#297

#61

#61

Merge remote-tracking branch 'origin/main' into feature/061

#61

#61

#61

#61

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#61

日づけ不詳の表示修正

Co-authored-by: miteruzo <miteruzo@naver.com>
Reviewed-on: #298

backend/.rspec

@@ -0,0 +1 @@
+--require spec_helper

backend/Gemfile

@@ -46,6 +46,8 @@ group :development, :test do
 
   # Omakase Ruby styling [https://github.com/rails/rubocop-rails-omakase/]
   gem "rubocop-rails-omakase", require: false
+
+  gem 'factory_bot_rails'
 end
 
 
@@ -63,3 +65,7 @@ gem 'diff-lcs'
 gem 'dotenv-rails'
 
 gem 'whenever', require: false
+
+gem 'discard'
+
+gem "rspec-rails", "~> 8.0", :groups => [:development, :test]

backend/Gemfile.lock

@@ -90,6 +90,8 @@ GEM
     crass (1.0.6)
     date (3.4.1)
     diff-lcs (1.6.2)
+    discard (1.4.0)
+      activerecord (>= 4.2, < 9.0)
     dotenv (3.1.8)
     dotenv-rails (3.1.8)
       dotenv (= 3.1.8)
@@ -97,6 +99,11 @@ GEM
     drb (2.2.1)
     ed25519 (1.4.0)
     erubi (1.13.1)
+    factory_bot (6.5.6)
+      activesupport (>= 6.1.0)
+    factory_bot_rails (6.5.1)
+      factory_bot (~> 6.5)
+      railties (>= 6.1.0)
     ffi (1.17.2-aarch64-linux-gnu)
     ffi (1.17.2-aarch64-linux-musl)
     ffi (1.17.2-arm-linux-gnu)
@@ -296,6 +303,23 @@ GEM
       io-console (~> 0.5)
     rexml (3.4.1)
     rouge (3.30.0)
+    rspec-core (3.13.6)
+      rspec-support (~> 3.13.0)
+    rspec-expectations (3.13.5)
+      diff-lcs (>= 1.2.0, < 2.0)
+      rspec-support (~> 3.13.0)
+    rspec-mocks (3.13.7)
+      diff-lcs (>= 1.2.0, < 2.0)
+      rspec-support (~> 3.13.0)
+    rspec-rails (8.0.2)
+      actionpack (>= 7.2)
+      activesupport (>= 7.2)
+      railties (>= 7.2)
+      rspec-core (~> 3.13)
+      rspec-expectations (~> 3.13)
+      rspec-mocks (~> 3.13)
+      rspec-support (~> 3.13)
+    rspec-support (3.13.6)
     rss (0.3.1)
       rexml
     rubocop (1.75.6)
@@ -420,7 +444,9 @@ DEPENDENCIES
   bootsnap
   brakeman
   diff-lcs
+  discard
   dotenv-rails
+  factory_bot_rails
   gollum
   image_processing (~> 1.14)
   jwt
@@ -430,6 +456,7 @@ DEPENDENCIES
   puma (>= 5.0)
   rack-cors
   rails (~> 8.0.2)
+  rspec-rails (~> 8.0)
   rubocop-rails-omakase
   sprockets-rails
   sqlite3 (>= 2.1)

backend/app/controllers/application_controller.rb

@@ -11,4 +11,15 @@ class ApplicationController < ActionController::API
     code = request.headers['X-Transfer-Code'] || request.headers['HTTP_X_TRANSFER_CODE']
     @current_user = User.find_by(inheritance_code: code)
   end
+
+  def bool? key, default: false
+    return default if params[key].nil?
+
+    s = params[key].to_s.strip.downcase
+    if default
+      !(s.in?(['0', 'false', 'off', 'no']))
+    else
+      s.in?(['', '1', 'true', 'on', 'yes'])
+    end
+  end
 end

backend/app/controllers/deerjikists_controller.rb

@@ -0,0 +1,47 @@
+class DeerjikistsController < ApplicationController
+  def show
+    platform = params[:platform].to_s.strip
+    code = params[:code].to_s.strip
+    return head :bad_request if platform.blank? || code.blank?
+
+    deerjikist = Deerjikist
+                 .joins(:tag)
+                 .includes(tag: :tag_name)
+                 .find_by(platform:, code:)
+    if deerjikist
+      render json: DeerjikistRepr.base(deerjikist)
+    else
+      head :not_found
+    end
+  end
+
+  def update
+    return head :unauthorized unless current_user
+    return head :forbidden unless current_user.gte_member?
+
+    platform = params[:platform].to_s.strip
+    code = params[:code].to_s.strip
+    tag_id = params[:tag_id].to_i
+    return head :bad_request if platform.blank? || code.blank? || tag_id <= 0
+
+    deerjikist = Deerjikist.find_or_initialize_by(platform:, code:).tap do |d|
+      d.tag_id = tag_id
+      d.save!
+    end
+
+    render json: DeerjikistRepr.base(deerjikist)
+  end
+
+  def destroy
+    return head :unauthorized unless current_user
+    return head :forbidden unless current_user.gte_member?
+
+    platform = params[:platform].to_s.strip
+    code = params[:code].to_s.strip
+    return head :bad_request if platform.blank? || code.blank?
+
+    Deerjikist.find([platform, code]).destroy!
+
+    head :no_content
+  end
+end

backend/app/controllers/ip_addresses_controller.rb

@@ -1,20 +0,0 @@
-class IpAddressesController < ApplicationController
-  def index
-    @ip_addresses = IpAddress.all
-
-    render json: @ip_addresses
-  end
-
-  def show
-    render json: @ip_address
-  end
-
-  def create
-  end
-
-  def update
-  end
-
-  def destroy
-  end
-end

backend/app/controllers/nico_tag_relation_controller.rb

@@ -1,16 +0,0 @@
-class NicoTagRelationController < ApplicationController
-  def index
-  end
-
-  def show
-  end
-
-  def create
-  end
-
-  def update
-  end
-
-  def destroy
-  end
-end

backend/app/controllers/nico_tags_controller.rb

@@ -3,10 +3,12 @@ class NicoTagsController < ApplicationController
     limit = (params[:limit] || 20).to_i
     cursor = params[:cursor].presence
 
-    q = Tag.nico_tags.includes(:linked_tags).order(updated_at: :desc)
+    q = Tag.nico_tags
+           .includes(:tag_name, tag_name: :wiki_page, linked_tags: { tag_name: :wiki_page })
+           .order(updated_at: :desc)
     q = q.where('tags.updated_at < ?', Time.iso8601(cursor)) if cursor
 
-    tags = q.limit(limit + 1)
+    tags = q.limit(limit + 1).to_a
 
     next_cursor = nil
     if tags.size > limit
@@ -15,13 +17,15 @@ class NicoTagsController < ApplicationController
     end
 
     render json: { tags: tags.map { |tag|
-      tag.as_json(include: :linked_tags)
+      TagRepr.base(tag).merge(linked_tags: tag.linked_tags.map { |lt|
+        TagRepr.base(lt)
+      })
     }, next_cursor: }
   end
 
   def update
     return head :unauthorized unless current_user
-    return head :forbidden unless current_user.member?
+    return head :forbidden unless current_user.gte_member?
 
     id = params[:id].to_i
 
@@ -30,12 +34,11 @@ class NicoTagsController < ApplicationController
 
     linked_tag_names = params[:tags].to_s.split(' ')
     linked_tags = Tag.normalise_tags(linked_tag_names, with_tagme: false)
-    return head :bad_request if linked_tags.filter { |t| t.category == 'nico' }.present?
+    return head :bad_request if linked_tags.any? { |t| t.category == 'nico' }
 
     tag.linked_tags = linked_tags
-    tag.updated_at = Time.now
     tag.save!
 
-    render json: tag.linked_tags, status: :ok
+    render json: tag.linked_tags.map { |t| TagRepr.base(t) }, status: :ok
   end
 end

backend/app/controllers/post_tags_controller.rb

@@ -1,16 +0,0 @@
-class PostTagsController < ApplicationController
-  def index
-  end
-
-  def show
-  end
-
-  def create
-  end
-
-  def update
-  end
-
-  def destroy
-  end
-end

backend/app/controllers/posts_controller.rb

@@ -1,29 +1,89 @@
-require 'open-uri'
-require 'nokogiri'
-
-
 class PostsController < ApplicationController
-  # GET /posts
+  Event = Struct.new(:post, :tag, :user, :change_type, :timestamp, keyword_init: true)
+
   def index
-    limit = params[:limit].presence&.to_i
-    cursor = params[:cursor].presence
+    url = params[:url].presence
+    title = params[:title].presence
+    original_created_from = params[:original_created_from].presence
+    original_created_to = params[:original_created_to].presence
+    created_between = params[:created_from].presence, params[:created_to].presence
+    updated_between = params[:updated_from].presence, params[:updated_to].presence
 
-    created_at = ('COALESCE(posts.original_created_before - INTERVAL 1 SECOND,' +
-                  'posts.original_created_from,' +
-                  'posts.created_at)')
-    q = filtered_posts.order(Arel.sql("#{ created_at } DESC"))
-    q = q.where("#{ created_at } < ?", Time.iso8601(cursor)) if cursor
-
-    posts = limit ? q.limit(limit + 1) : q
-
-    next_cursor = nil
-    if limit && posts.size > limit
-      next_cursor = posts.last.created_at.iso8601(6)
-      posts = posts.first(limit)
+    order = params[:order].to_s.split(':', 2).map(&:strip)
+    unless order[0].in?(['title', 'url', 'original_created_at', 'created_at', 'updated_at'])
+      order[0] = 'original_created_at'
+    end
+    unless order[1].in?(['asc', 'desc'])
+      order[1] =
+          if order[0].in?(['title', 'url'])
+            'asc'
+          else
+            'desc'
+          end
     end
 
+    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
+
+    pt_max_sql =
+        PostTag
+        .select('post_id, MAX(updated_at) AS max_updated_at')
+        .group('post_id')
+        .to_sql
+
+    updated_at_all_sql =
+        'GREATEST(posts.updated_at,' +
+        'COALESCE(pt_max.max_updated_at, posts.updated_at))'
+
+    q =
+        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(tags: { tag_name: :wiki_page })
+        .with_attached_thumbnail
+
+    q = q.where('posts.url LIKE ?', "%#{ url }%") if url
+    q = q.where('posts.title LIKE ?', "%#{ title }%") if title
+    if original_created_from
+      q = q.where('posts.original_created_before > ?', original_created_from)
+    end
+    if original_created_to
+      q = q.where('posts.original_created_from <= ?', original_created_to)
+    end
+    q = q.where('posts.created_at >= ?', created_between[0]) if created_between[0]
+    q = q.where('posts.created_at <= ?', created_between[1]) if created_between[1]
+    if updated_between[0]
+      q = q.where("#{ updated_at_all_sql } >= ?", updated_between[0])
+    end
+    if updated_between[1]
+      q = q.where("#{ updated_at_all_sql } <= ?", updated_between[1])
+    end
+
+    sort_sql =
+        case order[0]
+        when 'original_created_at'
+          'COALESCE(posts.original_created_before - INTERVAL 1 MINUTE,' +
+          'posts.original_created_from,' +
+          'posts.created_at) '
+        when 'updated_at'
+          updated_at_all_sql
+        else
+          "posts.#{ order[0] }"
+        end
+    posts = q.order(Arel.sql("#{ sort_sql } #{ order[1] }, posts.id #{ order[1] }"))
+             .limit(limit)
+             .offset(offset)
+             .to_a
+
+    q = q.except(:select, :order)
+
     render json: { posts: posts.map { |post|
-      post.as_json(include: { tags: { only: [:id, :name, :category, :post_count] } }).tap do |json|
+      PostRepr.base(post).merge(updated_at: post.updated_at_all).tap do |json|
         json['thumbnail'] =
             if post.thumbnail.attached?
               rails_storage_proxy_url(post.thumbnail, only_path: false)
@@ -31,58 +91,55 @@ class PostsController < ApplicationController
               nil
             end
       end
-    }, next_cursor: }
+    }, count: q.group_values.present? ? q.count.size : q.count }
   end
 
   def random
-    post = filtered_posts.order('RAND()').first
+    post = filtered_posts.preload(tags: { tag_name: :wiki_page })
+                         .order('RAND()')
+                         .first
     return head :not_found unless post
 
-    viewed = current_user&.viewed?(post) || false
-
-    render json: (post
-                  .as_json(include: { tags: { only: [:id, :name, :category, :post_count] } })
-                  .merge(viewed:))
+    render json: PostRepr.base(post, current_user)
   end
 
-  # GET /posts/1
   def show
-    post = Post.includes(:tags).find(params[:id])
+    post = Post.includes(tags: { tag_name: :wiki_page }).find_by(id: params[:id])
     return head :not_found unless post
 
-    viewed = current_user&.viewed?(post) || false
-
-    render json: (post
-                  .as_json(include: { tags: { only: [:id, :name, :category, :post_count] } })
-                  .merge(related: post.related(limit: 20), viewed:))
+    render json: PostRepr.base(post, current_user)
+                         .merge(tags: build_tag_tree_for(post.tags),
+                                related: post.related(limit: 20))
   end
 
-  # POST /posts
   def create
     return head :unauthorized unless current_user
-    return head :forbidden unless current_user.member?
+    return head :forbidden unless current_user.gte_member?
 
-    # TODO: URL が正規のものがチェック，不正ならエラー
-    # TODO: URL は必須にする（タイトルは省略可）．
     # TODO: サイトに応じて thumbnail_base 設定
-    title = params[:title]
+    title = params[:title].presence
     url = params[:url]
     thumbnail = params[:thumbnail]
-    tag_names = params[:tags].to_s.split(' ')
+    tag_names = params[:tags].to_s.split
     original_created_from = params[:original_created_from]
     original_created_before = params[:original_created_before]
 
-    post = Post.new(title:, url:, thumbnail_base: '', uploaded_user: current_user,
+    post = Post.new(title:, url:, thumbnail_base: nil, uploaded_user: current_user,
                     original_created_from:, original_created_before:)
     post.thumbnail.attach(thumbnail)
     if post.save
       post.resized_thumbnail!
-      post.tags = Tag.normalise_tags(tag_names)
-      render json: post.as_json(include: { tags: { only: [:id, :name, :category, :post_count] } }),
-             status: :created
+      tags = Tag.normalise_tags(tag_names)
+      tags = Tag.expand_parent_tags(tags)
+      sync_post_tags!(post, tags)
+
+      post.reload
+      render json: PostRepr.base(post), status: :created
     else
       render json: { errors: post.errors.full_messages }, status: :unprocessable_entity
     end
+  rescue Tag::NicoTagNormalisationError
+    head :bad_request
   end
 
   def viewed
@@ -99,47 +156,188 @@ class PostsController < ApplicationController
     head :no_content
   end
 
-  # PATCH/PUT /posts/1
   def update
     return head :unauthorized unless current_user
-    return head :forbidden unless current_user.member?
+    return head :forbidden unless current_user.gte_member?
 
-    title = params[:title]
-    tag_names = params[:tags].to_s.split(' ')
+    title = params[:title].presence
+    tag_names = params[:tags].to_s.split
     original_created_from = params[:original_created_from]
     original_created_before = params[:original_created_before]
 
     post = Post.find(params[:id].to_i)
-    tags = post.tags.where(category: 'nico').to_a + Tag.normalise_tags(tag_names)
-    if post.update(title:, tags:, original_created_from:, original_created_before:)
-      render json: post.as_json(include: { tags: { only: [:id, :name, :category, :post_count] } }),
-             status: :ok
+    if post.update(title:, original_created_from:, original_created_before:)
+      tags = post.tags.where(category: 'nico').to_a +
+             Tag.normalise_tags(tag_names, with_tagme: false)
+      tags = Tag.expand_parent_tags(tags)
+      sync_post_tags!(post, tags)
+
+      post.reload
+      json = post.as_json
+      json['tags'] = build_tag_tree_for(post.tags)
+      render json:, status: :ok
     else
       render json: post.errors, status: :unprocessable_entity
     end
+  rescue Tag::NicoTagNormalisationError
+    head :bad_request
   end
 
