete_discarded_tags_spec.rb

@@ -0,0 +1,124 @@
+require 'rails_helper'
+require_relative '../../db/migrate/20260921020000_delete_discarded_records_from_tags'
+require_relative '../../db/migrate/20260921030000_delete_discarded_records_from_tag_names'
+
+RSpec.describe 'discarded tag cleanup migrations' do
+  [DeleteDiscardedRecordsFromTags, DeleteDiscardedRecordsFromTagNames].each do |migration_class|
+    it "rejects rollback of #{ migration_class.name }" do
+      expect { migration_class.new.down }
+          .to raise_error(ActiveRecord::IrreversibleMigration)
+    end
+  end
+
+  context 'with legacy records' do
+    # Reproduce the historical schema required by these pre-multilingual migrations.
+    self.use_transactional_tests = false
+
+    before do
+      record_class = Class.new(ActiveRecord::Base) do
+        self.abstract_class = true
+      end
+      stub_const('TagCleanupMigrationRecord', record_class)
+      config = ActiveRecord::Base.connection_db_config.configuration_hash
+      @database = "btrc_hub_test_tag_cleanup_#{ Process.pid }_#{ SecureRandom.hex(4) }"
+      record_class.establish_connection(config.merge(database: nil))
+      @connection = record_class.lease_connection
+      @connection.create_database(@database)
+      @database_created = true
+      @connection.execute("USE #{ @connection.quote_table_name(@database) }")
+    end
+
+    after do
+      @connection.drop_database(@database) if @database_created
+    ensure
+      TagCleanupMigrationRecord.remove_connection
+    end
+
+    before do
+      @connection.create_table(:tag_names) do |t|
+        t.string :name, null: false, index: { unique: true }
+        t.bigint :canonical_id
+        t.datetime :discarded_at, index: true
+      end
+      @connection.add_foreign_key(:tag_names, :tag_names, column: :canonical_id)
+      @connection.create_table(:tags) do |t|
+        t.references :tag_name, null: false, foreign_key: true, index: { unique: true }
+        t.datetime :discarded_at, index: true
+      end
+      @connection.create_table(:nico_tag_relations) do |t|
+        t.references :tag, null: false, foreign_key: true
+        t.references :nico_tag, null: false, foreign_key: { to_table: :tags }
+      end
+      @connection.create_table(:tag_implications) do |t|
+        t.references :tag, null: false, foreign_key: true
+        t.references :parent_tag, null: false, foreign_key: { to_table: :tags }
+      end
+      [:tag_versions, :nico_tag_versions, :material_versions].each do |table|
+        @connection.create_table(table) do |t|
+          t.references :tag, null: false, foreign_key: true
+        end
+      end
+
+      @connection.execute(<<~SQL)
+        INSERT INTO tag_names (id, name, canonical_id, discarded_at) VALUES
+          (1, 'kept', NULL, NULL),
+          (2, 'merged_alias', 1, NULL),
+          (3, 'nico:deleted', NULL, '2026-09-20'),
+          (4, 'nico:kept', NULL, NULL),
+          (5, 'deleted_name', NULL, '2026-09-20')
+      SQL
+      @connection.execute(<<~SQL)
+        INSERT INTO tags (id, tag_name_id, discarded_at) VALUES
+          (1, 1, NULL), (2, 2, '2026-09-20'),
+          (3, 3, '2026-09-20'), (4, 4, NULL)
+      SQL
+      @connection.execute(<<~SQL)
+        INSERT INTO nico_tag_relations (id, tag_id, nico_tag_id) VALUES
+          (1, 1, 4), (2, 2, 4), (3, 1, 3), (4, 2, 3)
+      SQL
+      @connection.execute(<<~SQL)
+        INSERT INTO tag_implications (id, tag_id, parent_tag_id) VALUES
+          (1, 1, 4), (2, 2, 1), (3, 1, 2), (4, 2, 3)
+      SQL
+      @connection.execute('INSERT INTO tag_versions (tag_id) VALUES (1), (2)')
+      @connection.execute('INSERT INTO nico_tag_versions (tag_id) VALUES (3), (4)')
+      @connection.execute('INSERT INTO material_versions (tag_id) VALUES (1), (2)')
+    end
+
+    it 'removes discarded records and their links while retaining aliases and history' do
+      [DeleteDiscardedRecordsFromTags, DeleteDiscardedRecordsFromTagNames].each do |klass|
+        migration = klass.new
+        allow(migration).to receive(:connection).and_return(@connection)
+        migration.suppress_messages { migration.up }
+      end
+
+      expect(@connection.select_values('SELECT id FROM tags ORDER BY id')).to eq([1, 4])
+      expect(@connection.select_rows('SELECT id, canonical_id FROM tag_names ORDER BY id'))
+          .to eq([[1, nil], [2, 1], [4, nil]])
+      expect(@connection.select_values('SELECT id FROM nico_tag_relations')).to eq([1])
+      expect(@connection.select_values('SELECT id FROM tag_implications')).to eq([1])
+      expect(@connection.select_values('SELECT tag_id FROM tag_versions ORDER BY tag_id'))
+          .to eq([1, 2])
+      expect(@connection.select_values('SELECT tag_id FROM nico_tag_versions ORDER BY tag_id'))
+          .to eq([3, 4])
+      expect(@connection.select_values('SELECT tag_id FROM material_versions ORDER BY tag_id'))
+          .to eq([1, 2])
+
+      [:tags, :tag_names].each do |table|
+        expect(@connection.column_exists?(table, :discarded_at)).to be(false)
+        expect(@connection.index_exists?(table, :discarded_at)).to be(false)
+      end
+      [:tag_versions, :nico_tag_versions, :material_versions].each do |table|
+        expect(@connection.foreign_key_exists?(table, :tags, column: :tag_id)).to be(false)
+      end
+      expect(@connection.foreign_key_exists?(:tags, :tag_names)).to be(true)
+      expect(@connection.foreign_key_exists?(:tag_names, :tag_names, column: :canonical_id))
+          .to be(true)
+      expect(@connection.index_exists?(:tag_names, :name, unique: true)).to be(true)
+      expect(@connection.index_exists?(:tags, :tag_name_id, unique: true)).to be(true)
+      [:nico_tag_relations, :tag_implications].each do |table|
+        expect(@connection.foreign_keys(table).map(&:to_table)).to eq(['tags', 'tags'])
+      end
+    end
+  end
+end

backend/spec/db/external_tags_spec.rb

@@ -0,0 +1,191 @@
+require 'rails_helper'
+require_relative '../../db/migrate/20260921040000_create_external_tags'
+require_relative '../../db/migrate/20260921050000_create_post_external_tags'
+require_relative '../../db/migrate/20260921060000_change_foreign_key_on_nico_tag_relations'
+require_relative '../../db/migrate/20260921230000_migrate_external_tags'
+
+RSpec.describe 'external tag migrations' do
+  self.use_transactional_tests = false
+
+  before do
+    record_class = Class.new(ActiveRecord::Base) do
+      self.abstract_class = true
+    end
+    stub_const('ExternalTagMigrationRecord', record_class)
+    config = ActiveRecord::Base.connection_db_config.configuration_hash
+    @database = "btrc_hub_test_external_tags_#{ Process.pid }_#{ SecureRandom.hex(4) }"
+    record_class.establish_connection(config.merge(database: nil))
+    @connection = record_class.lease_connection
+    @connection.create_database(@database)
+    @database_created = true
+    @connection.execute("USE #{ @connection.quote_table_name(@database) }")
+    version_class = Class.new(record_class) do
+      self.table_name = 'post_versions'
+    end
+    stub_const('MigrateExternalTags::MigrationPostVersion', version_class)
+    create_legacy_tables
+    seed_legacy_records
+  end
+
+  after do
+    @connection.drop_database(@database) if @database_created
+  ensure
+    ExternalTagMigrationRecord.remove_connection
+  end
+
+  def migrate klass
+    migration = klass.new
+    allow(migration).to receive(:connection).and_return(@connection)
+    migration.suppress_messages { migration.migrate(:up) }
+  end
+
+  def create_legacy_tables
+    @connection.create_table(:tag_names) { |t| t.string :name }
+    @connection.create_table(:tags) do |t|
+      t.references :tag_name, foreign_key: true
+      t.string :category
+      t.integer :post_count
+      t.datetime :created_at
+    end
+    @connection.create_table(:posts)
+    @connection.create_table(:post_tags) do |t|
+      t.references :post, foreign_key: true
+      t.references :tag, foreign_key: true
+      t.datetime :created_at
+    end
+    @connection.create_table(:nico_tag_versions) do |t|
+      t.bigint :tag_id
+      t.integer :version_no
+      t.string :name
+      t.datetime :created_at
+    end
+    @connection.create_table(:nico_tag_relations) do |t|
+      t.references :tag, foreign_key: true
+      t.references :nico_tag, foreign_key: { to_table: :tags }
+    end
+    [:post_tag_sections, :materials, :theatre_skip_event_tags].each do |table|
+      @connection.create_table(table) { |t| t.references :tag, foreign_key: true }
+    end
+    @connection.create_table(:tag_implications) do |t|
+      t.references :tag, foreign_key: true
+      t.references :parent_tag, foreign_key: { to_table: :tags }
+    end
+    @connection.create_table(:tag_similarities) do |t|
+      t.references :tag, foreign_key: true
+      t.references :target_tag, foreign_key: { to_table: :tags }
+    end
+    @connection.create_table(:post_versions) { |t| t.json :tags_json, null: false }
+    @connection.add_check_constraint(:post_versions, 'JSON_VALID(tags_json)',
+                                     name: 'chk_post_versions_tags_json_schema')
+  end
+
+  def seed_legacy_records
+    @connection.execute(<<~SQL)
+      INSERT INTO tag_names (id, name) VALUES (1, 'internal'), (2, 'nico:raw tag[]');
+    SQL
+    @connection.execute(<<~SQL)
+      INSERT INTO tags (id, tag_name_id, category, post_count, created_at) VALUES
+        (1, 1, 'general', 1, '2026-09-01'), (2, 2, 'nico', 1, '2026-09-02')
+    SQL
+    @connection.execute('INSERT INTO posts (id) VALUES (1)')
+    @connection.execute(<<~SQL)
+      INSERT INTO post_tags (post_id, tag_id, created_at) VALUES
+        (1, 1, '2026-09-03'), (1, 2, '2026-09-04')
+    SQL
+    @connection.execute(<<~SQL)
+      INSERT INTO nico_tag_versions (tag_id, version_no, name, created_at) VALUES
+        (2, 1, 'nico:raw tag[]', '2026-09-02'),
+        (3, 1, 'nico:deleted', '2026-09-01'),
+        (3, 2, 'nico:deleted_later', '2026-09-02')
+    SQL
+    @connection.execute('INSERT INTO nico_tag_relations (tag_id, nico_tag_id) VALUES (1, 2)')
+    @connection.execute(<<~SQL)
+      INSERT INTO tag_similarities (tag_id, target_tag_id) VALUES (1, 1), (1, 2), (2, 1)
+    SQL
+    @connection.execute('INSERT INTO theatre_skip_event_tags (tag_id) VALUES (1), (2)')
+    @legacy_internal = { 'id' => 1, 'version_no' => 2,
+                         'name' => 'internal', 'category' => 'general',
+                         'sections' => [{ 'begin_ms' => 1000, 'end_ms' => nil }] }
+    snapshots = [@legacy_internal,
+                 { 'id' => 2, 'category' => 'nico' },
+                 { 'id' => 3, 'category' => 'nico' }]
+    @connection.execute(<<~SQL)
+      INSERT INTO post_versions (tags_json) VALUES
+        (#{ @connection.quote(snapshots.to_json) }), ('[]')
+    SQL
+  end
+
+  def prepare_external_tables
+    migrate(CreateExternalTags)
+    migrate(CreatePostExternalTags)
+    migrate(ChangeForeignKeyOnNicoTagRelations)
+  end
+
+  it 'preserves ids, raw names, counts, timestamps, post links and historical-only tags' do
+    prepare_external_tables
+
+    rows = @connection.select_rows(<<~SQL)
+      SELECT id, platform, name, post_count, DATE_FORMAT(created_at, '%Y-%m-%d')
+      FROM external_tags ORDER BY id
+    SQL
+    expect(rows).to eq([
+        [2, 'nico', 'raw tag[]', 1, '2026-09-02'],
+        [3, 'nico', 'deleted', 0, '2026-09-01']])
+    expect(@connection.select_rows(<<~SQL)).to eq([[1, 2, '2026-09-04']])
+      SELECT post_id, external_tag_id, DATE_FORMAT(created_at, '%Y-%m-%d')
+      FROM post_external_tags
+    SQL
+    expect(@connection.foreign_key_exists?(:nico_tag_relations, :external_tags,
+                                           column: :nico_tag_id)).to be(true)
+    expect(@connection.foreign_key_exists?(:nico_tag_relations, :tags,
+                                           column: :tag_id)).to be(true)
+  end
+
+  it 'converts snapshots and removes only obsolete internal rows and derived links' do
+    prepare_external_tables
+    migrate(MigrateExternalTags)
+
+    expect(@connection.select_values('SELECT id FROM tags')).to eq([1])
+    expect(@connection.select_values('SELECT id FROM tag_names')).to eq([1])
+    expect(@connection.select_values('SELECT tag_id FROM post_tags')).to eq([1])
+    expect(@connection.select_rows('SELECT tag_id, nico_tag_id FROM nico_tag_relations'))
+        .to eq([[1, 2]])
+    expect(@connection.select_rows('SELECT tag_id, target_tag_id FROM tag_similarities'))
+        .to eq([[1, 1]])
+    expect(@connection.select_values('SELECT tag_id FROM theatre_skip_event_tags')).to eq([1])
+    expect(@connection.select_value('SELECT COUNT(*) FROM nico_tag_versions')).to eq(3)
+    versions = MigrateExternalTags::MigrationPostVersion.order(:id)
+    expect(versions.first.tags_json).to eq([
+        @legacy_internal.except('id').merge('tag_id' => 1),
+        { 'external_tag_id' => 2 }, { 'external_tag_id' => 3 }])
+    expect(versions.last.tags_json).to eq([])
+
+    invalid_snapshots = [@legacy_internal,
+                         { 'external_tag_id' => 0 },
+                         { 'external_tag_id' => 2, 'tag_id' => 1 },
+                         { 'external_tag_id' => 2, 'name' => 'extra' },
+                         { 'tag_id' => 1, 'version_no' => 1 }]
+    invalid_snapshots.each do |snapshot|
+      expect {
+        MigrateExternalTags::MigrationPostVersion.create!(tags_json: [snapshot])
+      }.to raise_error(ActiveRecord::StatementInvalid, /check constraint/i)
+    end
+    expect { MigrateExternalTags.new.down }
+        .to raise_error(ActiveRecord::IrreversibleMigration)
+  end
+
+  { post_tag_sections: '(tag_id) VALUES (2)',
+    materials: '(tag_id) VALUES (2)',
+    tag_implications: '(tag_id, parent_tag_id) VALUES (1, 2)' }.each do |table, values|
+    it "aborts before deleting data when #{ table } references a legacy nico tag" do
+      prepare_external_tables
+      @connection.execute("INSERT INTO #{ table } #{ values }")
+
+      expect { migrate(MigrateExternalTags) }.to raise_error(RuntimeError, /#{ table }/)
+
+      expect(@connection.select_values('SELECT id FROM tags ORDER BY id')).to eq([1, 2])
+      expect(MigrateExternalTags::MigrationPostVersion.first.tags_json.first)
+          .to eq(@legacy_internal)
+    end
+  end
+end

backend/spec/factories/external_tags.rb

@@ -0,0 +1,6 @@
+FactoryBot.define do
+  factory :external_tag do
+    platform { :nico }
+    sequence(:name) { |n| "external_tag_#{ n }" }
+  end
+end

backend/spec/factories/tag_names.rb

@@ -1,5 +1,12 @@
 FactoryBot.define do
   factory :tag_name do
-    name { "tag-#{SecureRandom.hex(4)}" }
+    language_code { 'ja' }
+    script_code { 'Jpan' }
+    primary_flg { true }
+    sequence(:name) { |number| "tag-#{ SecureRandom.hex(4) }-#{ number }" }
+
+    trait :alias do
+      primary_flg { false }
+    end
   end
 end

backend/spec/factories/tags.rb

@@ -6,17 +6,15 @@ FactoryBot.define do
 
     category { :general }
     post_count { 0 }
+
     association :tag_name
 
     after(:build) do |tag, evaluator|
       tag.name = evaluator.name if evaluator.name.present?
     end
 
-    trait :nico do
+    after(:create) do |tag|
-      category { :nico }
+      tag.tag_name.update!(tag:) if tag.tag_name.tag_id != tag.id
-      transient do
-        name { "nico:#{ SecureRandom.hex(4) }" }
-      end
     end
   end
 end

backend/spec/models/external_tag_spec.rb

@@ -0,0 +1,38 @@
+require 'rails_helper'
+
+RSpec.describe ExternalTag, type: :model do
+  it 'preserves names without internal tag sanitisation or TagName records' do
+    external = nil
+
+    expect {
+      external = described_class.create!(platform: :nico, name: 'raw tag[]')
+    }.not_to change(TagName, :count)
+
+    expect(external.reload.name).to eq('raw tag[]')
+  end
+
+  it 'deletes post associations without deleting posts or version history' do
+    external = create(:external_tag)
+    post = create(:post)
+    PostExternalTag.create!(post:, external_tag: external)
+    version = NicoTagVersionRecorder.record!(
+        external_tag: external, event_type: :create, created_by_user: nil)
+
+    external.destroy!
+
+    expect(PostExternalTag.where(external_tag_id: external.id)).to be_empty
+    expect(post.reload.external_tags).to be_empty
+    expect(version.reload.tag_id).to eq(external.id)
+  end
+
+  it 'deletes external links without deleting linked internal tags' do
+    external = create(:external_tag)
+    tag = create(:tag)
+    NicoTagRelation.create!(nico_tag: external, tag:)
+
+    external.destroy!
+
+    expect(NicoTagRelation.where(nico_tag_id: external.id)).to be_empty
+    expect(Tag.exists?(tag.id)).to be(true)
+  end
+end

backend/spec/models/locale_spec.rb

@@ -0,0 +1,69 @@
+require 'rails_helper'
+
+RSpec.describe Locale, type: :model do
+  def prepare_french_reference!
+    Language.find_or_create_by!(code: 'fr') { _1.name = 'French' }
+    Script.find_or_create_by!(code: 'Latn') { _1.name = 'Latin' }
+  end
+
+  def create_french_locale!
+    prepare_french_reference!
+    described_class.create!(code: 'fr', language_code: 'fr',
+                            script_code: 'Latn', name: 'French')
+  end
+
+  it 'generates a primary name for every existing tag using the name generator' do
+    first = create(:tag, name: 'first_existing_tag')
+    second = create(:tag, name: 'second_existing_tag')
+    allow(TagName).to receive(:generate_name).and_call_original
+    allow(TagName).to receive(:generate_name)
+        .with(kind_of(described_class), first, first.name)
+        .and_return('name_from_generator')
+
+    locale = create_french_locale!
+
+    expect(TagName).to have_received(:generate_name).with(locale, first, first.name)
+    expect(TagName).to have_received(:generate_name).with(locale, second, second.name)
+    expect(first.tag_names.find_by!(language_code: 'fr', primary_flg: true))
+        .to have_attributes(name: 'name_from_generator', tag_id: first.id,
+                            language_code: 'fr', script_code: 'Latn',
+                            primary_flg: true)
+    expect(second.tag_names.find_by!(language_code: 'fr', primary_flg: true))
+        .to have_attributes(tag_id: second.id, language_code: 'fr',
+                            script_code: 'Latn', primary_flg: true)
+    expect(TagName.where(language_code: 'fr', primary_flg: true,
+                         tag_id: [first.id, second.id]).count).to eq(2)
+  end
+
+  it 'does not duplicate an existing primary name in the new language' do
+    prepare_french_reference!
+    tag = create(:tag, name: 'already_named')
+    existing = create(:tag_name, name: 'nom_existant', tag:,
+                                 language_code: 'fr', script_code: 'Latn')
+
+    create_french_locale!
+
+    expect(TagName.where(tag_id: tag.id, language_code: 'fr', primary_flg: true))
+        .to contain_exactly(existing)
+    expect(existing.reload).to have_attributes(
+        tag_id: tag.id, language_code: 'fr', script_code: 'Latn', primary_flg: true)
+  end
+
+  it 'creates a primary name when the language has only an alias' do
+    prepare_french_reference!
+    tag = create(:tag, name: 'alias_only_tag')
+    alias_name = create(:tag_name, :alias, name: 'alias_fr',
+                                          tag:,
+                                          language_code: 'fr', script_code: 'Latn')
+
+    create_french_locale!
+
+    expect(alias_name.reload).to have_attributes(
+        tag_id: tag.id,
+        language_code: 'fr', script_code: 'Latn', primary_flg: false)
+    generated = TagName.find_by!(tag_id: tag.id, language_code: 'fr', primary_flg: true)
+    expect(generated).to have_attributes(tag_id: tag.id, language_code: 'fr',
+                                         script_code: 'Latn', primary_flg: true)
+    expect(TagName.where(tag_id: tag.id, language_code: 'fr', primary_flg: true).count).to eq(1)
+  end
+end

backend/spec/models/material_export_item_spec.rb

@@ -2,7 +2,7 @@ require 'rails_helper'
 
