Merge remote-tracking branch 'origin/main' into feature/327

backend/app/controllers/nico_tags_controller.rb

@@ -33,8 +33,8 @@ class NicoTagsController < ApplicationController
     return head :bad_request unless tag.nico?
 
     linked_tag_names = params[:tags].to_s.split
-    linked_tags = Tag.normalise_tags(linked_tag_names, with_tagme: false,
-                                                       with_no_deerjikist: false)
+    linked_tags = Tag.normalise_tags!(linked_tag_names, with_tagme: false,
+                                                        with_no_deerjikist: false)
     return head :bad_request if linked_tags.any? { |t| t.nico? }
 
     ApplicationRecord.transaction do

backend/app/controllers/posts_controller.rb

@@ -109,7 +109,7 @@ class PostsController < ApplicationController
 
     render json: PostRepr.base(post, current_user)
                          .merge(tags: build_tag_tree_for(post.tags),
-                                related: post.related(limit: 20))
+                                related: PostRepr.many(post.related(limit: 20)))
   end
 
   def create
@@ -123,28 +123,36 @@ class PostsController < ApplicationController
     tag_names = params[:tags].to_s.split
     original_created_from = params[:original_created_from]
     original_created_before = params[:original_created_before]
+    parent_post_ids = parse_parent_post_ids
 
     post = Post.new(title:, url:, thumbnail_base: nil, uploaded_user: current_user,
                     original_created_from:, original_created_before:)
-    post.thumbnail.attach(thumbnail)
+    post.thumbnail.attach(thumbnail) if thumbnail.present?
 
     ApplicationRecord.transaction do
       post.save!
-      tags = Tag.normalise_tags(tag_names)
+
+      tags = Tag.normalise_tags!(tag_names)
       TagVersioning.record_tag_snapshots!(tags, created_by_user: current_user)
 
       tags = Tag.expand_parent_tags(tags)
       sync_post_tags!(post, tags)
+
+      sync_parent_posts!(post, parent_post_ids)
+
       post.resized_thumbnail!
+
       PostVersionRecorder.record!(post:, event_type: :create, created_by_user: current_user)
     end
 
     post.reload
     render json: PostRepr.base(post), status: :created
-  rescue ActiveRecord::RecordInvalid
-    render json: { errors: post.errors.full_messages }, status: :unprocessable_entity
   rescue Tag::NicoTagNormalisationError
     head :bad_request
+  rescue ArgumentError => e
+    render json: { errors: [e.message] }, status: :unprocessable_entity
+  rescue ActiveRecord::RecordInvalid => e
+    render json: { errors: e.record.errors.full_messages }, status: :unprocessable_entity
   end
 
   def viewed
@@ -169,6 +177,7 @@ class PostsController < ApplicationController
     tag_names = params[:tags].to_s.split
     original_created_from = params[:original_created_from]
     original_created_before = params[:original_created_before]
+    parent_post_ids = parse_parent_post_ids
 
     post = Post.find(params[:id].to_i)
 
@@ -177,12 +186,15 @@ class PostsController < ApplicationController
 
       post.update!(title:, original_created_from:, original_created_before:)
 
-      normalised_tags = Tag.normalise_tags(tag_names, with_tagme: false)
+      normalised_tags = Tag.normalise_tags!(tag_names, with_tagme: false)
       TagVersioning.record_tag_snapshots!(normalised_tags, created_by_user: current_user)
 
       tags = post.tags.nico.to_a + normalised_tags
       tags = Tag.expand_parent_tags(tags)
       sync_post_tags!(post, tags)
+
+      sync_parent_posts!(post, parent_post_ids)
+
       PostVersionRecorder.record!(post:, event_type: :update, created_by_user: current_user)
     end
 
@@ -190,10 +202,12 @@ class PostsController < ApplicationController
     json = post.as_json
     json['tags'] = build_tag_tree_for(post.tags)
     render json:, status: :ok
-  rescue ActiveRecord::RecordInvalid
-    render json: post.errors, status: :unprocessable_entity
   rescue Tag::NicoTagNormalisationError
     head :bad_request
+  rescue ArgumentError => e
+    render json: { errors: [e.message] }, status: :unprocessable_entity
+  rescue ActiveRecord::RecordInvalid => e
+    render json: { errors: e.record.errors.full_messages }, status: :unprocessable_entity
   end
 
   def changes
@@ -353,4 +367,41 @@ class PostsController < ApplicationController
 
     root_ids.filter_map { |id| build_node.call(id, []) }
   end
+
+  def parse_parent_post_ids
+    raise ArgumentError, 'parent_post_ids は必須です．' unless params.key?(:parent_post_ids)
+
+    params[:parent_post_ids].to_s.split.map { |token|
+      id = Integer(token, exception: false)
+      raise ArgumentError, "親投稿 Id. が不正です: #{ token }" if id.nil? || id <= 0
+
+      id
+    }.uniq
+  end
+
+  def sync_parent_posts! post, parent_post_ids
+    if parent_post_ids.include?(post.id)
+      post.errors.add(:base, '自分自身を親投稿にはできません．')
+      raise ActiveRecord::RecordInvalid, post
+    end
+
+    existing_ids = Post.where(id: parent_post_ids).pluck(:id)
+    missing_ids = parent_post_ids - existing_ids
+
+    if missing_ids.present?
+      post.errors.add(:base, "存在しない親投稿 ID があります: #{ missing_ids.join(' ') }")
+      raise ActiveRecord::RecordInvalid, post
+    end
+
+    current_ids = post.parent_posts.pluck(:id)
+
+    ids_to_add = parent_post_ids - current_ids
+    ids_to_remove = current_ids - parent_post_ids
+
+    PostImplication.where(post_id: post.id, parent_post_id: ids_to_remove).delete_all
+
+    ids_to_add.each do |parent_post_id|
+      PostImplication.create_or_find_by!(post_id: post.id, parent_post_id:)
+    end
+  end
 end

backend/app/controllers/tags_controller.rb

@@ -1,3 +1,7 @@
+require 'net/http'
+require 'uri'
+
+
 class TagsController < ApplicationController
   def index
     post_id = params[:post]
@@ -182,7 +186,8 @@ class TagsController < ApplicationController
              .find_by(id: params[:id])
     return head :not_found unless tag
 
-    render json: DeerjikistRepr.many(tag.deerjikists)
+    render json: { tag: TagRepr.base(tag),
+                   deerjikists: DeerjikistRepr.many(tag.deerjikists) }
   end
 
   def deerjikists_by_name
@@ -194,7 +199,31 @@ class TagsController < ApplicationController
              .find_by(tag_names: { name: })
     return head :not_found unless tag
 
-    render json: DeerjikistRepr.many(tag.deerjikists)
+    render json: { tag: TagRepr.base(tag),
+                   deerjikists: DeerjikistRepr.many(tag.deerjikists) }
+  end
+
+  def update_deerjikists
+    return head :unauthorized unless current_user
+    return head :forbidden unless current_user.gte_member?
+
+    tag = Tag.joins(:tag_name)
+             .includes(:tag_name, tag_name: :wiki_page)
+             .find_by(id: params[:id])
+    return head :not_found unless tag
+
+    ApplicationRecord.transaction do
+      tag.deerjikists = []
+      params[:_json].each do
+        platform = _1[:platform]
+        code = normalise_deerjikist_code(platform, _1[:code])
+        deerjikist = Deerjikist.find_or_initialize_by(platform:, code:)
+        deerjikist.tag = tag
+        deerjikist.save!
+      end
+    end
+
+    render json: DeerjikistRepr.many(tag.reload.deerjikists)
   end
 
   def materials_by_name
@@ -374,9 +403,9 @@ class TagsController < ApplicationController
   end
 
   def update_parent_tags! tag, parent_names
-    parent_tags = Tag.normalise_tags(parent_names, with_tagme: false,
-                                                   with_no_deerjikist: false,
-                                                   deny_nico: true)
+    parent_tags = Tag.normalise_tags!(parent_names, with_tagme: false,
+                                                    with_no_deerjikist: false,
+                                                    deny_nico: true)
 
     old_parent_tags = tag.parents.to_a
 
@@ -391,4 +420,21 @@ class TagsController < ApplicationController
       TagImplication.create!(tag:, parent_tag:)
     end
   end
+
+  def normalise_deerjikist_code platform, code
+    return code if platform != 'youtube' || code[0] != '@'
+
+    url = "https://www.youtube.com/#{ code }"
+
+    html = Net::HTTP.get(URI(url))
+
+    canonical = html[
+        /<link rel="canonical" href="https:\/\/www\.youtube\.com\/channel\/(UC[a-zA-Z0-9_-]{22})"/,
+        1]
+    return canonical if canonical
+
+    html[/"channelId":"(UC[a-zA-Z0-9_-]{22})"/, 1] || html[/\bUC[a-zA-Z0-9_-]{22}\b/]
+  rescue
+    nil
+  end
 end

backend/app/models/post.rb

@@ -1,7 +1,6 @@
 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, inverse_of: :post
@@ -13,6 +12,20 @@ class Post < ApplicationRecord
   has_many :post_similarities, dependent: :delete_all
   has_many :post_versions
 