-  # DELETE /posts/1
-  def destroy
+  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: { 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
-    tag_names = params[:tags]&.split(' ')
+    tag_names = params[:tags].to_s.split
     match_type = params[:match]
-    tag_names.present? ? filter_posts_by_tags(tag_names, match_type) : Post.all
+    if tag_names.present?
+      filter_posts_by_tags(tag_names, match_type)
+    else
+      Post.all
+    end
   end
 
   def filter_posts_by_tags tag_names, match_type
-    posts = Post.joins(:tags)
+    literals = tag_names.map do |raw_name|
+      { name: TagName.canonicalise(raw_name.sub(/\Anot:/i, '')).first,
+        negative: raw_name.downcase.start_with?('not:') }
+    end
+
+    return Post.all if literals.empty?
+
     if match_type == 'any'
-      posts = posts.where(tags: { name: tag_names }).distinct
+      literals.reduce(Post.none) do |posts, literal|
+        posts.or(tag_literal_relation(literal[:name], negative: literal[:negative]))
+      end
     else
-      tag_names.each do |tag|
-        posts = posts.where(id: Post.joins(:tags).where(tags: { name: tag }))
+      literals.reduce(Post.all) do |posts, literal|
+        ids = tagged_post_ids_for(literal[:name])
+        if literal[:negative]
+          posts.where.not(id: ids)
+        else
+          posts.where(id: ids)
+        end
       end
     end
-    posts.distinct
+  end
+
+  def tag_literal_relation name, negative:
+    ids = tagged_post_ids_for(name)
+    if negative
+      Post.where.not(id: ids)
+    else
+      Post.where(id: ids)
+    end
+  end
+
+  def tagged_post_ids_for(name) =
+      Post.joins(tags: :tag_name).where(tag_names: { name: }).select(:id)
+
+  def sync_post_tags! post, desired_tags
+    desired_tags.each do |t|
+      t.save! if t.new_record?
+    end
+
+    desired_ids = desired_tags.map(&:id).to_set
+    current_ids = post.tags.pluck(:id).to_set
+
+    to_add = desired_ids - current_ids
+    to_remove = current_ids - desired_ids
+
+    Tag.where(id: to_add).find_each do |tag|
+      begin
+        PostTag.create!(post:, tag:, created_user: current_user)
+      rescue ActiveRecord::RecordNotUnique
+        ;
+      end
+    end
+
+    PostTag.where(post_id: post.id, tag_id: to_remove.to_a).kept.find_each do |pt|
+      pt.discard_by!(current_user)
+    end
+  end
+
+  def build_tag_tree_for tags
+    tags = tags.to_a
+    tag_ids = tags.map(&:id)
+
+    implications = TagImplication.where(parent_tag_id: tag_ids, tag_id: tag_ids)
+
+    children_ids_by_parent = Hash.new { |h, k| h[k] = [] }
+    implications.each do |imp|
+      children_ids_by_parent[imp.parent_tag_id] << imp.tag_id
+    end
+
+    child_ids = children_ids_by_parent.values.flatten.uniq
+
+    root_ids = tag_ids - child_ids
+
+    tags_by_id = tags.index_by(&:id)
+
+    memo = { }
+
+    build_node = -> tag_id, path do
+      tag = tags_by_id[tag_id]
+      return nil unless tag
+
+      if path.include?(tag_id)
+        return TagRepr.base(tag).merge(children: [])
+      end
+
+      if memo.key?(tag_id)
+        return memo[tag_id]
+      end
+
+      new_path = path + [tag_id]
+      child_ids = children_ids_by_parent[tag_id] || []
+
+      children = child_ids.filter_map { |cid| build_node.(cid, new_path) }
+
+      memo[tag_id] = TagRepr.base(tag).merge(children:)
+    end
+
+    root_ids.filter_map { |id| build_node.call(id, []) }
   end
 end

backend/app/controllers/settings_controller.rb

@@ -1,16 +0,0 @@
-class SettingsController < ApplicationController
-  def index
-  end
-
-  def show
-  end
-
-  def create
-  end
-
-  def update
-  end
-
-  def destroy
-  end
-end

backend/app/controllers/tag_aliases_controller.rb

@@ -1,16 +0,0 @@
-class TagAliasesController < ApplicationController
-  def index
-  end
-
-  def show
-  end
-
-  def create
-  end
-
-  def update
-  end
-
-  def destroy
-  end
-end

backend/app/controllers/tag_children_controller.rb

@@ -0,0 +1,27 @@
+class TagChildrenController < ApplicationController
+  def create
+    return head :unauthorized unless current_user
+    return head :forbidden unless current_user.admin?
+
+    parent_id = params[:parent_id]
+    child_id = params[:child_id]
+    return head :bad_request if parent_id.blank? || child_id.blank?
+
+    Tag.find(parent_id).children << Tag.find(child_id) rescue nil
+
+    head :no_content
+  end
+
+  def destroy
+    return head :unauthorized unless current_user
+    return head :forbidden unless current_user.admin?
+
+    parent_id = params[:parent_id]
+    child_id = params[:child_id]
+    return head :bad_request if parent_id.blank? || child_id.blank?
+
+    Tag.find(parent_id).children.delete(Tag.find(child_id)) rescue nil
+
+    head :no_content
+  end
+end

backend/app/controllers/tags_controller.rb

@@ -1,46 +1,181 @@
 class TagsController < ApplicationController
   def index
     post_id = params[:post]
-    tags = if post_id.present?
-             Tag.joins(:posts).where(posts: { id: post_id })
-           else
-             Tag.all
-           end
-    render json: tags
+
+    name = params[:name].presence
+    category = params[:category].presence
+    post_count_between = (params[:post_count_gte].presence || -1).to_i,
+                         (params[:post_count_lte].presence || -1).to_i
+    post_count_between[0] = nil if post_count_between[0] < 0
+    post_count_between[1] = nil if post_count_between[1] < 0
+    created_between = params[:created_from].presence, params[:created_to].presence
+    updated_between = params[:updated_from].presence, params[:updated_to].presence
+
+    order = params[:order].to_s.split(':', 2).map(&:strip)
+    unless order[0].in?(['name', 'category', 'post_count', 'created_at', 'updated_at'])
+      order[0] = 'post_count'
+    end
+    unless order[1].in?(['asc', 'desc'])
+      order[1] = order[0].in?(['name', 'category']) ? 'asc' : 'desc'
+    end
+
+    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
+
+    q =
+        if post_id.present?
+          Tag.joins(:posts, :tag_name)
+        else
+          Tag.joins(:tag_name)
+        end
+        .includes(:tag_name, 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
+    q = q.where(category: category) if category
+    q = q.where('tags.post_count >= ?', post_count_between[0]) if post_count_between[0]
+    q = q.where('tags.post_count <= ?', post_count_between[1]) if post_count_between[1]
+    q = q.where('tags.created_at >= ?', created_between[0]) if created_between[0]
+    q = q.where('tags.created_at <= ?', created_between[1]) if created_between[1]
+    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]
+
+    sort_sql =
+        case order[0]
+        when 'name'
+          '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"
+        else
+          "tags.#{ 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.base(tags), count: q.size }
   end
 
   def autocomplete
-    q = params[:q].to_s.strip
-    return render json: [] if q.blank?
+    q = params[:q].to_s.strip.sub(/\Anot:/i, '')
 
-    tags = (Tag
-            .where('(category = ? AND name LIKE ?) OR name LIKE ?',
-                   'nico', "nico:#{ q }%", "#{ q }%")
-            .order('post_count DESC, name ASC')
-            .limit(20))
-    render json: tags
+    with_nico = bool?(:nico, default: true)
+    present_only = bool?(:present, default: true)
+
+    alias_rows =
+        TagName
+        .where('name LIKE ?', "#{ q }%")
+        .where.not(canonical_id: nil)
+        .pluck(:canonical_id, :name)
+
+    matched_alias_by_tag_name_id = { }
+    canonical_ids = []
+
+    alias_rows.each do |canonical_id, alias_name|
+      canonical_ids << canonical_id
+      matched_alias_by_tag_name_id[canonical_id] ||= alias_name
+    end
+
+    base = Tag.joins(:tag_name)
+              .includes(:tag_name, tag_name: :wiki_page)
+    base = base.where('tags.post_count > 0') if present_only
+
+    canonical_hit =
+        base
+        .where(((with_nico ? '(tags.category = ? AND tag_names.name LIKE ?) OR ' : '') +
+                'tag_names.name LIKE ?'),
+               *(with_nico ? ['nico', "nico:#{ q }%"] : []), "#{ q }%")
+
+    tags =
+        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
+
+    render json: tags.map { |tag|
+      TagRepr.base(tag).merge(matched_alias: matched_alias_by_tag_name_id[tag.tag_name_id])
+    }
   end
 
   def show
-    tag = Tag.find(params[:id])
-    render json: tag
-  end
-
-  def show_by_name
-    tag = Tag.find_by(name: params[:name])
+    tag = Tag.joins(:tag_name)
+             .includes(:tag_name, tag_name: :wiki_page)
+             .find_by(id: params[:id])
     if tag
-      render json: tag
+      render json: TagRepr.base(tag)
     else
       head :not_found
     end
   end
 
-  def create
+  def show_by_name
+    name = params[:name].to_s.strip
+    return head :bad_request if name.blank?
+
+    tag = Tag.joins(:tag_name)
+             .includes(:tag_name, tag_name: :wiki_page)
+             .find_by(tag_names: { name: })
+    if tag
+      render json: TagRepr.base(tag)
+    else
+      head :not_found
+    end
+  end
+
+  def deerjikists
+    tag = Tag.joins(:tag_name)
+             .includes(:tag_name, tag_name: :wiki_page)
+             .find_by(id: params[:id])
+    return head :not_found unless tag
+
+    render json: DeerjikistRepr.many(tag.deerjikists)
+  end
+
+  def deerjikists_by_name
+    name = params[:name].to_s.strip
+    return head :bad_request if name.blank?
+
+    tag = Tag.joins(:tag_name)
+             .includes(:tag_name, tag_name: :wiki_page)
+             .find_by(tag_names: { name: })
+    return head :not_found unless tag
+
+    render json: DeerjikistRepr.many(tag.deerjikists)
   end
 
   def update
-  end
+    return head :unauthorized unless current_user
+    return head :forbidden unless current_user.gte_member?
 
-  def destroy
+    name = params[:name].presence
+    category = params[:category].presence
+
+    tag = Tag.find(params[:id])
+
+    if name.present?
+      tag.tag_name.update!(name:)
+    end
+
+    if category.present?
+      tag.update!(category:)
+    end
+
+    render json: TagRepr.base(tag)
   end
 end

backend/app/controllers/theatre_comments_controller.rb

@@ -0,0 +1,32 @@
+class TheatreCommentsController < ApplicationController
+  def index
+    no_gt = params[:no_gt].to_i
+    no_gt = 0 if no_gt.negative?
+
+    comments = TheatreComment
+               .where(theatre_id: params[:theatre_id])
+               .where('no > ?', no_gt)
+               .order(no: :desc)
+
+    render json: comments.as_json(include: { user: { only: [:id, :name] } })
+  end
+
+  def create
+    return head :unauthorized unless current_user
+
+    content = params[:content]
+    return head :unprocessable_entity if content.blank?
+
+    theatre = Theatre.find_by(id: params[:theatre_id])
+    return head :not_found unless theatre
+
+    comment = nil
+    theatre.with_lock do
+      no = theatre.next_comment_no
+      comment = TheatreComment.create!(theatre:, no:, user: current_user, content:)
+      theatre.update!(next_comment_no: no + 1)
+    end
+
+    render json: comment, status: :created
+  end
+end

backend/app/controllers/theatres_controller.rb

@@ -0,0 +1,54 @@
+class TheatresController < ApplicationController
+  def show
+    theatre = Theatre.find_by(id: params[:id])
+    return head :not_found unless theatre
+
+    render json: TheatreRepr.base(theatre)
+  end
+
+  def watching
+    return head :unauthorized unless current_user
+
+    theatre = Theatre.find_by(id: params[:id])
+    return head :not_found unless theatre
+
+    host_flg = false
+    post_id = nil
+    post_started_at = nil
+
+    theatre.with_lock do
+      TheatreWatchingUser.find_or_initialize_by(theatre:, user: current_user).tap {
+        _1.expires_at = 30.seconds.from_now
+      }.save!
+
+      if (!(theatre.host_user_id?) ||
+          !(theatre.watching_users.exists?(id: theatre.host_user_id)))
+        theatre.update!(host_user_id: current_user.id)
+      end
+
+      host_flg = theatre.host_user_id == current_user.id
+      post_id = theatre.current_post_id
+      post_started_at = theatre.current_post_started_at
+    end
+
+    render json: {
+        host_flg:, post_id:, post_started_at:,
+        watching_users: theatre.watching_users.as_json(only: [:id, :name]) }
+  end
+
+  def next_post
+    return head :unauthorized unless current_user
+
+    theatre = Theatre.find_by(id: params[:id])
+    return head :not_found unless theatre
+    return head :forbidden if theatre.host_user != current_user
+
+    post = Post.where("url LIKE '%nicovideo.jp%'")
+           .or(Post.where("url LIKE '%youtube.com%'"))
+           .order('RAND()')
+           .first
+    theatre.update!(current_post: post, current_post_started_at: Time.current)
+
+    head :no_content
+  end
+end

backend/app/controllers/user_ips_controller.rb

@@ -1,16 +0,0 @@
-class UserIpsController < ApplicationController
-  def index
-  end
-
-  def show
-  end
-
-  def create
-  end
-
-  def update
-  end
-
-  def destroy
-  end
-end

backend/app/controllers/user_post_views_controller.rb

@@ -1,16 +0,0 @@
-class UserPostViewsController < ApplicationController
-  def index
-  end
-
-  def show
-  end
-
-  def create
-  end
-
-  def update
-  end
-
-  def destroy
-  end
-end

backend/app/controllers/users_controller.rb

@@ -6,15 +6,20 @@ class UsersController < ApplicationController
   end
 
   def verify
+    ip_bin = IPAddr.new(request.remote_ip).hton
+    ip_address = IpAddress.find_or_create_by!(ip_address: ip_bin)
+
     user = User.find_by(inheritance_code: params[:code])
-    render json: if user
-                   { valid: true, user: user.slice(:id, :name, :inheritance_code, :role) }
-                 else
-                   { valid: false }
-                 end
+    return render json: { valid: false } unless user
+
+    UserIp.find_or_create_by!(user:, ip_address:)
+
+    render json: { valid: true, user: user.slice(:id, :name, :inheritance_code, :role) }
   end
 
   def renew
+    return head :unauthorized unless current_user
+
     user = current_user
     user.inheritance_code = SecureRandom.uuid
     user.save!

backend/app/controllers/wiki_pages_controller.rb

@@ -1,35 +1,70 @@
 class WikiPagesController < ApplicationController
-  def index
-    wiki_pages = WikiPage.all
+  rescue_from Wiki::Commit::Conflict, with: :render_wiki_conflict
 
-    render json: wiki_pages
+  def index
+    title = params[:title].to_s.strip
+    if title.blank?
+      return render json: WikiPageRepr.base(WikiPage.joins(:tag_name).includes(:tag_name))
+    end
+
+    q = WikiPage.joins(:tag_name).includes(:tag_name)
+        .where('tag_names.name LIKE ?', "%#{ WikiPage.sanitize_sql_like(title) }%")
+    render json: WikiPageRepr.base(q.limit(20))
   end
 
   def show
-    render_wiki_page_or_404 WikiPage.find(params[:id])
+    page = WikiPage.joins(:tag_name)
+                   .includes(:tag_name)
+                   .find_by(id: params[:id])
+    render_wiki_page_or_404 page
   end
 
   def show_by_title
-    render_wiki_page_or_404 WikiPage.find_by(title: params[:title])
+    title = params[:title].to_s.strip
+    page = WikiPage.joins(:tag_name)
+                   .includes(:tag_name)
+                   .find_by(tag_name: { name: title })
+    render_wiki_page_or_404 page
+  end
+
+  def exists
+    if WikiPage.exists?(id: params[:id])
+      head :no_content
+    else
+      head :not_found
+    end
+  end
+
+  def exists_by_title
+    title = params[:title].to_s.strip
+    if WikiPage.joins(:tag_name).exists?(tag_names: { name: title })
+      head :no_content
+    else
+      head :not_found
+    end
   end
 
   def diff
     id = params[:id]
-    from = params[:from]
+    return head :bad_request if id.blank?
+
+    from = params[:from].presence
     to = params[:to].presence
-    return head :bad_request if id.blank? || from.blank?
 
-    wiki_page_from = WikiPage.find(id)
-    wiki_page_to = WikiPage.find(id)
-    wiki_page_from.sha = from
-    wiki_page_to.sha = to
+    page = WikiPage.joins(:tag_name).includes(:tag_name).find(id)
 
-    diffs = Diff::LCS.sdiff(wiki_page_from.body, wiki_page_to.body)
+    from_rev = from && page.wiki_revisions.find(from)
+    to_rev = to ? page.wiki_revisions.find(to) : page.current_revision
+    if ((from_rev && !(from_rev.content?)) || !(to_rev&.content?))
+      return head :unprocessable_entity
+    end
+
+    diffs = Diff::LCS.sdiff(from_rev&.body&.lines || [], to_rev.body.lines)
     diff_json = diffs.map { |change|
       case change.action
       when ?=
         { type: 'context', content: change.old_element }
-      when ?|
+      when ?!
         [{ type: 'removed', content: change.old_element },
          { type: 'added', content: change.new_element }]
       when ?+
@@ -39,97 +74,116 @@ class WikiPagesController < ApplicationController
       end
     }.flatten.compact
 
-    render json: { wiki_page_id:  wiki_page_from.id,
-                   title:         wiki_page_from.title,
-                   older_sha:     wiki_page_from.sha,
-                   newer_sha:     wiki_page_to.sha,
-                   diff:          diff_json }
+    render json: { wiki_page_id:      page.id,
+                   title:             page.title,
+                   older_revision_id: from_rev&.id,
+                   newer_revision_id: to_rev.id,
+                   diff:              diff_json }
   end
 
   def create
     return head :unauthorized unless current_user
-    return head :forbidden unless ['admin', 'member'].include?(current_user.role)
+    return head :forbidden unless current_user.gte_member?
 
-    wiki_page = WikiPage.new(title: params[:title], created_user: current_user, updated_user: current_user)
-    if wiki_page.save
-      wiki_page.set_body params[:body], user: current_user
-      render json: wiki_page, status: :created
+    name = params[:title]&.strip
+    body = params[:body].to_s
+
+    return head :unprocessable_entity if name.blank? || body.blank?
+
+    tag_name = TagName.find_undiscard_or_create_by!(name:)
+    page = WikiPage.new(tag_name:, created_user: current_user, updated_user: current_user)
+    if page.save
+      message = params[:message].presence
+      Wiki::Commit.content!(page:, body:, created_user: current_user, message:)
+
+      render json: WikiPageRepr.base(page), status: :created
     else
-      render json: { errors: wiki_page.errors.full_messages }, status: :unprocessable_entity
+      render json: { errors: page.errors.full_messages },
+             status: :unprocessable_entity
     end
   end
 
   def update
     return head :unauthorized unless current_user
-    return head :forbidden unless current_user.member?
+    return head :forbidden unless current_user.gte_member?
 
-    title = params[:title]
-    body = params[:body]
+    title = params[:title]&.strip
+    body = params[:body].to_s
 
     return head :unprocessable_entity if title.blank? || body.blank?
 