 RSpec.describe MaterialExportItem, type: :model do
   let(:user) { create(:user, :member) }
-  let(:tag) { Tag.create!(tag_name: TagName.create!(name: 'export_item'), category: :material) }
+  let(:tag) { create(:tag, name: 'export_item', category: :material) }
   let(:material) do
     Material.create!(tag:, url: 'https://example.com/material',
                      created_by_user: user, updated_by_user: user)

backend/spec/models/nico_tag_relation_spec.rb

@@ -0,0 +1,27 @@
+require 'rails_helper'
+
+RSpec.describe NicoTagRelation, type: :model do
+  it 'does not constrain the ExternalTag association to the nico platform' do
+    external_tag = create(:external_tag)
+    tag = create(:tag)
+    allow(external_tag).to receive(:platform).and_return('registered_external')
+    allow(external_tag).to receive(:nico?).and_return(false)
+
+    expect {
+      described_class.create!(nico_tag: external_tag, tag:)
+    }.to change(described_class, :count).by(1)
+    expect(tag.linked_nico_tags).to contain_exactly(external_tag)
+  end
+
+  it 'rejects an internal Tag through the external association type' do
+    expect {
+      described_class.new(nico_tag: create(:tag), tag: create(:tag))
+    }.to raise_error(ActiveRecord::AssociationTypeMismatch)
+  end
+
+  it 'rejects an ExternalTag through the internal association type' do
+    expect {
+      described_class.new(nico_tag: create(:external_tag), tag: create(:external_tag))
+    }.to raise_error(ActiveRecord::AssociationTypeMismatch)
+  end
+end

backend/spec/models/post_external_tag_spec.rb

@@ -0,0 +1,25 @@
+require 'rails_helper'
+
+RSpec.describe PostExternalTag, type: :model do
+  it 'exposes both sides and enforces a unique post and external tag pair' do
+    post = create(:post)
+    external_tag = create(:external_tag)
+    described_class.create!(post:, external_tag:)
+
+    expect(post.external_tags).to contain_exactly(external_tag)
+    expect(external_tag.posts).to contain_exactly(post)
+    expect { described_class.create!(post:, external_tag:) }
+        .to raise_error(ActiveRecord::RecordNotUnique)
+  end
+
+  it 'removes associations when the post is deleted while retaining the external tag' do
+    post = create(:post)
+    external_tag = create(:external_tag)
+    described_class.create!(post:, external_tag:)
+
+    post.destroy!
+
+    expect(described_class.where(post_id: post.id)).to be_empty
+    expect(external_tag.reload.posts).to be_empty
+  end
+end

backend/spec/models/post_spec.rb

@@ -6,6 +6,25 @@ RSpec.describe Post, type: :model do
     PostUrlSanitisationRule.unscoped.delete_all
   end
 
+  describe '#snapshot_tags_json' do
+    it 'keeps internal snapshots and external identifiers distinct, even with the same id' do
+      post = create(:post)
+      tag = create(:tag)
+      external = create(:external_tag, id: tag.id)
+      create(:post_tag, post:, tag:)
+      create(:post_tag_section, post:, tag:, begin_ms: 2000, end_ms: nil)
+      PostExternalTag.create!(post:, external_tag: external)
+
+      expect(post.snapshot_tags_json).to eq([
+          { 'tag_id' => tag.id,
+            'version_no' => tag.version_no,
+            'name' => tag.name,
+            'category' => tag.category,
+            'sections' => [{ 'begin_ms' => 2000, 'end_ms' => nil }] },
+          { 'external_tag_id' => external.id }])
+    end
+  end
+
   describe 'URL normalisation' do
     it 'normalises the HTTP URL before applying sanitisation rules' do
       PostUrlSanitisationRule.create!(
@@ -110,7 +129,7 @@ RSpec.describe Post, type: :model do
     end
 
     describe '.resized_thumbnail_attachment' do
-      it 'centre-crops a wide image to 180x180 without distorting it' do
+      it 'fits a wide image within 180x180 without distorting it' do
         blob = image_blob(
             width: 360,
             height: 180,
@@ -123,13 +142,13 @@ RSpec.describe Post, type: :model do
         resized = described_class.resized_thumbnail_attachment(upload_for(blob))
         image = read_image(resized)
 
-        expect(image.dimensions).to eq([180, 180])
+        expect(image.dimensions).to eq([180, 90])
-        expect_green(colour_at(image, 0, 90))
+        expect_red(colour_at(image, 0, 45))
-        expect_green(colour_at(image, 90, 90))
+        expect_green(colour_at(image, 90, 45))
-        expect_green(colour_at(image, 179, 90))
+        expect_red(colour_at(image, 179, 45))
       end
 
-      it 'centre-crops a tall image to 180x180 without distorting it' do
+      it 'fits a tall image within 180x180 without distorting it' do
         blob = image_blob(
             width: 180,
             height: 360,
@@ -142,10 +161,10 @@ RSpec.describe Post, type: :model do
         resized = described_class.resized_thumbnail_attachment(upload_for(blob))
         image = read_image(resized)
 
-        expect(image.dimensions).to eq([180, 180])
+        expect(image.dimensions).to eq([90, 180])
-        expect_green(colour_at(image, 90, 0))
+        expect_red(colour_at(image, 45, 0))
-        expect_green(colour_at(image, 90, 90))
+        expect_green(colour_at(image, 45, 90))
-        expect_green(colour_at(image, 90, 179))
+        expect_red(colour_at(image, 45, 179))
       end
 
       it 'keeps a square image square without distortion' do
@@ -192,7 +211,7 @@ RSpec.describe Post, type: :model do
 
         expect(post.thumbnail).to be_attached
         image = read_image(post.thumbnail)
-        expect(image.dimensions).to eq([180, 180])
+        expect(image.dimensions).to eq([180, 135])
       end
 
       it 'does not attach anything when thumbnail conversion fails' do

backend/spec/models/post_tag_spec.rb

@@ -1,5 +1,73 @@
+require 'rails_helper'
+
 RSpec.describe PostTag, type: :model do
+  describe 'uniqueness' do
+    it 'rejects duplicate post and tag pairs but allows either to be reused' do
+      post_tag = create(:post_tag)
+      duplicate = build(:post_tag, post: post_tag.post, tag: post_tag.tag)
+
+      expect(duplicate).not_to be_valid
+      expect(duplicate.errors.of_kind?(:post_id, :taken)).to be(true)
+      expect(build(:post_tag, post: post_tag.post, tag: create(:tag))).to be_valid
+      expect(build(:post_tag, post: create(:post), tag: post_tag.tag)).to be_valid
+    end
+
+    it 'enforces uniqueness in the database when validation is bypassed' do
+      post_tag = create(:post_tag)
+      duplicate = build(:post_tag, post: post_tag.post, tag: post_tag.tag)
+
+      expect { duplicate.save!(validate: false) }
+          .to raise_error(ActiveRecord::RecordNotUnique)
+    end
+  end
+
+  describe '#destroy!' do
+    it 'deletes only the selected pair and its sections and updates the counter' do
+      post_tag = create(:post_tag)
+      same_post = create(:post_tag, post: post_tag.post)
+      same_tag = create(:post_tag, tag: post_tag.tag)
+      sections = [post_tag, same_post, same_tag].map do |link|
+        create(:post_tag_section, post: link.post, tag: link.tag,
+                                  begin_ms: 1000, end_ms: 2000)
+      end
+
+      expect { post_tag.destroy! }.to change(described_class, :count).by(-1)
+          .and change(PostTagSection, :count).by(-1)
+          .and change { post_tag.tag.reload.post_count }.from(2).to(1)
+
+      expect(described_class.exists?(post: post_tag.post, tag: post_tag.tag)).to be(false)
+      expect(same_post.reload).to be_persisted
+      expect(same_tag.reload).to be_persisted
+      expect(PostTagSection.all).to contain_exactly(*sections.drop(1))
+      expect(post_tag.post.reload.tags).to contain_exactly(same_post.tag)
+      expect(post_tag.tag.reload.posts).to contain_exactly(same_tag.post)
+    end
+
+    it 'allows a removed tag to be added again without restoring old sections' do
+      post_tag = create(:post_tag)
+      create(:post_tag_section, post: post_tag.post, tag: post_tag.tag,
+                                begin_ms: 1000, end_ms: 2000)
+      post_tag.destroy!
+
+      replacement = create(:post_tag, post: post_tag.post, tag: post_tag.tag)
+
+      expect(replacement.reload.sections).to be_empty
+      expect(replacement.tag.reload.post_count).to eq(1)
+    end
+  end
+
   describe '#sections' do
+    it 'loads the owning post_tag from a section using both keys' do
+      post_tag = create(:post_tag)
+      create(:post_tag, post: post_tag.post)
+      create(:post_tag, tag: post_tag.tag)
+      section = create(:post_tag_section, post: post_tag.post,
+                                         tag: post_tag.tag,
+                                         begin_ms: 1000, end_ms: 2000)
+
+      expect(section.reload.post_tag).to eq(post_tag)
+    end
+
     it 'loads sections by post_id and tag_id' do
       post_tag = create(:post_tag)
       section = create(:post_tag_section,
@@ -12,18 +80,25 @@ RSpec.describe PostTag, type: :model do
     end
 
     it 'does not load sections for another tag on the same post' do
-      post = create(:post)
+      post_tag = create(:post_tag)
-      tag = create(:tag)
+      post = post_tag.post
       other_tag = create(:tag)
 
-      post_tag = create(:post_tag, post:, tag:)
+      own_section = create(:post_tag_section,
+                           post:,
+                           tag: post_tag.tag,
+                           begin_ms: 1000,
+                           end_ms: 2000)
+
+      create(:post_tag, post:, tag: other_tag)
+
       create(:post_tag_section,
              post:,
              tag: other_tag,
              begin_ms: 1000,
              end_ms: 2000)
 
-      expect(post_tag.sections).to be_empty
+      expect(post_tag.reload.sections).to contain_exactly(own_section)
     end
 
     it 'allows open-ended sections' do

backend/spec/models/post_version_spec.rb

@@ -1,8 +1,8 @@
 require 'rails_helper'
 
 RSpec.describe PostVersion, type: :model do
-  let!(:tag_name) { TagName.create!(name: 'post_version_spec_tag') }
+  let!(:tag_name) { create(:tag_name, name: 'post_version_spec_tag') }
-  let!(:tag) { Tag.create!(tag_name: tag_name, category: :general) }
+  let!(:tag) { create(:tag, tag_name: tag_name, category: :general) }
 
   let!(:post_record) do
     Post.create!(title: 'spec post', url: 'https://example.com/post-version-spec').tap do |post|
@@ -19,6 +19,7 @@ RSpec.describe PostVersion, type: :model do
       url: post_record.url,
       thumbnail_base: post_record.thumbnail_base,
       tags: post_record.snapshot_tag_names.join(' '),
+      tags_json: post_record.snapshot_tags_json,
       parent_post_ids: post_record.snapshot_parent_post_ids.join(' '),
       original_created_from: post_record.original_created_from,
       original_created_before: post_record.original_created_before,

backend/spec/models/tag_name_sanitisation_rule_spec.rb

@@ -34,9 +34,41 @@ RSpec.describe TagNameSanitisationRule, type: :model do
       described_class.create!(priority: 10, source_pattern: '_', replacement: '')
     end
 
+    context 'when only another language has the sanitised name' do
+      include_context 'English locale'
+
+      it 'keeps both names when sanitisation produces a cross-language match' do
+        japanese = create(:tag_name, name: 'foobar')
+        english = create(:tag_name, name: 'temporary',
+                                   language_code: 'en', script_code: 'Latn')
+        english.update_columns(name: 'foo_bar')
+
+        expect { described_class.apply! }.not_to change(TagName, :count)
+
+        expect(english.reload).to have_attributes(name: 'foobar', language_code: 'en')
+        expect(japanese.reload).to have_attributes(name: 'foobar', language_code: 'ja')
+      end
+
+      it 'renames without merging tags or deleting either language identity' do
+        japanese = create(:tag, name: 'foobar')
+        english_name = create(:tag_name, name: 'temporary',
+                                        language_code: 'en', script_code: 'Latn')
+        english = create(:tag, tag_name: english_name)
+        english_name.update_columns(name: 'foo_bar')
+
+        described_class.apply!
+
+        expect(english_name.reload).to have_attributes(
+            name: 'foobar', language_code: 'en', tag_id: english.id)
+        expect(japanese.reload.tag_name).to have_attributes(
+            name: 'foobar', language_code: 'ja', tag_id: japanese.id)
+        expect(english.reload.tag_name_id).to eq(english_name.id)
+      end
+    end
+
     context 'when no conflicting tag_name exists' do
       let!(:tag_name) do
-        TagName.create!(name: 'tmp').tap do |tn|
+        create(:tag_name, name: 'tmp').tap do |tn|
           tn.update_columns(name: 'foo_bar', updated_at: Time.current)
         end
       end
@@ -47,23 +79,23 @@ RSpec.describe TagNameSanitisationRule, type: :model do
       end
     end
 
-    context 'when a conflicting canonical tag_name exists' do
+    context 'when a conflicting primary tag name exists' do
-      let!(:existing) { TagName.create!(name: 'foobar') }
+      let!(:existing) { create(:tag_name, name: 'foobar') }
       let!(:source) do
-        TagName.create!(name: 'tmp').tap do |tn|
+        create(:tag_name, name: 'tmp').tap do |tn|
           tn.update_columns(name: 'foo_bar', updated_at: Time.current)
         end
       end
 
       it 'deletes the source tag_name' do
         described_class.apply!
-        expect(TagName.exists?(source.id)).to be(false)
+        expect(TagName.unscoped.exists?(source.id)).to be(false)
         expect(existing.reload.name).to eq('foobar')
       end
     end
 
     context 'when the source tag_name has a tag and the existing one has no tag' do
-      let!(:existing) { TagName.create!(name: 'foobar') }
+      let!(:existing) { create(:tag_name, name: 'foobar') }
       let!(:source_tag) { create(:tag, name: 'tmp', category: :general) }
       let!(:source_tag_name_id) { source_tag.tag_name_id }
 
@@ -73,18 +105,41 @@ RSpec.describe TagNameSanitisationRule, type: :model do
 
       it 'moves the tag to the existing tag_name' do
         described_class.apply!
-        expected_tag_name_id = existing.canonical_id || existing.id
+        expect(source_tag.reload.tag_name_id).to eq(existing.id)
-        expect(source_tag.reload.tag_name_id).to eq(expected_tag_name_id)
+        expect(TagName.unscoped.exists?(source_tag_name_id)).to be(false)
-        expect(TagName.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) }
+      let!(:alias_name) do
+        create(:tag_name, :alias, name: 'foobar', tag: existing_tag)
+      end
+      let!(:source) do
+        create(:tag_name, name: 'tmp').tap do |tn|
+          tn.update_columns(name: 'foo_bar', updated_at: Time.current)
+        end
+      end
+
+      it 'deletes only the source and preserves the alias and its owning tag' do
+        described_class.apply!
+
+        expect(TagName.unscoped.exists?(source.id)).to be(false)
+        expect(alias_name.reload).to have_attributes(
+            tag_id: existing_tag.id, language_code: 'ja', primary_flg: false)
+        expect(TagName.find_by!(tag_id: existing_tag.id,
+                                language_code: 'ja', primary_flg: true))
+            .to eq(existing_tag.tag_name)
+        expect(Tag.find(existing_tag.id)).to eq(existing_tag)
       end
     end
 
     context 'when both source and existing tag_names have tags' do
-      let!(:existing_tn) { TagName.create!(name: 'foobar') }
+      let!(:existing_tn) { create(:tag_name, name: 'foobar') }
-      let!(:existing_tag) { Tag.create!(tag_name: existing_tn, category: :general) }
+      let!(:existing_tag) { create(:tag, tag_name: existing_tn, category: :general) }
 
-      let!(:source_tn) { TagName.create!(name: 'tmp') }
+      let!(:source_tn) { create(:tag_name, name: 'tmp') }
-      let!(:source_tag) { Tag.create!(tag_name: source_tn, category: :general) }
+      let!(:source_tag) { create(:tag, tag_name: source_tn, category: :general) }
       let!(:source_tag_name_id) { source_tn.id }
 
       before do
@@ -92,13 +147,15 @@ RSpec.describe TagNameSanitisationRule, type: :model do
       end
 
       it 'merges the source tag into the existing tag and deletes the source tag_name' do
-        expect(TagName.find_by(name: 'foobar')&.tag&.id).to eq(existing_tag.id)
+        post = create(:post)
-        expect(TagName.find_by(name: 'foo_bar')&.tag&.id).to eq(source_tag.id)
+        PostTag.create!(post:, tag: source_tag)
 
         described_class.apply!
 
-        expect(Tag.exists?(source_tag.id)).to be(false)
+        expect(Tag.unscoped.exists?(source_tag.id)).to be(false)
-        expect(TagName.exists?(source_tag.tag_name_id)).to be(false)
+        expect(TagName.unscoped.exists?(source_tag_name_id)).to be(false)
+        expect(post.reload.tags).to contain_exactly(existing_tag)
+        expect(existing_tag.reload.name).to eq('foobar')
       end
     end
   end

backend/spec/models/tag_name_spec.rb

@@ -0,0 +1,94 @@
+require 'rails_helper'
+
+RSpec.describe TagName, type: :model do
+  include_context 'English locale'
+
+  it 'allows the same name in different languages' do
+    create(:tag_name, name: 'shared_name')
+    english = build(:tag_name, name: 'shared_name',
+                              language_code: 'en', script_code: 'Latn')
+
+    expect(english).to be_valid
+    expect { english.save! }.to change(described_class, :count).by(1)
+  end
+
+  it 'rejects a duplicate name within the same language' do
+    create(:tag_name, name: 'shared_name')
+    duplicate = build(:tag_name, name: 'shared_name')
+
+    expect(duplicate).to be_invalid
+    expect(duplicate.errors.of_kind?(:name, :taken)).to be(true)
+  end
+
+  it 'creates Japanese factory names without requiring a tag' do
+    name = create(:tag_name)
+
+    expect(name.reload).to have_attributes(
+        language_code: 'ja', script_code: 'Jpan', primary_flg: true, tag_id: nil)
+  end
+
+  it 'persists both sides of the representative tag factory association' do
+    tag = create(:tag)
+
+    expect(tag.reload.tag_name.reload.tag_id).to eq(tag.id)
+    expect(tag.tag_name.tag).to eq(tag)
+    expect(described_class.find_by!(tag_id: tag.id, language_code: 'ja', primary_flg: true))
+        .to eq(tag.tag_name)
+  end
+
+  it 'persists an alias owned by the same tag as its primary name' do
+    tag = create(:tag)
+    alias_name = create(:tag_name, :alias, name: 'valid_alias', tag:)
+
+    expect(alias_name.reload).to have_attributes(
+        tag_id: tag.id,
+        primary_flg: false, language_code: 'ja')
+    primary = described_class.find_by!(tag_id: alias_name.tag_id,
+                                       language_code: alias_name.language_code,
+                                       primary_flg: true)
+    expect(primary).to eq(tag.tag_name)
+  end
+
+  describe '.canonicalise' do
+    it 'resolves the primary name of the alias language on the same tag' do
+      tag = create(:tag, name: '日本語正本')
+      english_primary = create(:tag_name, tag:, name: 'english_primary',
+                                          language_code: 'en', script_code: 'Latn')
+      english_alias = create(:tag_name, :alias, tag:, name: 'english_alias',
+                                                 language_code: 'en', script_code: 'Latn')
+      representative_id = tag.tag_name_id
+
+      primary = described_class.find_by!(tag_id: english_alias.tag_id,
+                                         language_code: english_alias.language_code,
+                                         primary_flg: true)
+
+      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)
+    end
+
+    it 'resolves only aliases in the requested language' do
+      japanese = create(:tag, name: 'japanese_canonical')
+      english_name = create(:tag_name, name: 'english_canonical',
+                                      language_code: 'en', script_code: 'Latn')
+      english = create(:tag, tag_name: english_name)
+      japanese_alias = create(:tag_name, :alias, name: 'shared_alias',
+                                                 tag: japanese)
+      english_alias = create(:tag_name, :alias, name: 'shared_alias',
+                                                tag: english,
+                                                language_code: 'en', script_code: 'Latn')
+
+      expect(japanese_alias.reload).to have_attributes(
+          tag_id: japanese.id,
+          primary_flg: false, language_code: 'ja')
+      expect(english_alias.reload).to have_attributes(
+          tag_id: english.id,
+          primary_flg: false, language_code: 'en')
+      expect(described_class.canonicalise(locale, ['shared_alias']))
+          .to eq(['english_canonical'])
+      expect(described_class.canonicalise(Locale.nipponese, ['shared_alias']))
+          .to eq(['japanese_canonical'])
+    end
+  end
+end

backend/spec/models/tag_spec.rb

@@ -1,20 +1,72 @@
 require 'rails_helper'
 