+  has_many :parent_post_implications,
+           class_name: 'PostImplication',
+           foreign_key: :post_id,
+           dependent: :destroy,
+           inverse_of: :post
+  has_many :parents, through: :parent_post_implications, source: :parent_post
+
+  has_many :child_post_implications,
+           class_name: 'PostImplication',
+           foreign_key: :parent_post_id,
+           dependent: :destroy,
+           inverse_of: :parent_post
+  has_many :children, through: :child_post_implications, source: :post
+
   has_one_attached :thumbnail
 
   before_validation :normalise_url
@@ -22,17 +35,29 @@ class Post < ApplicationRecord
   validate :validate_original_created_range
   validate :url_must_be_http_url
 
+  def parent_posts = parents
+
+  def child_posts = children
+
+  def sibling_posts
+    parent_post_ids = parent_posts.order(:id).pluck(:id)
+
+    parent_post_ids.to_h { [_1, PostImplication.where(parent_post: _1).map(&:post)] }
+  end
+
   def as_json options = { }
-    super(options).merge({ thumbnail: thumbnail.attached? ?
-                                      Rails.application.routes.url_helpers.rails_blob_url(
-                                          thumbnail, only_path: false) :
-                                      nil })
+    super(options).merge(thumbnail: thumbnail.attached? ?
+                                    Rails.application.routes.url_helpers.rails_blob_url(
+                                        thumbnail, only_path: false) :
+                                    nil)
   rescue
     super(options).merge(thumbnail: nil)
   end
 
   def snapshot_tag_names = tags.joins(:tag_name).order('tag_names.name').pluck('tag_names.name')
 
+  def snapshot_parent_post_ids = parents.order(:id).pluck(:id)
+
   def related limit: nil
     ids = post_similarities.order(cos: :desc)
     ids = ids.limit(limit) if limit

backend/app/models/post_implication.rb

@@ -0,0 +1,19 @@
+class PostImplication < ApplicationRecord
+  self.primary_key = :post_id, :parent_post_id
+
+  belongs_to :post, inverse_of: :parent_post_implications
+  belongs_to :parent_post, class_name: 'Post', inverse_of: :child_post_implications
+
+  validates :post_id, presence: true, uniqueness: { scope: :parent_post_id }
+  validates :parent_post_id, presence: true
+
+  validate :parent_post_mustnt_be_itself
+
+  private
+
+  def parent_post_mustnt_be_itself
+    if parent_post_id == post_id
+      errors.add :parent_post_id, '親投稿に同じ投稿を設定することはできません．'
+    end
+  end
+end

backend/app/models/tag.rb

@@ -79,15 +79,18 @@ class Tag < ApplicationRecord
 
   def material_id = materials.first&.id
 
+  def has_deerjikists = deerjikists.present?
+
   def self.tagme = find_or_create_by_tag_name!('タグ希望', category: :meta)
   def self.bot = find_or_create_by_tag_name!('bot操作', category: :meta)
   def self.no_deerjikist = find_or_create_by_tag_name!('ニジラー情報不詳', category: :meta)
   def self.video = find_or_create_by_tag_name!('動画', category: :meta)
   def self.niconico = find_or_create_by_tag_name!('ニコニコ', category: :meta)
+  def self.youtube = find_or_create_by_tag_name!('YouTube', category: :meta)
 
-  def self.normalise_tags tag_names, with_tagme: true,
-                                     with_no_deerjikist: true,
-                                     deny_nico: true
+  def self.normalise_tags! tag_names, with_tagme: true,
+                                      with_no_deerjikist: true,
+                                      deny_nico: true
     if deny_nico && tag_names.any? { |n| n.downcase.start_with?('nico:') }
       raise NicoTagNormalisationError
     end

backend/app/representations/post_repr.rb

@@ -2,7 +2,8 @@
 
 
 module PostRepr
-  BASE = { include: { tags: TagRepr::BASE, uploaded_user: UserRepr::BASE } }.freeze
+  BASE = { include: { tags: TagRepr::BASE, uploaded_user: UserRepr::BASE },
+           methods: [:parent_posts, :child_posts, :sibling_posts] }.freeze
 
   module_function
 

backend/app/representations/tag_repr.rb

@@ -3,7 +3,7 @@
 
 module TagRepr
   BASE = { only: [:id, :category, :post_count, :created_at, :updated_at],
-           methods: [:name, :has_wiki, :material_id] }.freeze
+           methods: [:name, :has_wiki, :material_id, :has_deerjikists] }.freeze
 
   module_function
 

backend/app/services/post_version_recorder.rb

@@ -24,7 +24,7 @@ class PostVersionRecorder < VersionRecorder
       url: @record.url,
       thumbnail_base: @record.thumbnail_base,
       tags: @record.snapshot_tag_names.join(' '),
-      parent_id: @record.parent_id,
+      parent_post_ids: @record.snapshot_parent_post_ids.join(' '),
       original_created_from: @record.original_created_from,
       original_created_before: @record.original_created_before }
   end

backend/app/services/youtube/api_client.rb

@@ -0,0 +1,73 @@
+require 'json'
+require 'net/http'
+require 'uri'
+
+
+module Youtube
+  class ApiClient
+    ENDPOINT = 'https://www.googleapis.com/youtube/v3'
+
+    def initialize api_key: ENV.fetch('YOUTUBE_API_KEY')
+      @api_key = api_key
+    end
+
+    def search_videos q:, published_after: nil, published_before: nil, page_token: nil
+      get_json('/search', {
+          part:           'snippet',
+          type:           'video',
+          q:,
+          order:          'date',
+          maxResults:     50,
+          regionCode:     'JP',
+          relevanceLanguage: 'ja',
+          publishedAfter: published_after&.iso8601,
+          publishedBefore: published_before&.iso8601,
+          pageToken:      page_token }.compact)
+    end
+
+    def videos ids
+      return { 'items' => [] } if ids.empty?
+
+      get_json('/videos', part: 'snippet,status,contentDetails', id: ids.join(','))
+    end
+
+    def playlist_items playlist_id:, page_token: nil
+      get_json('/playlistItems', {
+          part:       'snippet,contentDetails,status',
+          playlistId: playlist_id,
+          maxResults: 50,
+          pageToken:  page_token }.compact)
+    end
+
+    def channel id: nil, handle: nil
+      raise ArgumentError, 'id or handle is required' if id.present? == handle.present?
+
+      params = { part: 'snippet,contentDetails' }
+      params[:id] = id if id.present?
+      params[:forHandle] = handle if handle.present?
+
+      get_json('/channels', params)
+    end
+
+    private
+
+    def get_json path, params
+      uri = URI(ENDPOINT + path)
+      uri.query = URI.encode_www_form(params.merge(key: @api_key))
+
+      response = Net::HTTP.start(uri.host,
+                                 uri.port,
+                                 use_ssl: true,
+                                 open_timeout: 10,
+                                 read_timeout: 30) do |http|
+        http.get(uri)
+      end
+
+      unless response.is_a?(Net::HTTPSuccess)
+        raise "YouTube API error: #{ response.code } #{ response.body }"
+      end
+
+      JSON.parse(response.body)
+    end
+  end
+end