-    wiki_page = WikiPage.find(params[:id])
-    wiki_page.title = title
-    wiki_page.updated_user = current_user
-    wiki_page.set_body(body, user: current_user)
-    wiki_page.save!
+    page = WikiPage.find(params[:id])
+    base_revision_id = page.current_revision.id
+
+    if params[:title].present? && params[:title].strip != page.title
+      return head :unprocessable_entity
+    end
+
+    message = params[:message].presence
+    Wiki::Commit.content!(page:,
+                          body:,
+                          created_user: current_user,
+                          message:,
+                          base_revision_id:)
 
     head :ok
   end
 
   def search
-    title = params[:title]&.strip
-
-    q = WikiPage.all
-    q = q.where('title LIKE ?', "%#{ WikiPage.sanitize_sql_like(title) }%") if title.present?
-
-    render json: q.limit(20)
+    index
   end
 
   def changes
-    id = params[:id]
-    log = if id.present?
-            wiki.page("#{ id }.md")&.versions
-          else
-            wiki.repo.log('main', nil)
-          end
-    return render json: [] unless log
+    id = params[:id].presence
+    q = WikiRevision.joins(wiki_page: :tag_name)
+                    .includes(:created_user, wiki_page: :tag_name)
+                    .order(id: :desc)
+    q = q.where(wiki_page_id: id) if id
 
-    render json: log.map { |commit|
-      wiki_page = WikiPage.find(commit.message.split(' ')[1].to_i)
-      wiki_page.sha = commit.id
-
-      next nil if wiki_page.sha.blank?
-
-      user = User.find(commit.author.name.to_i)
-
-      { sha:          wiki_page.sha,
-        pred:         wiki_page.pred,
-        succ:         wiki_page.succ,
-        wiki_page:    wiki_page && { id: wiki_page.id, title: wiki_page.title },
-        user:         user && { id: user.id, name: user.name },
-        change_type:  commit.message.split(' ')[0].downcase[0...(-1)],
-        timestamp:    commit.authored_date }
+    render json: q.limit(200).map { |rev|
+      { revision_id:  rev.id,
+        pred:         rev.base_revision_id,
+        succ:         nil,
+        wiki_page:    { id: rev.wiki_page_id, title: rev.wiki_page.title },
+        user:         rev.created_user && { id: rev.created_user.id, name: rev.created_user.name },
+        kind:         rev.kind,
+        message:      rev.message,
+        timestamp:    rev.created_at }
     }.compact
   end
 
   private
 
-  WIKI_PATH = Rails.root.join('wiki').to_s
+  def render_wiki_page_or_404 page
+    return head :not_found unless page
 
-  def wiki
-    @wiki ||= Gollum::Wiki.new(WIKI_PATH)
+    rev = find_revision(page)
+    return head :not_found unless rev
+
+    if rev.redirect?
+      return (
+          redirect_to wiki_page_by_title_path(title: rev.redirect_page.title),
+                      status: :moved_permanently)
+    end
+
+    body = rev.body
+    revision_id = rev.id
+    pred = page.pred_revision_id(revision_id)
+    succ = page.succ_revision_id(revision_id)
+    updated_at = rev.created_at
+
+    render json: WikiPageRepr.base(page).merge(body:, revision_id:, pred:, succ:, updated_at:)
   end
 
-  def render_wiki_page_or_404 wiki_page
-    return head :not_found unless wiki_page
+  def find_revision page
+    if params[:version].present?
+      page.wiki_revisions.find_by(id: params[:version])
+    else
+      page.current_revision
+    end
+  end
 
-    wiki_page.sha = params[:version].presence
-
-    body = wiki_page.body
-    sha = wiki_page.sha
-    pred = wiki_page.pred
-    succ = wiki_page.succ
-    render json: wiki_page.as_json.merge(body:, sha:, pred:, succ:)
+  def render_wiki_conflict err
+    render json: { error: 'conflict', message: err.message }, status: :conflict
   end
 end

backend/app/models/deerjikist.rb

@@ -0,0 +1,21 @@
+class Deerjikist < ApplicationRecord
+  self.primary_key = :platform, :code
+
+  belongs_to :tag
+
+  validates :platform, presence: true
+  validates :code, presence: true
+  validates :tag_id, presence: true
+
+  validate :tag_must_be_deerjikist
+
+  enum :platform, nico: 'nico', youtube: 'youtube'
+
+  private
+
+  def tag_must_be_deerjikist
+    if tag && !(tag.deerjikist?)
+      errors.add :tag, 'タグはニジラー・カテゴリである必要があります．'
+    end
+  end
+end

backend/app/models/my_discard.rb

@@ -0,0 +1,20 @@
+module MyDiscard
+  extend ActiveSupport::Concern
+
+  included { include Discard::Model }
+
+  class_methods do
+    def find_undiscard_or_create_by! attrs, &block
+      record = with_discarded.find_by(attrs)
+
+      if record&.discarded?
+        record.undiscard!
+        record.update_columns(created_at: record.reload.updated_at)
+      end
+
+      record or create!(attrs, &block)
+    rescue ActiveRecord::RecordNotUnique
+      retry
+    end
+  end
+end

backend/app/models/nico_tag_relation.rb

@@ -6,6 +6,7 @@ class NicoTagRelation < ApplicationRecord
   validates :tag_id, presence: true
 
   validate :nico_tag_must_be_nico
+  validate :tag_mustnt_be_nico
 
   private
 

backend/app/models/post.rb

@@ -1,21 +1,25 @@
-require 'mini_magick'
-
-
 class Post < ApplicationRecord
+  require 'mini_magick'
+
   belongs_to :parent, class_name: 'Post', optional: true, foreign_key: 'parent_id'
   belongs_to :uploaded_user, class_name: 'User', optional: true
-  has_many :post_tags, dependent: :destroy
-  has_many :tags, through: :post_tags
-  has_many :user_post_views, dependent: :destroy
-  has_many :post_similarities_as_post,
-           class_name: 'PostSimilarity',
-           foreign_key: :post_id
-  has_many :post_similarities_as_target_post,
-           class_name: 'PostSimilarity',
-           foreign_key: :target_post_id
+
+  has_many :post_tags, dependent: :destroy, inverse_of: :post
+  has_many :active_post_tags, -> { kept }, class_name: 'PostTag', inverse_of: :post
+  has_many :post_tags_with_discarded, -> { with_discarded }, class_name: 'PostTag'
+  has_many :tags, through: :active_post_tags
+
+  has_many :user_post_views, dependent: :delete_all
+  has_many :post_similarities, dependent: :delete_all
+
   has_one_attached :thumbnail
 
+  before_validation :normalise_url
+
+  validates :url, presence: true, uniqueness: true
+
   validate :validate_original_created_range
+  validate :url_must_be_http_url
 
   def as_json options = { }
     super(options).merge({ thumbnail: thumbnail.attached? ?
@@ -26,19 +30,15 @@ class Post < ApplicationRecord
     super(options).merge(thumbnail: nil)
   end
 
-  def related(limit: nil)
-    ids_with_cos =
-        post_similarities_as_post.select(:target_post_id, :cos)
-                                 .map { |ps| [ps.target_post_id, ps.cos] } +
-        post_similarities_as_target_post.select(:post_id, :cos)
-                                        .map { |ps| [ps.post_id, ps.cos] }
+  def related limit: nil
+    ids = post_similarities.order(cos: :desc)
+    ids = ids.limit(limit) if limit
+    ids = ids.pluck(:target_post_id)
+    return Post.none if ids.empty?
 
-    sorted = ids_with_cos.sort_by { |_, cos| -cos }
-
-    ids = sorted.map(&:first)
-    ids = ids.first(limit) if limit
-
-    Post.where(id: ids).index_by(&:id).values_at(*ids)
+    Post.where(id: ids)
+        .with_attached_thumbnail
+        .order(Arel.sql("FIELD(posts.id, #{ ids.join(',') })"))
   end
 
   def resized_thumbnail!
@@ -67,4 +67,33 @@ class Post < ApplicationRecord
       errors.add :original_created_before, 'オリジナルの作成日時の順番がをかしぃです．'
     end
   end
+
+  def url_must_be_http_url
+    begin
+      u = URI.parse(url)
+    rescue URI::InvalidURIError
+      errors.add(:url, 'URL が不正です．')
+      return
+    end
+
+    if !(u in URI::HTTP) || u.host.blank?
+      errors.add(:url, 'URL が不正です．')
+      return
+    end
+  end
+
+  def normalise_url
+    return if url.blank?
+
+    self.url = url.strip
+
+    u = URI.parse(url)
+    return unless u in URI::HTTP
+
+    u.host = u.host.downcase if u.host
+    u.path = u.path.sub(/\/\Z/, '') if u.path.present?
+    self.url = u.to_s
+  rescue URI::InvalidURIError
+    ;
+  end
 end

backend/app/models/post_similarity.rb

@@ -1,4 +1,6 @@
 class PostSimilarity < ApplicationRecord
-  belongs_to :post, class_name: 'Post', foreign_key: 'post_id'
-  belongs_to :target_post, class_name: 'Post', foreign_key: 'target_post_id'
+  self.primary_key = :post_id, :target_post_id
+
+  belongs_to :post
+  belongs_to :target_post, class_name: 'Post'
 end

backend/app/models/post_tag.rb

@@ -1,7 +1,29 @@
 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
 
   validates :post_id, presence: true
   validates :tag_id, presence: true
+  validates :post_id, uniqueness: {
+      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/tag.rb

@@ -1,72 +1,208 @@
 class Tag < ApplicationRecord
-  has_many :post_tags, dependent: :destroy
-  has_many :posts, through: :post_tags
-  has_many :tag_aliases, dependent: :destroy
+  include MyDiscard
+
+  class NicoTagNormalisationError < ArgumentError
+    ;
+  end
+
+  default_scope -> { kept }
+
+  has_many :post_tags, inverse_of: :tag
+  has_many :active_post_tags, -> { kept }, class_name: 'PostTag', inverse_of: :tag
+  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
+  has_many :reversed_nico_tag_relations,
+           class_name: 'NicoTagRelation', foreign_key: :tag_id, dependent: :destroy
   has_many :linked_nico_tags, through: :reversed_nico_tag_relations, source: :nico_tag
 
-  enum :category, { deerjikist:  'deerjikist',
-                    meme:        'meme',
-                    character:   'character',
-                    general:     'general',
-                    material:    'material',
-                    nico:        'nico',
-                    meta:        'meta' }
+  has_many :tag_implications, foreign_key: :parent_tag_id, dependent: :destroy
+  has_many :children, through: :tag_implications, source: :tag
+
+  has_many :reversed_tag_implications,
+           class_name: 'TagImplication', foreign_key: :tag_id, dependent: :destroy
+  has_many :parents, through: :reversed_tag_implications, source: :parent_tag
+
+  has_many :tag_similarities, dependent: :delete_all
+  has_many :tag_similarities_as_target,
+           class_name: 'TagSimilarity', foreign_key: :target_tag_id, dependent: :delete_all
+
+  has_many :deerjikists, dependent: :delete_all
+
+  belongs_to :tag_name
+  delegate :wiki_page, to: :tag_name
+
+  delegate :name, to: :tag_name, allow_nil: true
+  validates :tag_name, presence: true
+
+  enum :category, deerjikist:  'deerjikist',
+                  meme:        'meme',
+                  character:   'character',
+                  general:     'general',
+                  material:    'material',
+                  nico:        'nico',
+                  meta:        'meta'
 
-  validates :name, presence: true, length: { maximum: 255 }
   validates :category, presence: true, inclusion: { in: Tag.categories.keys }
 
   validate :nico_tag_name_must_start_with_nico
+  validate :tag_name_must_be_canonical
+  validate :category_must_be_deerjikist_with_deerjikists
 
-  scope :nico_tags, -> { where(category: :nico) }
+  scope :nico_tags, -> { nico }
 
   CATEGORY_PREFIXES = {
-      'gen:'  => 'general',
-      'djk:'  => 'deerjikist',
-      'meme:' => 'meme',
-      'chr:'  => 'character',
-      'mtr:'  => 'material',
-      'meta:' => 'meta' }.freeze
+      'general:'    => :general,
+      'gen:'        => :general,
+      'deerjikist:' => :deerjikist,
+      'djk:'        => :deerjikist,
+      'meme:'       => :meme,
+      'character:'  => :character,
+      'chr:'        => :character,
+      'material:'   => :material,
+      'mtr:'        => :material,
+      'meta:'       => :meta }.freeze
+
+  def name= val
+    (self.tag_name ||= build_tag_name).name = val
+  end
+
+  def has_wiki = wiki_page.present?
 
   def self.tagme
-    @tagme ||= Tag.find_or_initialize_by(name: 'タグ希望') do |tag|
-      tag.category = 'meta'
-    end
+    @tagme ||= find_or_create_by_tag_name!('タグ希望', category: :meta)
   end
 
   def self.bot
-    @bot ||= Tag.find_or_initialize_by(name: 'bot操作') do |tag|
-      tag.category = 'meta'
-    end
+    @bot ||= find_or_create_by_tag_name!('bot操作', category: :meta)
   end
 
-  def self.normalise_tags tag_names, with_tagme: true
+  def self.no_deerjikist
+    @no_deerjikist ||= find_or_create_by_tag_name!('ニジラー情報不詳', category: :meta)
+  end
+
+  def self.video
+    @video ||= find_or_create_by_tag_name!('動画', category: :meta)
+  end
+
+  def self.niconico
+    @niconico ||= find_or_create_by_tag_name!('ニコニコ', category: :meta)
+  end
+
+  def self.normalise_tags tag_names, with_tagme: true, deny_nico: true
+    if deny_nico && tag_names.any? { |n| n.downcase.start_with?('nico:') }
+      raise NicoTagNormalisationError
+    end
+
     tags = tag_names.map do |name|
-      pf, cat = CATEGORY_PREFIXES.find { |p, _| name.start_with?(p) } || ['', nil]
-      name.delete_prefix!(pf)
-      Tag.find_or_initialize_by(name:).tap do |tag|
-        if cat && tag.category != cat
-          tag.category = cat
-          tag.save!
-        end
+      pf, cat = CATEGORY_PREFIXES.find { |p, _| name.downcase.start_with?(p) } || ['', nil]
+      name = TagName.canonicalise(name.sub(/\A#{ pf }/i, '')).first
+      find_or_create_by_tag_name!(name, category: (cat || :general)).tap do |tag|
+        tag.update!(category: cat) if cat && tag.category != cat
       end
     end
-    tags << Tag.tagme if with_tagme && tags.size < 20 && tags.none?(Tag.tagme)
-    tags.uniq
+
+    tags << Tag.tagme if with_tagme && tags.size < 10 && tags.none?(Tag.tagme)
+    tags << Tag.no_deerjikist if tags.all? { |t| !(t.deerjikist?) }
+    tags.uniq(&:id)
+  end
+
+  def self.expand_parent_tags tags
+    return [] if tags.blank?
+
+    seen = Set.new
+    result = []
+    stack = tags.compact.dup
+
+    until stack.empty?
+      tag = stack.pop
+      next unless tag
+
+      tag.parents.each do |parent|
+        next if seen.include?(parent.id)
+
+        seen << parent.id
+        result << parent
+        stack << parent
+      end
+    end
+
+    (result + tags).uniq { |t| t.id }
+  end
+
+  def self.find_or_create_by_tag_name! name, category:
+    tn = TagName.find_undiscard_or_create_by!(name: name.to_s.strip)
+    tn = tn.canonical if tn.canonical_id?
+
+    Tag.find_undiscard_or_create_by!(tag_name_id: tn.id) do |t|
+      t.category = category
+    end
+  rescue ActiveRecord::RecordNotUnique
+    retry
+  end
+
+  def self.merge_tags! target_tag, source_tags
+    target_tag => Tag
+
+    Tag.transaction do
+      Array(source_tags).compact.uniq.each do |source_tag|
+        source_tag => Tag
+
+        next if source_tag == target_tag
+
+        source_tag.post_tags.kept.find_each do |source_pt|
+          post_id = source_pt.post_id
+          source_pt.discard_by!(nil)
+          unless PostTag.kept.exists?(post_id:, tag: target_tag)
+            PostTag.create!(post_id:, tag: target_tag)
+          end
+        end
+
+        source_tag_name = source_tag.tag_name
+
+        if source_tag_name.wiki_page.present?
+          raise ActiveRecord::RecordInvalid.new(source_tag_name)
+        end
+
+        source_tag.discard!
+
+        if source_tag.nico?
+          source_tag_name.discard!
+        else
+          source_tag_name.update_columns(canonical_id: target_tag.tag_name_id,
+                                         updated_at: Time.current)
+        end
+      end
+
+      # 投稿件数を再集計
+      target_tag.update_columns(post_count: PostTag.kept.where(tag: target_tag).count)
+    end
+
+    target_tag.reload
   end
 
   private
 
   def nico_tag_name_must_start_with_nico
-    if ((category == 'nico' && !(name.start_with?('nico:'))) || 
-        (category != 'nico' && name.start_with?('nico:')))
+    n = name.to_s
+    if ((nico? && !(n.downcase.start_with?('nico:'))) || 
+        (!(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
+
+  def tag_name_must_be_canonical
+    if tag_name&.canonical_id?
+      errors.add :tag_name, 'tag_names へは実体を示す必要があります．'
+    end
+  end
+
+  def category_must_be_deerjikist_with_deerjikists
+    if !(deerjikist?) && deerjikists.exists?
+      errors.add :category, 'ニジラーと紐づいてゐるタグはニジラー・カテゴリである必要があります．'
+    end
+  end
 end

backend/app/models/tag_alias.rb

@@ -1,6 +0,0 @@
-class TagAlias < ApplicationRecord
-  belongs_to :tag
-
-  validates :tag_id, presence: true
-  validates :name, presence: true, length: { maximum: 255 }, uniqueness: true
-end

backend/app/models/tag_implication.rb

@@ -0,0 +1,17 @@
+class TagImplication < ApplicationRecord
+  belongs_to :tag, class_name: 'Tag'
+  belongs_to :parent_tag, class_name: 'Tag'
+
+  validates :tag_id, presence: true, uniqueness: { scope: :parent_tag_id }
+  validates :parent_tag_id, presence: true
+
+  validate :parent_tag_mustnt_be_itself
+
+  private
+
+  def parent_tag_mustnt_be_itself
+    if parent_tag == tag
+      errors.add :parent_tag_id, '親タグは子タグと同一であってはなりません．'
+    end
+  end
+end