 RSpec.describe Tag, type: :model do
+  describe 'external tag separation' do
+    ['nico:reserved', 'NiCo:reserved'].each do |name|
+      it "rejects the reserved prefix #{ name } for internal tags" do
+        tag = build(:tag, name:)
+
+        expect(tag).to be_invalid
+        expect(tag.errors[:name]).to be_present
+        expect {
+          described_class.normalise_tags!(Locale.nipponese, [name])
+        }.to raise_error(Tag::NicoTagNormalisationError)
+      end
+    end
+
+    it 'finds external links by the internal tag id even when ids differ' do
+      tag = create(:tag)
+      external = create(:external_tag, id: tag.id + 10_000)
+      # The migration retains existing links without running model validation.
+      NicoTagRelation.insert_all!([{ tag_id: tag.id, nico_tag_id: external.id }])
+
+      expect(tag.linked_nico_tags).to contain_exactly(external)
+    end
+  end
+
   describe '.normalise_tags!' do
+    it 'canonicalises aliases in the supplied language only' do
+      Language.find_or_create_by!(code: 'en') { _1.name = 'English' }
+      Script.find_or_create_by!(code: 'Latn') { _1.name = 'Latin' }
+      Locale.insert_all!([
+          { code: 'en', language_code: 'en', script_code: 'Latn',
+            name: 'English', created_at: Time.current }]) unless Locale.exists?(code: 'en')
+      english_locale = Locale.find('en')
+      japanese = create(:tag, name: 'japanese_canonical')
+      english_name = create(:tag_name, name: 'english_canonical',
+                                      language_code: 'en', script_code: 'Latn')
+      english = create(:tag, tag_name: english_name)
+      japanese_alias = create(:tag_name, :alias, name: 'shared_alias',
+                                                 tag: japanese)
+      english_alias = create(:tag_name, :alias, name: 'shared_alias',
+                                                tag: english,
+                                                language_code: 'en', script_code: 'Latn')
+
+      expect(japanese_alias.reload).to have_attributes(
+          tag_id: japanese.id,
+          primary_flg: false, language_code: 'ja')
+      expect(english_alias.reload).to have_attributes(
+          tag_id: english.id,
+          primary_flg: false, language_code: 'en')
+      expect(described_class.normalise_tags!(
+          english_locale, ['shared_alias'],
+          with_tagme: false, with_no_deerjikist: false)).to eq([english])
+      expect(described_class.normalise_tags!(
+          Locale.nipponese, ['shared_alias'],
+          with_tagme: false, with_no_deerjikist: false)).to eq([japanese])
+    end
+
     it 'rejects deprecated tags when deny_deprecated is enabled' do
-      tag_name = TagName.create!(name: 'normalise deprecated tag')
+      tag_name = create(:tag_name, name: 'normalise deprecated tag')
-      deprecated_tag = Tag.create!(
+      deprecated_tag = create(:tag,
-        tag_name:,
+          tag_name:,
-        category: :general,
+          category: :general,
-        deprecated_at: 1.day.from_now
+          deprecated_at: 1.day.from_now)
-      )
 
       expect {
-        described_class.normalise_tags!(
+        described_class.normalise_tags!(Locale.nipponese,
-          [deprecated_tag.name],
+            [deprecated_tag.name],
-          deny_deprecated: true
+            deny_deprecated: true)
-        )
       }.to raise_error(Tag::DeprecatedTagNormalisationError) { |error|
         expect(error.tag_names).to eq([deprecated_tag.name])
       }
@@ -22,88 +74,79 @@ RSpec.describe Tag, type: :model do
 
     it 'rejects invalid section literals instead of treating them as zero' do
       expect {
-        described_class.normalise_tags!(
+        described_class.normalise_tags!(Locale.nipponese,
-          ['normalise_invalid_section[1:aa-2:00]'],
+            ['normalise_invalid_section[1:aa-2:00]'],
-          with_sections: true
+            with_sections: true)
-        )
       }.to raise_error(Tag::SectionLiteralParseError)
     end
 
     it 'parses open-ended section literals' do
-      result = described_class.normalise_tags!(
+      result = described_class.normalise_tags!(Locale.nipponese,
-        ['伊地知ニジカ[1:00-]'],
+          ['伊地知ニジカ[1:00-]'],
-        with_sections: true
+          with_sections: true)
-      )
 
       tag = result.fetch(:tags).find { _1.name == '伊地知ニジカ' }
       expect(result.fetch(:sections).fetch(tag.id)).to eq([[60_000, nil]])
     end
 
     it 'parses omitted begin as zero' do
-      result = described_class.normalise_tags!(
+      result = described_class.normalise_tags!(Locale.nipponese,
-        ['伊地知ニジカ[-1:00]'],
+          ['伊地知ニジカ[-1:00]'],
-        with_sections: true
+          with_sections: true)
-      )
 
       tag = result.fetch(:tags).find { _1.name == '伊地知ニジカ' }
       expect(result.fetch(:sections).fetch(tag.id)).to eq([[0, 60_000]])
     end
 
     it 'treats fully open section literals as plain tags' do
-      result = described_class.normalise_tags!(
+      result = described_class.normalise_tags!(Locale.nipponese,
-        ['伊地知ニジカ[-]'],
+          ['伊地知ニジカ[-]'],
-        with_sections: true
+          with_sections: true)
-      )
 
       tag = result.fetch(:tags).find { _1.name == '伊地知ニジカ' }
       expect(result.fetch(:sections)[tag.id]).to be_nil
     end
 
     it 'treats [0:00-] as a plain tag' do
-      result = described_class.normalise_tags!(
+      result = described_class.normalise_tags!(Locale.nipponese,
-        ['伊地知ニジカ[0:00-]'],
+          ['伊地知ニジカ[0:00-]'],
-        with_sections: true
+          with_sections: true)
-      )
 
       tag = result.fetch(:tags).find { _1.name == '伊地知ニジカ' }
       expect(result.fetch(:sections)[tag.id]).to be_nil
     end
 
     it 'expands zero-width sections to one millisecond' do
-      result = described_class.normalise_tags!(
+      result = described_class.normalise_tags!(Locale.nipponese,
-        ['伊地知ニジカ[1:00-1:00]'],
+          ['伊地知ニジカ[1:00-1:00]'],
-        with_sections: true
+          with_sections: true)
-      )
 
       tag = result.fetch(:tags).find { _1.name == '伊地知ニジカ' }
       expect(result.fetch(:sections).fetch(tag.id)).to eq([[60_000, 60_001]])
     end
 
     it 'swaps reversed section boundaries' do
-      result = described_class.normalise_tags!(
+      result = described_class.normalise_tags!(Locale.nipponese,
-        ['伊地知ニジカ[2:00-1:00]'],
+          ['伊地知ニジカ[2:00-1:00]'],
-        with_sections: true
+          with_sections: true)
-      )
 
       tag = result.fetch(:tags).find { _1.name == '伊地知ニジカ' }
       expect(result.fetch(:sections).fetch(tag.id)).to eq([[60_000, 120_000]])
     end
 
     it 'merges open-ended sections over later bounded sections' do
-      result = described_class.normalise_tags!(
+      result = described_class.normalise_tags!(Locale.nipponese,
-        ['伊地知ニジカ[1:00-][2:00-3:00]'],
+          ['伊地知ニジカ[1:00-][2:00-3:00]'],
-        with_sections: true
+          with_sections: true)
-      )
 
       tag = result.fetch(:tags).find { _1.name == '伊地知ニジカ' }
       expect(result.fetch(:sections).fetch(tag.id)).to eq([[60_000, nil]])
     end
 
     it 'merges adjacent bounded and open-ended sections' do
-      result = described_class.normalise_tags!(
+      result = described_class.normalise_tags!(Locale.nipponese,
-        ['伊地知ニジカ[1:00-3:00][3:00-]'],
+          ['伊地知ニジカ[1:00-3:00][3:00-]'],
-        with_sections: true
+          with_sections: true)
-      )
 
       tag = result.fetch(:tags).find { _1.name == '伊地知ニジカ' }
       expect(result.fetch(:sections).fetch(tag.id)).to eq([[60_000, nil]])
@@ -159,17 +202,109 @@ RSpec.describe Tag, type: :model do
     end
   end
 
-  describe 'deprecated validation' do
+  describe '.find_or_create_by_tag_name!' do
-    it 'rejects deprecated nico tags' do
+    context 'with an explicit locale' do
-      tag = build(
+      include_context 'English locale'
-        :tag,
-        name: 'nico:deprecated_validation',
-        category: :nico,
-        deprecated_at: Time.current
-      )
 
-      expect(tag).not_to be_valid
+      it 'creates the representative name with locale attributes and ownership' do
-      expect(tag.errors[:deprecated_at]).to include('ニコタグは廃止できません．')
+        tag = described_class.find_or_create_by_tag_name!(
+            locale, 'english_name', category: :character)
+
+        expect(tag.tag_name.reload).to have_attributes(
+            language_code: 'en', script_code: 'Latn',
+            primary_flg: true, tag_id: tag.id)
+        expect(tag.category).to eq('character')
+      end
+
+      it 'creates separate tag identities for the same name in different languages' do
+        japanese = described_class.find_or_create_by_tag_name!(
+            Locale.nipponese, 'same_name', category: :general)
+        english = described_class.find_or_create_by_tag_name!(
+            locale, 'same_name', category: :character)
+
+        expect(english).not_to eq(japanese)
+        expect(english.tag_name.language_code).to eq('en')
+        expect(japanese.tag_name.language_code).to eq('ja')
+        expect(described_class.find_or_create_by_tag_name!(
+            locale, 'same_name', category: :general)).to eq(english)
+        expect(described_class.find_or_create_by_tag_name!(
+            Locale.nipponese, 'same_name', category: :general)).to eq(japanese)
+      end
+
+      it 'preserves the V1 representative when looking up another primary language' do
+        tag = create(:tag, name: '日本語代表名')
+        representative_id = tag.tag_name_id
+        english = create(:tag_name, name: 'english_primary', tag:,
+            language_code: 'en', script_code: 'Latn')
+
+        found = described_class.find_or_create_by_tag_name!(
+            locale, english.name, category: :general)
+
+        expect(found).to eq(tag)
+        expect(tag.reload.tag_name_id).to eq(representative_id)
+        expect(english.reload.tag_id).to eq(tag.id)
+      end
+
+      it 'normalises names using the supplied locale' do
+        tags = described_class.normalise_tags!(
+            locale, ['character:normalised_english'],
+            with_tagme: false, with_no_deerjikist: false)
+
+        expect(tags.length).to eq(1)
+        expect(tags.first.tag_name).to have_attributes(
+            name: 'normalised_english', language_code: 'en', script_code: 'Latn',
+            primary_flg: true, tag_id: tags.first.id)
+      end
+    end
+
+    it 'creates a tag and name with the requested category after stripping whitespace' do
+      tag = nil
+
+      expect {
+        tag = described_class.find_or_create_by_tag_name!(Locale.nipponese,
+            '  lookup_new  ', category: :character)
+      }.to change(Tag, :count).by(1).and change(TagName, :count).by(1)
+
+      expect(tag.name).to eq('lookup_new')
+      expect(tag.category).to eq('character')
+    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
+      alias_name = create(:tag_name, :alias, name: 'lookup_alias', tag:)
+      expect(alias_name.reload).to have_attributes(
+          tag_id: tag.id,
+          primary_flg: false, language_code: 'ja')
+      found = nil
+
+      expect {
+        found = described_class.find_or_create_by_tag_name!(Locale.nipponese,
+            alias_name.name, category: :general)
+      }.to change(Tag, :count).by(0).and change(TagName, :count).by(0)
+
+      expect(found).to eq(tag)
+      expect(found.category).to eq('character')
+      expect(tag.reload.tag_name_id).to eq(representative_id)
+    end
+
+    it 'reuses the owning tag through another alias' do
+      tag = create(:tag)
+      primary = tag.tag_name
+      alias_name = create(:tag_name, :alias, name: 'lookup_alias', tag:)
+      other_alias = create(:tag_name, :alias, name: 'lookup_other_alias', tag:)
+
+      expect([alias_name.reload, other_alias.reload]).to all(have_attributes(
+          tag_id: tag.id,
+          primary_flg: false, language_code: 'ja'))
+
+      expect {
+        found = described_class.find_or_create_by_tag_name!(Locale.nipponese,
+            alias_name.name, category: :general)
+        expect(found).to eq(tag)
+      }.to change(Tag, :count).by(0).and change(TagName, :count).by(0)
+
+      expect(tag.reload.tag_name).to eq(primary)
     end
   end
 
@@ -185,19 +320,16 @@ RSpec.describe Tag, type: :model do
     context 'when merging a simple source tag' do
       let!(:source_post_tag) { PostTag.create!(post: post_record, tag: source_tag) }
 
-      it 'discards the source post_tag, creates an active target post_tag, discards the source tag, and aliases the source tag_name' do
+      it 'deletes the source tag, moves its post link, and keeps its name as an alias' do
         described_class.merge_tags!(target_tag, [source_tag])
 
-        source_pt = PostTag.with_discarded.find(source_post_tag.id)
+        target_link = PostTag.find_by(post: post_record, tag: target_tag)
-        active_target = PostTag.kept.find_by(post_id: post_record.id, tag_id: target_tag.id)
 
-        expect(source_pt.discarded_at).to be_present
+        expect(PostTag.exists?(post: post_record, tag: source_tag)).to be(false)
-        expect(source_pt.tag_id).to eq(source_tag.id)
+        expect(target_link).to be_present
-        expect(active_target).to be_present
+        expect(Tag.unscoped.exists?(source_tag.id)).to be(false)
-
+        expect(source_tag_name.reload).to have_attributes(
-        expect(Tag.with_discarded.find(source_tag.id)).to be_discarded
+            tag_id: target_tag.id, language_code: 'ja', primary_flg: false)
-        expect(TagName.with_discarded.find(source_tag_name.id)).not_to be_discarded
-        expect(source_tag_name.reload.canonical_id).to eq(target_tag.tag_name_id)
         expect(target_tag.reload.post_count).to eq(1)
       end
     end
@@ -206,39 +338,104 @@ RSpec.describe Tag, type: :model do
       let!(:target_post_tag) { PostTag.create!(post: post_record, tag: target_tag) }
       let!(:source_post_tag) { PostTag.create!(post: post_record, tag: source_tag) }
 
-      it 'discards the source post_tag, keeps one active target post_tag, discards the source tag, and aliases the source tag_name' do
+      it 'deletes the source link and preserves the existing target link' do
+        create(:post_tag_section, post: post_record, tag: source_tag,
+                                  begin_ms: 1000, end_ms: 2000)
+        target_section = create(:post_tag_section, post: post_record,
+                                                   tag: target_tag,
+                                                   begin_ms: 3000, end_ms: nil)
+
         described_class.merge_tags!(target_tag, [source_tag])
 
-        source_pt = PostTag.with_discarded.find(source_post_tag.id)
+        target_links = PostTag.where(post: post_record, tag: target_tag)
-        active = PostTag.kept.where(post_id: post_record.id, tag_id: target_tag.id)
 
-        expect(source_pt.discarded_at).to be_present
+        expect(PostTag.exists?(post: post_record, tag: source_tag)).to be(false)
-        expect(source_pt.tag_id).to eq(source_tag.id)
+        expect(target_links).to contain_exactly(target_post_tag)
-        expect(active.count).to eq(1)
+        expect(PostTagSection.where(post: post_record, tag: source_tag)).to be_empty
-        expect(active.first.id).to eq(target_post_tag.id)
+        expect(target_post_tag.reload.sections).to contain_exactly(target_section)
 
-        expect(Tag.with_discarded.find(source_tag.id)).to be_discarded
+        expect(Tag.unscoped.exists?(source_tag.id)).to be(false)
-        expect(TagName.with_discarded.find(source_tag_name.id)).not_to be_discarded
+        expect(source_tag_name.reload).to have_attributes(
-        expect(source_tag_name.reload.canonical_id).to eq(target_tag.tag_name_id)
+            tag_id: target_tag.id, language_code: 'ja', primary_flg: false)
         expect(target_tag.reload.post_count).to eq(1)
       end
     end
 
+    it 'keeps source history and records the new target alias after deleting the source' do
+      user = create_member_user!
+      source_name = source_tag.name
+      source_alias = create(:tag_name, :alias, name: 'merge_alias', tag: source_tag)
+      TagVersioning.ensure_snapshot!(source_tag, created_by_user: user)
+      original_version = source_tag.tag_versions.first
+
+      described_class.merge_tags!(target_tag, [source_tag], created_by_user: user)
+
+      versions = TagVersion.where(tag_id: source_tag.id).order(:version_no)
+      expect(versions.pluck(:version_no, :event_type))
+          .to eq([[1, 'create'], [2, 'discard']])
+      expect(versions.first).to eq(original_version)
+      expect(versions.last).to have_attributes(
+          name: source_name, aliases: source_alias.name, created_by_user: user)
+      expect(Tag.unscoped.exists?(source_tag.id)).to be(false)
+
+      target_versions = target_tag.tag_versions.order(:version_no)
+      expect(target_versions.pluck(:event_type)).to eq(['create', 'update'])
+      expect(target_versions.last.aliases.split).to eq([source_name])
+    end
+
+    it 'deletes source relationships while preserving unrelated relationships' do
+      parent = create(:tag)
+      child = create(:tag)
+      nico_tag = create(:external_tag)
+      TagImplication.create!(tag: source_tag, parent_tag: parent)
+      TagImplication.create!(tag: child, parent_tag: source_tag)
+      kept_implication = TagImplication.create!(tag: target_tag, parent_tag: parent)
+      NicoTagRelation.create!(tag: source_tag, nico_tag:)
+      kept_relation = NicoTagRelation.create!(tag: target_tag, nico_tag:)
+      TagSimilarity.create!(tag: source_tag, target_tag:, cos: 0.5)
+      TagSimilarity.create!(tag: target_tag, target_tag: source_tag, cos: 0.5)
+      kept_similarity = TagSimilarity.create!(tag: target_tag, target_tag: parent,
+                                               cos: 0.5)
+
+      described_class.merge_tags!(target_tag, [source_tag])
+
+      expect(TagImplication.all).to contain_exactly(kept_implication)
+      expect(NicoTagRelation.all).to contain_exactly(kept_relation)
+      expect(TagSimilarity.all).to contain_exactly(kept_similarity)
+      expect(TagVersion.where(tag_id: source_tag.id).order(:version_no).last.parent_tag_ids)
+          .to eq(parent.id.to_s)
+    end
+
+    it 'preserves material history referencing the deleted source tag' do
+      source_tag.update!(category: :material)
+      target_tag.update!(category: :material)
+      material = Material.create!(tag: source_tag, url: 'https://example.com/material')
+      version = MaterialVersionRecorder.record!(
+          material:, event_type: :create, created_by_user: nil)
+      material.update!(tag: target_tag)
+
+      described_class.merge_tags!(target_tag, [source_tag])
+
+      expect(version.reload).to have_attributes(
+          tag_id: source_tag.id, tag_name: source_tag_name.name, tag_category: 'material')
+      expect(Tag.unscoped.exists?(source_tag.id)).to be(false)
+      expect(material.reload.tag).to eq(target_tag)
+    end
+
     context 'when source_tags includes the target itself' do
       let!(:source_post_tag) { PostTag.create!(post: post_record, tag: source_tag) }
 
       it 'ignores the target in source_tags while still merging the source tag' do
         described_class.merge_tags!(target_tag, [source_tag, target_tag])
 
-        source_pt = PostTag.with_discarded.find(source_post_tag.id)
+        target_link = PostTag.find_by(post: post_record, tag: target_tag)
-        active_target = PostTag.kept.find_by(post_id: post_record.id, tag_id: target_tag.id)
 
         expect(Tag.find(target_tag.id)).to be_present
-        expect(Tag.with_discarded.find(source_tag.id)).to be_discarded
+        expect(Tag.unscoped.exists?(source_tag.id)).to be(false)
-        expect(source_pt.discarded_at).to be_present
+        expect(PostTag.exists?(post: post_record, tag: source_tag)).to be(false)
-        expect(source_pt.tag_id).to eq(source_tag.id)
+        expect(target_link).to be_present
-        expect(active_target).to be_present
+        expect(source_tag_name.reload).to have_attributes(
-        expect(source_tag_name.reload.canonical_id).to eq(target_tag.tag_name_id)
+            tag_id: target_tag.id, language_code: 'ja', primary_flg: false)
         expect(target_tag.reload.post_count).to eq(1)
       end
     end
@@ -260,18 +457,17 @@ RSpec.describe Tag, type: :model do
         )
       end
 