backend/app/services/youtube/sync.rb

@@ -0,0 +1,168 @@
+require 'open-uri'
+require 'set'
+require 'time'
+
+
+module Youtube
+  class Sync
+    def initialize client: ApiClient.new
+      @client = client
+    end
+
+    def sync!
+      video_ids = discover_video_ids
+      return if video_ids.empty?
+
+      video_ids.each_slice(50) do |ids|
+        @client.videos(ids).fetch('items', []).each do |item|
+          sync_video!(VideoItem.new(item))
+        end
+      end
+    end
+
+    private
+
+    def discover_video_ids
+      ids = Set.new
+
+      query_terms.each do |q|
+        response = @client.search_videos(q:, published_after: sync_since)
+
+        response.fetch('items', []).each do |item|
+          video_id = item.dig('id', 'videoId')
+          ids << video_id if video_id.present?
+        end
+      end
+
+      playlist_ids.each do |playlist_id|
+        each_playlist_item(playlist_id) do |item|
+          video_id = item.dig('contentDetails', 'videoId')
+          video_id ||= item.dig('snippet', 'resourceId', 'videoId')
+
+          ids << video_id if video_id.present?
+        end
+      end
+
+      ids.to_a
+    end
+
+    def sync_video! video
+      post = Post.where('url REGEXP ?', youtube_url_regexp(video.id)).first
+
+      original_created_from = video.published_at.change(sec: 0)
+      original_created_before = original_created_from + 1.minute
+
+      post_created = false
+      post_changed = false
+
+      if post
+        post.assign_attributes(title: video.title,
+                               original_created_from:,
+                               original_created_before:,
+                               thumbnail_base: video.thumbnail_url)
+
+        post_changed = post.changed?
+        post.save! if post_changed
+
+        attach_thumbnail_if_needed!(post, video.thumbnail_url)
+      else
+        post_created = true
+        post = Post.create!(
+            title: video.title,
+            url: video.url,
+            thumbnail_base: video.thumbnail_url,
+            uploaded_user_id: nil,
+            original_created_from:,
+            original_created_before:)
+
+        attach_thumbnail_if_needed!(post, video.thumbnail_url)
+
+        sync_post_tags!(post, [Tag.tagme.id, Tag.bot.id, Tag.youtube.id, Tag.video.id])
+      end
+
+      kept_tag_ids = post.tags.pluck(:id).to_set
+      desired_tag_ids = kept_tag_ids.to_a
+
+      deerjikist = Deerjikist.find_by(platform: :youtube, code: video.channel_id)
+      if deerjikist
+        desired_tag_ids.delete(Tag.no_deerjikist.id)
+        desired_tag_ids << deerjikist.tag_id
+      elsif post.tags.where(category: :deerjikist).none?
+        desired_tag_ids << Tag.no_deerjikist.id
+      end
+
+      desired_tag_ids.uniq!
+
+      sync_post_tags!(post, desired_tag_ids, current_tag_ids: kept_tag_ids)
+
+      if post_created
+        PostVersionRecorder.record!(post:, event_type: :create, created_by_user: nil)
+      elsif post_changed || kept_tag_ids != desired_tag_ids.to_set
+        PostVersionRecorder.ensure_snapshot!(post, created_by_user: nil)
+        PostVersionRecorder.record!(post:, event_type: :update, created_by_user: nil)
+      end
+    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
+
+    def attach_thumbnail_if_needed! post, thumbnail_url
+      return if post.thumbnail.attached?
+      return if thumbnail_url.blank?
+
+      post.thumbnail.attach(
+          io:           URI.open(thumbnail_url),
+          filename:     File.basename(URI.parse(thumbnail_url).path),
+          content_type: 'image/jpeg')
+
+      post.resized_thumbnail!
+    end
+
+    def youtube_url_regexp id
+      escaped = Regexp.escape(id)
+      "(youtube\\.com/watch\\?v=#{ escaped }|youtu\\.be/#{ escaped })([^A-Za-z0-9_-]|$)"
+    end
+
+    def query_terms = ['ぼざろクリーチャーシリーズ', '伊地知ニジカ', '伊地知虹鹿']
+
+    def playlist_ids
+      ['PLrOch4zHkI5vu29b-f9umUQQ4tQkuWLPX',
+       'PLrOch4zHkI5vOK0RaytQq6PbucxQkkL0K',
+       'PLrOch4zHkI5tdwm9vSegiDQJOM-hgpcOC']
+    end
+
+    def sync_since = 14.days.ago
+
+    def each_playlist_item playlist_id
+      page_token = nil
+
+      loop do
+        response = @client.playlist_items(playlist_id:, page_token:)
+
+        response.fetch('items', []).each do |item|
+          yield item
+        end
+
+        page_token = response['nextPageToken']
+        break if page_token.blank?
+      end
+    end
+  end
+end

backend/app/services/youtube/video_item.rb

@@ -0,0 +1,32 @@
+require 'time'
+
+
+module Youtube
+  class VideoItem
+    attr_reader :id, :title, :channel_id, :published_at, :thumbnail_url, :raw_tags
+
+    def initialize item
+      snippet = item.fetch('snippet')
+
+      @id = item.fetch('id')
+      @title = snippet['title']
+      @channel_id = snippet['channelId']
+      @published_at = Time.iso8601(snippet['publishedAt'])
+      @thumbnail_url = pick_thumbnail(snippet['thumbnails'] || { })
+      @raw_tags = snippet['tags'] || []
+    end
+
+    def url = "https://www.youtube.com/watch?v=#{ @id }"
+
+    private
+
+    def pick_thumbnail thumbnails
+      ['maxres', 'standard', 'high', 'medium', 'default'].each do |key|
+        url = thumbnails.dig(key, 'url')
+        return url if url.present?
+      end
+
+      nil
+    end
+  end
+end

backend/config/routes.rb

@@ -24,6 +24,7 @@ Rails.application.routes.draw do
       patch '', action: :update
 
       get :deerjikists
+      put :deerjikists, action: :update_deerjikists
     end
   end
 

backend/config/schedule.rb

@@ -17,3 +17,11 @@ every 1.day, at: '0:00 am' do
   rake 'post_similarity:calc', environment: 'production'
   rake 'tag_similarity:calc', environment: 'production'
 end
+
+every 1.day, at: '7:50 am' do
+  rake 'nico:export', environment: 'production'
+end
+
+every :hour do
+  rake 'post:sync', environment: 'production'
+end

backend/db/migrate/20260427214800_create_post_implications.rb

@@ -0,0 +1,24 @@
+class CreatePostImplications < ActiveRecord::Migration[8.0]
+  def up
+    create_table :post_implications, primary_key: [:post_id, :parent_post_id] do |t|
+      t.references :post, null: false, foreign_key: true, index: false
+      t.references :parent_post, null: false, foreign_key: { to_table: :posts }
+      t.timestamps
+
+      t.check_constraint 'post_id <> parent_post_id',
+                         name: 'chk_post_implications_no_self'
+    end
+
+    add_column :post_versions, :parent_post_ids, :text, null: false, after: :parent_id
+    remove_column :post_versions, :parent_id, :bigint
+    remove_reference :posts, :parent, foreign_key: { to_table: :posts }
+  end
+
+  def down
+    add_reference :posts, :parent, foreign_key: { to_table: :posts }, after: :thumbnail_base
+    add_column :post_versions, :parent_id, :bigint, after: :post_id
+    remove_column :post_versions, :parent_post_ids, :text
+
+    drop_table :post_implications
+  end
+end

backend/lib/tasks/sync_posts.rake

@@ -0,0 +1,6 @@
+namespace :post do
+  desc '投稿同期（ニコニコ以外）'
+  task sync: :environment do
+    Youtube::Sync.new.sync!
+  end
+end