backend/app/models/tag_name.rb

@@ -0,0 +1,53 @@
+class TagName < ApplicationRecord
+  include MyDiscard
+
+  default_scope -> { kept }
+
+  has_one :tag
+  has_one :wiki_page
+
+  belongs_to :canonical, class_name: 'TagName', optional: true
+  has_many :aliases, class_name: 'TagName', foreign_key: :canonical_id
+
+  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 :name_must_be_sanitised
+
+  def self.canonicalise 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)
+
+    names.map { |name| tns[name]&.canonical&.name || name }.uniq
+  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?(':')
+      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
+    if canonical_id? && (tag || 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．'
+    end
+  end
+
+  def name_must_be_sanitised
+    if name? && name != TagNameSanitisationRule.sanitise(name)
+      errors.add :name, '名前に使用できない文字が含まれてゐます．'
+    end
+  end
+end

backend/app/models/tag_name_sanitisation_rule.rb

@@ -0,0 +1,58 @@
+class TagNameSanitisationRule < ApplicationRecord
+  include Discard::Model
+
+  self.primary_key = :priority
+
+  default_scope -> { kept }
+
+  validates :source_pattern, presence: true, uniqueness: true
+
+  validate :source_pattern_must_be_regexp
+
+  class << self
+    def sanitise(name) =
+        rules.reduce(name.dup) { |name, (pattern, replacement)| name.gsub(pattern, replacement) }
+
+    def apply!
+      TagName.find_each do |tn|
+        name = sanitise(tn.name)
+        next if name == tn.name
+
+        TagName.transaction do
+          existing_tn = TagName.find_by(name:)
+          if existing_tn
+            existing_tn = existing_tn.canonical || existing_tn
+            next if existing_tn.id == tn.id
+
+            existing_tag = Tag.find_by(tag_name_id: existing_tn.id)
+            source_tag = Tag.find_by(tag_name_id: tn.id)
+
+            if existing_tag
+              Tag.merge_tags!(existing_tag, source_tag) if tn.tag
+            elsif source_tag
+              source_tag.update_columns(tag_name_id: existing_tn.id, updated_at: Time.current)
+            end
+            tn.discard!
+
+            next
+          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
+
+    private
+
+    def rules = kept.order(:priority).map { |r| [Regexp.new(r.source_pattern), r.replacement] }
+  end
+
+  private
+
+  def source_pattern_must_be_regexp
+    Regexp.new(source_pattern)
+  rescue RegexpError
+    errors.add :source_pattern, '変な正規表現だね〜（笑）'
+  end
+end

backend/app/models/tag_similarity.rb

@@ -0,0 +1,6 @@
+class TagSimilarity < ApplicationRecord
+  self.primary_key = :tag_id, :target_tag_id
+
+  belongs_to :tag
+  belongs_to :target_tag, class_name: 'Tag'
+end

backend/app/models/theatre.rb

@@ -0,0 +1,13 @@
+class Theatre < ApplicationRecord
+  include MyDiscard
+
+  has_many :comments, class_name: 'TheatreComment'
+  has_many :theatre_watching_users, dependent: :delete_all
+  has_many :active_theatre_watching_users, -> { active },
+           class_name: 'TheatreWatchingUser', inverse_of: :theatre
+  has_many :watching_users, through: :active_theatre_watching_users, source: :user
+
+  belongs_to :host_user, class_name: 'User', optional: true
+  belongs_to :current_post, class_name: 'Post', optional: true
+  belongs_to :created_by_user, class_name: 'User'
+end

backend/app/models/theatre_comment.rb

@@ -0,0 +1,8 @@
+class TheatreComment < ApplicationRecord
+  include Discard::Model
+
+  self.primary_key = :theatre_id, :no
+
+  belongs_to :theatre
+  belongs_to :user
+end

backend/app/models/theatre_watching_user.rb

@@ -0,0 +1,13 @@
+class TheatreWatchingUser < ApplicationRecord
+  self.primary_key = :theatre_id, :user_id
+
+  belongs_to :theatre
+  belongs_to :user
+
+  scope :active, -> { where('expires_at >= ?', Time.current) }
+  scope :expired, -> { where('expires_at < ?', Time.current) }
+
+  def active? = expires_at >= Time.current
+
+  def refresh! = update!(expires_at: 30.seconds.from_now)
+end

backend/app/models/user.rb

@@ -1,30 +1,23 @@
 class User < ApplicationRecord
-  enum :role, { guest: 'guest', member: 'member', admin: 'admin' }
+  enum :role, guest: 'guest', member: 'member', admin: 'admin'
 
   validates :name, length: { maximum: 255 }
   validates :inheritance_code, presence: true, length: { maximum: 64 }
   validates :role, presence: true, inclusion: { in: roles.keys }
   validates :banned, inclusion: { in: [true, false] }
 
-  has_many :posts
+  has_many :created_posts,
+           class_name: 'Post', foreign_key: :uploaded_user_id, dependent: :nullify
   has_many :settings
-  has_many :ip_addresses
   has_many :user_ips, dependent: :destroy
   has_many :ip_addresses, through: :user_ips
   has_many :user_post_views, dependent: :destroy
   has_many :viewed_posts, through: :user_post_views, source: :post
-  has_many :created_wiki_pages, class_name: 'WikiPage', foreign_key: 'created_user_id', dependent: :nullify
-  has_many :updated_wiki_pages, class_name: 'WikiPage', foreign_key: 'updated_user_id', dependent: :nullify
+  has_many :created_wiki_pages,
+           class_name: 'WikiPage', foreign_key: :created_user_id, dependent: :nullify
+  has_many :updated_wiki_pages,
+           class_name: 'WikiPage', foreign_key: :updated_user_id, dependent: :nullify
 
-  def viewed? post
-    user_post_views.exists? post_id: post.id
-  end
-
-  def member?
-    ['member', 'admin'].include?(role)
-  end
-
-  def admin?
-    role == 'admin'
-  end
+  def viewed?(post) = user_post_views.exists?(post_id: post.id)
+  def gte_member? = member? || admin?
 end

backend/app/models/user_ip.rb

@@ -1,4 +1,6 @@
 class UserIp < ApplicationRecord
+  self.primary_key = :user_id, :ip_address_id
+
   belongs_to :user
   belongs_to :ip_address
 

backend/app/models/user_post_view.rb

@@ -1,4 +1,6 @@
 class UserPostView < ApplicationRecord
+  self.primary_key = :user_id, :post_id
+
   belongs_to :user
   belongs_to :post
 

backend/app/models/wiki_line.rb

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

backend/app/models/wiki_page.rb

@@ -1,80 +1,56 @@
-require 'gollum-lib'
+require 'set'
 
 
 class WikiPage < ApplicationRecord
-  belongs_to :tag, optional: true
-  belongs_to :created_user, class_name: 'User', foreign_key: 'created_user_id'
-  belongs_to :updated_user, class_name: 'User', foreign_key: 'updated_user_id'
+  include MyDiscard
 
-  validates :title, presence: true, length: { maximum: 255 }, uniqueness: true
+  default_scope -> { kept }
 
-  def as_json options = { }
-    self.sha = nil
-    super options
+  has_many :wiki_revisions, dependent: :destroy
+  belongs_to :created_user, class_name: 'User'
+  belongs_to :updated_user, class_name: 'User'
+
+  has_many :redirected_from_revisions,
+           class_name: 'WikiRevision',
+           foreign_key: :redirect_page_id,
+           dependent: :nullify
+
+  belongs_to :tag_name
+  validates :tag_name, presence: true
+
+  def title = tag_name.name
+
+  def title= val
+    (self.tag_name ||= build_tag_name).name = val
   end
 
-  def sha= val
-    if val.present?
-      @sha = val
-      @page = wiki.page("#{ id }.md", @sha)
-    else
-      @page = wiki.page("#{ id }.md")
-      @sha = @page.versions.first.id
-    end
-    vers = @page.versions
-    idx = vers.find_index { |ver| ver.id == @sha }
-    if idx
-      @pred = vers[idx + 1]&.id
-      @succ = idx.positive? ? vers[idx - 1].id : nil
-      @updated_at = vers[idx].authored_date
-    else
-      @sha = nil
-      @pred = nil
-      @succ = nil
-      @updated_at = nil
-    end
-    @sha
-  end
-
-  def sha
-    @sha
-  end
-
-  def pred
-    @pred
-  end
-
-  def succ
-    @succ
-  end
-
-  def updated_at
-    @updated_at
-  end
+  def current_revision = wiki_revisions.order(id: :desc).first
 
   def body
-    sha = nil unless @page
-    @page&.raw_data&.force_encoding('UTF-8')
+    rev = current_revision
+    rev.body if rev&.content?
   end
 
-  def set_body content, user:
-    commit_info = { name:   user.id.to_s,
-                    email:  'dummy@example.com' }
-    page = wiki.page("#{ id }.md")
-    if page
-      commit_info[:message] = "Updated #{ id }"
-      wiki.update_page(page, id.to_s, :markdown, content, commit_info)
-    else
-      commit_info[:message] = "Created #{ id }"
-      wiki.write_page(id.to_s, :markdown, content, commit_info)
+  def resolve_redirect limit: 10
+    page = self
+    visited = Set.new
+
+    limit.times do
+      return page if visited.include?(page.id)
+
+      visited.add(page.id)
+
+      rev = page.current_revision
+      return page if !(rev&.redirect?) || !(rev.redirect_page)
+
+      page = rev.redirect_page
     end
+
+    page
   end
 
-  private
-
-  WIKI_PATH = Rails.root.join('wiki').to_s
-
-  def wiki
-    @wiki ||= Gollum::Wiki.new(WIKI_PATH)
-  end
+  def pred_revision_id(revision_id) =
+      wiki_revisions.where('id < ?', revision_id).order(id: :desc).limit(1).pick(:id)
+  def succ_revision_id(revision_id) =
+      wiki_revisions.where('id > ?', revision_id).order(id: :asc).limit(1).pick(:id)
 end

backend/app/models/wiki_revision.rb

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

backend/app/models/wiki_revision_line.rb

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

backend/app/representations/deerjikist_repr.rb

@@ -0,0 +1,16 @@
+# frozen_string_literal: true
+
+
+module DeerjikistRepr
+  BASE = { only: [:platform, :code], include: { tag: TagRepr::BASE } }.freeze
+
+  module_function
+
+  def base deerjikist
+    deerjikist.as_json(BASE)
+  end
+
+  def many deerjikists
+    deerjikists.map { |d| base(d) }
+  end
+end

backend/app/representations/post_repr.rb

@@ -0,0 +1,20 @@
+# frozen_string_literal: true
+
+
+module PostRepr
+  BASE = { include: { tags: TagRepr::BASE, uploaded_user: UserRepr::BASE } }.freeze
+
+  module_function
+
+  def base post, current_user = nil
+    json = post.as_json(BASE)
+    return json.merge(viewed: false) unless current_user
+
+    viewed = current_user.viewed?(post)
+    json.merge(viewed:)
+  end
+
+  def many posts, current_user = nil
+    posts.map { |p| base(p, current_user) }
+  end
+end

backend/app/representations/tag_repr.rb

@@ -0,0 +1,17 @@
+# frozen_string_literal: true
+
+
+module TagRepr
+  BASE = { only: [:id, :category, :post_count, :created_at, :updated_at],
+           methods: [:name, :has_wiki] }.freeze
+
+  module_function
+
+  def base tag
+    tag.as_json(BASE)
+  end
+
+  def many tags
+    tags.map { |t| base(t) }
+  end
+end

backend/app/representations/theatre_repr.rb

@@ -0,0 +1,17 @@
+# frozen_string_literal: true
+
+
+module TheatreRepr
+  BASE = { only: [:id, :name, :opens_at, :closes_at, :created_at, :updated_at],
+           include: { created_by_user: { only: [:id, :name] } } }.freeze
+
+  module_function
+
+  def base theatre
+    theatre.as_json(BASE)
+  end
+
+  def many theatre
+    theatre.map { |t| base(t) }
+  end
+end

backend/app/representations/user_repr.rb

@@ -0,0 +1,16 @@
+# frozen_string_literal: true
+
+
+module UserRepr
+  BASE = { only: [:id, :name] }.freeze
+
+  module_function
+
+  def base user
+    user.as_json(BASE)
+  end
+
+  def many users
+    users.map { |u| base(u) }
+  end
+end

backend/app/representations/wiki_page_repr.rb

@@ -0,0 +1,16 @@
+# frozen_string_literal: true
+
+
+module WikiPageRepr
+  BASE = { methods: [:title] }.freeze
+
+  module_function
+
+  def base wiki_page
+    wiki_page.as_json(BASE)
+  end
+
+  def many wiki_pages
+    wiki_pages.map { |p| base(p) }
+  end
+end

backend/app/services/similarity/calc.rb

@@ -0,0 +1,106 @@
+module Similarity
+  class Calc
+    def self.call model, tgt
+      similarity_model = "#{ model.name }Similarity".constantize
+
+      # 最大保存件数
+      n = 20
+
+      similarity_model.delete_all
+
+      posts = model.includes(tgt).select(:id).to_a
+
+      tag_ids = { }
+      tag_cnts = { }
+
+      posts.each do |p|
+        arr = p.public_send(tgt).map(&:id).sort
+        tag_ids[p.id] = arr
+        tag_cnts[p.id] = arr.size
+      end
+
+      intersection_size = -> a, b do
+        i = 0
+        j = 0
+        cnt = 0
+        while i < a.size && j < b.size
+          a_i = a[i]
+          b_j = b[j]
+          if a_i == b_j
+            cnt += 1
+            i += 1
+            j += 1
+          elsif a_i < b_j
+            i += 1
+          else
+            j += 1
+          end
+        end
+        cnt
+      end
+
+      push_topk = -> list, cos, target_id do
+        return if list.size >= n && cos <= list[-1][0]
+
+        idx = nil
+        list.each_with_index do |(c, tid), i|
+          if tid == target_id
+            idx = i
+            break
+          end
+        end
+        if idx
+          return if cos <= list[idx][0]
+          list.delete_at(idx)
+        end
+
+        insert_at = list.size
+        list.each_with_index do |(c, _), i|
+          if cos > c
+            insert_at = i
+            break
+          end
+        end
+        list.insert(insert_at, [cos, target_id])
+        list.pop if list.size > n
+      end
+
+      top = Hash.new { |h, key| h[key] = [] }
+
+      ids = posts.map(&:id)
+      ids.each_with_index do |post_id, i|
+        a = tag_ids[post_id]
+        a_cnt = tag_cnts[post_id]
+
+        ((i + 1)...ids.size).each do |j|
+          target_id = ids[j]
+          b = tag_ids[target_id]
+          b_cnt = tag_cnts[target_id]
+
+          norm = Math.sqrt(a_cnt * b_cnt)
+          cos = norm.zero? ? 0.0 : intersection_size.(a, b).fdiv(norm)
+
+          push_topk.(top[post_id], cos, target_id)
+          push_topk.(top[target_id], cos, post_id)
+        end
+      end
+
+      buf = []
+      flush = -> do
+        return if buf.empty?
+        similarity_model.insert_all!(buf)
+        buf.clear
+      end
+
+      top.each do |post_id, list|
+        list.each do |cos, target_post_id|
+          buf << { "#{ model.name.underscore }_id".to_sym => post_id,
+                   "target_#{ model.name.underscore }_id".to_sym => target_post_id,
+                   cos: }
+          flush.call if buf.size >= 1_000
+        end
+      end
+      flush.call
+    end
+  end
+end

backend/app/services/wiki/commit.rb

@@ -0,0 +1,122 @@
+require 'digest'
+
+
+module Wiki
+  class Commit
+    class Conflict < StandardError
+      ;
+    end
+
+    def self.content! page:, body:, created_user:, message: nil, base_revision_id: nil
+      new(page:, created_user:).content!(body:, message:, base_revision_id:)
+    end
+
+    def self.redirect! page:, redirect_page:, created_user:, message: nil, base_revision_id: nil
+      new(page:, created_user:).redirect!(redirect_page:, message:, base_revision_id:)
+    end
+
+    def initialize page:, created_user:
+      @page = page
+      @created_user = created_user
+    end
+
+    def content! body:, message:, base_revision_id:
+      normalised = normalise_body(body)
+      lines = split_lines(normalised)
+
+      line_shas = lines.map { |line| Digest::SHA256.hexdigest(line) }
+      tree_sha = Digest::SHA256.hexdigest(line_shas.join(','))
+
+      line_id_by_sha = upsert_lines!(lines, line_shas)
+      line_ids = line_shas.map { |sha| line_id_by_sha.fetch(sha) }
+
+      ActiveRecord::Base.transaction do
+        @page.lock!
+
+        if base_revision_id.present?
+          current_id = @page.wiki_revisions.maximum(:id)
+          if current_id && current_id != base_revision_id.to_i
+            raise Conflict,
+                "競合が発生してゐます（現在の Id.：#{ current_id }，ベース Id.：#{ base_revision_id }）．"
+          end
+        end
+
+        rev = WikiRevision.create!(
+            wiki_page:        @page,
+            base_revision_id:,
+            created_user:     @created_user,
+            kind:             :content,
+            redirect_page_id: nil,
+            message:,
+            lines_count:      lines.length,
+            tree_sha256:      tree_sha)
+
+        rows = line_ids.each_with_index.map do |line_id, pos|
+          { wiki_revision_id: rev.id, wiki_line_id: line_id, position: pos }
+        end
+        WikiRevisionLine.insert_all!(rows)
+
+        rev
+      end
+    end
+
+    def redirect! redirect_page:, message:, base_revision_id:
+      ActiveRecord::Base.transaction do
+        @page.lock!
+
+        if base_revision_id.present?
+          current_id = @page.wiki_revisions.maximum(:id)
+          if current_id && current_id != base_revision_id.to_i
+            raise Conflict,
+                "競合が発生してゐます（現在の Id.：#{ current_id }，ベース Id.：#{ base_revision_id }）．"
+          end
+        end
+
+        WikiRevision.create!(
+            wiki_page:        @page,
+            base_revision_id:,
+            created_user:     @created_user,
+            kind:             :redirect,
+            redirect_page:,
+            message:,
+            lines_count:      0,
+            tree_sha256:      nil)
+      end
+    end
+
+    private
+
+    def normalise_body body
+      s = body.to_s
+      s.gsub!("\r\n", "\n")
+      s.encode('UTF-8', invalid: :replace, undef: :replace, replace: '🖕')
+    end
+
+    def split_lines body
+      body.split("\n")
+    end
+
+    def upsert_lines! lines, line_shas
+      now = Time.current
+
+      id_by_sha = WikiLine.where(sha256: line_shas).pluck(:sha256, :id).to_h
+
+      missing_rows = []
+      line_shas.each_with_index do |sha, i|
+        next if id_by_sha.key?(sha)
+
+        missing_rows << { sha256:     sha,
+                          body:       lines[i],
+                          created_at: now,
+                          updated_at: now }
+      end
+
+      if missing_rows.any?
+        WikiLine.upsert_all(missing_rows)
+        id_by_sha = WikiLine.where(sha256: line_shas).pluck(:sha256, :id).to_h
+      end
+
+      id_by_sha
+    end
+  end
+end

backend/config/application.rb

@@ -11,6 +11,9 @@ module Backend
     # Initialize configuration defaults for originally generated Rails version.
     config.load_defaults 8.0
 