-      it 'still merges, but discards the source tag_name instead of aliasing it' do
+      it 'still merges and keeps the source name as an alias without validating it' do
         described_class.merge_tags!(target_tag, [source_tag])
 
-        source_pt = PostTag.with_discarded.find(source_post_tag.id)
+        target_link = PostTag.find_by(post: post_record, tag: target_tag)
-        active_target = PostTag.kept.find_by(post_id: post_record.id, tag_id: target_tag.id)
-        discarded_source_tag_name = TagName.with_discarded.find(source_tag_name.id)
 
-        expect(source_pt.discarded_at).to be_present
+        expect(PostTag.exists?(post: post_record, tag: source_tag)).to be(false)
-        expect(source_pt.tag_id).to eq(source_tag.id)
+        expect(target_link).to be_present
-        expect(active_target).to be_present
 
-        expect(Tag.with_discarded.find(source_tag.id)).to be_discarded
+        expect(Tag.unscoped.exists?(source_tag.id)).to be(false)
+        expect(source_tag_name.reload).to have_attributes(
+            tag_id: target_tag.id, language_code: 'ja', primary_flg: false)
         expect(target_tag.reload.post_count).to eq(1)
       end
     end
@@ -288,34 +484,30 @@ RSpec.describe Tag, type: :model do
             message: 'init')
       end
 
-      it 'rolls back the transaction' do
+      it 'rolls back earlier deletions, links, and history when a later source has a wiki' do
+        earlier_source = create(:tag)
+        earlier_name = earlier_source.tag_name
+        source_section = create(:post_tag_section, post: post_record,
+                                                   tag: source_tag,
+                                                   begin_ms: 1000, end_ms: 2000)
+
         expect {
-          described_class.merge_tags!(target_tag, [source_tag])
+          described_class.merge_tags!(target_tag, [earlier_source, source_tag])
         }.to raise_error(ActiveRecord::RecordInvalid)
 
-        expect(Tag.with_discarded.find(source_tag.id)).not_to be_discarded
+        expect(Tag.unscoped.exists?(earlier_source.id)).to be(true)
-        expect(TagName.with_discarded.find(source_tag_name.id)).not_to be_discarded
+        expect(earlier_name.reload).to have_attributes(
-        expect(PostTag.kept.find(source_post_tag.id).tag_id).to eq(source_tag.id)
+            tag_id: earlier_source.id, language_code: 'ja', primary_flg: true)
-        expect(PostTag.kept.find_by(post_id: post_record.id, tag_id: target_tag.id)).to be_nil
+        expect(TagVersion.where(tag_id: [earlier_source.id, source_tag.id, target_tag.id]))
-        expect(source_tag_name.reload.canonical_id).to be_nil
+            .to be_empty
-        expect(target_tag.reload.post_count).to eq(0)
+        expect(Tag.unscoped.exists?(source_tag.id)).to be(true)
-      end
+        expect(TagName.unscoped.exists?(source_tag_name.id)).to be(true)
-    end
+        expect(source_post_tag.reload.tag_id).to eq(source_tag.id)
-
+        expect(source_post_tag.sections).to contain_exactly(source_section)
-    context 'when merging a nico source tag' do
+        expect(PostTag.find_by(post: post_record, tag: target_tag)).to be_nil
-      let!(:target_tag) { create(:tag, category: :nico, name: 'nico:foo') }
+        expect(source_tag.reload.post_count).to eq(1)
-      let!(:source_tag) { create(:tag, category: :nico, name: 'nico:bar') }
+        expect(source_tag_name.reload).to have_attributes(
-      let!(:source_tag_name_id) { source_tag.tag_name_id }
+            tag_id: source_tag.id, language_code: 'ja', primary_flg: true)
-
-      it 'discards the source tag_name instead of aliasing it' do
-        described_class.merge_tags!(target_tag, [source_tag])
-
-        discarded_source_tag = Tag.with_discarded.find(source_tag.id)
-        discarded_source_tag_name = TagName.with_discarded.find(source_tag_name_id)
-
-        expect(discarded_source_tag).to be_discarded
-        expect(discarded_source_tag_name).to be_discarded
-        expect(discarded_source_tag_name.canonical_id).to be_nil
         expect(target_tag.reload.post_count).to eq(0)
       end
     end
@@ -333,6 +525,7 @@ RSpec.describe Tag, type: :model do
         url: post.url,
         thumbnail_base: post.thumbnail_base,
         tags: snapshot_tags(post),
+        tags_json: post.snapshot_tags_json,
         parent_post_ids: post.snapshot_parent_post_ids.join(' '),
         original_created_from: post.original_created_from,
         original_created_before: post.original_created_before,
@@ -364,12 +557,15 @@ RSpec.describe Tag, type: :model do
         expect(latest.event_type).to eq('update')
         expect(latest.created_by_user).to be_nil
         expect(latest.tags).to eq(snapshot_tags(post_record.reload))
+        expect(latest.tags_json.map { |item| item.fetch('tag_id') }).to eq([target_tag.id])
+        expect(affected_versions.first.tags_json.map { |item| item.fetch('tag_id') })
+            .to eq([source_tag.id])
 
         expect(unaffected_post.reload.post_versions.count).to eq(1)
       end
     end
 
-    context 'when the source tag has no active post_tags' do
+    context 'when the source tag has no post_tags' do
       let!(:another_post) do
         Post.create!(url: 'https://example.com/posts/3', title: 'another post')
       end

backend/spec/models/version_record_spec.rb

@@ -2,7 +2,7 @@ require 'rails_helper'
 
 RSpec.describe VersionRecord, type: :model do
   let!(:tag) { create(:tag, name: 'version_record_tag') }
-  let!(:nico_tag) { create(:tag, :nico, name: 'nico:version_record_tag') }
+  let!(:nico_tag) { create(:external_tag, name: 'version_record_tag') }
 
   it 'makes TagVersion read only after create' do
     version = TagVersion.create!(
@@ -42,10 +42,10 @@ RSpec.describe VersionRecord, type: :model do
 
   it 'makes NicoTagVersion read only after create' do
     version = NicoTagVersion.create!(
-      tag: nico_tag,
+      external_tag: nico_tag,
       version_no: 1,
       event_type: 'create',
-      name: nico_tag.name,
+      name: "nico:#{ nico_tag.name }",
       linked_tags: '',
       created_at: Time.current,
       created_by_user: nil
@@ -58,10 +58,10 @@ RSpec.describe VersionRecord, type: :model do
 
   it 'prevents NicoTagVersion destroy' do
     version = NicoTagVersion.create!(
-      tag: nico_tag,
+      external_tag: nico_tag,
       version_no: 1,
       event_type: 'create',
-      name: nico_tag.name,
+      name: "nico:#{ nico_tag.name }",
       linked_tags: '',
       created_at: Time.current,
       created_by_user: nil

backend/spec/requests/gekanator_learning_spec.rb

@@ -898,12 +898,11 @@ RSpec.describe 'Gekanator learning API', type: :request do
 
   describe 'GET /gekanator/questions' do
     it 'omits questions for deprecated tags' do
-      active_tag = Tag.create!(name: 'active_question_tag', category: :general)
+      active_tag = create(:tag, name: 'active_question_tag', category: :general)
-      deprecated_tag = Tag.create!(
+      deprecated_tag = create(:tag,
-        name: 'deprecated_question_tag',
+          name: 'deprecated_question_tag',
-        category: :general,
+          category: :general,
-        deprecated_at: Time.current
+          deprecated_at: Time.current)
-      )
 
       [active_tag, deprecated_tag].each do |question_tag|
         GekanatorQuestion.create!(

backend/spec/requests/gekanator_posts_spec.rb

@@ -4,12 +4,11 @@ require 'rails_helper'
 RSpec.describe 'Gekanator posts API', type: :request do
   describe 'GET /gekanator/posts' do
     it 'omits deprecated tags and returns the stored similarity cosine' do
-      active_tag = Tag.create!(name: 'active tag', category: :general)
+      active_tag = create(:tag, name: 'active tag', category: :general)
-      deprecated_tag = Tag.create!(
+      deprecated_tag = create(:tag,
-        name: 'deprecated tag',
+          name: 'deprecated tag',
-        category: :general,
+          category: :general,
-        deprecated_at: Time.current
+          deprecated_at: Time.current)
-      )
       post_record = Post.create!(title: 'source', url: 'https://example.com/source')
       target_post = Post.create!(title: 'target', url: 'https://example.com/target')
 

backend/spec/requests/locale_write_paths_spec.rb

@@ -0,0 +1,236 @@
+require 'rails_helper'
+
+RSpec.describe 'Locale propagation on write paths', type: :request do
+  include_context 'English locale'
+
+  let(:member) { create(:user, :member) }
+
+  before do
+    sign_in_as(member)
+  end
+
+  def expect_localised_tag(name, expected_locale)
+    tag_name = TagName.find_by!(name:, language_code: expected_locale.language_code)
+    expect(tag_name).to have_attributes(
+        script_code: expected_locale.script_code, primary_flg: true)
+    expect(tag_name.tag_id).to be_present
+    expect(tag_name.tag.tag_name_id).to eq(tag_name.id)
+    tag_name.tag
+  end
+
+  ['en', nil].each do |requested_locale|
+    context "with locale #{ requested_locale.inspect }" do
+      let(:locale_params) { requested_locale ? { locale: requested_locale } : { } }
+      let(:expected_locale) { requested_locale ? locale : Locale.nipponese }
+
+      it 'creates post tags in the requested language or Japanese fallback' do
+        post '/posts', params: locale_params.merge(
+            title: 'Locale post', url: 'https://example.com/locale-post',
+            tags: 'locale_post_tag', parent_post_ids: '')
+
+        expect(response).to have_http_status(:created), response.body
+        tag = expect_localised_tag('locale_post_tag', expected_locale)
+        expect(Post.find(json.fetch('id')).tags).to include(tag)
+      end
+
+      it 'updates post tags in the requested language or Japanese fallback' do
+        record = create(:post)
+        PostVersionRecorder.record!(post: record, event_type: :create, created_by_user: member)
+
+        put "/posts/#{ record.id }", params: locale_params.merge(
+            title: record.title, tags: 'locale_updated_tag', parent_post_ids: '',
+            base_version_no: record.reload.version_no)
+
+        expect(response).to have_http_status(:ok), response.body
+        tag = expect_localised_tag('locale_updated_tag', expected_locale)
+        expect(record.reload.tags).to include(tag)
+      end
+
+      it 'passes the resolved locale to bulk creation' do
+        # Worker propagation is exercised in post_bulk_creator_spec.
+        expect_any_instance_of(PostBulkCreator).to receive(:run)
+            .with(expected_locale).and_return(results: [])
+        manifest = [{ title: 'Bulk locale', url: 'https://example.com/bulk-locale',
+                      tags: 'bulk_locale_tag', parent_post_ids: '' }]
+
+        post '/posts/bulk', params: locale_params.merge(posts: JSON.generate(manifest)),
+                            headers: { 'CONTENT_TYPE' => 'multipart/form-data' }
+
+        expect(response).to have_http_status(:ok), response.body
+      end
+
+      it 'creates materials with tags in the resolved locale' do
+        post '/materials', params: locale_params.merge(
+            tag: 'locale_material', url: 'https://example.com/material')
+
+        expect(response).to have_http_status(:created), response.body
+        tag = expect_localised_tag('locale_material', expected_locale)
+        expect(Material.find(json.fetch('id')).tag).to eq(tag)
+      end
+
+      it 'updates materials with tags in the resolved locale' do
+        tag = create(:tag, category: :material)
+        material = Material.create!(tag:, url: 'https://example.com/material')
+
+        put "/materials/#{ material.id }", params: locale_params.merge(
+            tag: 'locale_material_updated', url: material.url)
+
+        expect(response).to have_http_status(:ok), response.body
+        resolved_tag = expect_localised_tag('locale_material_updated', expected_locale)
+        expect(material.reload.tag).to eq(resolved_tag)
+      end
+
+      it 'links Nico external tags to internal tags in the resolved locale' do
+        external = create(:external_tag)
+        NicoTagVersionRecorder.record!(
+            external_tag: external, event_type: :create, created_by_user: member)
+
+        put "/tags/nico/#{ external.id }", params: locale_params.merge(tags: 'locale_link')
+
+        expect(response).to have_http_status(:ok), response.body
+        tag = expect_localised_tag('locale_link', expected_locale)
+        expect(external.reload.linked_tags).to contain_exactly(tag)
+      end
+
+      it 'creates parent tags in the resolved locale' do
+        tag = create(:tag)
+
+        put "/tags/#{ tag.id }", params: locale_params.merge(
+            name: tag.name, category: tag.category, deprecated: false,
+            aliases: '', parent_tags: 'locale_parent')
+
+        expect(response).to have_http_status(:ok), response.body
+        parent = expect_localised_tag('locale_parent', expected_locale)
+        expect(TagImplication.where(tag:).pluck(:parent_tag_id)).to eq([parent.id])
+      end
+    end
+  end
+
+  context 'with existing names in both languages' do
+    let!(:english_name) do
+      create(:tag_name, name: 'shared_name', language_code: 'en', script_code: 'Latn')
+    end
+    let!(:english_tag) { create(:tag, tag_name: english_name, category: :material) }
+    let!(:japanese_tag) do
+      create(:tag, name: 'temporary_japanese', category: :general).tap do |tag|
+        # Isolate lookup from the separately tested uniqueness validation.
+        tag.tag_name.update_columns(name: 'shared_name')
+      end
+    end
+
+    it 'plans and creates the post using the English identity and category' do
+      post '/posts', params: {
+          locale: 'en', title: 'English identity',
+          url: 'https://example.com/english-identity', tags: 'shared_name', parent_post_ids: '' }
+
+      expect(response).to have_http_status(:created), response.body
+      record = Post.find(json.fetch('id'))
+      expect(record.tags).to include(english_tag)
+      expect(record.tags).not_to include(japanese_tag)
+      expect(english_tag.reload.category).to eq('material')
+      expect(japanese_tag.reload.category).to eq('general')
+    end
+
+    it 'updates the post using the English identity' do
+      record = create(:post)
+      PostVersionRecorder.record!(post: record, event_type: :create, created_by_user: member)
+
+      put "/posts/#{ record.id }", params: {
+          locale: 'en', title: record.title, tags: 'shared_name', parent_post_ids: '',
+          base_version_no: record.reload.version_no }
+
+      expect(response).to have_http_status(:ok), response.body
+      expect(record.reload.tags).to include(english_tag)
+      expect(record.tags).not_to include(japanese_tag)
+    end
+
+    it 'resolves the English material tag' do
+      post '/materials', params: {
+          locale: 'en', tag: 'shared_name', url: 'https://example.com/english-material' }
+
+      expect(response).to have_http_status(:created), response.body
+      expect(Material.find(json.fetch('id')).tag).to eq(english_tag)
+      expect(Material.where(tag: japanese_tag)).to be_empty
+    end
+
+    it 'resolves the English parent tag' do
+      child = create(:tag)
+
+      put "/tags/#{ child.id }", params: {
+          locale: 'en', name: child.name, category: child.category, deprecated: false,
+          aliases: '', parent_tags: 'shared_name' }
+
+      expect(response).to have_http_status(:ok), response.body
+      expect(TagImplication.where(tag: child).pluck(:parent_tag_id)).to eq([english_tag.id])
+    end
+
+    it 'resolves the English internal tag for a Nico link' do
+      external = create(:external_tag)
+      NicoTagVersionRecorder.record!(
+          external_tag: external, event_type: :create, created_by_user: member)
+
+      put "/tags/nico/#{ external.id }", params: { locale: 'en', tags: 'shared_name' }
+
+      expect(response).to have_http_status(:ok), response.body
+      expect(external.reload.linked_tags).to contain_exactly(english_tag)
+    end
+  end
+
+  context 'when renaming or updating aliases in English' do
+    let!(:english_name) do
+      create(:tag_name, name: 'english_original', language_code: 'en', script_code: 'Latn')
+    end
+    let!(:tag) { create(:tag, tag_name: english_name) }
+
+    it 'allows a rename to a name already used in Japanese' do
+      japanese = create(:tag, name: 'rename_target')
+
+      patch "/tags/#{ tag.id }", params: { locale: 'en', name: 'rename_target' }
+
+      expect(response).to have_http_status(:ok), response.body
+      expect(tag.reload.tag_name).to have_attributes(
+          name: 'rename_target', language_code: 'en', tag_id: tag.id)
+      expect(japanese.reload.tag_name).to have_attributes(
+          name: 'rename_target', language_code: 'ja', tag_id: japanese.id)
+    end
+
+    it 'creates aliases in the requested language' do
+      put "/tags/#{ tag.id }", params: {
+          locale: 'en', name: tag.name, category: tag.category, deprecated: false,
+          aliases: 'english_alias', parent_tags: '' }
+
+      expect(response).to have_http_status(:ok), response.body
+      expect(TagName.find_by!(language_code: 'en', name: 'english_alias'))
+          .to have_attributes(
+              script_code: 'Latn',
+              tag_id: tag.id, primary_flg: false, language_code: 'en')
+      expect(tag.reload.tag_name_id).to eq(english_name.id)
+      primary = TagName.find_by!(tag_id: tag.id, language_code: 'en', primary_flg: true)
+      expect(primary).to have_attributes(name: 'english_original', script_code: 'Latn')
+    end
+
+    it 'does not take an alias from another language' do
+      japanese = create(:tag, name: 'japanese_owner')
+      japanese_alias = create(:tag_name, :alias, name: 'shared_alias',
+                                                tag: japanese)
+      expect(japanese_alias.reload).to have_attributes(
+          tag_id: japanese.id,
+          primary_flg: false, language_code: 'ja')
+
+      put "/tags/#{ tag.id }", params: {
+          locale: 'en', name: tag.name, category: tag.category, deprecated: false,
+          aliases: 'shared_alias', parent_tags: '' }
+
+      expect(response).to have_http_status(:ok), response.body
+      expect(japanese_alias.reload).to have_attributes(
+          tag_id: japanese.id,
+          primary_flg: false, language_code: 'ja')
+      expect(TagName.find_by!(language_code: 'en', name: 'shared_alias'))
+          .to have_attributes(
+              tag_id: tag.id, script_code: 'Latn',
+              primary_flg: false, language_code: 'en')
+      expect(TagName.where(name: 'shared_alias').pluck(:language_code, :tag_id))
+          .to contain_exactly(['ja', japanese.id], ['en', tag.id])
+    end
+  end
+end

backend/spec/requests/materials_spec.rb

@@ -26,10 +26,10 @@ RSpec.describe 'Materials API', type: :request do
 
   describe 'GET /materials' do
     let!(:tag_a) do
-      Tag.create!(tag_name: TagName.create!(name: 'material_index_a'), category: :material)
+      create(:tag, name: 'material_index_a', category: :material)
     end
     let!(:tag_b) do
-      Tag.create!(tag_name: TagName.create!(name: 'material_index_b'), category: :material)
+      create(:tag, name: 'material_index_b', category: :material)
     end
 
     let!(:material_a) do
@@ -116,20 +116,20 @@ RSpec.describe 'Materials API', type: :request do
 
     it 'filters by descendant tags and returns stable parent tag groups' do
       root =
-          Tag.create!(tag_name: TagName.create!(name: 'material_scope_root'),
+          create(:tag, name: 'material_scope_root',
                       category: :material)
       child_b =
-          Tag.create!(tag_name: TagName.create!(name: 'material_scope_b'),
+          create(:tag, name: 'material_scope_b',
                       category: :material)
       child_a =
-          Tag.create!(tag_name: TagName.create!(name: 'material_scope_a'),
+          create(:tag, name: 'material_scope_a',
                       category: :material)
       deprecated =
-          Tag.create!(tag_name: TagName.create!(name: 'material_scope_old'),
+          create(:tag, name: 'material_scope_old',
                       category: :material,
                       deprecated_at: Time.current)
       grandchild =
-          Tag.create!(tag_name: TagName.create!(name: 'material_scope_grandchild'),
+          create(:tag, name: 'material_scope_grandchild',
                       category: :material)
       root_material =
           build_material(tag: root, user: member_user,
@@ -179,7 +179,7 @@ RSpec.describe 'Materials API', type: :request do
 
   describe 'GET /materials/:id' do
     let!(:tag) do
-      Tag.create!(tag_name: TagName.create!(name: 'material_show'), category: :material)
+      create(:tag, name: 'material_show', category: :material)
     end
     let!(:material) do
       build_material(tag:, user: member_user, file: dummy_upload(filename: 'show.png'))
@@ -323,8 +323,8 @@ RSpec.describe 'Materials API', type: :request do
       end
 