backend/spec/models/post_implication_spec.rb

@@ -0,0 +1,51 @@
+require 'rails_helper'
+
+RSpec.describe PostImplication, type: :model do
+  let!(:post_record) do
+    Post.create!(
+      title: 'post',
+      url: 'https://example.com/post-implication-post'
+    )
+  end
+
+  let!(:parent_post) do
+    Post.create!(
+      title: 'parent post',
+      url: 'https://example.com/post-implication-parent'
+    )
+  end
+
+  it 'is valid with post and parent_post' do
+    implication = described_class.new(
+      post: post_record,
+      parent_post:
+    )
+
+    expect(implication).to be_valid
+  end
+
+  it 'does not allow same post as parent_post' do
+    implication = described_class.new(
+      post: post_record,
+      parent_post: post_record
+    )
+
+    expect(implication).not_to be_valid
+    expect(implication.errors[:parent_post_id]).to be_present
+  end
+
+  it 'does not allow duplicate pair' do
+    described_class.create!(
+      post: post_record,
+      parent_post:
+    )
+
+    duplicate = described_class.new(
+      post: post_record,
+      parent_post:
+    )
+
+    expect(duplicate).not_to be_valid
+    expect(duplicate.errors[:post_id]).to be_present
+  end
+end

backend/spec/models/post_version_spec.rb

@@ -19,7 +19,7 @@ RSpec.describe PostVersion, type: :model do
       url: post_record.url,
       thumbnail_base: post_record.thumbnail_base,
       tags: post_record.snapshot_tag_names.join(' '),
-      parent: post_record.parent,
+      parent_post_ids: post_record.snapshot_parent_post_ids.join(' '),
       original_created_from: post_record.original_created_from,
       original_created_before: post_record.original_created_before,
       created_at: Time.current,

backend/spec/models/tag_spec.rb

@@ -161,7 +161,7 @@ RSpec.describe Tag, type: :model do
         url: post.url,
         thumbnail_base: post.thumbnail_base,
         tags: snapshot_tags(post),
-        parent: post.parent,
+        parent_post_ids: post.snapshot_parent_post_ids.join(' '),
         original_created_from: post.original_created_from,
         original_created_before: post.original_created_before,
         created_at: Time.current,

backend/spec/requests/posts_spec.rb

@@ -15,6 +15,31 @@ RSpec.describe 'Posts API', type: :request do
     Rack::Test::UploadedFile.new(StringIO.new('dummy'), 'image/jpeg', original_filename: 'dummy.jpg')
   end
 
+  def post_write_params params = { }
+    { parent_post_ids: '' }.merge(params)
+  end
+
+  def create_parent_post! title:, url:
+    Post.create!(title:, url:)
+  end
+
+  def create_post_version_for! post
+    PostVersion.create!(
+      post:,
+      version_no: 1,
+      event_type: 'create',
+      title: post.title,
+      url: post.url,
+      thumbnail_base: post.thumbnail_base,
+      tags: post.snapshot_tag_names.join(' '),
+      parent_post_ids: post.snapshot_parent_post_ids.join(' '),
+      original_created_from: post.original_created_from,
+      original_created_before: post.original_created_before,
+      created_at: post.created_at,
+      created_by_user: post.uploaded_user
+    )
+  end
+
   let!(:tag_name) { TagName.create!(name: 'spec_tag') }
   let!(:tag)      { Tag.create!(tag_name: tag_name, category: :general) }
 
@@ -457,6 +482,65 @@ RSpec.describe 'Posts API', type: :request do
         expect(json).to have_key('viewed')
         expect([true, false]).to include(json['viewed'])
       end
+
+      context 'when post has parent, child, and sibling posts' do
+        let!(:parent_post) do
+          create_parent_post!(
+            title: 'shared parent post',
+            url: 'https://example.com/shared-parent-post'
+          )
+        end
+
+        let!(:child_post) do
+          Post.create!(
+            title: 'child post',
+            url: 'https://example.com/show-child-post'
+          )
+        end
+
+        let!(:sibling_post) do
+          Post.create!(
+            title: 'sibling post',
+            url: 'https://example.com/show-sibling-post'
+          )
+        end
+
+        before do
+          PostImplication.create!(
+            post: post_record,
+            parent_post:
+          )
+
+          PostImplication.create!(
+            post: child_post,
+            parent_post: post_record
+          )
+
+          PostImplication.create!(
+            post: sibling_post,
+            parent_post:
+          )
+        end
+
+        it 'returns parent_posts, child_posts, and sibling_posts' do
+          get "/posts/#{post_record.id}"
+
+          expect(response).to have_http_status(:ok)
+
+          parent_ids = json.fetch('parent_posts').map { |p| p.fetch('id') }
+          child_ids = json.fetch('child_posts').map { |p| p.fetch('id') }
+
+          expect(parent_ids).to include(parent_post.id)
+          expect(child_ids).to include(child_post.id)
+
+          sibling_posts_by_parent = json.fetch('sibling_posts')
+          siblings = sibling_posts_by_parent.fetch(parent_post.id.to_s)
+
+          sibling_ids = siblings.map { |p| p.fetch('id') }
+          expect(sibling_ids).to include(post_record.id)
+          expect(sibling_ids).to include(sibling_post.id)
+        end
+      end
     end
 
     context 'when post does not exist' do
@@ -475,25 +559,28 @@ RSpec.describe 'Posts API', type: :request do
 
     it '401 when not logged in' do
       sign_out
-      post '/posts', params: { title: 't', url: 'https://example.com/x', tags: 'a', thumbnail: dummy_upload }
+      post '/posts', params: post_write_params(title: 't', url: 'https://example.com/x', tags: 'a',
+                                               thumbnail: dummy_upload)
+
       expect(response).to have_http_status(:unauthorized)
     end
 
     it '403 when not member' do
       sign_in_as(create(:user, role: 'guest'))
-      post '/posts', params: { title: 't', url: 'https://example.com/x', tags: 'a', thumbnail: dummy_upload }
+      post '/posts', params: post_write_params(title: 't', url: 'https://example.com/x', tags: 'a',
+                                               thumbnail: dummy_upload)
       expect(response).to have_http_status(:forbidden)
     end
 
     it '201 and creates post + tags when member' do
       sign_in_as(member)
 
-      post '/posts', params: {
+      post '/posts', params: post_write_params(
         title: 'new post',
         url: 'https://example.com/new',
         tags: 'spec_tag', # 既存タグ名を投げる
         thumbnail: dummy_upload
-      }
+      )
 
       expect(response).to have_http_status(:created)
       expect(json).to include('id', 'title', 'url')
@@ -507,12 +594,12 @@ RSpec.describe 'Posts API', type: :request do
     it '201 and creates post + tags when member and tags have aliases' do
       sign_in_as(member)
 
-      post '/posts', params: {
+      post '/posts', params: post_write_params(
         title: 'new post',
         url: 'https://example.com/new',
         tags: 'manko', # 既存タグ名を投げる
         thumbnail: dummy_upload
-      }
+      )
 
       expect(response).to have_http_status(:created)
       expect(json).to include('id', 'title', 'url')
@@ -533,13 +620,14 @@ RSpec.describe 'Posts API', type: :request do
       it 'return 400' do
         sign_in_as(member)
 
-        post '/posts', params: {
-            title: 'new post',
-            url: 'https://example.com/nico_tag',
-            tags: 'nico:nico_tag',
-            thumbnail: dummy_upload }
+        post '/posts', params: post_write_params(
+          title: 'new post',
+          url: 'https://example.com/nico-tag-post',
+          tags: 'nico:nico_tag',
+          thumbnail: dummy_upload
+        )
 
-        expect(response).to have_http_status(:bad_request)
+        expect(response).to have_http_status(:bad_request), response.body
       end
     end
 
@@ -547,11 +635,11 @@ RSpec.describe 'Posts API', type: :request do
       it 'returns 422' do
         sign_in_as(member)
 
-        post '/posts', params: {
+        post '/posts', params: post_write_params(
             title: 'new post',
             url: '   ',
             tags: 'spec_tag', # 既存タグ名を投げる
-            thumbnail: dummy_upload }
+            thumbnail: dummy_upload)
 
         expect(response).to have_http_status(:unprocessable_entity)
       end
@@ -561,14 +649,154 @@ RSpec.describe 'Posts API', type: :request do
       it 'returns 422' do
         sign_in_as(member)
 