+    config.i18n.available_locales = [:ja, :en]
+    config.i18n.default_locale = :ja
+
     # Please, add to the `ignore` list any other `lib` subdirectories that do
     # not contain `.rb` files, or that should not be reloaded or eager loaded.
     # Common ones are `templates`, `generators`, or `middleware`, for example.

backend/config/locales/en.yml

@@ -28,4 +28,8 @@
 #       enabled: "ON"
 
 en:
-  hello: "Hello world"
+  activerecord:
+    errors:
+      messages:
+        record_invalid: "Validation failed: %{errors}"
+        taken: 'イキスギ!'

backend/config/locales/ja.yml

@@ -0,0 +1,2 @@
+ja:
+  hello: 'ぬ゛〜゛ん゛'

backend/config/routes.rb

@@ -1,45 +1,84 @@
 Rails.application.routes.draw do
-  get 'tags/nico', to: 'nico_tags#index'
-  put 'tags/nico/:id', to: 'nico_tags#update'
-  get 'tags/autocomplete', to: 'tags#autocomplete'
-  get 'tags/name/:name', to: 'tags#show_by_name'
-  get 'posts/random', to: 'posts#random'
-  post 'posts/:id/viewed', to: 'posts#viewed'
-  delete 'posts/:id/viewed', to: 'posts#unviewed'
-  get 'preview/title', to: 'preview#title'
-  get 'preview/thumbnail', to: 'preview#thumbnail'
-  get 'wiki/title/:title', to: 'wiki_pages#show_by_title'
-  get 'wiki/search', to: 'wiki_pages#search'
-  get 'wiki/changes', to: 'wiki_pages#changes'
-  get 'wiki/:id/diff', to: 'wiki_pages#diff'
-  get 'wiki/:id', to: 'wiki_pages#show'
-  get 'wiki', to: 'wiki_pages#index'
-  post 'wiki', to: 'wiki_pages#create'
-  put 'wiki/:id', to: 'wiki_pages#update'
-  post 'users/code/renew', to: 'users#renew'
+  resources :nico_tags, path: 'tags/nico', only: [:index, :update]
+
+  scope 'tags/:parent_id/children', controller: :tag_children do
+    post ':child_id', action: :create
+    delete ':child_id', action: :destroy
+  end
+
+  resources :tags, only: [:index, :show, :update] do
+    collection do
+      get :autocomplete
+
+      scope :name do
+        get ':name/deerjikists', action: :deerjikists_by_name
+        get ':name', action: :show_by_name
+      end
+    end
+
+    member do
+      get :deerjikists
+    end
+  end
+
+  scope :preview, controller: :preview do
+    get :title
+    get :thumbnail
+  end
+
+  resources :wiki_pages, path: 'wiki', only: [:index, :show, :create, :update] do
+    collection do
+      get :search
+      get :changes
+
+      scope :title do
+        get ':title/exists', action: :exists_by_title
+        get ':title', action: :show_by_title
+      end
+    end
+
+    member do
+      get :exists
+      get :diff
+    end
+  end
+
+  resources :posts, only: [:index, :show, :create, :update] do
+    collection do
+      get :random
+      get :changes
+    end
+
+    member do
+      post :viewed
+      delete :viewed, action: :unviewed
+    end
+  end
 
-  resources :posts
-  resources :ip_addresses
-  resources :nico_tag_relations
-  resources :post_tags
-  resources :settings
-  resources :tag_aliases
-  resources :tags
-  resources :user_ips
-  resources :user_post_views
   resources :users, only: [:create, :update] do
     collection do
       post :verify
       get :me
+      post 'code/renew', action: :renew
     end
   end
 
-  # Define your application routes per the DSL in https://guides.rubyonrails.org/routing.html
+  resources :deerjikists, only: [] do
+    collection do
+      scope ':platform/:code' do
+        get '', action: :show
+        put '', action: :update
+        delete '', action: :destroy
+      end
+    end
+  end
 
-  # Reveal health status on /up that returns 200 if the app boots with no exceptions, otherwise 500.
-  # Can be used by load balancers and uptime monitors to verify that the app is live.
-  # get "up" => "rails/health#show", as: :rails_health_check
+  resources :theatres, only: [:show] do
+    member do
+      put :watching
+      patch :next_post
+    end
 
-  # Defines the root path route ("/")
-  # root "posts#index"
+    resources :comments, controller: :theatre_comments, only: [:index, :create]
+  end
 end

backend/db/migrate/20251009222200_create_tag_implications.rb

@@ -0,0 +1,9 @@
+class CreateTagImplications < ActiveRecord::Migration[8.0]
+  def change
+    create_table :tag_implications do |t|
+      t.references :tag, null: false, foreign_key: { to_table: :tags }
+      t.references :parent_tag, null: false, foreign_key: { to_table: :tags }
+      t.timestamps
+    end
+  end
+end

backend/db/migrate/20251011200300_add_discard_to_post_tags.rb

@@ -0,0 +1,36 @@
+class AddDiscardToPostTags < ActiveRecord::Migration[8.0]
+  def up
+    execute <<~SQL
+      DELETE
+        pt1
+      FROM
+        post_tags pt1
+        INNER JOIN
+          post_tags pt2
+          ON
+            pt1.post_id = pt2.post_id
+            AND pt1.tag_id = pt2.tag_id
+            AND pt1.id > pt2.id
+      ;
+    SQL
+
+    add_column :post_tags, :discarded_at, :datetime
+    add_index :post_tags, :discarded_at
+
+    add_column :post_tags, :is_active, :boolean,
+               as: 'discarded_at IS NULL', stored: true
+
+    add_column :post_tags, :active_unique_key, :string,
+               as: "CASE WHEN discarded_at IS NULL THEN CONCAT(post_id, ':', tag_id) ELSE NULL END",
+               stored: true
+
+    add_index :post_tags, :active_unique_key, unique: true, name: 'idx_post_tags_active_unique'
+
+    add_index :post_tags, [:post_id, :discarded_at]
+    add_index :post_tags, [:tag_id, :discarded_at]
+  end
+
+  def down
+    raise ActiveRecord::IrreversibleMigration, '戻せません．'
+  end
+end

backend/db/migrate/20251126231500_rename_ip_adress_column_to_ip_addresses.rb

@@ -0,0 +1,5 @@
+class RenameIpAdressColumnToIpAddresses < ActiveRecord::Migration[8.0]
+  def change
+    rename_column :ip_addresses, :ip_adress, :ip_address
+  end
+end

backend/db/migrate/20251210123200_add_unique_index_to_tag_implications.rb

@@ -0,0 +1,27 @@
+class AddUniqueIndexToTagImplications < ActiveRecord::Migration[8.0]
+  def up
+    execute <<~SQL
+      DELETE
+        ti1
+      FROM
+        tag_implications ti1
+        INNER JOIN
+          tag_implications ti2
+          ON
+            ti1.tag_id = ti2.tag_id
+            AND ti1.parent_tag_id = ti2.parent_tag_id
+            AND ti1.id > ti2.id
+      ;
+    SQL
+
+    add_index :tag_implications, [:tag_id, :parent_tag_id],
+              unique: true,
+              name: 'index_tag_implications_on_tag_id_and_parent_tag_id'
+  end
+
+  def down
+    # NOTE: 重複削除は復元されなぃ．
+    remove_index :tag_implications,
+                 name: 'index_tag_implications_on_tag_id_and_parent_tag_id'
+  end
+end

backend/db/migrate/20251229012100_remove_tag_from_wiki_pages.rb

@@ -0,0 +1,5 @@
+class RemoveTagFromWikiPages < ActiveRecord::Migration[7.0]
+  def change
+    remove_reference :wiki_pages, :tag, if_exists: true
+  end
+end

backend/db/migrate/20251229020700_create_wiki_lines.rb

@@ -0,0 +1,11 @@
+class CreateWikiLines < ActiveRecord::Migration[7.0]
+  def change
+    create_table :wiki_lines do |t|
+      t.string :sha256, null: false, limit: 64
+      t.text :body, null: false
+      t.timestamps
+    end
+
+    add_index :wiki_lines, :sha256, unique: true
+  end
+end

backend/db/migrate/20251229021000_create_wiki_revisions.rb

@@ -0,0 +1,19 @@
+class CreateWikiRevisions < ActiveRecord::Migration[7.0]
+  def change
+    create_table :wiki_revisions do |t|
+      t.references :wiki_page, null: false, foreign_key: true
+      t.references :base_revision, foreign_key: { to_table: :wiki_revisions }
+      t.references :created_user, null: false, foreign_key: { to_table: :users }
+      t.integer :kind, null: false, default: 0  # 0: content, 1: redirect
+      t.references :redirect_page, foreign_key: { to_table: :wiki_pages }
+      t.string :message
+      t.integer :lines_count, null: false, default: 0
+      t.string :tree_sha256, limit: 64
+      t.timestamps
+    end
+
+    add_index :wiki_revisions, :tree_sha256
+    add_index :wiki_revisions, [:wiki_page_id, :id]
+    add_index :wiki_revisions, :kind
+  end
+end

backend/db/migrate/20251229022100_create_wiki_revision_lines.rb

@@ -0,0 +1,12 @@
+class CreateWikiRevisionLines < ActiveRecord::Migration[7.0]
+  def change
+    create_table :wiki_revision_lines do |t|
+      t.references :wiki_revision, null: false, foreign_key: true
+      t.integer :position, null: false
+      t.references :wiki_line, null: false, foreign_key: true
+    end
+
+    add_index :wiki_revision_lines, [:wiki_revision_id, :position], unique: true
+    add_index :wiki_revision_lines, [:wiki_revision_id, :wiki_line_id]
+  end
+end

backend/db/migrate/20251230143400_make_thumbnail_base_nullable_in_posts.rb

@@ -0,0 +1,27 @@
+class MakeThumbnailBaseNullableInPosts < ActiveRecord::Migration[7.0]
+  def up
+    change_column_null :posts, :thumbnail_base, true
+
+    execute <<~SQL
+      UPDATE
+        posts
+      SET
+        thumbnail_base = NULL
+      WHERE
+        thumbnail_base = ''
+    SQL
+  end
+
+  def down
+    execute <<~SQL
+      UPDATE
+        posts
+      SET
+        thumbnail_base = ''
+      WHERE
+        thumbnail_base IS NULL
+    SQL
+
+    change_column_null :posts, :thumbnail_base, false
+  end
+end

backend/db/migrate/20260107034300_make_title_nullable_in_posts.rb

@@ -0,0 +1,28 @@
+class MakeTitleNullableInPosts < ActiveRecord::Migration[7.0]
+  def up
+    change_column_null :posts, :title, true
+
+    execute <<~SQL
+      UPDATE
+        posts
+      SET
+        title = NULL
+      WHERE
+        title = ''
+    SQL
+  end
+
+  def down
+    execute <<~SQL
+      UPDATE
+        posts
+      SET
+        title = ''
+      WHERE
+        title IS NULL
+    SQL
+
+    change_column_null :posts, :title, false
+  end
+end
+

backend/db/migrate/20260111180600_create_tag_names.rb

@@ -0,0 +1,10 @@
+class CreateTagNames < ActiveRecord::Migration[7.0]
+  def change
+    create_table :tag_names do |t|
+      t.string :name, limit: 255, null: false
+      t.references :canonical, null: true, foreign_key: { to_table: :tag_names }, index: true
+      t.timestamps
+    end
+    add_index :tag_names, :name, unique: true
+  end
+end

backend/db/migrate/20260111192600_add_tag_name_to_tags.rb

@@ -0,0 +1,42 @@
+class AddTagNameToTags < ActiveRecord::Migration[7.0]
+  class Tag < ApplicationRecord
+    self.table_name = 'tags'
+  end
+
+  class TagName < ApplicationRecord
+    self.table_name = 'tag_names'
+  end
+
+  def up
+    add_reference :tags, :tag_name, null: true, foreign_key: true, index: false, after: :id
+    add_index :tags, :tag_name_id, unique: true
+
+    Tag.find_each do |tag|
+      name = tag.read_attribute(:name)
+      tn = TagName.find_or_create_by!(name:) do |r|
+        r.canonical_id = nil
+      end
+      tag.update_columns(tag_name_id: tn.id)
+    end
+
+    change_column_null :tags, :tag_name_id, false
+
+    remove_column :tags, :name
+  end
+
+  def down
+    add_column :tags, :name, :string, limit: 255, null: true, after: :id
+
+    Tag.find_each do |tag|
+      tag_name_id = tag.read_attribute(:tag_name_id)
+      name = TagName.find(tag_name_id).read_attribute(:name)
+      tag.update_columns(name:)
+    end
+
+    change_column_null :tags, :name, false
+
+    remove_foreign_key :tags, column: :tag_name_id
+    remove_index :tags, :tag_name_id
+    remove_column :tags, :tag_name_id
+  end
+end

backend/db/migrate/20260111204400_add_tag_name_to_wiki_pages.rb

@@ -0,0 +1,42 @@
+class AddTagNameToWikiPages < ActiveRecord::Migration[7.0]
+  class WikiPage < ApplicationRecord
+    self.table_name = 'wiki_pages'
+  end
+
+  class TagName < ApplicationRecord
+    self.table_name = 'tag_names'
+  end
+
+  def up
+    add_reference :wiki_pages, :tag_name, null: true, foreign_key: true, index: false, after: :id
+    add_index :wiki_pages, :tag_name_id, unique: true
+
+    WikiPage.find_each do |page|
+      name = page.read_attribute(:title)
+      tn = TagName.find_or_create_by!(name:) do |r|
+        r.canonical_id = nil
+      end
+      page.update_columns(tag_name_id: tn.id)
+    end
+
+    change_column_null :wiki_pages, :tag_name_id, false
+
+    remove_column :wiki_pages, :title
+  end
+
+  def down
+    add_column :wiki_pages, :title, :string, limit: 255, null: true, after: :id
+
+    WikiPage.find_each do |page|
+      tag_name_id = page.read_attribute(:tag_name_id)
+      title = TagName.find(tag_name_id).read_attribute(:name)
+      page.update_columns(title:)
+    end
+
+    change_column_null :wiki_pages, :title, false
+
+    remove_foreign_key :wiki_pages, column: :tag_name_id
+    remove_index :wiki_pages, :tag_name_id
+    remove_column :wiki_pages, :tag_name_id
+  end
+end

backend/db/migrate/20260112111800_drop_tag_aliases.rb

@@ -0,0 +1,9 @@
+class DropTagAliases < ActiveRecord::Migration[7.0]
+  def up
+    drop_table :tag_aliases
+  end
+
+  def down
+    raise ActiveRecord::IrreversibleMigration, '戻せません．'
+  end
+end

backend/db/migrate/20260118144400_add_unique_index_to_url_in_posts.rb

@@ -0,0 +1,6 @@
+class AddUniqueIndexToUrlInPosts < ActiveRecord::Migration[7.1]
+  def change
+    change_column :posts, :url, :string, limit: 768
+    add_index :posts, :url, unique: true, name: 'index_posts_on_url'
+  end
+end

backend/db/migrate/20260121024000_change_post_similarities_to_composite_pk.rb

@@ -0,0 +1,43 @@
+class ChangePostSimilaritiesToCompositePk < ActiveRecord::Migration[8.0]
+  def up
+    execute <<~SQL
+      ALTER TABLE
+        post_similarities
+          MODIFY COLUMN id BIGINT NOT NULL
+      ;
+    SQL
+
+    execute <<~SQL
+      ALTER TABLE
+        post_similarities
+          DROP PRIMARY KEY
+      ;
+    SQL
+
+    remove_column :post_similarities, :id
+
+    execute <<~SQL
+      ALTER TABLE
+        post_similarities
+          ADD PRIMARY KEY (post_id, target_post_id)
+      ;
+    SQL
+  end
+
+  def down
+    execute <<~SQL
+      ALTER TABLE
+        post_similarities
+          DROP PRIMARY KEY
+      ;
+    SQL
+
+    execute <<~SQL
+      ALTER TABLE
+        post_similarities
+          ADD COLUMN id BIGINT NOT NULL AUTO_INCREMENT FIRST
+        , ADD PRIMARY KEY (id)
+      ;
+    SQL
+  end
+end