       it 'returns 422 when the existing tag is not material/character' do
-        general_tag_name = TagName.create!(name: 'material_create_general_tag')
+        general_tag_name = create(:tag_name, name: 'material_create_general_tag')
-        Tag.create!(tag_name: general_tag_name, category: :general)
+        create(:tag, tag_name: general_tag_name, category: :general)
 
         post '/materials', params: {
           tag: 'material_create_general_tag',
@@ -384,7 +384,7 @@ RSpec.describe 'Materials API', type: :request do
 
   describe 'PUT /materials/:id' do
     let!(:tag) do
-      Tag.create!(tag_name: TagName.create!(name: 'material_update_old'), category: :material)
+      create(:tag, name: 'material_update_old', category: :material)
     end
     let!(:material) do
       build_material(tag:, user: member_user, file: dummy_upload(filename: 'old.png'))
@@ -508,7 +508,7 @@ RSpec.describe 'Materials API', type: :request do
 
       it 'backfills a create tag_version for an existing material tag without history' do
         existing_tag =
-            Tag.create!(tag_name: TagName.create!(name: 'material_update_existing_no_history'),
+            create(:tag, name: 'material_update_existing_no_history',
                         category: :material)
 
         expect(existing_tag.tag_versions).to be_empty
@@ -531,7 +531,7 @@ RSpec.describe 'Materials API', type: :request do
 
       it 'backfills a create tag_version for an existing character tag without history' do
         existing_tag =
-            Tag.create!(tag_name: TagName.create!(name: 'material_update_character_no_history'),
+            create(:tag, name: 'material_update_character_no_history',
                         category: :character)
 
         expect(existing_tag.tag_versions).to be_empty
@@ -651,8 +651,8 @@ RSpec.describe 'Materials API', type: :request do
   end
 
   describe 'GET /materials/download.zip' do
-    let!(:tag_a) { Tag.create!(tag_name: TagName.create!(name: 'zip_a'), category: :material) }
+    let!(:tag_a) { create(:tag, name: 'zip_a', category: :material) }
-    let!(:tag_b) { Tag.create!(tag_name: TagName.create!(name: 'zip_b'), category: :material) }
+    let!(:tag_b) { create(:tag, name: 'zip_b', category: :material) }
     let!(:material_a) do
       build_material(tag: tag_a, user: member_user,
                      file: dummy_upload(filename: 'a.png', body: 'zip-a'))
@@ -701,7 +701,7 @@ RSpec.describe 'Materials API', type: :request do
 
   describe 'GET /materials/versions' do
     let!(:tag) do
-      Tag.create!(tag_name: TagName.create!(name: 'material_history'), category: :material)
+      create(:tag, name: 'material_history', category: :material)
     end
     let!(:material) do
       build_material(tag:, user: member_user, file: dummy_upload(filename: 'history.png'))
@@ -776,7 +776,7 @@ RSpec.describe 'Materials API', type: :request do
 
   describe 'DELETE /materials/:id' do
     let!(:tag) do
-      Tag.create!(tag_name: TagName.create!(name: 'material_destroy'), category: :material)
+      create(:tag, name: 'material_destroy', category: :material)
     end
     let!(:material) do
       build_material(tag:, user: member_user, file: dummy_upload(filename: 'destroy.png'))

backend/spec/requests/nico_tags_spec.rb

@@ -3,10 +3,34 @@ require 'rails_helper'
 
 RSpec.describe 'NicoTags', type: :request do
   describe 'GET /tags/nico' do
-    it 'returns paginated tags and total count' do
+    it 'returns the legacy Tag-compatible external fields' do
-      create_list(:tag, 3, :nico)
+      external = create(:external_tag, name: 'legacy_external', post_count: 3)
 
-      get '/tags/nico', params: { page: 2, limit: 2 }
+      get '/tags/nico', params: { name: 'legacy_external' }
+
+      expect(response).to have_http_status(:ok)
+      expect(json.fetch('count')).to eq(1)
+      expect(json.fetch('tags')).to contain_exactly(
+          a_hash_including(
+              'id' => external.id,
+              'name' => 'nico:legacy_external',
+              'category' => 'nico',
+              'post_count' => 3,
+              'created_at' => external.created_at.as_json,
+              'updated_at' => external.created_at.as_json,
+              'deprecated_at' => nil,
+              'aliases' => [],
+              'parents' => [],
+              'has_wiki' => false,
+              'material_id' => nil,
+              'has_deerjikists' => false,
+              'linked_tags' => []))
+    end
+
+    it 'returns paginated tags and total count' do
+      3.times { |i| create(:external_tag, name: "pagination_#{ i }") }
+
+      get '/tags/nico', params: { page: 2, limit: 2, name: 'pagination_' }
 
       expect(response).to have_http_status(:ok)
       expect(json['tags'].size).to eq(1)
@@ -14,12 +38,12 @@ RSpec.describe 'NicoTags', type: :request do
     end
 
     it 'filters by nico tag name, linked tag name, and link status' do
-      linked = create(:tag, :nico)
+      linked = create(:external_tag)
-      linked.tag_name.update!(name: 'nico:search_linked')
+      linked.update!(name: 'search_linked')
-      unlinked = create(:tag, :nico)
+      unlinked = create(:external_tag)
-      unlinked.tag_name.update!(name: 'nico:search_unlinked')
+      unlinked.update!(name: 'search_unlinked')
-      other = create(:tag, :nico)
+      other = create(:external_tag)
-      other.tag_name.update!(name: 'nico:other')
+      other.update!(name: 'other')
       destination = create(:tag, :general)
       destination.tag_name.update!(name: 'destination_search')
       NicoTagRelation.create!(nico_tag: linked, tag: destination)
@@ -41,37 +65,77 @@ RSpec.describe 'NicoTags', type: :request do
       expect(json.fetch('tags').map { |tag| tag['id'] }).to eq([unlinked.id])
     end
 
+    it 'filters by the qualified legacy name as well as the raw name' do
+      external = create(:external_tag, name: 'qualified_filter')
+      create(:external_tag, name: 'unrelated_filter')
+
+      ['qualified_filter', 'nico:qualified_filter'].each do |name|
+        get '/tags/nico', params: { name: }
+
+        expect(response).to have_http_status(:ok)
+        expect(json.fetch('count')).to eq(1)
+        expect(json.fetch('tags')).to contain_exactly(
+            a_hash_including('id' => external.id, 'name' => 'nico:qualified_filter'))
+      end
+    end
+
     it 'sorts by name and timestamps' do
-      older = create(:tag, :nico)
+      older = create(:external_tag)
-      older.tag_name.update!(name: 'nico:a')
+      older.update!(name: 'ordered_a')
       older.update_columns(created_at: 2.days.ago)
-      newer = create(:tag, :nico)
+      newer = create(:external_tag)
-      newer.tag_name.update!(name: 'nico:b')
+      newer.update!(name: 'ordered_b')
       newer.update_columns(created_at: 1.day.ago)
       older_post_tag =
-        PostTag.create!(post: Post.create!(url: 'https://example.com/nico-older'), tag: older)
+        PostExternalTag.create!(post: create(:post), external_tag: older)
       older_post_tag.update_columns(created_at: 1.hour.ago)
       newer_post_tag =
-        PostTag.create!(post: Post.create!(url: 'https://example.com/nico-newer'), tag: newer)
+        PostExternalTag.create!(post: create(:post), external_tag: newer)
       newer_post_tag.update_columns(created_at: 2.hours.ago)
 
-      get '/tags/nico', params: { order: 'name:desc' }
+      get '/tags/nico', params: { order: 'name:desc', name: 'ordered_' }
       expect(json.fetch('tags').map { |tag| tag['id'] }).to eq([newer.id, older.id])
 
-      get '/tags/nico', params: { order: 'created_at:asc' }
+      get '/tags/nico', params: { order: 'created_at:asc', name: 'ordered_' }
       expect(json.fetch('tags').map { |tag| tag['id'] }).to eq([older.id, newer.id])
 
-      get '/tags/nico', params: { order: 'updated_at:desc' }
+      get '/tags/nico', params: { order: 'updated_at:desc', name: 'ordered_' }
       expect(json.fetch('tags').map { |tag| tag['id'] }).to eq([older.id, newer.id])
       expect(Time.zone.parse(json.fetch('tags').first.fetch('recent_post_tag_created_at')))
         .to be_within(1.second).of(older_post_tag.created_at)
     end
   end
 
+  describe 'GET /tags/nico/:id' do
+    it 'returns the external tag even when an internal tag has the same id' do
+      internal = create(:tag)
+      external = create(
+          :external_tag,
+          id: internal.id,
+          name: 'external_detail')
+
+      get "/tags/nico/#{ external.id }"
+
+      expect(response).to have_http_status(:ok)
+      expect(json).to include(
+          'id' => external.id,
+          'name' => 'nico:external_detail',
+          'category' => 'nico')
+    end
+
+    it 'returns 404 when the external tag does not exist' do
+      internal = create(:tag)
+
+      get "/tags/nico/#{ internal.id }"
+
+      expect(response).to have_http_status(:not_found)
+    end
+  end
+
   describe 'PATCH /tags/nico/:id' do
     let(:member) { create(:user, :member) }
     let(:admin) { create(:user, :admin) }
-    let(:nico_tag) { create(:tag, :nico) }
+    let(:nico_tag) { create(:external_tag) }
 
     it '401 when not logged in' do
       sign_out
@@ -85,26 +149,27 @@ RSpec.describe 'NicoTags', type: :request do
       expect(response).to have_http_status(:forbidden)
     end
 
-    it '400 when target is not nico category' do
+    it '404 when only an internal tag exists for the target id' do
       sign_in_as(member)
       non_nico = create(:tag, :general)
+      expect(ExternalTag.exists?(non_nico.id)).to be(false)
       patch "/tags/nico/#{non_nico.id}", params: { tags: 'a b' }
-      expect(response).to have_http_status(:bad_request)
+      expect(response).to have_http_status(:not_found)
     end
 
     it '200 and updates linked tags while recording tag versions' do
       sign_in_as(admin)
 
-      nico_tag_name = TagName.create!(name: 'nico:nico_tags_spec_source')
+      nico_tag = create(:external_tag, name: 'nico_tags_spec_source')
-      nico_tag = Tag.create!(tag_name: nico_tag_name, category: :nico)
 
-      linked_a_name = TagName.create!(name: 'nico_linked_a')
+      linked_a_name = create(:tag_name, name: 'nico_linked_a')
-      linked_a = Tag.create!(tag_name: linked_a_name, category: :general)
+      linked_a = create(:tag, tag_name: linked_a_name, category: :general)
 
-      linked_b_name = TagName.create!(name: 'nico_linked_b')
+      linked_b_name = create(:tag_name, name: 'nico_linked_b')
-      linked_b = Tag.create!(tag_name: linked_b_name, category: :general)
+      linked_b = create(:tag, tag_name: linked_b_name, category: :general)
 
-      TagVersioning.ensure_snapshot!(nico_tag, created_by_user: admin)
+      NicoTagVersionRecorder.record!(external_tag: nico_tag,
+                                     event_type: :create, created_by_user: admin)
 
       expect {
         patch "/tags/nico/#{nico_tag.id}", params: {
@@ -126,26 +191,26 @@ RSpec.describe 'NicoTags', type: :request do
       expect(versions.map(&:event_type)).to eq(['create', 'update'])
       expect(versions.last.linked_tags.split).to match_array([
         'nico_linked_a',
-        'nico_linked_b'
+        'nico_linked_b'])
-      ])
       expect(versions.last.created_by_user_id).to eq(admin.id)
     end
 
-    it 'returns 422 when linked tag normalises to nico tag' do
+    it 'clears existing links and records the empty mapping for a member' do
       sign_in_as(member)
-
+      linked = create(:tag)
-      other_nico = create(:tag, :nico, name: 'nico:linked_ng')
+      NicoTagRelation.insert_all!([{ nico_tag_id: nico_tag.id, tag_id: linked.id }])
-      TagName.create!(name: 'linked_ng_alias', canonical: other_nico.tag_name)
+      NicoTagVersionRecorder.record!(external_tag: nico_tag,
-
+                                     event_type: :create, created_by_user: member)
-      TagVersioning.ensure_snapshot!(nico_tag, created_by_user: member)
 
       expect {
-        patch "/tags/nico/#{nico_tag.id}", params: { tags: 'linked_ng_alias' }
+        patch "/tags/nico/#{ nico_tag.id }", params: { tags: '' }
-      }.not_to change(NicoTagVersion, :count)
+      }.to change(NicoTagVersion, :count).by(1)
 
-      expect(response).to have_http_status(:unprocessable_entity)
+      expect(response).to have_http_status(:ok)
-      expect(json.fetch('errors')).to include(
+      expect(json).to eq([])
-          'tags' => ['ニコニコ・タグ同士は連携できません．'])
+      expect(nico_tag.reload.linked_tags).to be_empty
+      expect(nico_tag.nico_tag_versions.order(:version_no).last)
+          .to have_attributes(linked_tags: '', created_by_user: member)
     end
 
     it 'returns the tags field error when a nico tag is specified directly' do

backend/spec/requests/post_imports_spec.rb

@@ -1,184 +0,0 @@
-require 'rails_helper'
-
-RSpec.describe 'Post imports API', type: :request do
-  let(:member) { create(:user, :member) }
-
-  before do
-    allow(Preview::UrlSafety).to receive(:validate) do |url|
-      [URI.parse(url), ['8.8.8.8']]
-    end
-    allow(PostMetadataFetcher).to receive(:fetch).and_return(
-      title: 'fetched title',
-      thumbnail_base: nil,
-      tags: ''
-    )
-  end
-
-  describe 'POST /posts/import/preview' do
-    it 'requires a member' do
-      sign_out
-      post '/posts/import/preview', params: { source: 'https://example.com/post' }
-      expect(response).to have_http_status(:unauthorized)
-
-      sign_in_as(create(:user, :guest))
-      post '/posts/import/preview', params: { source: 'https://example.com/post' }
-      expect(response).to have_http_status(:forbidden)
-    end
-
-    it 'parses a URL list and returns preview rows' do
-      sign_in_as(member)
-
-      post '/posts/import/preview', params: {
-        source: " https://example.com/one \r\n\r\nhttps://example.com/two"
-      }
-
-      expect(response).to have_http_status(:ok)
-      expect(json.fetch('rows').map { _1.fetch('source_row') }).to eq([1, 3])
-      expect(json.fetch('rows').map { _1.fetch('url') }).to eq([
-        'https://example.com/one',
-        'https://example.com/two'
-      ])
-    end
-
-    it 'returns a safe 400 response for an invalid source' do
-      sign_in_as(member)
-
-      post '/posts/import/preview', params: { source: '' }
-
-      expect(response).to have_http_status(:bad_request)
-      expect(json.fetch('message')).to eq('URL を入力してください．')
-    end
-  end
-
-  describe 'POST /posts/import/validate' do
-    it 'accepts camel-case row properties and returns their warnings' do
-      sign_in_as(member)
-
-      post '/posts/import/validate', params: {
-        rows: [{
-          sourceRow: '1',
-          url: 'https://example.com/post',
-          metadataUrl: 'https://example.com/post',
-          attributes: { title: 'manual title' },
-          provenance: { url: 'manual', title: 'manual' },
-          tagSources: { automatic: '', manual: '' },
-          fieldWarnings: { title: ['old warning'] },
-          baseWarnings: ['base warning']
-        }],
-        changed_row: -1
-      }
-
-      expect(response).to have_http_status(:ok)
-      result = json.fetch('rows').first
-      expect(result.fetch('source_row')).to eq(1)
-      expect(result.fetch('tag_sources')).to eq('automatic' => '', 'manual' => '')
-      expect(result.fetch('field_warnings')).to eq('title' => ['old warning'])
-      expect(result.fetch('base_warnings')).to eq(['base warning'])
-    end
-
-    it 'rejects a non-array rows value with 400' do
-      sign_in_as(member)
-
-      post '/posts/import/validate', params: { rows: { sourceRow: 1 }, changed_row: -1 }
-
-      expect(response).to have_http_status(:bad_request)
-      expect(json.fetch('message')).to eq('取込行の形式が不正です．')
-    end
-
-    it 'returns original created datetime validation errors for minute precision' do
-      sign_in_as(member)
-
-      post '/posts/import/validate', params: {
-        rows: [{
-          sourceRow: 1,
-          url: 'https://example.com/post',
-          metadataUrl: 'https://example.com/post',
-          attributes: {
-            originalCreatedFrom: '2020-01-01T00:00:30Z',
-            originalCreatedBefore: '2020-01-01T00:01Z' },
-          provenance: {
-            url: 'manual',
-            originalCreatedFrom: 'manual',
-            originalCreatedBefore: 'manual' },
-          tagSources: { automatic: '', manual: '' }
-        }],
-        changed_row: -1
-      }
-
-      expect(response).to have_http_status(:ok)
-      expect(json.fetch('rows').first.fetch('validation_errors')).to include(
-        'original_created_from' => ['オリジナルの作成日時は分単位で入力してください．']
-      )
-      expect(json.fetch('rows').first.fetch('validation_errors'))
-          .not_to have_key('original_created_at')
-    end
-  end
-
-  describe 'POST /posts/import' do
-    it 'keeps the duration string contract through preview, validate, and import' do
-      sign_in_as(member)
-      allow(PostMetadataFetcher).to receive(:fetch).and_return(
-        title: 'fetched title',
-        thumbnail_base: nil,
-        duration: '2.5',
-        tags: '動画'
-      )
-
-      post '/posts/import/preview', params: {
-        source: 'https://example.com/video'
-      }
-      preview_row = json.fetch('rows').first
-      expect(preview_row.dig('attributes', 'duration')).to eq('2.5')
-
-      post '/posts/import/validate', params: {
-        rows: [{
-          sourceRow: preview_row.fetch('source_row'),
-          url: preview_row.fetch('url'),
-          attributes: preview_row.fetch('attributes'),
-          provenance: preview_row.fetch('provenance'),
-          tagSources: preview_row.fetch('tag_sources'),
-          metadataUrl: preview_row.fetch('metadata_url')
-        }],
-        changed_row: -1
-      }
-      validated_row = json.fetch('rows').first
-      expect(validated_row.dig('attributes', 'duration')).to eq('2.5')
-
-      post '/posts/import', params: {
-        rows: [{
-          sourceRow: validated_row.fetch('source_row'),
-          url: validated_row.fetch('url'),
-          attributes: validated_row.fetch('attributes'),
-          provenance: validated_row.fetch('provenance'),
-          tagSources: validated_row.fetch('tag_sources'),
-          metadataUrl: validated_row.fetch('metadata_url')
-        }]
-      }
-
-      expect(response).to have_http_status(:ok)
-      expect(Post.order(:id).last.video_ms).to eq(2_500)
-    end
-
-    it 'returns a formal skipped result for an existing post' do
-      existing = create(:post, url: 'https://example.com/existing')
-      sign_in_as(member)
-
-      post '/posts/import', params: {
-        rows: [{
-          sourceRow: 1,
-          url: existing.url,
-          attributes: { title: 'ignored' },
-          provenance: { url: 'manual', title: 'manual' },
-          tagSources: { automatic: '', manual: '' }
-        }]
-      }
-
-      expect(response).to have_http_status(:ok)
-      expect(json).to include('created' => 0, 'skipped' => 1, 'failed' => 0)
-      expect(json.fetch('rows').first).to include(
-        'status' => 'skipped',
-        'existing_post_id' => existing.id
-      )
-    end
-  end
-end

backend/spec/requests/tag_children_spec.rb

@@ -80,38 +80,6 @@ RSpec.describe "TagChildren", type: :request do
         expect(response).to have_http_status(:not_found)
       end
     end
-
-    context 'when parent is nico' do
-      before { stub_current_user(admin) }
-
-      let!(:parent) { create(:tag, :nico, name: 'nico:parent_ng') }
-      let(:parent_id) { parent.id }
-      let(:child_id) { child.id }
-
-      it 'returns 400 and does not create relation' do
-        expect {
-          do_request
-        }.not_to change(TagImplication, :count)
-
-        expect(response).to have_http_status(:bad_request)
-      end
-    end
-
-    context 'when child is nico' do
-      before { stub_current_user(admin) }
-
-      let!(:child) { create(:tag, :nico, name: 'nico:child_ng') }
-      let(:parent_id) { parent.id }
-      let(:child_id) { child.id }
-
-      it 'returns 400 and does not create relation' do
-        expect {
-          do_request
-        }.not_to change(TagImplication, :count)
-
-        expect(response).to have_http_status(:bad_request)
-      end
-    end
   end
 
   describe "DELETE /tag_children" do
@@ -186,31 +154,5 @@ RSpec.describe "TagChildren", type: :request do
         expect(response).to have_http_status(:not_found)
       end
     end
-
-    context 'when parent is nico' do
-      before { stub_current_user(admin) }
-
-      let!(:parent) { create(:tag, :nico, name: 'nico:parent_ng_delete') }
-      let(:parent_id) { parent.id }
-      let(:child_id) { child.id }
-
-      it 'returns 400' do
-        do_request
-        expect(response).to have_http_status(:bad_request)
-      end
-    end
-
-    context 'when child is nico' do
-      before { stub_current_user(admin) }
-
-      let!(:child) { create(:tag, :nico, name: 'nico:child_ng_delete') }
-      let(:parent_id) { parent.id }
-      let(:child_id) { child.id }
-
-      it 'returns 400' do
-        do_request
-        expect(response).to have_http_status(:bad_request)
-      end
-    end
   end
 end

backend/spec/requests/tag_versions_spec.rb

@@ -232,8 +232,8 @@ RSpec.describe 'TagVersions API', type: :request do
     end
 
     it 'does not create tag versions by wiki updates when tag has no versions yet' do
-      wiki_tag_name = TagName.create!(name: 'tag_versions_from_wiki')
+      wiki_tag_name = create(:tag_name, name: 'tag_versions_from_wiki')
-      wiki_tag = Tag.create!(tag_name: wiki_tag_name, category: :general)
+      wiki_tag = create(:tag, tag_name: wiki_tag_name, category: :general)
 
       wiki_page =
           Wiki::Commit.create_content!(

backend/spec/requests/tag_wiki_history_integrity_spec.rb

@@ -8,8 +8,8 @@ RSpec.describe 'Tag and wiki history integrity', type: :request do
   end
 
   def create_tag! name:, category: :general
-    tag_name = TagName.create!(name:)
+    tag_name = create(:tag_name, name:)
-    Tag.create!(tag_name:, category:)
+    create(:tag, tag_name:, category:)
   end
 
   def create_wiki_for_tag! tag:, body: 'wiki body', user: member_user

backend/spec/requests/tags_deerjikists_spec.rb

@@ -226,6 +226,14 @@ RSpec.describe 'Tags deerjikists API', type: :request do
               [platform2, code2],
             )
         end
+
+        it 'locks the tag before replacing the complete list' do
+          expect_any_instance_of(Tag).to receive(:lock!).and_call_original
+
+          do_request
+
+          expect(response).to have_http_status(:ok)
+        end
       end
 
       context 'when tag already has deerjikists' do
@@ -299,6 +307,81 @@ RSpec.describe 'Tags deerjikists API', type: :request do
         end
       end
 