-        post '/posts', params: {
-          title: 'new post',
-          url: 'ぼざクリタグ広場',
-          tags: 'spec_tag', # 既存タグ名を投げる
+        post '/posts', params: post_write_params(
+            title: 'new post',
+            url: 'ぼざクリタグ広場',
+            tags: 'spec_tag', # 既存タグ名を投げる
+            thumbnail: dummy_upload)
+
+        expect(response).to have_http_status(:unprocessable_entity)
+      end
+    end
+
+    context 'when parent_post_ids is provided' do
+      let!(:parent_post_1) do
+        create_parent_post!(
+          title: 'parent post 1',
+          url: 'https://example.com/parent-post-1'
+        )
+      end
+
+      let!(:parent_post_2) do
+        create_parent_post!(
+          title: 'parent post 2',
+          url: 'https://example.com/parent-post-2'
+        )
+      end
+
+      it 'creates post implications for parent posts' do
+        sign_in_as(member)
+
+        expect {
+          post '/posts', params: {
+              title: 'child post',
+              url: 'https://example.com/child-post',
+              tags: 'spec_tag',
+              parent_post_ids: "#{parent_post_1.id} #{parent_post_2.id}",
+              thumbnail: dummy_upload }
+        }.to change(PostImplication, :count).by(2)
+
+        expect(response).to have_http_status(:created)
+
+        created_post = Post.find(json.fetch('id'))
+        expect(created_post.parent_posts.order(:id).pluck(:id)).to eq(
+          [parent_post_1.id, parent_post_2.id].sort
+        )
+
+        expect(PostImplication.exists?(
+          post_id: created_post.id,
+          parent_post_id: parent_post_1.id
+        )).to be(true)
+
+        expect(PostImplication.exists?(
+          post_id: created_post.id,
+          parent_post_id: parent_post_2.id
+        )).to be(true)
+      end
+
+      it 'deduplicates parent_post_ids' do
+        sign_in_as(member)
+
+        expect {
+          post '/posts', params: post_write_params(
+            title: 'dedup child post',
+            url: 'https://example.com/dedup-child-post',
+            tags: 'spec_tag',
+            parent_post_ids: "#{parent_post_1.id} #{parent_post_1.id}",
+            thumbnail: dummy_upload
+          )
+        }.to change(PostImplication, :count).by(1)
+
+        expect(response).to have_http_status(:created)
+
+        created_post = Post.find(json.fetch('id'))
+        expect(created_post.parent_posts.pluck(:id)).to eq([parent_post_1.id])
+      end
+
+      it 'records parent_post_ids in post version' do
+        sign_in_as(member)
+
+        post '/posts', params: post_write_params(
+          title: 'versioned child post',
+          url: 'https://example.com/versioned-child-post',
+          tags: 'spec_tag',
+          parent_post_ids: "#{parent_post_1.id} #{parent_post_2.id}",
           thumbnail: dummy_upload
-        }
+        )
+
+        expect(response).to have_http_status(:created)
+
+        created_post = Post.find(json.fetch('id'))
+        version = PostVersion.find_by!(post: created_post, version_no: 1)
+
+        expect(version.parent_post_ids.split.map(&:to_i)).to eq(
+          [parent_post_1.id, parent_post_2.id].sort
+        )
+      end
+    end
+
+    context 'when parent_post_ids is missing' do
+      it 'returns 422' do
+        sign_in_as(member)
+
+        expect {
+          post '/posts', params: {
+              title: 'missing parent_post_ids',
+              url: 'https://example.com/missing-parent-post-ids',
+              tags: 'spec_tag',
+              thumbnail: dummy_upload }
+        }.not_to change(Post, :count)
+
+        expect(response).to have_http_status(:unprocessable_entity)
+        expect(json.fetch('errors')).to be_present
+      end
+    end
+
+    context 'when parent_post_ids includes invalid token' do
+      it 'returns 422 and does not create post' do
+        sign_in_as(member)
+
+        expect {
+          post '/posts', params: post_write_params(
+            title: 'invalid parent ids',
+            url: 'https://example.com/invalid-parent-ids',
+            tags: 'spec_tag',
+            parent_post_ids: 'abc',
+            thumbnail: dummy_upload
+          )
+        }.not_to change(Post, :count)
 
         expect(response).to have_http_status(:unprocessable_entity)
+        expect(json.fetch('errors')).to be_present
+      end
+    end
+
+    context 'when parent_post_ids includes nonexistent post id' do
+      it 'returns 422 and does not create post implication' do
+        sign_in_as(member)
+
+        expect {
+          post '/posts', params: post_write_params(
+            title: 'missing parent post',
+            url: 'https://example.com/missing-parent-post',
+            tags: 'spec_tag',
+            parent_post_ids: '999999999',
+            thumbnail: dummy_upload
+          )
+        }.not_to change(PostImplication, :count)
+
+        expect(response).to have_http_status(:unprocessable_entity)
+        expect(json.fetch('errors')).to be_present
       end
     end
   end
@@ -578,13 +806,13 @@ RSpec.describe 'Posts API', type: :request do
 
     it '401 when not logged in' do
       sign_out
-      put "/posts/#{post_record.id}", params: { title: 'updated', tags: 'spec_tag' }
+      put "/posts/#{post_record.id}", params: post_write_params(title: 'updated', tags: 'spec_tag')
       expect(response).to have_http_status(:unauthorized)
     end
 
     it '403 when not member' do
       sign_in_as(create(:user, role: 'guest'))
-      put "/posts/#{post_record.id}", params: { title: 'updated', tags: 'spec_tag' }
+      put "/posts/#{post_record.id}", params: post_write_params(title: 'updated', tags: 'spec_tag')
       expect(response).to have_http_status(:forbidden)
     end
 
@@ -595,10 +823,9 @@ RSpec.describe 'Posts API', type: :request do
       tn2 = TagName.create!(name: 'spec_tag_2')
       Tag.create!(tag_name: tn2, category: :general)
 
-      put "/posts/#{post_record.id}", params: {
-        title: 'updated title',
-        tags: 'spec_tag_2'
-      }
+      put "/posts/#{post_record.id}", params: post_write_params(
+          title: 'updated title',
+          tags: 'spec_tag_2')
 
       expect(response).to have_http_status(:ok)
       expect(json).to have_key('tags')
@@ -619,11 +846,178 @@ RSpec.describe 'Posts API', type: :request do
       it 'return 400' do
         sign_in_as(member)
 
-        put "/posts/#{ post_record.id }", params: {
+        put "/posts/#{post_record.id}", params: post_write_params(
+          title: 'updated title',
+          tags: 'nico:nico_tag'
+        )
+
+        expect(response).to have_http_status(:bad_request), response.body
+      end
+    end
+
+    context 'when parent_post_ids is provided' do
+      let!(:old_parent_post) do
+        create_parent_post!(
+          title: 'old parent post',
+          url: 'https://example.com/old-parent-post'
+        )
+      end
+
+      let!(:new_parent_post_1) do
+        create_parent_post!(
+          title: 'new parent post 1',
+          url: 'https://example.com/new-parent-post-1'
+        )
+      end
+
+      let!(:new_parent_post_2) do
+        create_parent_post!(
+          title: 'new parent post 2',
+          url: 'https://example.com/new-parent-post-2'
+        )
+      end
+
+      before do
+        PostImplication.create!(
+          post: post_record,
+          parent_post: old_parent_post
+        )
+      end
+
+      it 'replaces parent posts' do
+        sign_in_as(member)
+
+        put "/posts/#{post_record.id}", params: post_write_params(
+          title: 'updated title',
+          tags: 'spec_tag',
+          parent_post_ids: "#{new_parent_post_1.id} #{new_parent_post_2.id}"
+        )
+
+        expect(response).to have_http_status(:ok)
+
+        expect(post_record.reload.parent_posts.order(:id).pluck(:id)).to eq(
+          [new_parent_post_1.id, new_parent_post_2.id].sort
+        )
+
+        expect(PostImplication.exists?(
+          post_id: post_record.id,
+          parent_post_id: old_parent_post.id
+        )).to be(false)
+      end
+
+      it 'clears parent posts when parent_post_ids is blank' do
+        sign_in_as(member)
+
+        put "/posts/#{post_record.id}", params: post_write_params(
+          title: 'updated title',
+          tags: 'spec_tag',
+          parent_post_ids: ''
+        )
+
+        expect(response).to have_http_status(:ok)
+        expect(post_record.reload.parent_posts).to be_empty
+      end
+
+      it 'records changed parent_post_ids in post version' do
+        sign_in_as(member)
+        create_post_version_for!(post_record.reload)
+
+        put "/posts/#{post_record.id}", params: post_write_params(
+          title: 'updated title',
+          tags: 'spec_tag',
+          parent_post_ids: "#{new_parent_post_1.id} #{new_parent_post_2.id}"
+        )
+
+        expect(response).to have_http_status(:ok)
+
+        version = post_record.reload.post_versions.order(:version_no).last
+
+        expect(version.version_no).to eq(2)
+        expect(version.parent_post_ids.split.map(&:to_i)).to eq(
+          [new_parent_post_1.id, new_parent_post_2.id].sort
+        )
+      end
+    end
+
+    context 'when parent_post_ids is missing' do
+      it 'returns 422' do
+        sign_in_as(member)
+
+        put "/posts/#{post_record.id}", params: {
             title: 'updated title',
-            tags: 'nico:nico_tag' }
+            tags: 'spec_tag' }
 