backend/db/migrate/20260121024800_change_tag_similarities_to_composite_pk.rb

@@ -0,0 +1,43 @@
+class ChangeTagSimilaritiesToCompositePk < ActiveRecord::Migration[8.0]
+  def up
+    execute <<~SQL
+      ALTER TABLE
+        tag_similarities
+          MODIFY COLUMN id BIGINT NOT NULL
+      ;
+    SQL
+
+    execute <<~SQL
+      ALTER TABLE
+        tag_similarities
+          DROP PRIMARY KEY
+      ;
+    SQL
+
+    remove_column :tag_similarities, :id
+
+    execute <<~SQL
+      ALTER TABLE
+        tag_similarities
+          ADD PRIMARY KEY (tag_id, target_tag_id)
+      ;
+    SQL
+  end
+
+  def down
+    execute <<~SQL
+      ALTER TABLE
+        tag_similarities
+          DROP PRIMARY KEY
+      ;
+    SQL
+
+    execute <<~SQL
+      ALTER TABLE
+        tag_similarities
+          ADD COLUMN id BIGINT NOT NULL AUTO_INCREMENT FIRST
+        , ADD PRIMARY KEY (id)
+      ;
+    SQL
+  end
+end

backend/db/migrate/20260121213900_add_index_to_post_similarities.rb

@@ -0,0 +1,9 @@
+class AddIndexToPostSimilarities < ActiveRecord::Migration[8.0]
+  def change
+    remove_index :post_similarities, name: 'index_post_similarities_on_post_id'
+
+    add_index :post_similarities, [:post_id, :cos],
+              order: { cos: :desc },
+              name: 'index_post_similarities_on_post_id_and_cos'
+  end
+end

backend/db/migrate/20260121225600_add_index_to_tag_similarities.rb

@@ -0,0 +1,9 @@
+class AddIndexToTagSimilarities < ActiveRecord::Migration[8.0]
+  def change
+    remove_index :tag_similarities, name: 'index_tag_similarities_on_tag_id'
+
+    add_index :tag_similarities, [:tag_id, :cos],
+              order: { cos: :desc },
+              name: 'index_tag_similarities_on_tag_id_and_cos'
+  end
+end

backend/db/migrate/20260126124100_add_unique_index_to_ip_addresses.rb

@@ -0,0 +1,5 @@
+class AddUniqueIndexToIpAddresses < ActiveRecord::Migration[8.0]
+  def change
+    add_index :ip_addresses, :ip_address, unique: true, name: 'index_ip_addresses_on_ip_address'
+  end
+end

backend/db/migrate/20260127000900_change_user_ips_to_composite_pk.rb

@@ -0,0 +1,47 @@
+class ChangeUserIpsToCompositePk < ActiveRecord::Migration[8.0]
+  def up
+    execute <<~SQL
+      ALTER TABLE
+        user_ips
+          MODIFY COLUMN id BIGINT NOT NULL
+      ;
+    SQL
+
+    execute <<~SQL
+      ALTER TABLE
+        user_ips
+          DROP PRIMARY KEY
+      ;
+    SQL
+
+    remove_column :user_ips, :id
+
+    execute <<~SQL
+      ALTER TABLE
+        user_ips
+          ADD PRIMARY KEY (user_id, ip_address_id)
+      ;
+    SQL
+
+    remove_index :user_ips, name: 'index_user_ips_on_user_id'
+  end
+
+  def down
+    execute <<~SQL
+      ALTER TABLE
+        user_ips
+          DROP PRIMARY KEY
+      ;
+    SQL
+
+    execute <<~SQL
+      ALTER TABLE
+        user_ips
+          ADD COLUMN id BIGINT NOT NULL AUTO_INCREMENT FIRST
+        , ADD PRIMARY KEY (id)
+      ;
+    SQL
+
+    add_index :user_ips, :user_id, name: 'index_user_ips_on_user_id'
+  end
+end

backend/db/migrate/20260127005300_change_user_post_views_to_composite_pk.rb

@@ -0,0 +1,47 @@
+class ChangeUserPostViewsToCompositePk < ActiveRecord::Migration[8.0]
+  def up
+    execute <<~SQL
+      ALTER TABLE
+        user_post_views
+          MODIFY COLUMN id BIGINT NOT NULL
+      ;
+    SQL
+
+    execute <<~SQL
+      ALTER TABLE
+        user_post_views
+          DROP PRIMARY KEY
+      ;
+    SQL
+
+    remove_column :user_post_views, :id
+
+    execute <<~SQL
+      ALTER TABLE
+        user_post_views
+          ADD PRIMARY KEY (user_id, post_id)
+      ;
+    SQL
+
+    remove_index :user_post_views, name: 'index_user_post_views_on_user_id'
+  end
+
+  def down
+    execute <<~SQL
+      ALTER TABLE
+        user_post_views
+          DROP PRIMARY KEY
+      ;
+    SQL
+
+    execute <<~SQL
+      ALTER TABLE
+        user_post_views
+          ADD COLUMN id BIGINT NOT NULL AUTO_INCREMENT FIRST
+        , ADD PRIMARY KEY (id)
+      ;
+    SQL
+
+    add_index :user_post_views, :user_id, name: 'index_user_post_views_on_user_id'
+  end
+end

backend/db/migrate/20260303122700_create_deerjikists.rb

@@ -0,0 +1,10 @@
+class CreateDeerjikists < ActiveRecord::Migration[8.0]
+  def change
+    create_table :deerjikists, primary_key: [:platform, :code] do |t|
+      t.string :platform, null: false, limit: 16
+      t.string :code, null: false
+      t.references :tag, null: false
+      t.timestamps
+    end
+  end
+end

backend/db/migrate/20260309123200_create_tag_name_sanitisation_rules.rb

@@ -0,0 +1,31 @@
+class CreateTagNameSanitisationRules < ActiveRecord::Migration[8.0]
+  def up
+    create_table :tag_name_sanitisation_rules, id: :integer, primary_key: :priority do |t|
+      t.string :source_pattern, null: false
+      t.string :replacement, null: false
+      t.timestamps
+      t.datetime :discarded_at
+      t.index :source_pattern, unique: true
+      t.index :discarded_at
+    end
+
+    now = ActiveRecord::Base.connection.quote(Time.current)
+    execute <<~SQL
+      INSERT INTO
+        tag_name_sanitisation_rules(priority, source_pattern, replacement, created_at, updated_at)
+      VALUES
+        (10, '\\\\*',           '_',         #{ now }, #{ now })
+      , (20, '\\\\?',           '_',         #{ now }, #{ now })
+      , (25, '\\\\/',           '_',         #{ now }, #{ now })
+      , (30, '_+',              '_',         #{ now }, #{ now })
+      , (40, '_$',              '',          #{ now }, #{ now })
+      , (45, '^([^:]+\\\\:)?_', '\\\\1',     #{ now }, #{ now })
+      , (50, '^([^:]+\\\\:)?$', '\\\\1null', #{ now }, #{ now })
+      ;
+    SQL
+  end
+
+  def down
+    drop_table :tag_name_sanitisation_rules
+  end
+end

backend/db/migrate/20260311123100_add_discarded_at_to_tags.rb

@@ -0,0 +1,6 @@
+class AddDiscardedAtToTags < ActiveRecord::Migration[8.0]
+  def change
+    add_column :tags, :discarded_at, :datetime
+    add_index :tags, :discarded_at
+  end
+end

backend/db/migrate/20260311232100_add_discarded_at_to_tag_names.rb

@@ -0,0 +1,6 @@
+class AddDiscardedAtToTagNames < ActiveRecord::Migration[8.0]
+  def change
+    add_column :tag_names, :discarded_at, :datetime
+    add_index :tag_names, :discarded_at
+  end
+end

backend/db/migrate/20260311232300_add_discarded_at_to_wiki_pages.rb

@@ -0,0 +1,6 @@
+class AddDiscardedAtToWikiPages < ActiveRecord::Migration[8.0]
+  def change
+    add_column :wiki_pages, :discarded_at, :datetime
+    add_index :wiki_pages, :discarded_at
+  end
+end

backend/db/migrate/20260316082500_create_theatres.rb

@@ -0,0 +1,17 @@
+class CreateTheatres < ActiveRecord::Migration[8.0]
+  def change
+    create_table :theatres do |t|
+      t.string :name
+      t.datetime :opens_at, null: false, index: true
+      t.datetime :closes_at, index: true
+      t.integer :kind, null: false, index: true
+      t.references :current_post, foreign_key: { to_table: :posts }, index: true
+      t.datetime :current_post_started_at
+      t.integer :next_comment_no, null: false, default: 1
+      t.references :host_user, foreign_key: { to_table: :users }
+      t.references :created_by_user, null: false, foreign_key: { to_table: :users }, index: true
+      t.timestamps
+      t.datetime :discarded_at, index: true
+    end
+  end
+end

backend/db/migrate/20260316083500_create_theatre_comments.rb

@@ -0,0 +1,12 @@
+class CreateTheatreComments < ActiveRecord::Migration[8.0]
+  def change
+    create_table :theatre_comments, primary_key: [:theatre_id, :no] do |t|
+      t.references :theatre, null: false, foreign_key: { to_table: :theatres }
+      t.integer :no, null: false
+      t.references :user, foreign_key: { to_table: :users }
+      t.text :content, null: false
+      t.timestamps
+      t.datetime :discarded_at, index: true
+    end
+  end
+end

backend/db/migrate/20260317015000_create_theatre_watching_users.rb

@@ -0,0 +1,12 @@
+class CreateTheatreWatchingUsers < ActiveRecord::Migration[8.0]
+  def change
+    create_table :theatre_watching_users, primary_key: [:theatre_id, :user_id] do |t|
+      t.references :theatre, null: false, foreign_key: { to_table: :theatres }
+      t.references :user, null: false, foreign_key: { to_table: :users }, index: true
+      t.datetime :expires_at, null: false, index: true
+      t.timestamps
+
+      t.index [:theatre_id, :expires_at]
+    end
+  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: 2025_09_09_075500) do
+ActiveRecord::Schema[8.0].define(version: 2026_03_17_015000) 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
@@ -39,11 +39,21 @@ ActiveRecord::Schema[8.0].define(version: 2025_09_09_075500) do
     t.index ["blob_id", "variation_digest"], name: "index_active_storage_variant_records_uniqueness", unique: true
   end
 
+  create_table "deerjikists", primary_key: ["platform", "code"], charset: "utf8mb4", collation: "utf8mb4_0900_ai_ci", force: :cascade do |t|
+    t.string "platform", limit: 16, null: false
+    t.string "code", null: false
+    t.bigint "tag_id", null: false
+    t.datetime "created_at", null: false
+    t.datetime "updated_at", null: false
+    t.index ["tag_id"], name: "index_deerjikists_on_tag_id"
+  end
+
   create_table "ip_addresses", charset: "utf8mb4", collation: "utf8mb4_0900_ai_ci", force: :cascade do |t|
-    t.binary "ip_adress", limit: 16, null: false
+    t.binary "ip_address", limit: 16, null: false
     t.boolean "banned", default: false, null: false
     t.datetime "created_at", null: false
     t.datetime "updated_at", null: false
+    t.index ["ip_address"], name: "index_ip_addresses_on_ip_address", unique: true
   end
 
   create_table "nico_tag_relations", charset: "utf8mb4", collation: "utf8mb4_0900_ai_ci", force: :cascade do |t|
@@ -55,11 +65,11 @@ ActiveRecord::Schema[8.0].define(version: 2025_09_09_075500) do
     t.index ["tag_id"], name: "index_nico_tag_relations_on_tag_id"
   end
 
-  create_table "post_similarities", charset: "utf8mb4", collation: "utf8mb4_0900_ai_ci", force: :cascade do |t|
+  create_table "post_similarities", primary_key: ["post_id", "target_post_id"], charset: "utf8mb4", collation: "utf8mb4_0900_ai_ci", force: :cascade do |t|
     t.bigint "post_id", null: false
     t.bigint "target_post_id", null: false
     t.float "cos", null: false
-    t.index ["post_id"], name: "index_post_similarities_on_post_id"
+    t.index ["post_id", "cos"], name: "index_post_similarities_on_post_id_and_cos", order: { cos: :desc }
     t.index ["target_post_id"], name: "index_post_similarities_on_target_post_id"
   end
 
@@ -70,16 +80,23 @@ ActiveRecord::Schema[8.0].define(version: 2025_09_09_075500) do
     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
 
   create_table "posts", charset: "utf8mb4", collation: "utf8mb4_0900_ai_ci", force: :cascade do |t|
-    t.string "title", null: false
-    t.string "url", limit: 2000, null: false
-    t.string "thumbnail_base", limit: 2000, null: false
+    t.string "title"
+    t.string "url", limit: 768, null: false
+    t.string "thumbnail_base", limit: 2000
     t.bigint "parent_id"
     t.bigint "uploaded_user_id"
     t.datetime "created_at", null: false
@@ -88,6 +105,7 @@ ActiveRecord::Schema[8.0].define(version: 2025_09_09_075500) do
     t.datetime "updated_at", null: false
     t.index ["parent_id"], name: "index_posts_on_parent_id"
     t.index ["uploaded_user_id"], name: "index_posts_on_uploaded_user_id"
+    t.index ["url"], name: "index_posts_on_url", unique: true
   end
 
   create_table "settings", charset: "utf8mb4", collation: "utf8mb4_0900_ai_ci", force: :cascade do |t|
@@ -99,46 +117,117 @@ ActiveRecord::Schema[8.0].define(version: 2025_09_09_075500) do
     t.index ["user_id"], name: "index_settings_on_user_id"
   end
 
-  create_table "tag_aliases", charset: "utf8mb4", collation: "utf8mb4_0900_ai_ci", force: :cascade do |t|
+  create_table "tag_implications", charset: "utf8mb4", collation: "utf8mb4_0900_ai_ci", force: :cascade do |t|
     t.bigint "tag_id", null: false
-    t.string "name", null: false
+    t.bigint "parent_tag_id", null: false
     t.datetime "created_at", null: false
     t.datetime "updated_at", null: false
-    t.index ["tag_id"], name: "index_tag_aliases_on_tag_id"
+    t.index ["parent_tag_id"], name: "index_tag_implications_on_parent_tag_id"
+    t.index ["tag_id", "parent_tag_id"], name: "index_tag_implications_on_tag_id_and_parent_tag_id", unique: true
+    t.index ["tag_id"], name: "index_tag_implications_on_tag_id"
   end
 
-  create_table "tag_similarities", charset: "utf8mb4", collation: "utf8mb4_0900_ai_ci", force: :cascade do |t|
+  create_table "tag_name_sanitisation_rules", primary_key: "priority", id: :integer, charset: "utf8mb4", collation: "utf8mb4_0900_ai_ci", force: :cascade do |t|
+    t.string "source_pattern", null: false
+    t.string "replacement", null: false
+    t.datetime "created_at", null: false
+    t.datetime "updated_at", null: false
+    t.datetime "discarded_at"
+    t.index ["discarded_at"], name: "index_tag_name_sanitisation_rules_on_discarded_at"
+    t.index ["source_pattern"], name: "index_tag_name_sanitisation_rules_on_source_pattern", unique: true
+  end
+
+  create_table "tag_names", charset: "utf8mb4", collation: "utf8mb4_0900_ai_ci", force: :cascade do |t|
+    t.string "name", null: false
+    t.bigint "canonical_id"
+    t.datetime "created_at", null: false
+    t.datetime "updated_at", null: false
+    t.datetime "discarded_at"
+    t.index ["canonical_id"], name: "index_tag_names_on_canonical_id"
+    t.index ["discarded_at"], name: "index_tag_names_on_discarded_at"
+    t.index ["name"], name: "index_tag_names_on_name", unique: true
+  end
+
+  create_table "tag_similarities", primary_key: ["tag_id", "target_tag_id"], charset: "utf8mb4", collation: "utf8mb4_0900_ai_ci", force: :cascade do |t|
     t.bigint "tag_id", null: false
     t.bigint "target_tag_id", null: false
     t.float "cos", null: false
-    t.index ["tag_id"], name: "index_tag_similarities_on_tag_id"
+    t.index ["tag_id", "cos"], name: "index_tag_similarities_on_tag_id_and_cos", order: { cos: :desc }
     t.index ["target_tag_id"], name: "index_tag_similarities_on_target_tag_id"
   end
 
   create_table "tags", charset: "utf8mb4", collation: "utf8mb4_0900_ai_ci", force: :cascade do |t|
-    t.string "name", null: false
+    t.bigint "tag_name_id", null: false
     t.string "category", default: "general", null: false
     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.index ["discarded_at"], name: "index_tags_on_discarded_at"
+    t.index ["tag_name_id"], name: "index_tags_on_tag_name_id", unique: true
   end
 