+      context 'when platform is outside the enum' do
+        let(:payload) do
+          [
+            { platform: 'invalid', code: code1 },
+          ]
+        end
+
+        it 'returns 422 with an indexed platform error without changing the list' do
+          Deerjikist.create!(platform: platform1, code: code1, tag: tag)
+
+          expect {
+            do_request
+          }.not_to change { Deerjikist.where(tag: tag).map { |d| [d.platform, d.code] } }
+
+          expect(response).to have_http_status(:unprocessable_entity)
+          expect(json.fetch('errors')).to include(
+            'deerjikists.0.platform' => [be_present],
+          )
+        end
+      end
+
+      context 'when a requested deerjikist belongs to another tag' do
+        let!(:other_tag) { create(:tag, category: :deerjikist) }
+        let!(:owned_deerjikist) do
+          Deerjikist.create!(platform: platform1, code: code1, tag: tag)
+        end
+        let!(:conflicting_deerjikist) do
+          Deerjikist.create!(platform: platform2, code: code2, tag: other_tag)
+        end
+        let(:payload) do
+          [
+            { platform: 'nico', code: 'new-code' },
+            { platform: platform2, code: code2 },
+          ]
+        end
+
+        before do
+          other_tag.tag_name.update!(name: 'existing-deerjikist')
+        end
+
+        it 'returns an indexed 422 error and rolls back the complete replacement' do
+          expect {
+            do_request
+          }.not_to change { Deerjikist.order(:platform, :code).pluck(:platform, :code, :tag_id) }
+
+          expect(response).to have_http_status(:unprocessable_entity)
+          expect(json.fetch('errors')).to include(
+            'deerjikists.1.code' => [include('existing-deerjikist')],
+          )
+          expect(owned_deerjikist.reload.tag_id).to eq(tag.id)
+          expect(conflicting_deerjikist.reload.tag_id).to eq(other_tag.id)
+        end
+      end
+
+      context 'when a requested deerjikist already belongs to the same tag' do
+        let!(:existing_deerjikist) do
+          Deerjikist.create!(platform: platform1, code: code1, tag: tag)
+        end
+        let(:payload) do
+          [
+            { platform: platform1, code: code1 },
+          ]
+        end
+
+        it 'keeps the existing row' do
+          expect {
+            do_request
+          }.not_to change { existing_deerjikist.reload.created_at }
+
+          expect(response).to have_http_status(:ok)
+          expect(Deerjikist.where(tag: tag).pluck(:platform, :code))
+            .to eq([[platform1, code1]])
+        end
+      end
+
       context 'when youtube code is handle' do
         let(:channel_id) { 'UCabcdefghijklmnopqrstuv' }
         let(:payload) do

backend/spec/requests/tags_spec.rb

@@ -2,13 +2,13 @@ require 'cgi'
 require 'rails_helper'
 
 RSpec.describe 'Tags API', type: :request do
-  let!(:tn) { TagName.create!(name: 'spec_tag') }
+  let!(:tn) { create(:tag_name, name: 'spec_tag') }
-  let!(:tag) { Tag.create!(tag_name: tn, category: :general) }
+  let!(:tag) { create(:tag, tag_name: tn, category: :general) }
-  let!(:alias_tn) { TagName.create!(name: 'unko', canonical: tn) }
+  let!(:alias_tn) { create(:tag_name, :alias, name: 'unko', tag:) }
   let!(:post) { Post.create!(url: 'https://example.com/unkounkounko') }
   let!(:post_tag) { PostTag.create!(post:, tag:) }
-  let!(:tn2) { TagName.create!(name: 'unknown') }
+  let!(:tn2) { create(:tag_name, name: 'unknown') }
-  let!(:tag2) { Tag.create!(tag_name: tn2, category: :general) }
+  let!(:tag2) { create(:tag, tag_name: tn2, category: :general) }
 
   def response_tags
     json.fetch('tags')
@@ -30,6 +30,30 @@ RSpec.describe 'Tags API', type: :request do
   end
 
   describe 'GET /tags' do
+    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)
+
+      get '/tags', params: { name: 'spec_' }
+
+      expect(response).to have_http_status(:ok)
+      expect(json.fetch('count')).to eq(2)
+      expect(response_tags).to contain_exactly(
+          a_hash_including('id' => tag.id, 'name' => tag.name, 'category' => 'general'),
+          a_hash_including(
+              'id' => external.id,
+              'name' => 'nico:spec_external',
+              'category' => 'nico',
+              'post_count' => 3,
+              'created_at' => external.created_at.as_json,
+              'updated_at' => external.created_at.as_json,
+              'deprecated_at' => nil,
+              'aliases' => [],
+              'parents' => [],
+              'has_wiki' => false,
+              'material_id' => nil,
+              'has_deerjikists' => false))
+    end
+
     it 'returns tags with count and metadata' do
       get '/tags'
 
@@ -67,7 +91,7 @@ RSpec.describe 'Tags API', type: :request do
     end
 
     it 'filters tags by category' do
-      meme = Tag.create!(tag_name: TagName.create!(name: 'meme_only'), category: :meme)
+      meme = create(:tag, name: 'meme_only', category: :meme)
 
       get '/tags', params: { category: 'meme' }
 
@@ -77,12 +101,11 @@ RSpec.describe 'Tags API', type: :request do
     end
 
     it 'filters tags by deprecated state' do
-      deprecated_tag = Tag.create!(
+      deprecated_tag = create(:tag,
-        name: 'deprecated_filter',
+          name: 'deprecated_filter',
-        category: :general,
+          category: :general,
-        deprecated_at: 1.day.from_now
+          deprecated_at: 1.day.from_now)
-      )
+      active_tag = create(:tag, name: 'active_filter', category: :general)
-      active_tag = Tag.create!(name: 'active_filter', category: :general)
 
       get '/tags', params: { name: '_filter', deprecated: '1' }
 
@@ -98,9 +121,9 @@ RSpec.describe 'Tags API', type: :request do
     end
 
     it 'filters tags by post_count range' do
-      low = Tag.create!(tag_name: TagName.create!(name: 'pc_low'), category: :general)
+      low = create(:tag, name: 'pc_low', category: :general)
-      mid = Tag.create!(tag_name: TagName.create!(name: 'pc_mid'), category: :general)
+      mid = create(:tag, name: 'pc_mid', category: :general)
-      high = Tag.create!(tag_name: TagName.create!(name: 'pc_high'), category: :general)
+      high = create(:tag, name: 'pc_high', category: :general)
 
       low.update_columns(post_count: 1)
       mid.update_columns(post_count: 3)
@@ -118,8 +141,8 @@ RSpec.describe 'Tags API', type: :request do
     end
 
     it 'filters tags by created_at range' do
-      old_tag = Tag.create!(tag_name: TagName.create!(name: 'created_old'), category: :general)
+      old_tag = create(:tag, name: 'created_old', category: :general)
-      new_tag = Tag.create!(tag_name: TagName.create!(name: 'created_new'), category: :general)
+      new_tag = create(:tag, name: 'created_new', category: :general)
 
       old_time = Time.zone.local(2024, 1, 1, 0, 0, 0)
       new_time = Time.zone.local(2024, 2, 1, 0, 0, 0)
@@ -138,8 +161,8 @@ RSpec.describe 'Tags API', type: :request do
     end
 
     it 'filters tags by updated_at range' do
-      old_tag = Tag.create!(tag_name: TagName.create!(name: 'updated_old'), category: :general)
+      old_tag = create(:tag, name: 'updated_old', category: :general)
-      new_tag = Tag.create!(tag_name: TagName.create!(name: 'updated_new'), category: :general)
+      new_tag = create(:tag, name: 'updated_new', category: :general)
 
       old_time = Time.zone.local(2024, 3, 1, 0, 0, 0)
       new_time = Time.zone.local(2024, 4, 1, 0, 0, 0)
@@ -158,31 +181,90 @@ RSpec.describe 'Tags API', type: :request do
     end
 
     it 'orders tags by custom category order' do
-      Tag.create!(tag_name: TagName.create!(name: 'cat_deerjikist'), category: :deerjikist)
+      create(:tag, name: 'cat_deerjikist', category: :deerjikist)
-      Tag.create!(tag_name: TagName.create!(name: 'cat_meme'), category: :meme)
+      create(:tag, name: 'cat_meme', category: :meme)
-      Tag.create!(tag_name: TagName.create!(name: 'cat_character'), category: :character)
+      create(:tag, name: 'cat_character', category: :character)
-      Tag.create!(tag_name: TagName.create!(name: 'cat_general'), category: :general)
+      create(:tag, name: 'cat_general', category: :general)
-      Tag.create!(tag_name: TagName.create!(name: 'cat_material'), category: :material)
+      create(:tag, name: 'cat_material', category: :material)
-      Tag.create!(tag_name: TagName.create!(name: 'cat_meta'), category: :meta)
+      create(:tag, name: 'cat_meta', category: :meta)
-      Tag.create!(tag_name: TagName.create!(name: 'nico:cat_nico'), category: :nico)
+      create(:external_tag, name: 'cat_nico')
 
       get '/tags', params: { name: 'cat_', order: 'category:asc', limit: 20 }
 
       expect(response).to have_http_status(:ok)
-      expect(response_names).to eq(%w[
+      expect(response_names).to eq([
-          cat_deerjikist
+          'cat_deerjikist', 'cat_meme', 'cat_character',
-          cat_meme
+          'cat_general', 'cat_material', 'cat_meta', 'nico:cat_nico'])
-          cat_character
+      expect(json.fetch('count')).to eq(7)
-          cat_general
+    end
-          cat_material
+
-          cat_meta
+    context 'with mixed legacy pagination' do
-          nico:cat_nico
+      let!(:first_tag) do
-      ])
+        create(:tag,
+            tag_name: create(:tag_name, name: 'a_mixed_page'),
+            category: :meme)
+      end
+
+      let!(:middle_tag) do
+        create(:tag,
+            tag_name: create(:tag_name, name: 'm_mixed_page'),
+            category: :meta)
+      end
+
+      let!(:last_tag) do
+        create(:tag,
+            tag_name: create(:tag_name, name: 'z_mixed_page'),
+            category: :general)
+      end
+
+      let!(:first_external) do
+        create(:external_tag, id: first_tag.id, name: 'a_mixed_page')
+      end
+      let!(:last_external) do
+        create(:external_tag, id: last_tag.id, name: 'z_mixed_page')
+      end
+
+      let(:name_order) do
+        [
+            [first_tag.id, 'a_mixed_page'], [middle_tag.id, 'm_mixed_page'],
+            [first_external.id, 'nico:a_mixed_page'], [last_external.id, 'nico:z_mixed_page'],
+            [last_tag.id, 'z_mixed_page']]
+      end
+      let(:category_order) do
+        [
+            [first_tag.id, 'a_mixed_page'], [last_tag.id, 'z_mixed_page'],
+            [middle_tag.id, 'm_mixed_page'], [first_external.id, 'nico:a_mixed_page'],
+            [last_external.id, 'nico:z_mixed_page']]
+      end
+
+      ['name', 'category'].each do |order|
+        ['asc', 'desc'].each do |direction|
+          it "orders the combined records by #{ order }:#{ direction } before paging" do
+            ascending = order == 'name' ? name_order : category_order
+            expected = direction == 'asc' ? ascending : ascending.reverse
+
+            [2, 3].each do |limit|
+              pages = expected.each_slice(limit).to_a + [[]]
+              pages.each.with_index(1) do |expected_page, page|
+                get '/tags', params: {
+                    name: 'mixed_page', order: "#{ order }:#{ direction }", page:, limit: }
+
+                expect(response).to have_http_status(:ok)
+                expect(json.fetch('count')).to eq(5)
+                expect(response_tags.size).to eq(expected_page.size)
+                expect(response_tags.size).to be <= limit
+                expect(response_tags.map { [_1.fetch('id'), _1.fetch('name')] })
+                    .to eq(expected_page)
+              end
+            end
+          end
+        end
+      end
     end
 
     it 'paginates and keeps total count' do
       %w[pag_a pag_b pag_c].each do |name|
-        Tag.create!(tag_name: TagName.create!(name:), category: :general)
+        create(:tag, tag_name: create(:tag_name, name:), category: :general)
       end
 
       get '/tags', params: { name: 'pag_', order: 'name:asc', page: 2, limit: 2 }
@@ -193,8 +275,8 @@ RSpec.describe 'Tags API', type: :request do
     end
 
     it 'falls back to default ordering when order is invalid' do
-      low = Tag.create!(tag_name: TagName.create!(name: 'fallback_low'), category: :general)
+      low = create(:tag, name: 'fallback_low', category: :general)
-      high = Tag.create!(tag_name: TagName.create!(name: 'fallback_high'), category: :general)
+      high = create(:tag, name: 'fallback_high', category: :general)
 
       low.update_columns(post_count: 1)
       high.update_columns(post_count: 9)
@@ -207,7 +289,7 @@ RSpec.describe 'Tags API', type: :request do
 
     it 'normalises invalid page and limit' do
       %w[norm_a norm_b].each do |name|
-        Tag.create!(tag_name: TagName.create!(name:), category: :general)
+        create(:tag, tag_name: create(:tag_name, name:), category: :general)
       end
 
       get '/tags', params: { name: 'norm_', order: 'name:asc', page: 0, limit: 0 }
@@ -219,10 +301,9 @@ RSpec.describe 'Tags API', type: :request do
     end
 
     it 'returns aliases and parent tags' do
-      parent_tag = Tag.create!(
+      parent_tag = create(:tag,
-        tag_name: TagName.create!(name: 'index_parent_tag'),
+          tag_name: create(:tag_name, name: 'index_parent_tag'),
-        category: :meme
+          category: :meme)
-      )
       TagImplication.create!(tag:, parent_tag:)
 
       get '/tags', params: { name: 'spec_tag' }
@@ -266,10 +347,9 @@ RSpec.describe 'Tags API', type: :request do
       end
 
       it 'returns aliases and parent tags' do
-        parent_tag = Tag.create!(
+        parent_tag = create(:tag,
-          tag_name: TagName.create!(name: 'show_parent_tag'),
+            tag_name: create(:tag_name, name: 'show_parent_tag'),
-          category: :character
+            category: :character)
-        )
         TagImplication.create!(tag:, parent_tag:)
 
         request
@@ -296,9 +376,127 @@ RSpec.describe 'Tags API', type: :request do
         expect(response).to have_http_status(:not_found)
       end
     end
+
+    it 'falls back to ExternalTag when no internal Tag has the id' do
+      external = create(
+          :external_tag,
+          id: Tag.maximum(:id).to_i + 10_000,
+          name: 'legacy_id_lookup')
+
+      get "/tags/#{ external.id }"
+
+      expect(response).to have_http_status(:ok)
+      expect(json).to include(
+          'id' => external.id,
+          'name' => 'nico:legacy_id_lookup',
+          'category' => 'nico')
+    end
+
+    it 'prefers Tag when Tag and ExternalTag have the same id' do
+      internal = create(
+          :tag,
+          tag_name: create(:tag_name, name: 'internal_collision'))
+      create(
+          :external_tag,
+          id: internal.id,
+          name: 'external_collision')
+
+      get "/tags/#{ internal.id }"
+
+      expect(response).to have_http_status(:ok)
+      expect(json).to include(
+          'id' => internal.id,
+          'name' => 'internal_collision',
+          'category' => internal.category)
+    end
   end
 
   describe 'GET /tags/autocomplete' do
+    it 'combines internal and external matches without conflating equal ids' do
+      internal = create(:tag, category: :general, name: 'mixed_internal', post_count: 2)
+      external = create(:external_tag, id: internal.id,
+                                       name: 'mixed_external', post_count: 3)
+
+      get '/tags/autocomplete', params: { q: 'not:mixed' }
+
+      expect(response).to have_http_status(:ok)
+      expect(json.map { |row| row.fetch('name') })
+          .to eq(['nico:mixed_external', 'mixed_internal'])
+      expect(json.first).to include(
+          'id' => external.id, 'category' => 'nico', 'post_count' => 3,
+          'created_at' => external.created_at.as_json,
+          'updated_at' => external.created_at.as_json,
+          'deprecated_at' => nil, 'matched_alias' => nil,
+          'aliases' => [], 'parents' => [], 'has_wiki' => false,
+          'material_id' => nil, 'has_deerjikists' => false)
+    end
+
+    it 'matches an external tag by its platform prefix' do
+      create(:external_tag, name: 'prefix_match', post_count: 1)
+
+      get '/tags/autocomplete', params: { q: 'nico:prefix' }
+
+      expect(json.map { |row| row.fetch('name') }).to eq(['nico:prefix_match'])
+    end
+
+    it 'excludes unused external tags unless present is false' do
+      create(:external_tag, name: 'unused_external')
+
+      get '/tags/autocomplete', params: { q: 'unused' }
+      expect(json).to be_empty
+
+      get '/tags/autocomplete', params: { q: 'unused', present: '0' }
+      expect(json.map { |row| row.fetch('name') }).to eq(['nico:unused_external'])
+    end
+
+    it 'limits the combined results to 20 and sorts ties by displayed name' do
+      11.times do |i|
+        name = "combined_#{ i.to_s.rjust(2, '0') }"
+        create(:tag, category: :general, name:, post_count: 1)
+        create(:external_tag, name:, post_count: 1)
+      end
+
+      get '/tags/autocomplete', params: { q: 'combined' }
+
+      expected = 11.times.map { |i| "combined_#{ i.to_s.rjust(2, '0') }" }
+      expected += expected.map { |name| "nico:#{ name }" }
+      expect(json.map { |row| row.fetch('name') }).to eq(expected.first(20))
+    end
+
+    it 'excludes external tags but preserves internal alias matches when nico is false' do
+      internal = create(:tag, category: :general, name: 'switch_internal', post_count: 1)
+      alias_target = create(:tag, category: :general, name: 'alias_target', post_count: 1)
+      create(:tag_name, :alias, name: 'switch_alias', tag: alias_target)
+      create(:external_tag, name: 'switch_external', post_count: 1)
+
+      get '/tags/autocomplete', params: { q: 'switch', nico: '0' }
+
+      expect(response).to have_http_status(:ok)
+      expect(json).to contain_exactly(
+          a_hash_including('id' => internal.id, 'name' => internal.name),
+          a_hash_including('id' => alias_target.id, 'name' => alias_target.name,
+                           'matched_alias' => 'switch_alias'))
+    end
+
+    ['%', '_'].each do |wildcard|
+      it "treats #{ wildcard } literally for primary, alias, and external names" do
+        literal = "literal#{ wildcard }match"
+        create(:tag, category: :general, name: literal, post_count: 1)
+        alias_target = create(
+            :tag, category: :general, name: 'literal_alias_target', post_count: 1)
+        create(:tag_name, :alias, name: "#{ literal }_alias",
+                                  tag: alias_target)
+        create(:external_tag, name: literal, post_count: 1)
+        create(:tag, category: :general, name: 'literalXmatch', post_count: 2)
+        create(:external_tag, name: 'literalXmatch', post_count: 2)
+
+        get '/tags/autocomplete', params: { q: "literal#{ wildcard }" }
+
+        expect(json.map { |row| row.fetch('name') })
+            .to contain_exactly(literal, alias_target.name, "nico:#{ literal }")
+      end
+    end
+
     it 'returns matching tags by q' do
       get '/tags/autocomplete', params: { q: 'spec' }
 