-        expect(response).to have_http_status(:bad_request)
+        expect(response).to have_http_status(:unprocessable_entity)
+        expect(json.fetch('errors')).to be_present
+      end
+    end
+
+    context 'when parent_post_ids includes invalid token' do
+      it 'returns 422 and does not change parent posts' do
+        sign_in_as(member)
+
+        parent_post = create_parent_post!(
+          title: 'valid parent post',
+          url: 'https://example.com/valid-parent-post'
+        )
+
+        PostImplication.create!(
+          post: post_record,
+          parent_post:
+        )
+
+        put "/posts/#{post_record.id}", params: post_write_params(
+          title: 'updated title',
+          tags: 'spec_tag',
+          parent_post_ids: 'abc'
+        )
+
+        expect(response).to have_http_status(:unprocessable_entity)
+        expect(post_record.reload.parent_posts.pluck(:id)).to eq([parent_post.id])
+      end
+    end
+
+    context 'when parent_post_ids includes nonexistent post id' do
+      it 'returns 422 and does not change parent posts' do
+        sign_in_as(member)
+
+        parent_post = create_parent_post!(
+          title: 'existing parent post',
+          url: 'https://example.com/existing-parent-post'
+        )
+
+        PostImplication.create!(
+          post: post_record,
+          parent_post:
+        )
+
+        put "/posts/#{post_record.id}", params: post_write_params(
+          title: 'updated title',
+          tags: 'spec_tag',
+          parent_post_ids: '999999999'
+        )
+
+        expect(response).to have_http_status(:unprocessable_entity)
+        expect(post_record.reload.parent_posts.pluck(:id)).to eq([parent_post.id])
+      end
+    end
+
+    context 'when parent_post_ids includes self id' do
+      it 'returns 422 and does not create self implication' do
+        sign_in_as(member)
+
+        put "/posts/#{post_record.id}", params: post_write_params(
+          title: 'updated title',
+          tags: 'spec_tag',
+          parent_post_ids: post_record.id.to_s
+        )
+
+        expect(response).to have_http_status(:unprocessable_entity)
+
+        expect(PostImplication.exists?(
+          post_id: post_record.id,
+          parent_post_id: post_record.id
+        )).to be(false)
       end
     end
   end
@@ -773,20 +1167,20 @@ RSpec.describe 'Posts API', type: :request do
       post.snapshot_tag_names.join(' ')
     end
 
-    def create_post_version!(post, version_no:, event_type:, created_by_user:, created_at:)
+    def create_post_version! post, version_no:, event_type:, created_by_user:, created_at:
       PostVersion.create!(
-        post: post,
-        version_no: version_no,
-        event_type: event_type,
+        post:,
+        version_no:,
+        event_type:,
         title: post.title,
         url: post.url,
         thumbnail_base: post.thumbnail_base,
         tags: snapshot_tags(post),
-        parent: post.parent,
+        parent_post_ids: post.snapshot_parent_post_ids.join(' '),
         original_created_from: post.original_created_from,
         original_created_before: post.original_created_before,
-        created_at: created_at,
-        created_by_user: created_by_user
+        created_at:,
+        created_by_user:
       )
     end
 
@@ -1015,33 +1409,15 @@ RSpec.describe 'Posts API', type: :request do
       post.snapshot_tag_names.join(' ')
     end
 
-    def create_post_version_for!(post)
-      PostVersion.create!(
-        post: post,
-        version_no: 1,
-        event_type: 'create',
-        title: post.title,
-        url: post.url,
-        thumbnail_base: post.thumbnail_base,
-        tags: snapshot_tags(post),
-        parent: post.parent,
-        original_created_from: post.original_created_from,
-        original_created_before: post.original_created_before,
-        created_at: post.created_at,
-        created_by_user: post.uploaded_user
-      )
-    end
-
     it 'creates version 1 on POST /posts' do
       sign_in_as(member)
 
       expect do
-        post '/posts', params: {
-          title: 'versioned post',
-          url: 'https://example.com/versioned-post',
-          tags: 'spec_tag',
-          thumbnail: dummy_upload
-        }
+        post '/posts', params: post_write_params(
+            title: 'versioned post',
+            url: 'https://example.com/versioned-post',
+            tags: 'spec_tag',
+            thumbnail: dummy_upload)
       end.to change(PostVersion, :count).by(1)
 
       expect(response).to have_http_status(:created)
@@ -1064,10 +1440,9 @@ RSpec.describe 'Posts API', type: :request do
       Tag.create!(tag_name: tag_name2, category: :general)
 
       expect do
-        put "/posts/#{post_record.id}", params: {
-          title: 'updated title',
-          tags: 'spec_tag_2'
-        }
+        put "/posts/#{post_record.id}", params: post_write_params(
+            title: 'updated title',
+            tags: 'spec_tag_2')
       end.to change(PostVersion, :count).by(1)
 
       expect(response).to have_http_status(:ok)
@@ -1087,10 +1462,9 @@ RSpec.describe 'Posts API', type: :request do
       create_post_version_for!(post_record.reload)
 
       expect {
-        put "/posts/#{post_record.id}", params: {
-          title: post_record.title,
-          tags: 'spec_tag'
-        }
+        put "/posts/#{post_record.id}", params: post_write_params(
+            title: post_record.title,
+            tags: 'spec_tag')
       }.not_to change(PostVersion, :count)
       expect(response).to have_http_status(:ok)
 
@@ -1104,12 +1478,11 @@ RSpec.describe 'Posts API', type: :request do
       sign_in_as(member)
 
       expect do
-        post '/posts', params: {
-          title: 'invalid post',
-          url: 'ぼざクリタグ広場',
-          tags: 'spec_tag',
-          thumbnail: dummy_upload
-        }
+        post '/posts', params: post_write_params(
+            title: 'invalid post',
+            url: 'ぼざクリタグ広場',
+            tags: 'spec_tag',
+            thumbnail: dummy_upload)
       end.not_to change(PostVersion, :count)
 
       expect(response).to have_http_status(:unprocessable_entity)
@@ -1120,12 +1493,11 @@ RSpec.describe 'Posts API', type: :request do
       create_post_version_for!(post_record)
 
       expect do
-        put "/posts/#{post_record.id}", params: {
-          title: 'updated title',
-          tags: 'spec_tag',
-          original_created_from: Time.zone.local(2020, 1, 2, 0, 0, 0).iso8601,
-          original_created_before: Time.zone.local(2020, 1, 1, 0, 0, 0).iso8601
-        }
+        put "/posts/#{post_record.id}", params: post_write_params(
+            title: 'updated title',
+            tags: 'spec_tag',
+            original_created_from: Time.zone.local(2020, 1, 2, 0, 0, 0).iso8601,
+            original_created_before: Time.zone.local(2020, 1, 1, 0, 0, 0).iso8601)
       end.not_to change(PostVersion, :count)
 