-  create_table "user_ips", charset: "utf8mb4", collation: "utf8mb4_0900_ai_ci", force: :cascade do |t|
+  create_table "theatre_comments", primary_key: ["theatre_id", "no"], charset: "utf8mb4", collation: "utf8mb4_0900_ai_ci", force: :cascade do |t|
+    t.bigint "theatre_id", null: false
+    t.integer "no", null: false
+    t.bigint "user_id"
+    t.text "content", null: false
+    t.datetime "created_at", null: false
+    t.datetime "updated_at", null: false
+    t.datetime "discarded_at"
+    t.index ["discarded_at"], name: "index_theatre_comments_on_discarded_at"
+    t.index ["theatre_id"], name: "index_theatre_comments_on_theatre_id"
+    t.index ["user_id"], name: "index_theatre_comments_on_user_id"
+  end
+
+  create_table "theatre_watching_users", primary_key: ["theatre_id", "user_id"], charset: "utf8mb4", collation: "utf8mb4_0900_ai_ci", force: :cascade do |t|
+    t.bigint "theatre_id", null: false
+    t.bigint "user_id", null: false
+    t.datetime "expires_at", null: false
+    t.datetime "created_at", null: false
+    t.datetime "updated_at", null: false
+    t.index ["expires_at"], name: "index_theatre_watching_users_on_expires_at"
+    t.index ["theatre_id", "expires_at"], name: "index_theatre_watching_users_on_theatre_id_and_expires_at"
+    t.index ["theatre_id"], name: "index_theatre_watching_users_on_theatre_id"
+    t.index ["user_id"], name: "index_theatre_watching_users_on_user_id"
+  end
+
+  create_table "theatres", charset: "utf8mb4", collation: "utf8mb4_0900_ai_ci", force: :cascade do |t|
+    t.string "name"
+    t.datetime "opens_at", null: false
+    t.datetime "closes_at"
+    t.integer "kind", null: false
+    t.bigint "current_post_id"
+    t.datetime "current_post_started_at"
+    t.integer "next_comment_no", default: 1, null: false
+    t.bigint "host_user_id"
+    t.bigint "created_by_user_id", null: false
+    t.datetime "created_at", null: false
+    t.datetime "updated_at", null: false
+    t.datetime "discarded_at"
+    t.index ["closes_at"], name: "index_theatres_on_closes_at"
+    t.index ["created_by_user_id"], name: "index_theatres_on_created_by_user_id"
+    t.index ["current_post_id"], name: "index_theatres_on_current_post_id"
+    t.index ["discarded_at"], name: "index_theatres_on_discarded_at"
+    t.index ["host_user_id"], name: "index_theatres_on_host_user_id"
+    t.index ["kind"], name: "index_theatres_on_kind"
+    t.index ["opens_at"], name: "index_theatres_on_opens_at"
+  end
+
+  create_table "user_ips", primary_key: ["user_id", "ip_address_id"], charset: "utf8mb4", collation: "utf8mb4_0900_ai_ci", force: :cascade do |t|
     t.bigint "user_id", null: false
     t.bigint "ip_address_id", null: false
     t.datetime "created_at", null: false
     t.datetime "updated_at", null: false
     t.index ["ip_address_id"], name: "index_user_ips_on_ip_address_id"
-    t.index ["user_id"], name: "index_user_ips_on_user_id"
   end
 
-  create_table "user_post_views", charset: "utf8mb4", collation: "utf8mb4_0900_ai_ci", force: :cascade do |t|
+  create_table "user_post_views", primary_key: ["user_id", "post_id"], charset: "utf8mb4", collation: "utf8mb4_0900_ai_ci", force: :cascade do |t|
     t.bigint "user_id", null: false
     t.bigint "post_id", null: false
     t.datetime "created_at", null: false
     t.datetime "updated_at", null: false
     t.index ["post_id"], name: "index_user_post_views_on_post_id"
-    t.index ["user_id"], name: "index_user_post_views_on_user_id"
   end
 
   create_table "users", charset: "utf8mb4", collation: "utf8mb4_0900_ai_ci", force: :cascade do |t|
@@ -150,18 +239,57 @@ ActiveRecord::Schema[8.0].define(version: 2025_09_09_075500) do
     t.datetime "updated_at", null: false
   end
 
+  create_table "wiki_lines", charset: "utf8mb4", collation: "utf8mb4_0900_ai_ci", force: :cascade do |t|
+    t.string "sha256", limit: 64, null: false
+    t.text "body", null: false
+    t.datetime "created_at", null: false
+    t.datetime "updated_at", null: false
+    t.index ["sha256"], name: "index_wiki_lines_on_sha256", unique: true
+  end
+
   create_table "wiki_pages", charset: "utf8mb4", collation: "utf8mb4_0900_ai_ci", force: :cascade do |t|
-    t.string "title", null: false
-    t.bigint "tag_id"
+    t.bigint "tag_name_id", null: false
     t.bigint "created_user_id", null: false
     t.bigint "updated_user_id", null: false
     t.datetime "created_at", null: false
     t.datetime "updated_at", null: false
+    t.datetime "discarded_at"
     t.index ["created_user_id"], name: "index_wiki_pages_on_created_user_id"
-    t.index ["tag_id"], name: "index_wiki_pages_on_tag_id"
+    t.index ["discarded_at"], name: "index_wiki_pages_on_discarded_at"
+    t.index ["tag_name_id"], name: "index_wiki_pages_on_tag_name_id", unique: true
     t.index ["updated_user_id"], name: "index_wiki_pages_on_updated_user_id"
   end
 
+  create_table "wiki_revision_lines", charset: "utf8mb4", collation: "utf8mb4_0900_ai_ci", force: :cascade do |t|
+    t.bigint "wiki_revision_id", null: false
+    t.integer "position", null: false
+    t.bigint "wiki_line_id", null: false
+    t.index ["wiki_line_id"], name: "index_wiki_revision_lines_on_wiki_line_id"
+    t.index ["wiki_revision_id", "position"], name: "index_wiki_revision_lines_on_wiki_revision_id_and_position", unique: true
+    t.index ["wiki_revision_id", "wiki_line_id"], name: "index_wiki_revision_lines_on_wiki_revision_id_and_wiki_line_id"
+    t.index ["wiki_revision_id"], name: "index_wiki_revision_lines_on_wiki_revision_id"
+  end
+
+  create_table "wiki_revisions", charset: "utf8mb4", collation: "utf8mb4_0900_ai_ci", force: :cascade do |t|
+    t.bigint "wiki_page_id", null: false
+    t.bigint "base_revision_id"
+    t.bigint "created_user_id", null: false
+    t.integer "kind", default: 0, null: false
+    t.bigint "redirect_page_id"
+    t.string "message"
+    t.integer "lines_count", default: 0, null: false
+    t.string "tree_sha256", limit: 64
+    t.datetime "created_at", null: false
+    t.datetime "updated_at", null: false
+    t.index ["base_revision_id"], name: "index_wiki_revisions_on_base_revision_id"
+    t.index ["created_user_id"], name: "index_wiki_revisions_on_created_user_id"
+    t.index ["kind"], name: "index_wiki_revisions_on_kind"
+    t.index ["redirect_page_id"], name: "index_wiki_revisions_on_redirect_page_id"
+    t.index ["tree_sha256"], name: "index_wiki_revisions_on_tree_sha256"
+    t.index ["wiki_page_id", "id"], name: "index_wiki_revisions_on_wiki_page_id_and_id"
+    t.index ["wiki_page_id"], name: "index_wiki_revisions_on_wiki_page_id"
+  end
+
   add_foreign_key "active_storage_attachments", "active_storage_blobs", column: "blob_id"
   add_foreign_key "active_storage_variant_records", "active_storage_blobs", column: "blob_id"
   add_foreign_key "nico_tag_relations", "tags"
@@ -175,14 +303,30 @@ ActiveRecord::Schema[8.0].define(version: 2025_09_09_075500) do
   add_foreign_key "posts", "posts", column: "parent_id"
   add_foreign_key "posts", "users", column: "uploaded_user_id"
   add_foreign_key "settings", "users"
-  add_foreign_key "tag_aliases", "tags"
+  add_foreign_key "tag_implications", "tags"
+  add_foreign_key "tag_implications", "tags", column: "parent_tag_id"
+  add_foreign_key "tag_names", "tag_names", column: "canonical_id"
   add_foreign_key "tag_similarities", "tags"
   add_foreign_key "tag_similarities", "tags", column: "target_tag_id"
+  add_foreign_key "tags", "tag_names"
+  add_foreign_key "theatre_comments", "theatres"
+  add_foreign_key "theatre_comments", "users"
+  add_foreign_key "theatre_watching_users", "theatres"
+  add_foreign_key "theatre_watching_users", "users"
+  add_foreign_key "theatres", "posts", column: "current_post_id"
+  add_foreign_key "theatres", "users", column: "created_by_user_id"
+  add_foreign_key "theatres", "users", column: "host_user_id"
   add_foreign_key "user_ips", "ip_addresses"
   add_foreign_key "user_ips", "users"
   add_foreign_key "user_post_views", "posts"
   add_foreign_key "user_post_views", "users"
-  add_foreign_key "wiki_pages", "tags"
+  add_foreign_key "wiki_pages", "tag_names"
   add_foreign_key "wiki_pages", "users", column: "created_user_id"
   add_foreign_key "wiki_pages", "users", column: "updated_user_id"
+  add_foreign_key "wiki_revision_lines", "wiki_lines"
+  add_foreign_key "wiki_revision_lines", "wiki_revisions"
+  add_foreign_key "wiki_revisions", "users", column: "created_user_id"
+  add_foreign_key "wiki_revisions", "wiki_pages"
+  add_foreign_key "wiki_revisions", "wiki_pages", column: "redirect_page_id"
+  add_foreign_key "wiki_revisions", "wiki_revisions", column: "base_revision_id"
 end

backend/lib/tasks/calc_post_similarities.rake

@@ -1,28 +1,6 @@
 namespace :post_similarity do
   desc '関聯投稿テーブル作成'
   task calc: :environment do
-    dot = -> a, b { (a.keys & b.keys).sum { |k| a[k] * b[k] } }
-    norm = -> v { Math.sqrt(v.values.sum { |e| e * e }) }
-    cos = -> a, b do
-      na = norm.(a)
-      nb = norm.(b)
-      if na.zero? || nb.zero?
-        0.0
-      else
-        dot.(a, b) / na / nb
-      end
-    end
-
-    posts = Post.includes(:tags).to_a
-    posts.each_with_index do |post, i|
-      existence_of_tags = post.tags.index_with(1)
-      ((i + 1)...posts.size).each do |j|
-        target_post = posts[j]
-        existence_of_target_tags = target_post.tags.index_with(1)
-        PostSimilarity.find_or_initialize_by(post:, target_post:).tap { |ps|
-          ps.cos = cos.(existence_of_tags, existence_of_target_tags)
-        }.save!
-      end
-    end
+    Similarity::Calc.call(Post, :tags)
   end
 end

backend/lib/tasks/calc_tag_similarities.rake

@@ -0,0 +1,6 @@
+namespace :tag_similarity do
+  desc '関聯タグ・テーブル作成'
+  task calc: :environment do
+    Similarity::Calc.call(Tag, :posts)
+  end
+end

backend/lib/tasks/link_nico.rake

@@ -1,12 +0,0 @@
-namespace :nico do
-  desc 'ニコタグ連携'
-  task link: :environment do
-    Post.find_each do |post|
-      tags = post.tags.where(category: 'nico')
-      tags.each do |tag|
-        post.tags.concat(tag.linked_tags) if tag.linked_tags.present?
-      end
-      post.tags = post.tags.to_a.uniq
-    end
-  end
-end

backend/lib/tasks/migrate_wiki.rake

@@ -0,0 +1,74 @@
+namespace :wiki do
+  desc 'Wiki 移行'
+  task migrate: :environment do
+    require 'digest'
+    require 'gollum-lib'
+
+    wiki = Gollum::Wiki.new(Rails.root.join('wiki').to_s)
+
+    WikiPage.where.missing(:wiki_revisions).find_each do |wiki_page|
+      page = wiki.page("#{ wiki_page.id }.md")
+      next unless page
+
+      versions = page.versions
+      next if versions.blank?
+
+      base_revision_id = nil
+      versions.reverse_each do |version|
+        pg = wiki.page("#{ wiki_page.id }.md", version.id)
+        raw = pg&.raw_data
+        next unless raw
+
+        lines = raw.force_encoding('UTF-8').split("\n")
+
+        line_shas = lines.map { |l| Digest::SHA256.hexdigest(l) }
+        tree_sha = Digest::SHA256.hexdigest(line_shas.join(','))
+
+        at = version.authored_date
+
+        line_id_by_sha = WikiLine.where(sha256: line_shas).pluck(:sha256, :id).to_h
+
+        missing_rows = []
+        line_shas.each_with_index do |sha, i|
+          next if line_id_by_sha.key?(sha)
+
+          missing_rows << { sha256:     sha,
+                            body:       lines[i],
+                            created_at: at,
+                            updated_at: at }
+        end
+
+        if missing_rows.any?
+          WikiLine.upsert_all(missing_rows)
+          line_id_by_sha = WikiLine.where(sha256: line_shas).pluck(:sha256, :id).to_h
+        end
+        line_ids = line_shas.map { |sha| line_id_by_sha.fetch(sha) }
+
+        rev = nil
+        ActiveRecord::Base.transaction do
+          wiki_page.lock!
+
+          rev = WikiRevision.create!(
+              wiki_page:,
+              base_revision_id:,
+              created_user_id:  (Integer(version.author.name) rescue 2),
+              kind:             :content,
+              redirect_page_id: nil,
+              message:          nil,
+              lines_count:      lines.length,
+              tree_sha256:      tree_sha,
+              created_at:       at,
+              updated_at:       at)
+
+          rows = line_ids.each_with_index.map do |line_id, pos|
+            { wiki_revision_id: rev.id,
+              wiki_line_id:     line_id,
+              position:         pos }
+          end
+          WikiRevisionLine.insert_all!(rows)
+        end
+        base_revision_id = rev.id
+      end
+    end
+  end
+end

backend/lib/tasks/sync_nico.rake

@@ -1,16 +1,39 @@
 namespace :nico do
   desc 'ニコニコ DB 同期'
   task sync: :environment do
-    require 'open3'
-    require 'open-uri'
+    require 'json'
     require 'nokogiri'
+    require 'open-uri'
+    require 'open3'
+    require 'set'
+    require 'time'
 
-    fetch_thumbnail = -> url {
+    fetch_thumbnail = -> url do
       html = URI.open(url, read_timeout: 60, 'User-Agent' => 'Mozilla/5.0').read
       doc = Nokogiri::HTML(html)
 
       doc.at('meta[name="thumbnail"]')&.[]('content').presence
-    }
+    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
+      desired_tag_ids = desired_tag_ids.compact.to_set
+
+      to_add = desired_tag_ids - current_tag_ids
+      to_remove = current_tag_ids - desired_tag_ids
+
+      Tag.where(id: to_add.to_a).find_each do |tag|
+        begin
+          PostTag.create!(post:, tag:)
+        rescue ActiveRecord::RecordNotUnique
+          ;
+        end
+      end
+
+      PostTag.where(post_id: post.id, tag_id: to_remove.to_a).kept.find_each do |pt|
+        pt.discard_by!(nil)
+      end
+    end
 
     mysql_user = ENV['MYSQL_USER']
     mysql_pass = ENV['MYSQL_PASS']
@@ -19,43 +42,104 @@ namespace :nico do
         { 'MYSQL_USER' => mysql_user, 'MYSQL_PASS' => mysql_pass },
         'python3', "#{ nizika_nico_path }/get_videos.py")
 
-    if status.success?
-      data = JSON.parse(stdout)
-      data.each do |datum|
-        post = Post.where('url LIKE ?', '%nicovideo.jp%').find { |post|
-          post.url =~ %r{#{ Regexp.escape(datum['code']) }(?!\d)}
-        }
-        unless post
-          title = datum['title']
-          url = "https://www.nicovideo.jp/watch/#{ datum['code'] }"
-          thumbnail_base = fetch_thumbnail.(url) || '' rescue ''
-          post = Post.new(title:, url:, thumbnail_base:, uploaded_user: nil)
+    unless status.success?
+      warn stderr
+      abort
+    end
+
+    data = JSON.parse(stdout)
+    data.each do |datum|
+      code = datum['code']
+      post =
+          Post
+          .where('url REGEXP ?', "nicovideo\\.jp/watch/#{ Regexp.escape(code) }([^0-9]|$)")
+          .first
+
+      title = datum['title']
+      original_created_at = datum['uploaded_at'] &&
+          Time.strptime(datum['uploaded_at'], '%Y-%m-%d %H:%M:%S')
+      original_created_from = original_created_at&.change(sec: 0)
+      original_created_before = original_created_from&.+(1.minute)
+
+      if post
+        attrs = { title:, original_created_from:, original_created_before: }
+
+        unless post.thumbnail.attached?
+          thumbnail_base = fetch_thumbnail.(post.url) rescue nil
           if thumbnail_base.present?
             post.thumbnail.attach(
                 io:           URI.open(thumbnail_base),
                 filename:     File.basename(URI.parse(thumbnail_base).path),
                 content_type: 'image/jpeg')
+            attrs[:thumbnail_base] = thumbnail_base
           end
-          post.save!
-          post.resized_thumbnail!
         end
 