@@ -311,7 +509,7 @@ RSpec.describe 'Tags API', type: :request do
       expect(t['matched_alias']).to be(nil)
     end
 
-    it 'returns matching canonical tags by q with aliases' do
+    it 'returns matching primary tag names by q with aliases' do
       get '/tags/autocomplete', params: { q: 'unk' }
 
       expect(response).to have_http_status(:ok)
@@ -324,11 +522,10 @@ RSpec.describe 'Tags API', type: :request do
     end
 
     it 'omits deprecated tags' do
-      deprecated_tag = Tag.create!(
+      deprecated_tag = create(:tag,
-        name: 'spec_deprecated',
+          name: 'spec_deprecated',
-        category: :general,
+          category: :general,
-        deprecated_at: Time.current
+          deprecated_at: Time.current)
-      )
       deprecated_tag.update_columns(post_count: 1)
 
       get '/tags/autocomplete', params: { q: 'spec_', present: '0' }
@@ -340,6 +537,27 @@ RSpec.describe 'Tags API', type: :request do
   end
 
   describe 'GET /tags/name/:name' do
+    it 'preserves qualified external name lookup used by wiki pages' do
+      external = create(:external_tag, name: 'detail_external', post_count: 3)
+
+      get "/tags/name/#{ CGI.escape('nico:detail_external') }"
+
+      expect(response).to have_http_status(:ok)
+      expect(json).to include(
+          'id' => external.id,
+          'name' => 'nico:detail_external',
+          'category' => 'nico',
+          'post_count' => 3,
+          'created_at' => external.created_at.as_json,
+          'updated_at' => external.created_at.as_json,
+          'deprecated_at' => nil,
+          'aliases' => [],
+          'parents' => [],
+          'has_wiki' => false,
+          'material_id' => nil,
+          'has_deerjikists' => false)
+    end
+
     it 'returns tag by name' do
       get "/tags/name/#{ CGI.escape('spec_tag') }"
 
@@ -487,18 +705,6 @@ RSpec.describe 'Tags API', type: :request do
         expect(json.fetch('deprecated_at')).to be_present
       end
 
-      it 'rejects deprecating a nico tag' do
-        nico_tag = Tag.create!(name: 'nico:deprecated_update', category: :nico)
-
-        patch "/tags/#{ nico_tag.id }", params: { deprecated: '1' }
-
-        expect(response).to have_http_status(:unprocessable_entity)
-        expect(nico_tag.reload.deprecated_at).to be_nil
-        expect(json.fetch('errors')).to include(
-          'deprecated' => ['ニコタグは廃止できません．']
-        )
-      end
-
       it 'returns 422 when changing normal tag category to nico' do
         expect {
           patch "/tags/#{tag.id}", params: { category: 'nico' }
@@ -508,32 +714,6 @@ RSpec.describe 'Tags API', type: :request do
         expect(tag.reload.category).to eq('general')
       end
 
-      it 'returns 422 when updating nico tag name' do
-        nico_tag_name = TagName.create!(name: 'nico:tags_spec_source')
-        nico_tag = Tag.create!(tag_name: nico_tag_name, category: :nico)
-
-        expect {
-          patch "/tags/#{ nico_tag.id }", params: { name: 'nico:tags_spec_renamed' }
-        }.not_to change(NicoTagVersion, :count)
-
-        expect(response).to have_http_status(:unprocessable_entity)
-
-        expect(nico_tag.reload.name).to eq('nico:tags_spec_source')
-        expect(nico_tag.category).to eq('nico')
-      end
-
-      it 'returns 422 when changing nico tag category to normal category' do
-        nico_tag_name = TagName.create!(name: 'nico:category_change_ng')
-        nico_tag = Tag.create!(tag_name: nico_tag_name, category: :nico)
-
-        expect {
-          patch "/tags/#{nico_tag.id}", params: { category: 'general' }
-        }.not_to change(NicoTagVersion, :count)
-
-        expect(response).to have_http_status(:unprocessable_entity)
-        expect(nico_tag.reload.category).to eq('nico')
-      end
-
       it 'PATCH で tag の name を変更すると対応する wiki version を作成する' do
         wiki_page =
             Wiki::Commit.create_content!(
@@ -592,7 +772,8 @@ RSpec.describe 'Tags API', type: :request do
         }
 
         expect(response).to have_http_status(:ok)
-        expect(TagName.find_by!(name: 'spec_tag').canonical).to eq(tag.reload.tag_name)
+        expect(TagName.find_by!(language_code: 'ja', name: 'spec_tag'))
+            .to have_attributes(tag_id: tag.id, primary_flg: false)
 
         patch "/tags/#{ tag.id }", params: { name: 'spec_tag' }
 
@@ -601,8 +782,10 @@ RSpec.describe 'Tags API', type: :request do
         tag.reload
 
         expect(tag.name).to eq('spec_tag')
-        expect(tag.tag_name.canonical_id).to be_nil
+        expect(tag.tag_name).to have_attributes(
-        expect(TagName.find_by!(name: 'patch_roundtrip_target').canonical).to eq(tag.tag_name)
+            tag_id: tag.id, language_code: 'ja', primary_flg: true)
+        expect(TagName.find_by!(language_code: 'ja', name: 'patch_roundtrip_target'))
+            .to have_attributes(tag_id: tag.id, primary_flg: false)
       end
 
       it '別 tag の正規名には変更できない' do
@@ -621,7 +804,8 @@ RSpec.describe 'Tags API', type: :request do
         )
 
         expect(tag.reload.name).to eq('spec_tag')
-        expect(tag.tag_name.aliases.map(&:name)).to contain_exactly('unko')
+        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(tag.tag_name)
       end
 
@@ -638,27 +822,27 @@ RSpec.describe 'Tags API', type: :request do
 
   describe 'GET /tags/with-depth' do
     let!(:root_meme) do
-      Tag.create!(tag_name: TagName.create!(name: 'depth_a_root_meme'), category: :meme)
+      create(:tag, name: 'depth_a_root_meme', category: :meme)
     end
 
     let!(:root_material) do
-      Tag.create!(tag_name: TagName.create!(name: 'depth_b_root_material'), category: :material)
+      create(:tag, name: 'depth_b_root_material', category: :material)
     end
 
     let!(:hidden_general_root) do
-      Tag.create!(tag_name: TagName.create!(name: 'depth_hidden_general_root'), category: :general)
+      create(:tag, name: 'depth_hidden_general_root', category: :general)
     end
 
     let!(:child_character) do
-      Tag.create!(tag_name: TagName.create!(name: 'depth_child_character'), category: :character)
+      create(:tag, name: 'depth_child_character', category: :character)
     end
 
     let!(:grandchild_material) do
-      Tag.create!(tag_name: TagName.create!(name: 'depth_grandchild_material'), category: :material)
+      create(:tag, name: 'depth_grandchild_material', category: :material)
     end
 
     let!(:child_general) do
-      Tag.create!(tag_name: TagName.create!(name: 'depth_child_general'), category: :general)
+      create(:tag, name: 'depth_child_general', category: :general)
     end
 
     before do
@@ -701,15 +885,13 @@ RSpec.describe 'Tags API', type: :request do
     end
 
     it 'passes through deprecated tags when finding children' do
-      deprecated_middle = Tag.create!(
+      deprecated_middle = create(:tag,
-        name: 'depth_deprecated_middle',
+          name: 'depth_deprecated_middle',
-        category: :character,
+          category: :character,
-        deprecated_at: Time.current
+          deprecated_at: Time.current)
-      )
+      visible_descendant = create(:tag,
-      visible_descendant = Tag.create!(
+          name: 'depth_visible_descendant',
-        name: 'depth_visible_descendant',
+          category: :material)
-        category: :material
-      )
       TagImplication.create!(parent_tag: root_material, tag: deprecated_middle)
       TagImplication.create!(parent_tag: deprecated_middle, tag: visible_descendant)
 
@@ -721,24 +903,20 @@ RSpec.describe 'Tags API', type: :request do
     end
 
     it 'passes through multiple deprecated tags for roots and has_children' do
-      active_child = Tag.create!(
+      active_child = create(:tag,
-        name: 'depth_active_child_below_deprecated',
+          name: 'depth_active_child_below_deprecated',
-        category: :character
+          category: :character)
-      )
+      deprecated_parent = create(:tag,
-      deprecated_parent = Tag.create!(
+          name: 'depth_deprecated_parent',
-        name: 'depth_deprecated_parent',
+          category: :character,
-        category: :character,
+          deprecated_at: Time.current)
-        deprecated_at: Time.current
+      deprecated_grandparent = create(:tag,
-      )
+          name: 'depth_deprecated_grandparent',
-      deprecated_grandparent = Tag.create!(
+          category: :material,
-        name: 'depth_deprecated_grandparent',
+          deprecated_at: Time.current)
-        category: :material,
+      active_ancestor = create(:tag,
-        deprecated_at: Time.current
+          name: 'depth_active_ancestor',
-      )
+          category: :meme)
-      active_ancestor = Tag.create!(
-        name: 'depth_active_ancestor',
-        category: :meme
-      )
       TagImplication.create!(tag: active_child, parent_tag: deprecated_parent)
       TagImplication.create!(tag: deprecated_parent, parent_tag: deprecated_grandparent)
       TagImplication.create!(tag: deprecated_grandparent, parent_tag: active_ancestor)
@@ -763,15 +941,13 @@ RSpec.describe 'Tags API', type: :request do
     end
 
     it 'treats an active tag with only deprecated ancestors as a root' do
-      active_child = Tag.create!(
+      active_child = create(:tag,
-        name: 'depth_root_below_deprecated',
+          name: 'depth_root_below_deprecated',
-        category: :character
+          category: :character)
-      )
+      deprecated_parent = create(:tag,
-      deprecated_parent = Tag.create!(
+          name: 'depth_root_deprecated_parent',
-        name: 'depth_root_deprecated_parent',
+          category: :material,
-        category: :material,
+          deprecated_at: Time.current)
-        deprecated_at: Time.current
-      )
       TagImplication.create!(tag: active_child, parent_tag: deprecated_parent)
 
       get '/tags/with-depth'
@@ -785,16 +961,14 @@ RSpec.describe 'Tags API', type: :request do
     end
 
     it 'terminates when deprecated implications contain a cycle' do
-      first = Tag.create!(
+      first = create(:tag,
-        name: 'depth_cycle_first',
+          name: 'depth_cycle_first',
-        category: :character,
+          category: :character,
-        deprecated_at: Time.current
+          deprecated_at: Time.current)
-      )
+      second = create(:tag,
-      second = Tag.create!(
+          name: 'depth_cycle_second',
-        name: 'depth_cycle_second',
+          category: :material,
-        category: :material,
+          deprecated_at: Time.current)
-        deprecated_at: Time.current
-      )
       TagImplication.create!(tag: first, parent_tag: root_material)
       TagImplication.create!(tag: second, parent_tag: first)
       now = Time.current
@@ -820,19 +994,19 @@ RSpec.describe 'Tags API', type: :request do
     let!(:material_user) { create_member_user! }
 
     let!(:root_tag) do
-      Tag.create!(tag_name: TagName.create!(name: 'materials_root'), category: :material)
+      create(:tag, name: 'materials_root', category: :material)
     end
 
     let!(:child_a_tag) do
-      Tag.create!(tag_name: TagName.create!(name: 'materials_child_a'), category: :material)
+      create(:tag, name: 'materials_child_a', category: :material)
     end
 
     let!(:child_b_tag) do
-      Tag.create!(tag_name: TagName.create!(name: 'materials_child_b'), category: :character)
+      create(:tag, name: 'materials_child_b', category: :character)
     end
 
     let!(:grandchild_tag) do
-      Tag.create!(tag_name: TagName.create!(name: 'materials_grandchild'), category: :material)
+      create(:tag, name: 'materials_grandchild', category: :material)
     end
 
     let!(:root_material) do
@@ -976,14 +1150,12 @@ RSpec.describe 'Tags API', type: :request do
       end
 
       it 'name, category, aliases, parent tags をまとめて更新できる' do
-        old_parent = Tag.create!(
+        old_parent = create(:tag,
-          tag_name: TagName.create!(name: 'put_old_parent'),
+            tag_name: create(:tag_name, name: 'put_old_parent'),
-          category: :general
+            category: :general)
-        )
+        kept_parent = create(:tag,
-        kept_parent = Tag.create!(
+            tag_name: create(:tag_name, name: 'put_kept_parent'),
-          tag_name: TagName.create!(name: 'put_kept_parent'),
+            category: :general)
-          category: :general
-        )
         TagImplication.create!(tag:, parent_tag: old_parent)
         TagImplication.create!(tag:, parent_tag: kept_parent)
 
@@ -1002,14 +1174,17 @@ RSpec.describe 'Tags API', type: :request do
         expect(tag.name).to eq('put_renamed_tag')
         expect(tag.category).to eq('meme')
 
-        expect(TagName.find_by(name: 'put_alias_a').canonical).to eq(tag.tag_name)
+        expect(TagName.find_by!(language_code: 'ja', name: 'put_alias_a'))
-        expect(TagName.find_by(name: 'put_alias_b').canonical).to eq(tag.tag_name)
+            .to have_attributes(tag_id: tag.id, primary_flg: false)
+        expect(TagName.find_by!(language_code: 'ja', name: 'put_alias_b'))
+            .to have_attributes(tag_id: tag.id, primary_flg: false)
 
         old_name_alias = TagName.find_by(name: 'spec_tag')
         expect(old_name_alias).to be_present
-        expect(old_name_alias.canonical).to eq(tag.tag_name)
+        expect(old_name_alias).to have_attributes(
+            tag_id: tag.id, language_code: 'ja', primary_flg: false)
 
-        expect(alias_tn.reload.canonical).to be_nil
+        expect(alias_tn.reload.tag_id).to be_nil
 
         expect(tag.parents.map(&:name)).to contain_exactly(
           'put_kept_parent',
@@ -1044,7 +1219,8 @@ RSpec.describe 'Tags API', type: :request do
 
         tag.reload
 
-        expect(TagName.find_by(name: 'put_alias_self_test').canonical).to eq(tag.tag_name)
+        expect(TagName.find_by!(language_code: 'ja', name: 'put_alias_self_test'))
+            .to have_attributes(tag_id: tag.id, primary_flg: false)
         expect(json['aliases']).to include('put_alias_self_test')
         expect(json['aliases']).not_to include('spec_tag')
       end
@@ -1115,10 +1291,14 @@ RSpec.describe 'Tags API', type: :request do
         tag.reload
 
         expect(tag.name).to eq('spec_tag')
-        expect(TagName.find_by!(name: 'put_roundtrip_b').canonical).to eq(tag.tag_name)
+        expect(TagName.find_by!(language_code: 'ja', name: 'put_roundtrip_b'))
-        expect(tag.tag_name.aliases.map(&:name)).to contain_exactly('put_roundtrip_b', 'unko')
+            .to have_attributes(tag_id: tag.id, primary_flg: false)
-        expect(tag.tag_name.aliases.map(&:name)).not_to include('spec_tag')
+        expect(TagName.where(tag_id: tag.id, language_code: 'ja', primary_flg: false).pluck(:name))
-        expect(alias_tn.reload.canonical).to eq(tag.tag_name)
+            .to contain_exactly('put_roundtrip_b', 'unko')
+        expect(TagName.where(tag_id: tag.id, language_code: 'ja', primary_flg: false).pluck(:name))
+            .not_to include('spec_tag')
+        expect(alias_tn.reload).to have_attributes(
+            tag_id: tag.id, language_code: 'ja', primary_flg: false)
 
         version = tag.tag_versions.order(:version_no).last
 
@@ -1128,14 +1308,12 @@ RSpec.describe 'Tags API', type: :request do
       end
 
       it 'parent tag の snapshot も作成する' do
-        old_parent = Tag.create!(
+        old_parent = create(:tag,
-          tag_name: TagName.create!(name: 'put_snapshot_old_parent'),
+            tag_name: create(:tag_name, name: 'put_snapshot_old_parent'),
-          category: :general
+            category: :general)
-        )
+        new_parent = create(:tag,
-        new_parent = Tag.create!(
+            tag_name: create(:tag_name, name: 'put_snapshot_new_parent'),
-          tag_name: TagName.create!(name: 'put_snapshot_new_parent'),
+            category: :general)
-          category: :general
-        )
         TagImplication.create!(tag:, parent_tag: old_parent)
 
         put "/tags/#{ tag.id }", params: {
@@ -1169,28 +1347,6 @@ RSpec.describe 'Tags API', type: :request do
         expect(tag.category).to eq('general')
       end
 
-      it 'nico tag は更新できない' do
-        nico_tag = Tag.create!(
-          tag_name: TagName.create!(name: 'nico:put_update_all_ng'),
-          category: :nico
-        )
-
-        expect {
-          put "/tags/#{ nico_tag.id }", params: {
-            name: 'nico:put_update_all_renamed',
-            category: 'nico',
-            aliases: '',
-            parent_tags: '',
-            deprecated: '0',
-          }
-        }.not_to change(NicoTagVersion, :count)
-
-        expect(response).to have_http_status(:unprocessable_entity)
-
-        expect(nico_tag.reload.name).to eq('nico:put_update_all_ng')
-        expect(nico_tag.category).to eq('nico')
-      end
-
       it 'system tag の name は変更できない' do
         system_tag = Tag.tagme
         old_name = system_tag.name
@@ -1251,7 +1407,7 @@ RSpec.describe 'Tags API', type: :request do
         )
       end
 
-      it 'wiki を持つ tag を旧 alias へ戻しても wiki を新 canonical へ移す' do
+      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!(
                 tag_name: tag.tag_name,
@@ -1285,7 +1441,8 @@ RSpec.describe 'Tags API', type: :request do
 
         expect(wiki_page.reload.tag_name).to eq(tag.tag_name)
         expect(TagName.find_by!(name: 'put_wiki_roundtrip_b').wiki_page).to be_nil
-        expect(TagName.find_by!(name: 'put_wiki_roundtrip_b').canonical).to eq(tag.tag_name)
+        expect(TagName.find_by!(language_code: 'ja', name: 'put_wiki_roundtrip_b'))
+            .to have_attributes(tag_id: tag.id, primary_flg: false)
 
         versions = wiki_page.wiki_versions.order(:version_no).last(2)
 
@@ -1294,16 +1451,16 @@ RSpec.describe 'Tags API', type: :request do
       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
-        old_owner = Tag.create!(
+        old_owner = create(:tag,
-          tag_name: TagName.create!(name: 'put_alias_old_owner'),
+            tag_name: create(:tag_name, name: 'put_alias_old_owner'),
-          category: :general
+            category: :general)
-        )
+        stolen_alias = create(:tag_name, :alias,
-        stolen_alias = TagName.create!(
+            name: 'put_stolen_alias',
-          name: 'put_stolen_alias',
+            tag: old_owner)
-          canonical: old_owner.tag_name
-        )
 
-        expect(old_owner.tag_name.aliases.map(&:name)).to include('put_stolen_alias')
+        expect(TagName.where(tag_id: old_owner.id, language_code: 'ja',
+                              primary_flg: false).pluck(:name))
+            .to include('put_stolen_alias')
 
         expect {
           put "/tags/#{ tag.id }", params: {
@@ -1319,8 +1476,11 @@ RSpec.describe 'Tags API', type: :request do
 
         expect(response).to have_http_status(:ok)
 
-        expect(stolen_alias.reload.canonical).to eq(tag.tag_name)
+        expect(stolen_alias.reload).to have_attributes(
-        expect(old_owner.reload.tag_name.aliases.map(&:name)).not_to include('put_stolen_alias')
+            tag_id: tag.id, language_code: 'ja', primary_flg: false)
+        expect(TagName.where(tag_id: old_owner.id, language_code: 'ja',
+                              primary_flg: false).pluck(:name))
+            .not_to include('put_stolen_alias')
 
         old_owner_versions = old_owner.tag_versions.order(:version_no)
 
@@ -1332,14 +1492,12 @@ RSpec.describe 'Tags API', type: :request do
       end
 
       it '別 tag の alias 名を rename で奪へる' do
-        old_owner = Tag.create!(
+        old_owner = create(:tag,
-          tag_name: TagName.create!(name: 'put_alias_collision_owner'),
+            tag_name: create(:tag_name, name: 'put_alias_collision_owner'),
-          category: :general
+            category: :general)
-        )
+        stolen_alias = create(:tag_name, :alias,
-        stolen_alias = TagName.create!(
+            name: 'put_alias_collision_name',
-          name: 'put_alias_collision_name',
+            tag: old_owner)
-          canonical: old_owner.tag_name
-        )
         wiki_page =
             Wiki::Commit.create_content!(
                 tag_name: tag.tag_name,
@@ -1355,16 +1513,20 @@ RSpec.describe 'Tags API', type: :request do
           deprecated: '0',
         }
 