       expect(response).to have_http_status(:unprocessable_entity)
@@ -1139,12 +1511,11 @@ RSpec.describe 'Posts API', type: :request do
       sign_in_as(member)
 
       expect {
-        post '/posts', params: {
-          title: 'tag versioned post',
-          url: 'https://example.com/tag-versioned-post',
-          tags: 'spec_tag',
-          thumbnail: dummy_upload
-        }
+        post '/posts', params: post_write_params(
+            title: 'tag versioned post',
+            url: 'https://example.com/tag-versioned-post',
+            tags: 'spec_tag',
+            thumbnail: dummy_upload)
       }.to change { tag.reload.tag_versions.count }.by(1)
 
       expect(response).to have_http_status(:created)
@@ -1164,10 +1535,9 @@ RSpec.describe 'Posts API', type: :request do
       tag2 = Tag.create!(tag_name: tag_name2, category: :general)
 
       expect {
-        put "/posts/#{post_record.id}", params: {
-          title: 'updated title',
-          tags: 'spec_tag_2'
-        }
+        put "/posts/#{post_record.id}", params: post_write_params(
+            title: 'updated title',
+            tags: 'spec_tag_2')
       }.to change { tag2.reload.tag_versions.count }.by(1)
 
       expect(response).to have_http_status(:ok)

backend/spec/requests/tags_deerjikists_spec.rb

@@ -8,23 +8,35 @@ RSpec.describe 'Tags deerjikists API', type: :request do
 
   let!(:tag) { create(:tag, category: :deerjikist) }
 
+  let(:member) { create(:user, :member) }
+  let(:guest) { create(:user, role: :guest) }
+
   before do
-    # show_by_name / deerjikists_by_name 用に名前を固定
     tag.tag_name.update!(name: 'deerjika')
   end
 
   describe 'GET /tags/:id/deerjikists' do
     subject(:do_request) do
-      get "/tags/#{ tag_id }/deerjikists"
+      get "/tags/#{tag_id}/deerjikists"
     end
 
     let(:tag_id) { tag.id }
 
     context 'when tag exists and has no deerjikists' do
-      it 'returns 200 and empty array' do
+      it 'returns 200 with tag and empty deerjikists array' do
         do_request
+
         expect(response).to have_http_status(:ok)
-        expect(json).to eq([])
+
+        expect(json).to be_a(Hash)
+
+        expect(json['tag']).to be_a(Hash)
+        expect(json['tag']['id']).to eq(tag.id)
+        expect(json['tag']['name']).to eq('deerjika')
+        expect(json['tag']['category']).to eq('deerjikist')
+        expect(json['tag']['has_deerjikists']).to eq(false)
+
+        expect(json['deerjikists']).to eq([])
       end
     end
 
@@ -34,17 +46,27 @@ RSpec.describe 'Tags deerjikists API', type: :request do
         Deerjikist.create!(platform: platform2, code: code2, tag: tag)
       end
 
-      it 'returns 200 and deerjikists array' do
+      it 'returns 200 with tag and deerjikists array' do
         do_request
+
         expect(response).to have_http_status(:ok)
 
-        expect(json).to be_a(Array)
-        expect(json.size).to eq(2)
+        expect(json).to be_a(Hash)
 
-        expect(json.map { |h| [h['platform'], h['code']] }).to contain_exactly(
-          [platform1, code1],
-          [platform2, code2],
-        )
+        expect(json['tag']).to be_a(Hash)
+        expect(json['tag']['id']).to eq(tag.id)
+        expect(json['tag']['name']).to eq('deerjika')
+        expect(json['tag']['category']).to eq('deerjikist')
+        expect(json['tag']['has_deerjikists']).to eq(true)
+
+        expect(json['deerjikists']).to be_a(Array)
+        expect(json['deerjikists'].size).to eq(2)
+
+        expect(json['deerjikists'].map { |h| [h['platform'], h['code']] })
+          .to contain_exactly(
+            [platform1, code1],
+            [platform2, code2],
+          )
       end
     end
 
@@ -53,6 +75,7 @@ RSpec.describe 'Tags deerjikists API', type: :request do
 
       it 'returns 404' do
         do_request
+
         expect(response).to have_http_status(:not_found)
       end
     end
@@ -60,7 +83,7 @@ RSpec.describe 'Tags deerjikists API', type: :request do
 
   describe 'GET /tags/name/:name/deerjikists' do
     subject(:do_request) do
-      get "/tags/name/#{ name }/deerjikists"
+      get "/tags/name/#{name}/deerjikists"
     end
 
     let(:name) { 'deerjika' }
@@ -70,6 +93,7 @@ RSpec.describe 'Tags deerjikists API', type: :request do
 
       it 'returns 400' do
         do_request
+
         expect(response).to have_http_status(:bad_request)
       end
     end
@@ -79,23 +103,209 @@ RSpec.describe 'Tags deerjikists API', type: :request do
 
       it 'returns 404' do
         do_request
+
         expect(response).to have_http_status(:not_found)
       end
     end
 
+    context 'when tag exists and has no deerjikists' do
+      it 'returns 200 with tag and empty deerjikists array' do
+        do_request
+
+        expect(response).to have_http_status(:ok)
+
+        expect(json).to be_a(Hash)
+
+        expect(json['tag']).to be_a(Hash)
+        expect(json['tag']['id']).to eq(tag.id)
+        expect(json['tag']['name']).to eq('deerjika')
+        expect(json['tag']['category']).to eq('deerjikist')
+        expect(json['tag']['has_deerjikists']).to eq(false)
+
+        expect(json['deerjikists']).to eq([])
+      end
+    end
+
     context 'when tag exists and has deerjikists' do
       before do
         Deerjikist.create!(platform: platform1, code: code1, tag: tag)
       end
 
-      it 'returns 200 and deerjikists array' do
+      it 'returns 200 with tag and deerjikists array' do
         do_request
+
         expect(response).to have_http_status(:ok)
 