-        current_tags = post.tags.where(category: 'nico').pluck(:name).sort
-        new_tags = datum['tags'].map { |tag| "nico:#{ tag }" }.sort
-        if current_tags != new_tags
-          post.tags.destroy(post.tags.where(name: current_tags))
-          tags_to_add = []
-          new_tags.each do |name|
-            tag = Tag.find_or_initialize_by(name:) do |t|
-              t.category = 'nico'
-            end
-            tags_to_add.concat([tag] + tag.linked_tags)
-          end
-          tags_to_add << Tag.tagme if post.tags.size < 20
-          tags_to_add << Tag.bot
-          post.tags = (post.tags + tags_to_add).uniq
+        post.assign_attributes(attrs)
+        if post.changed?
+          post.save!
+          post.resized_thumbnail! if post.thumbnail.attached?
+        end
+      else
+        url = "https://www.nicovideo.jp/watch/#{ code }"
+        thumbnail_base = fetch_thumbnail.(url) rescue nil
+        post = Post.new(title:, url:, thumbnail_base:, uploaded_user: nil,
+                        original_created_from:, original_created_before:)
+        if thumbnail_base.present?
+          post.thumbnail.attach(
+              io:           URI.open(thumbnail_base),
+              filename:     File.basename(URI.parse(thumbnail_base).path),
+              content_type: 'image/jpeg')
+        end
+        post.save!
+        post.resized_thumbnail!
+        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
+      # うち内部タグ Id. 集合
+      kept_non_nico_tag_ids = tags.not_nico.pluck(:id).to_set
+
+      # 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 = []
+
+      datum['tags'].each do |raw|
+        name = TagNameSanitisationRule.sanitise("nico:#{ raw }")
+        tag = Tag.find_or_create_by_tag_name!(name, category: :nico)
+        desired_nico_tag_based_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)
+          linked_ids = tag.linked_tags.pluck(:id)
+          desired_non_nico_tag_ids.concat(linked_ids)
+          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_nico_tag_based_ids << deerjikist.tag_id
+      elsif !(Tag.where(id: kept_non_nico_tag_ids).where(category: :deerjikist).exists?)
+        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_all_tag_ids = kept_non_nico_tag_ids.to_a + desired_nico_tag_based_ids
+      desired_non_nico_tag_ids.concat(kept_non_nico_tag_ids.to_a)
+      desired_non_nico_tag_ids.uniq!
+      if kept_non_nico_tag_ids != desired_non_nico_tag_ids.to_set
+        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)
     end
   end
 end

backend/spec/factories/tag_names.rb

@@ -0,0 +1,5 @@
+FactoryBot.define do
+  factory :tag_name do
+    name { "tag-#{SecureRandom.hex(4)}" }
+  end
+end

backend/spec/factories/tags.rb

@@ -0,0 +1,22 @@
+FactoryBot.define do
+  factory :tag do
+    transient do
+      name { nil }
+    end
+
+    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
+      category { :nico }
+      transient do
+        name { "nico:#{ SecureRandom.hex(4) }" }
+      end
+    end
+  end
+end

backend/spec/factories/theatre_comments.rb

@@ -0,0 +1,8 @@
+FactoryBot.define do
+  factory :theatre_comment do
+    association :theatre
+    association :user
+    sequence (:no) { |n| n }
+    content { 'test comment' }
+  end
+end

backend/spec/factories/theatres.rb

@@ -0,0 +1,11 @@
+FactoryBot.define do
+  factory :theatre do
+    name { 'Test Theatre' }
+    kind { 1 }
+    opens_at { Time.current }
+    closes_at { 1.day.from_now }
+    next_comment_no { 1 }
+
+    association :created_by_user, factory: :user
+  end
+end

backend/spec/factories/users.rb

@@ -0,0 +1,15 @@
+FactoryBot.define do
+  factory :user do
+    name { "test-user" }
+    inheritance_code { SecureRandom.uuid }
+    role { "guest" }
+
+    trait :member do
+      role { "member" }
+    end
+
+    trait :admin do
+      role { 'admin' }
+    end
+  end
+end

backend/spec/factories/wiki_pages.rb

@@ -0,0 +1,7 @@
+FactoryBot.define do
+  factory :wiki_page do
+    title { "TestPage" }
+    association :created_user, factory: :user
+    association :updated_user, factory: :user
+  end
+end

backend/spec/models/tag_name_sanitisation_rule_spec.rb

@@ -0,0 +1,101 @@
+require 'rails_helper'
+
+RSpec.describe TagNameSanitisationRule, type: :model do
+  describe '.sanitise' do
+    before do
+      described_class.create!(priority: 10, source_pattern: '_', replacement: '')
+      described_class.create!(priority: 20, source_pattern: 'ABC', replacement: 'abc')
+    end
+
+    it 'applies sanitisation rules sequentially in priority order' do
+      expect(described_class.sanitise('A_B_C')).to eq('abc')
+    end
+
+    it 'does not fail when a rule does not match' do
+      expect { described_class.sanitise('xyz') }.not_to raise_error
+      expect(described_class.sanitise('xyz')).to eq('xyz')
+    end
+  end
+
+  describe 'validations' do
+    it 'is invalid when source_pattern is not a valid regexp' do
+      rule = described_class.new(priority: 10, source_pattern: '[', replacement: '')
+      expect(rule).to be_invalid
+      expect(rule.errors[:source_pattern]).to be_present
+    end
+  end
+
+  describe '.apply!' do
+    before do
+      described_class.create!(priority: 10, source_pattern: '_', replacement: '')
+    end
+
+    context 'when no conflicting tag_name exists' do
+      let!(:tag_name) do
+        TagName.create!(name: 'tmp').tap do |tn|
+          tn.update_columns(name: 'foo_bar', updated_at: Time.current)
+        end
+      end
+
+      it 'renames the tag_name' do
+        described_class.apply!
+        expect(tag_name.reload.name).to eq('foobar')
+      end
+    end
+
+    context 'when a conflicting canonical tag_name exists' do
+      let!(:existing) { TagName.create!(name: 'foobar') }
+      let!(:source) do
+        TagName.create!(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(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!(:source_tag) { create(:tag, name: 'tmp', category: :general) }
+      let!(:source_tag_name_id) { source_tag.tag_name_id }
+
+      before do
+        source_tag.tag_name.update_columns(name: 'foo_bar', updated_at: Time.current)
+      end
+
+      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(expected_tag_name_id)
+        expect(TagName.exists?(source_tag_name_id)).to be(false)
+      end
+    end
+
+    context 'when both source and existing tag_names have tags' do
+      let!(:existing_tn) { TagName.create!(name: 'foobar') }
+      let!(:existing_tag) { Tag.create!(tag_name: existing_tn, category: :general) }
+
+      let!(:source_tn) { TagName.create!(name: 'tmp') }
+      let!(:source_tag) { Tag.create!(tag_name: source_tn, category: :general) }
+      let!(:source_tag_name_id) { source_tn.id }
+
+      before do
+        source_tn.update_columns(name: 'foo_bar', updated_at: Time.current)
+      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)
+        expect(TagName.find_by(name: 'foo_bar')&.tag&.id).to eq(source_tag.id)
+
+        described_class.apply!
+
+        expect(Tag.exists?(source_tag.id)).to be(false)
+        expect(TagName.exists?(source_tag.tag_name_id)).to be(false)
+      end
+    end
+  end
+end

backend/spec/models/tag_spec.rb

@@ -0,0 +1,149 @@
+require 'rails_helper'
+
+RSpec.describe Tag, type: :model do
+  describe '.merge_tags!' do
+    let!(:target_tag) { create(:tag, category: :general) }
+    let!(:source_tag) { create(:tag, category: :general) }
+    let!(:source_tag_name) { source_tag.tag_name }
+
+    let!(:post_record) do
+      Post.create!(url: 'https://example.com/posts/1', title: 'test post')
+    end
+
+    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
+        described_class.merge_tags!(target_tag, [source_tag])
+
+        source_pt = PostTag.with_discarded.find(source_post_tag.id)
+        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(source_pt.tag_id).to eq(source_tag.id)
+        expect(active_target).to be_present
+
+        expect(Tag.with_discarded.find(source_tag.id)).to be_discarded
+        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
+
+    context 'when the target already has the same post_tag' 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
+        described_class.merge_tags!(target_tag, [source_tag])
+
+        source_pt = PostTag.with_discarded.find(source_post_tag.id)
+        active = PostTag.kept.where(post_id: post_record.id, tag_id: target_tag.id)
+
+        expect(source_pt.discarded_at).to be_present
+        expect(source_pt.tag_id).to eq(source_tag.id)
+        expect(active.count).to eq(1)
+        expect(active.first.id).to eq(target_post_tag.id)
+
+        expect(Tag.with_discarded.find(source_tag.id)).to be_discarded
+        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
+
+    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)
+        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(source_pt.discarded_at).to be_present
+        expect(source_pt.tag_id).to eq(source_tag.id)
+        expect(active_target).to be_present
+        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
+
+    context 'when the source tag_name is invalid under sanitisation rules' do
+      let!(:source_post_tag) { PostTag.create!(post: post_record, tag: source_tag) }
+      let!(:sanitisation_rule) do
+        TagNameSanitisationRule.create!(
+          priority: 99_999,
+          source_pattern: 'INVALIDTOKEN',
+          replacement: ''
+        )
+      end
+
+      before do
+        source_tag_name.update_columns(
+          name: "#{ source_tag_name.name }INVALIDTOKEN",
+          updated_at: Time.current
+        )
+      end
+
+      it 'still merges, but discards the source tag_name instead of aliasing it' do
+        described_class.merge_tags!(target_tag, [source_tag])
+
+        source_pt = PostTag.with_discarded.find(source_post_tag.id)
+        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(source_pt.tag_id).to eq(source_tag.id)
+        expect(active_target).to be_present
+
+        expect(Tag.with_discarded.find(source_tag.id)).to be_discarded
+        expect(target_tag.reload.post_count).to eq(1)
+      end
+    end
+
+    context 'when the source tag_name has a wiki_page' do
+      let!(:source_post_tag) { PostTag.create!(post: post_record, tag: source_tag) }
+      let!(:wiki_page) do
+        WikiPage.create!(
+          tag_name: source_tag_name,
+          created_user: create_admin_user!,
+          updated_user: create_admin_user!
+        )
+      end
+
+      it 'rolls back the transaction' do
+        expect {
+          described_class.merge_tags!(target_tag, [source_tag])
+        }.to raise_error(ActiveRecord::RecordInvalid)
+
+        expect(Tag.with_discarded.find(source_tag.id)).not_to be_discarded
+        expect(TagName.with_discarded.find(source_tag_name.id)).not_to be_discarded
+        expect(PostTag.kept.find(source_post_tag.id).tag_id).to eq(source_tag.id)
+        expect(PostTag.kept.find_by(post_id: post_record.id, tag_id: target_tag.id)).to be_nil
+        expect(source_tag_name.reload.canonical_id).to be_nil
+        expect(target_tag.reload.post_count).to eq(0)
+      end
+    end
+
+    context 'when merging a nico source tag' do
+      let!(:target_tag) { create(:tag, category: :nico, name: 'nico:foo') }
+      let!(:source_tag) { create(:tag, category: :nico, name: 'nico:bar') }
+      let!(:source_tag_name_id) { source_tag.tag_name_id }
+
+      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
+  end
+end

backend/spec/rails_helper.rb

@@ -0,0 +1,90 @@
+# This file is copied to spec/ when you run 'rails generate rspec:install'
+require 'spec_helper'
+ENV['RAILS_ENV'] ||= 'test'
+require_relative '../config/environment'
+# Prevent database truncation if the environment is production
+abort("The Rails environment is running in production mode!") if Rails.env.production?
+# Uncomment the line below in case you have `--require rails_helper` in the `.rspec` file
+# that will avoid rails generators crashing because migrations haven't been run yet
+# return unless Rails.env.test?
+require 'rspec/rails'
+Dir[Rails.root.join('spec/support/**/*.rb')].each do |f|
+  require f
+end
+
+# Add additional requires below this line. Rails is not loaded until this point!
+
+# Requires supporting ruby files with custom matchers and macros, etc, in
+# spec/support/ and its subdirectories. Files matching `spec/**/*_spec.rb` are
+# run as spec files by default. This means that files in spec/support that end
+# in _spec.rb will both be required and run as specs, causing the specs to be
+# run twice. It is recommended that you do not name files matching this glob to
+# end with _spec.rb. You can configure this pattern with the --pattern
+# option on the command line or in ~/.rspec, .rspec or `.rspec-local`.
+#
+# The following line is provided for convenience purposes. It has the downside
+# of increasing the boot-up time by auto-requiring all files in the support
+# directory. Alternatively, in the individual `*_spec.rb` files, manually
+# require only the support files necessary.
+#
+# Rails.root.glob('spec/support/**/*.rb').sort_by(&:to_s).each { |f| require f }
+
+# Ensures that the test database schema matches the current schema file.
+# If there are pending migrations it will invoke `db:test:prepare` to
+# recreate the test database by loading the schema.
+# If you are not using ActiveRecord, you can remove these lines.
+begin
+  ActiveRecord::Migration.maintain_test_schema!
+rescue ActiveRecord::PendingMigrationError => e
+  abort e.to_s.strip
+end
+RSpec.configure do |config|
+  config.before do
+    I18n.locale = :en
+  end
+
+  config.include TestRecords
+  config.include RakeTaskHelper
+
+  # FactoryBot の create / create_list を使へるやぅにする
+  config.include FactoryBot::Syntax::Methods
+
+  # request spec で helper 使へるやぅにする
+  config.include AuthHelper, type: :request
+  config.include JsonHelper, type: :request
+
+  # Remove this line if you're not using ActiveRecord or ActiveRecord fixtures
+  config.fixture_paths = [
+    Rails.root.join('spec/fixtures')
+  ]
+
+  # If you're not using ActiveRecord, or you'd prefer not to run each of your
+  # examples within a transaction, remove the following line or assign false
+  # instead of true.
+  config.use_transactional_fixtures = true
+
+  # You can uncomment this line to turn off ActiveRecord support entirely.
+  # config.use_active_record = false
+
+  # RSpec Rails uses metadata to mix in different behaviours to your tests,
+  # for example enabling you to call `get` and `post` in request specs. e.g.:
+  #
+  #     RSpec.describe UsersController, type: :request do
+  #       # ...
+  #     end
+  #
+  # The different available types are documented in the features, such as in
+  # https://rspec.info/features/8-0/rspec-rails
+  #
+  # You can also this infer these behaviours automatically by location, e.g.
+  # /spec/models would pull in the same behaviour as `type: :model` but this
+  # behaviour is considered legacy and will be removed in a future version.
+  #
+  # To enable this behaviour uncomment the line below.
+  # config.infer_spec_type_from_file_location!
+
+  # Filter lines from Rails gems in backtraces.
+  config.filter_rails_from_backtrace!
+  # arbitrary gems may also be filtered via:
+  # config.filter_gems_from_backtrace("gem name")
+end

backend/spec/requests/deerjikists_spec.rb

@@ -0,0 +1,181 @@
+require 'rails_helper'
+
+RSpec.describe 'Deerjikists API', type: :request do
+  let(:platform) { 'nico' }
+  let(:code) { 'deerjika-bot' }
+
+  let!(:tag1) { create(:tag, category: :deerjikist) }
+  let!(:tag2) { create(:tag, category: :deerjikist) }
+
+  let(:member) { create(:user, :member) }
+  let(:guest) { create(:user, role: :guest) }
+
+  describe 'GET /deerjikists/:platform/:code' do
+    subject(:do_request) do
+      get "/deerjikists/#{ platform }/#{ code }"
+    end
+
+    context 'when deerjikist exists' do
+      before do
+        Deerjikist.create!(platform:, code:, tag: tag1)
+      end
+
+      it 'returns 200 and deerjikist json' do
+        do_request
+        expect(response).to have_http_status(:ok)
+
+        expect(json).to be_a(Hash)
+        expect(json['platform']).to eq(platform)
+        expect(json['code']).to eq(code)
+
+        expect(json['tag']).to be_a(Hash)
+        expect(json['tag']['id']).to eq(tag1.id)
+        expect(json['tag']['name']).to eq(tag1.name)
+      end
+    end
+
+    context 'when deerjikist does not exist' do
+      it 'returns 404' do
+        do_request
+        expect(response).to have_http_status(:not_found)
+      end
+    end
+
+    context 'when platform or code become blank after strip' do
+      it 'returns 400' do
+        get '/deerjikists/%20/%20'
+        expect(response).to have_http_status(:bad_request)
+      end
+    end
+  end
+
+  describe 'PUT /deerjikists/:platform/:code' do
+    subject(:do_request) do
+      put "/deerjikists/#{ platform }/#{ code }", params: payload
+    end
+
+    let(:payload) { { tag_id: tag1.id } }
+
+    context 'when not legged in' do
+      it 'returns 401' do
+        sign_out
+        do_request
+        expect(response).to have_http_status(:unauthorized)
+      end
+    end
+
+    context 'when logged in but not member' do
+      it 'returns 403' do
+        sign_in_as guest
+        do_request
+        expect(response).to have_http_status(:forbidden)
+      end
+    end
+
+    context 'when member' do
+      before do
+        sign_in_as member
+      end
+
+      context 'when params invalid' do
+        it 'returns 400 when tag_id is missing or invalid' do
+          put "/deerjikists/#{ platform }/#{ code }", params: { tag_id: 0 }
+          expect(response).to have_http_status(:bad_request)
+        end
+
+        it 'returns 400 when platform or code blank after strip' do
+          put '/deerjikists/%20/%20', params: { tag_id: tag1.id }
+          expect(response).to have_http_status(:bad_request)
+        end
+      end
+
+      context 'when creating new deerjikist' do
+        it 'creates and returns 200 with json' do
+          expect { do_request }.to change { Deerjikist.count }.by(1)
+          expect(response).to have_http_status(:ok)
+
+          d = Deerjikist.find_by(platform:, code:)
+          expect(d).to be_present
+          expect(d.tag_id).to eq(tag1.id)
+
+          expect(json['platform']).to eq(platform)
+          expect(json['code']).to eq(code)
+        end
+      end
+
+      context 'when updating existing deerjikist' do
+        before do
+          Deerjikist.create!(platform:, code:, tag: tag1)
+        end
+
+        let(:payload) { { tag_id: tag2.id } }
+
+        it 'updates tag_id and returns 200' do
+          expect { do_request }.not_to change { Deerjikist.count }
+          expect(response).to have_http_status(:ok)
+
+          d = Deerjikist.find_by(platform:, code:)
+          expect(d.tag_id).to eq(tag2.id)
+
+          expect(json['platform']).to eq(platform)
+          expect(json['code']).to eq(code)
+        end
+      end
+    end
+  end
+
+  describe 'DELETE /deerjikists/:platform/:code' do
+    subject(:do_request) do
+      delete "/deerjikists/#{ platform }/#{ code }"
+    end
+
+    context 'when not logged in' do
+      it 'returns 401' do
+        sign_out
+        do_request
+        expect(response).to have_http_status(:unauthorized)
+      end
+    end
+
+    context 'when logged in but not member' do
+      it 'returns 403' do
+        sign_in_as guest
+        do_request
+        expect(response).to have_http_status(:forbidden)
+      end
+    end
+
+    context 'when member' do
+      before do
+        sign_in_as member
+      end
+
+      it 'returns 400 when platform/code blank after strip' do
+        delete '/deerjikists/%20/%20'
+        expect(response).to have_http_status(:bad_request)
+      end
+
+      context 'when deerjikist exists' do
+        before do
+          Deerjikist.create!(platform: platform, code: code, tag: tag1)
+        end
+
+        it 'destroys and returns 204' do
+          expect {
+            do_request
+          }.to change { Deerjikist.exists?(platform: platform, code: code) }
+            .from(true).to(false)
+
+          expect(response).to have_http_status(:no_content)
+        end
+      end
+
+      context 'when deerjikist does not exist' do
+        it 'returns 404' do
+          do_request
+          expect(response).to have_http_status(:not_found)
+        end
+      end
+    end
+  end
+end