-        expect(response).to have_http_status(:ok)
+        expect(response).to have_http_status(:ok), response.body
 
         tag.reload
         old_owner.reload
         stolen_alias.reload
 
         expect(tag.name).to eq('put_alias_collision_name')
-        expect(stolen_alias.canonical_id).to be_nil
+        expect(stolen_alias).to have_attributes(
-        expect(TagName.find_by!(name: 'spec_tag').canonical).to eq(tag.tag_name)
+            tag_id: tag.id, language_code: 'ja', primary_flg: true)
-        expect(old_owner.tag_name.aliases.map(&:name)).not_to include('put_alias_collision_name')
+        expect(TagName.find_by!(language_code: 'ja', name: 'spec_tag'))
+            .to have_attributes(tag_id: tag.id, primary_flg: false)
+        expect(TagName.where(tag_id: old_owner.id, language_code: 'ja',
+                              primary_flg: false).pluck(:name))
+            .not_to include('put_alias_collision_name')
 
         old_owner_versions = old_owner.tag_versions.order(:version_no)
 
@@ -1374,10 +1536,9 @@ RSpec.describe 'Tags API', type: :request do
       end
 
       it 'parent_tags に指定すると循環する tag は 422 にする' do
-        child = Tag.create!(
+        child = create(:tag,
-          tag_name: TagName.create!(name: 'put_cycle_child'),
+            tag_name: create(:tag_name, name: 'put_cycle_child'),
-          category: :general
+            category: :general)
-        )
 
         TagImplication.create!(tag: child, parent_tag: tag)
 

backend/spec/requests/wiki_body_search_pending_spec.rb

@@ -1,27 +0,0 @@
-require 'rails_helper'
-
-RSpec.describe 'Wiki body search', type: :request do
-  let!(:user) { create_member_user! }
-
-  it 'searches wiki pages by body text' do
-    pending '#336 で対応予定'
-
-    Wiki::Commit.create_content!(
-        tag_name: TagName.create!(name: 'wiki_body_search_hit'),
-        body: 'unique body keyword for wiki search',
-        created_by_user: user,
-        message: 'init')
-
-    Wiki::Commit.create_content!(
-        tag_name: TagName.create!(name: 'wiki_body_search_miss'),
-        body: 'ordinary body',
-        created_by_user: user,
-        message: 'init')
-
-    get '/wiki/search', params: { body: 'unique body keyword' }
-
-    expect(response).to have_http_status(:ok)
-    expect(json.map { |page| page['title'] }).to include('wiki_body_search_hit')
-    expect(json.map { |page| page['title'] }).not_to include('wiki_body_search_miss')
-  end
-end

backend/spec/requests/wiki_conflict_spec.rb

@@ -10,7 +10,7 @@ RSpec.describe 'Wiki conflict handling', type: :request do
   it 'returns 409 when base_revision_id is stale' do
     page =
         Wiki::Commit.create_content!(
-            tag_name: TagName.create!(name: 'wiki_conflict_request'),
+            tag_name: create(:tag_name, name: 'wiki_conflict_request'),
             body: 'first',
             created_by_user: user,
             message: 'init')

backend/spec/requests/wiki_history_integrity_spec.rb

@@ -10,7 +10,7 @@ RSpec.describe 'Wiki history integrity', type: :request do
 
   def create_wiki_page title:, body: 'body', message: 'init', user: self.user
     Wiki::Commit.create_content!(
-        tag_name: TagName.create!(name: title),
+        tag_name: create(:tag_name, name: title),
         body:,
         created_by_user: user,
         message:)

backend/spec/requests/wiki_restore_pending_spec.rb

@@ -1,37 +0,0 @@
-require 'rails_helper'
-
-RSpec.describe 'Wiki restore', type: :request do
-  let!(:user) { create_member_user! }
-
-  def auth_headers user
-    { 'X-Transfer-Code' => user.inheritance_code }
-  end
-
-  it 'restores wiki page to previous version' do
-    pending '#337 で対応予定'
-
-    page =
-        Wiki::Commit.create_content!(
-            tag_name: TagName.create!(name: 'wiki_restore_page'),
-            body: 'v1',
-            created_by_user: user,
-            message: 'init')
-
-    v1 = page.wiki_versions.order(:version_no).last
-
-    Wiki::Commit.content!(
-        page:,
-        body: 'v2',
-        created_user: user,
-        message: 'edit',
-        base_revision_id: page.current_revision.id)
-
-    post "/wiki/#{ page.id }/restore",
-         params: { version_no: v1.version_no },
-         headers: auth_headers(user)
-
-    expect(response).to have_http_status(:ok)
-    expect(page.reload.body).to eq('v1')
-    expect(page.wiki_versions.order(:version_no).last.event_type).to eq('restore')
-  end
-end

backend/spec/requests/wiki_spec.rb

@@ -10,7 +10,7 @@ RSpec.describe 'Wiki API', type: :request do
 
   let!(:user) { create_member_user! }
 
-  let!(:tn) { TagName.create!(name: 'spec_wiki_title') }
+  let!(:tn) { create(:tag_name, name: 'spec_wiki_title') }
   let!(:page) do
     Wiki::Commit.create_content!(
         tag_name: tn,
@@ -19,11 +19,10 @@ RSpec.describe 'Wiki API', type: :request do
         message: 'init')
   end
   let!(:tag) do
-    Tag.create!(
+    create(:tag,
-      tag_name: tn,
+        tag_name: tn,
-      category: :general,
+        category: :general,
-      deprecated_at: Time.zone.local(2026, 6, 1)
+        deprecated_at: Time.zone.local(2026, 6, 1))
-    )
   end
 
   describe 'GET /wiki' do
@@ -208,7 +207,7 @@ RSpec.describe 'Wiki API', type: :request do
       { 'X-Transfer-Code' => user.inheritance_code }
     end
 
-    let!(:test_tag_name) { TagName.create!(name: 'TestPage') }
+    let!(:test_tag_name) { create(:tag_name, name: 'TestPage') }
 
     let!(:page) do
       Wiki::Commit.create_content!(
@@ -275,8 +274,8 @@ RSpec.describe 'Wiki API', type: :request do
       end
 
       it 'wiki body だけを変更しても tag version は作成しない' do
-        linked_tag_name = TagName.create!(name: 'wiki_body_only_tag')
+        linked_tag_name = create(:tag_name, name: 'wiki_body_only_tag')
-        linked_tag = Tag.create!(tag_name: linked_tag_name, category: :general)
+        linked_tag = create(:tag, tag_name: linked_tag_name, category: :general)
 
         TagVersionRecorder.record!(
             tag: linked_tag,
@@ -359,13 +358,13 @@ RSpec.describe 'Wiki API', type: :request do
   describe 'GET /wiki/search' do
     before do
       Wiki::Commit.create_content!(
-          tag_name: TagName.create!(name: 'spec_wiki_title_2'),
+          tag_name: create(:tag_name, name: 'spec_wiki_title_2'),
           body: 'search body 2',
           created_by_user: user,
           message: 'init')
 
       Wiki::Commit.create_content!(
-          tag_name: TagName.create!(name: 'unrelated_title'),
+          tag_name: create(:tag_name, name: 'unrelated_title'),
           body: 'unrelated body',
           created_by_user: user,
           message: 'init')
@@ -434,7 +433,7 @@ 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 = TagName.create!(name: 'spec_no_rev')
+      tn2 = create(:tag_name, name: 'spec_no_rev')
       # 異常データ: revision 無し WikiPage を直接作る
       p2 = WikiPage.create!(
           tag_name: tn2,
@@ -514,7 +513,7 @@ RSpec.describe 'Wiki API', type: :request do
 
   describe 'Wiki::Commit.redirect!' do
     it 'raises because redirect revisions are deprecated' do
-      target_tag_name = TagName.create!(name: 'redirect_deprecated_target')
+      target_tag_name = create(:tag_name, name: 'redirect_deprecated_target')
       target =
           Wiki::Commit.create_content!(
               tag_name: target_tag_name,
@@ -535,8 +534,8 @@ RSpec.describe 'Wiki API', type: :request do
   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 = TagName.create!(name: 'wiki_linked_tag_for_version')
+    linked_tag_name = create(:tag_name, name: 'wiki_linked_tag_for_version')
-    linked_tag = Tag.create!(tag_name: linked_tag_name, category: :general)
+    linked_tag = create(:tag, tag_name: linked_tag_name, category: :general)
 
     linked_page =
         Wiki::Commit.create_content!(

backend/spec/requests/wiki_title_collision_spec.rb

@@ -9,7 +9,7 @@ RSpec.describe 'Wiki title collision', type: :request do
 
   def create_wiki_page title:, body:
     Wiki::Commit.create_content!(
-        tag_name: TagName.create!(name: title),
+        tag_name: create(:tag_name, name: title),
         body:,
         created_by_user: user,
         message: 'init')

backend/spec/services/material_sync_importer_spec.rb

@@ -2,7 +2,7 @@ require 'rails_helper'
 
 RSpec.describe MaterialSyncImporter do
   let(:user) { create(:user, :member) }
-  let(:tag) { Tag.create!(tag_name: TagName.create!(name: 'sync_tag'), category: :material) }
+  let(:tag) { create(:tag, name: 'sync_tag', category: :material) }
 
   def tempfile_for body
     Tempfile.new(['material-sync-importer', '.png']).tap do |file|

backend/spec/services/nico_tag_version_recorder_spec.rb

@@ -0,0 +1,76 @@
+require 'rails_helper'
+
+RSpec.describe NicoTagVersionRecorder do
+  let(:external_tag) { create(:external_tag, name: 'raw tag[]') }
+  let(:member) { create(:user, :member) }
+
+  def record event_type
+    described_class.record!(external_tag:, event_type:, created_by_user: member)
+  end
+
+  it 'records the external association and platform-qualified name' do
+    version = record(:create)
+
+    expect(version).to have_attributes(
+        external_tag:, version_no: 1, event_type: 'create',
+        name: 'nico:raw tag[]', linked_tags: '', created_by_user: member)
+    expect(external_tag.reload.nico_tag_versions).to contain_exactly(version)
+  end
+
+  it 'uses the latest history number when the record has no version_no column' do
+    first = record(:create)
+    external_tag.update!(name: 'changed')
+    second = record(:update)
+
+    expect(second).to have_attributes(version_no: 2, name: 'nico:changed')
+    expect(first.reload.name).to eq('nico:raw tag[]')
+    expect(external_tag.reload.has_attribute?(:version_no)).to be(false)
+  end
+
+  it 'builds the qualified name from the registered platform value' do
+    external = create(:external_tag, name: 'foo')
+    locked_scope = instance_double(ActiveRecord::Relation)
+    allow(ExternalTag).to receive(:unscoped).and_return(locked_scope)
+    allow(locked_scope).to receive(:lock).and_return(locked_scope)
+    allow(locked_scope).to receive(:find).with(external.id).and_return(external)
+    allow(external).to receive(:platform).and_return('registered_external')
+
+    version = described_class.record!(
+        external_tag: external, event_type: :create, created_by_user: member)
+
+    expect(version).to have_attributes(
+        external_tag: external, name: 'registered_external:foo', version_no: 1,
+        event_type: 'create', linked_tags: '', created_by_user: member)
+  end
+
+  it 'returns the latest version without appending an unchanged snapshot' do
+    first = record(:create)
+
+    expect { expect(record(:update)).to eq(first) }
+        .not_to change(NicoTagVersion, :count)
+  end
+
+  it 'still requires a create event before any update' do
+    expect { record(:update) }
+        .to raise_error(RuntimeError, 'NicoTagVersion first event must be create')
+    expect(external_tag.nico_tag_versions).to be_empty
+  end
+
+  it 'still rejects a second create event' do
+    first = record(:create)
+
+    expect { record(:create) }
+        .to raise_error(RuntimeError, 'NicoTagVersion create event already exists')
+    expect(external_tag.nico_tag_versions).to contain_exactly(first)
+  end
+
+  it 'records sorted linked internal names and later link removal' do
+    tags = ['z_link', 'a_link'].map { |name| create(:tag, name:, category: :general) }
+    tags.each { |tag| NicoTagRelation.create!(nico_tag: external_tag, tag:) }
+
+    expect(record(:create).linked_tags).to eq('a_link z_link')
+    external_tag.linked_tags = [tags.first]
+
+    expect(record(:update)).to have_attributes(version_no: 2, linked_tags: 'z_link')
+  end
+end

backend/spec/services/post_bulk_creator_spec.rb

@@ -0,0 +1,68 @@
+require 'rails_helper'
+
+RSpec.describe PostBulkCreator do
+  include_context 'English locale'
+
+  it 'limits workers to two and keeps failures in their request slots' do
+    actor = instance_double(User, id: 123)
+    allow(User).to receive(:find).with(123) {
+      instance_double(User, id: 123)
+    }
+    mutex = Mutex.new
+    active = 0
+    maximum_active = 0
+    creators = []
+
+    allow(PostCreatePreflight).to receive(:new) do |attributes:, **|
+      preflight = instance_double(PostCreatePreflight)
+      allow(preflight).to receive(:run) do
+        mutex.synchronize do
+          active += 1
+          maximum_active = [maximum_active, active].max
+        end
+        sleep 0.02
+        mutex.synchronize { active -= 1 }
+        attributes.symbolize_keys.merge(
+            existing_post_id: nil,
+            field_warnings: { },
+            base_warnings: [])
+      end
+      preflight
+    end
+    allow(PostCreator).to receive(:new) do |attributes:, **|
+      creator = instance_double(PostCreator)
+      mutex.synchronize { creators << creator }
+      if attributes[:title] == 'broken'
+        allow(creator).to receive(:create!).and_raise(StandardError, 'broken')
+      else
+        post = instance_double(Post, id: attributes[:title].delete_prefix('post ').to_i)
+        allow(creator).to receive(:create!).and_return(post)
+      end
+      creator
+    end
+    posts = [
+        { 'title' => 'post 1', 'url' => 'https://example.com/1' },
+        { 'title' => 'broken', 'url' => 'https://example.com/2' },
+        { 'title' => 'post 3', 'url' => 'https://example.com/3' },
+        { 'title' => 'post 4', 'url' => 'https://example.com/4' }]
+
+    results = described_class.new(
+        actor:,
+        posts:,
+        thumbnails: { }).run(locale).fetch(:results)
+
+    expect(creators.length).to eq(posts.length)
+    creators.each do |creator|
+      expect(creator).to have_received(:create!).with(locale).once
+    end
+
+    expect(maximum_active).to eq(2)
+    expect(results.length).to eq(posts.length)
+    expect(results.map { _1[:status] }).to eq(
+        ['created', 'failed', 'created', 'created'])
+    expect(results[0].dig(:post, :id)).to eq(1)
+    expect(results[1]).to include(status: 'failed', recoverable: false)
+    expect(results[2].dig(:post, :id)).to eq(3)
+    expect(results[3].dig(:post, :id)).to eq(4)
+  end
+end

backend/spec/services/post_create_plan_spec.rb

@@ -0,0 +1,144 @@
+require 'rails_helper'
+
+RSpec.describe PostCreatePlan do
+  def create_tag! name, category
+    create(:tag, name:, category:)
+  end
+
+  before do
+    create_tag!('タグ希望', :meta)
+    create_tag!('ニジラー情報不詳', :meta)
+  end
+
+  context 'with an explicit locale' do
+    include_context 'English locale'
+
+    it 'resolves the matching language identity and its parents' do
+      english_name = create(:tag_name, name: 'shared_name',
+                                      language_code: 'en', script_code: 'Latn')
+      english = create(:tag, tag_name: english_name, category: :character)
+      japanese = create(:tag, name: 'temporary_japanese', category: :general)
+      # The DB permits this identity; validation has its own contract spec.
+      japanese.tag_name.update_columns(name: 'shared_name')
+      english_parent = create(:tag, name: 'english_parent', category: :material)
+      japanese_parent = create(:tag, name: 'japanese_parent', category: :general)
+      TagImplication.create!(tag: english, parent_tag: english_parent)
+      TagImplication.create!(tag: japanese, parent_tag: japanese_parent)
+
+      plan = described_class.new(attributes: { tags: 'shared_name' }).build!(locale)
+
+      expect(plan[:direct_tag_specs]).to eq(
+          [{ name: 'shared_name', category: :character }])
+      expect(plan[:post_tag_specs]).to include(
+          { name: english_parent.name, category: :material })
+      expect(plan[:post_tag_specs].pluck(:name)).not_to include(japanese_parent.name)
+    end
+
+    it 'resolves aliases within the requested language' do
+      japanese = create(:tag, name: 'japanese_canonical')
+      english_name = create(:tag_name, name: 'english_canonical',
+                                      language_code: 'en', script_code: 'Latn')
+      english = create(:tag, tag_name: english_name, category: :character)
+      japanese_alias = create(:tag_name, :alias, name: 'shared_alias',
+                                                tag: japanese)
+      english_alias = create(:tag_name, :alias, name: 'shared_alias',
+                                               tag: english,
+                                               language_code: 'en', script_code: 'Latn')
+
+      expect(japanese_alias.reload).to have_attributes(
+          tag_id: japanese.id,
+          primary_flg: false, language_code: 'ja')
+      expect(english_alias.reload).to have_attributes(
+          tag_id: english.id,
+          primary_flg: false, language_code: 'en')
+
+      plan = described_class.new(attributes: { tags: 'shared_alias' }).build!(locale)
+
+      expect(plan[:direct_tag_specs]).to eq(
+          [{ name: english.name, category: :character }])
+    end
+  end
+
+  it 'plans direct and existing default tags without persisting records' do
+    counts = [TagName.count, Tag.count]
+
+    plan = described_class.new(
+        attributes: {
+            url: 'https://example.com/post',
+            title: 'title',
+            tags: 'character:new_character',
+            parent_post_ids: '' }).build!(Locale.nipponese)
+
+    expect(plan[:tags]).to eq('new_character')
+    expect(plan[:direct_tag_specs]).to eq(
+        [{ name: 'new_character', category: :character }])
+    expect(plan[:default_tag_specs]).to include(
+        { name: 'タグ希望', category: :meta },
+        { name: 'ニジラー情報不詳', category: :meta })
+    expect([TagName.count, Tag.count]).to eq(counts)
+  end
+
+  it 'resolves aliases and keeps tag sections separate from primary names' do
+    tag = create_tag!('虹夏', :character)
+    create(:tag_name, :alias, name: 'にじか', tag:)
+    create_tag!('動画', :meta)
+
+    plan = described_class.new(
+        attributes: {
+            url: 'https://example.com/video',
+            title: 'video',
+            tags: '動画 にじか[0:10-0:20]',
+            duration: '1:00',
+            parent_post_ids: '' }).build!(Locale.nipponese)
+
+    expect(plan[:tags].split).to include('動画', '虹夏[0:10-0:20]')
+    expect(plan[:display_tags]).to include(
+        { name: '虹夏',
+          category: 'character',
+          section_literals: ['[0:10-0:20]'] })
+    expect(plan[:video_ms]).to eq(60_000)
+  end
+
+  it 'rejects direct external tag input without creating internal records' do
+    create(:external_tag, name: 'reserved')
+    counts = [Tag.count, TagName.count, ExternalTag.count]
+
+    expect {
+      described_class.new(attributes: { tags: 'NiCo:reserved' }).build!(Locale.nipponese)
+    }.to raise_error(ActiveRecord::RecordInvalid) { |error|
+      expect(error.record.errors[:tags]).to be_present
+    }
+
+    expect([Tag.count, TagName.count, ExternalTag.count]).to eq(counts)
+  end
+
+  it 'validates a new tag name without persisting it' do
+    long_name = 'a' * 256
+    counts = [TagName.count, Tag.count]
+
+    expect {
+      described_class.new(
+          attributes: {
+              url: 'https://example.com/post',
+              title: 'title',
+              tags: long_name,
+              parent_post_ids: '' }).build!(Locale.nipponese)
+    }.to raise_error(ActiveRecord::RecordInvalid) { |error|
+      expect(error.record.errors[:tags]).not_to be_empty
+    }
+    expect([TagName.count, Tag.count]).to eq(counts)
+  end
+
+  it 'ignores duration when the planned tags do not include video' do
+    plan = described_class.new(
+        attributes: {
+            url: 'https://example.com/post',
+            title: 'title',
+            tags: 'ordinary_tag',
+            duration: 'invalid',
+            parent_post_ids: '' }).build!(Locale.nipponese)
+
+    expect(plan[:duration]).to eq('invalid')
+    expect(plan[:video_ms]).to be_nil
+  end
+end