-        expect(json).to be_a(Array)
-        expect(json.size).to eq(1)
-        expect(json[0]['platform']).to eq(platform1)
-        expect(json[0]['code']).to eq(code1)
+        expect(json).to be_a(Hash)
+
+        expect(json['tag']).to be_a(Hash)
+        expect(json['tag']['id']).to eq(tag.id)
+        expect(json['tag']['name']).to eq('deerjika')
+        expect(json['tag']['category']).to eq('deerjikist')
+        expect(json['tag']['has_deerjikists']).to eq(true)
+
+        expect(json['deerjikists']).to be_a(Array)
+        expect(json['deerjikists'].size).to eq(1)
+
+        expect(json['deerjikists'][0]['platform']).to eq(platform1)
+        expect(json['deerjikists'][0]['code']).to eq(code1)
+      end
+    end
+  end
+
+  describe 'PUT /tags/:id/deerjikists' do
+    subject(:do_request) do
+      put "/tags/#{tag_id}/deerjikists", params: payload, as: :json
+    end
+
+    let(:tag_id) { tag.id }
+    let(:payload) do
+      [
+        { platform: platform1, code: code1 },
+        { platform: platform2, code: code2 },
+      ]
+    end
+
+    context 'when not logged in' do
+      it 'returns 401' do
+        do_request
+
+        expect(response).to have_http_status(:unauthorized)
+      end
+    end
+
+    context 'when logged in but not member' do
+      before do
+        sign_in_as guest
+      end
+
+      it 'returns 403' do
+        do_request
+
+        expect(response).to have_http_status(:forbidden)
+      end
+    end
+
+    context 'when tag does not exist' do
+      let(:tag_id) { 9_999_999 }
+
+      before do
+        sign_in_as member
+      end
+
+      it 'returns 404' do
+        do_request
+
+        expect(response).to have_http_status(:not_found)
+      end
+    end
+
+    context 'when logged in as member' do
+      before do
+        sign_in_as member
+      end
+
+      context 'when tag has no deerjikists' do
+        it 'creates deerjikists and returns deerjikists array' do
+          expect {
+            do_request
+          }.to change { Deerjikist.where(tag: tag).count }.from(0).to(2)
+
+          expect(response).to have_http_status(:ok)
+
+          expect(json).to be_a(Array)
+          expect(json.map { |h| [h['platform'], h['code']] })
+            .to contain_exactly(
+              [platform1, code1],
+              [platform2, code2],
+            )
+
+          expect(Deerjikist.where(tag: tag).map { |d| [d.platform, d.code] })
+            .to contain_exactly(
+              [platform1, code1],
+              [platform2, code2],
+            )
+        end
+      end
+
+      context 'when tag already has deerjikists' do
+        before do
+          Deerjikist.create!(platform: platform1, code: 'old-code-1', tag: tag)
+          Deerjikist.create!(platform: platform2, code: 'old-code-2', tag: tag)
+        end
+
+        it 'replaces deerjikists and returns deerjikists array' do
+          do_request
+
+          expect(response).to have_http_status(:ok)
+
+          expect(Deerjikist.where(tag: tag).map { |d| [d.platform, d.code] })
+            .to contain_exactly(
+              [platform1, code1],
+              [platform2, code2],
+            )
+
+          expect(Deerjikist.exists?(platform: platform1, code: 'old-code-1')).to eq(false)
+          expect(Deerjikist.exists?(platform: platform2, code: 'old-code-2')).to eq(false)
+
+          expect(json).to be_a(Array)
+          expect(json.map { |h| [h['platform'], h['code']] })
+            .to contain_exactly(
+              [platform1, code1],
+              [platform2, code2],
+            )
+        end
+      end
+
+      context 'when payload is empty array' do
+        let(:payload) { [] }
+
+        before do
+          Deerjikist.create!(platform: platform1, code: code1, tag: tag)
+          Deerjikist.create!(platform: platform2, code: code2, tag: tag)
+        end
+
+        it 'clears deerjikists and returns empty array' do
+          expect {
+            do_request
+          }.to change { Deerjikist.where(tag: tag).count }.from(2).to(0)
+
+          expect(response).to have_http_status(:ok)
+          expect(json).to eq([])
+        end
+      end
+
+      context 'when youtube code is handle' do
+        let(:channel_id) { 'UCabcdefghijklmnopqrstuv' }
+        let(:payload) do
+          [
+            { platform: 'youtube', code: '@deerjika' },
+          ]
+        end
+
+        before do
+          allow(Net::HTTP).to receive(:get).and_return(
+            %(<link rel="canonical" href="https://www.youtube.com/channel/#{channel_id}">),
+          )
+        end
+
+        it 'normalises youtube handle to channel id' do
+          expect {
+            do_request
+          }.to change { Deerjikist.where(tag: tag).count }.from(0).to(1)
+
+          expect(response).to have_http_status(:ok)
+
+          expect(Net::HTTP).to have_received(:get)
+
+          expect(Deerjikist.exists?(platform: 'youtube', code: channel_id, tag: tag))
+            .to eq(true)
+
+          expect(json).to be_a(Array)
+          expect(json.size).to eq(1)
+          expect(json[0]['platform']).to eq('youtube')
+          expect(json[0]['code']).to eq(channel_id)
+        end
       end
     end
   end

backend/spec/services/youtube/api_client_spec.rb

@@ -0,0 +1,130 @@
+require 'rails_helper'
+
+RSpec.describe Youtube::ApiClient do
+  let(:api_key) { 'test-api-key' }
+  let(:client) { described_class.new(api_key:) }
+
+  describe '#search_videos' do
+    it 'calls YouTube search API with expected params' do
+      published_after = Time.zone.parse('2026-05-01 00:00:00')
+      published_before = Time.zone.parse('2026-05-02 00:00:00')
+
+      expect(client).to receive(:get_json).with(
+        '/search',
+        {
+          part: 'snippet',
+          type: 'video',
+          q: 'ぼざろクリーチャー',
+          order: 'date',
+          maxResults: 50,
+          regionCode: 'JP',
+          relevanceLanguage: 'ja',
+          publishedAfter: published_after.iso8601,
+          publishedBefore: published_before.iso8601,
+          pageToken: 'NEXT'
+        }
+      ).and_return({ 'items' => [] })
+
+      client.search_videos(
+        q: 'ぼざろクリーチャー',
+        published_after:,
+        published_before:,
+        page_token: 'NEXT'
+      )
+    end
+
+    it 'omits nil optional params' do
+      expect(client).to receive(:get_json).with(
+        '/search',
+        hash_excluding(:publishedAfter, :publishedBefore, :pageToken)
+      ).and_return({ 'items' => [] })
+
+      client.search_videos(q: 'ぼざろクリーチャー')
+    end
+  end
+
+  describe '#videos' do
+    it 'returns empty items when ids are empty' do
+      expect(client).not_to receive(:get_json)
+
+      expect(client.videos([])).to eq({ 'items' => [] })
+    end
+
+    it 'calls videos API with comma separated ids' do
+      expect(client).to receive(:get_json).with(
+        '/videos',
+        {
+          part: 'snippet,status,contentDetails',
+          id: 'video-1,video-2'
+        }
+      ).and_return({ 'items' => [] })
+
+      client.videos(['video-1', 'video-2'])
+    end
+  end
+
+  describe '#playlist_items' do
+    it 'calls playlistItems API with page token' do
+      expect(client).to receive(:get_json).with(
+        '/playlistItems',
+        {
+          part: 'snippet,contentDetails,status',
+          playlistId: 'PL123',
+          maxResults: 50,
+          pageToken: 'NEXT'
+        }
+      ).and_return({ 'items' => [] })
+
+      client.playlist_items(playlist_id: 'PL123', page_token: 'NEXT')
+    end
+
+    it 'omits page token when nil' do
+      expect(client).to receive(:get_json).with(
+        '/playlistItems',
+        {
+          part: 'snippet,contentDetails,status',
+          playlistId: 'PL123',
+          maxResults: 50
+        }
+      ).and_return({ 'items' => [] })
+
+      client.playlist_items(playlist_id: 'PL123')
+    end
+  end
+
+  describe '#channel' do
+    it 'calls channels API by id' do
+      expect(client).to receive(:get_json).with(
+        '/channels',
+        {
+          part: 'snippet,contentDetails',
+          id: 'UC123'
+        }
+      ).and_return({ 'items' => [] })
+
+      client.channel(id: 'UC123')
+    end
+
+    it 'calls channels API by handle' do
+      expect(client).to receive(:get_json).with(
+        '/channels',
+        {
+          part: 'snippet,contentDetails',
+          forHandle: '@some_handle'
+        }
+      ).and_return({ 'items' => [] })
+
+      client.channel(handle: '@some_handle')
+    end
+
+    it 'raises when neither id nor handle is given' do
+      expect { client.channel }.to raise_error(ArgumentError, 'id or handle is required')
+    end
+
+    it 'raises when both id and handle are given' do
+      expect do
+        client.channel(id: 'UC123', handle: '@some_handle')
+      end.to raise_error(ArgumentError, 'id or handle is required')
+    end
+  end
+end

backend/spec/services/youtube/sync_spec.rb

@@ -0,0 +1,310 @@
+require 'rails_helper'
+
+RSpec.describe Youtube::Sync do
+  let(:client) { instance_double(Youtube::ApiClient) }
+  let(:sync) { described_class.new(client:) }
+
+  before do
+    allow(PostVersionRecorder).to receive(:record!)
+    allow(PostVersionRecorder).to receive(:ensure_snapshot!)
+    allow(sync).to receive(:attach_thumbnail_if_needed!)
+  end
+
+  describe '#sync!' do
+    it 'returns without fetching video details when no video ids are discovered' do
+      allow(sync).to receive(:query_terms).and_return([])
+      allow(sync).to receive(:playlist_ids).and_return([])
+
+      expect(client).not_to receive(:videos)
+
+      sync.sync!
+    end
+
+    it 'discovers ids from search and all playlist pages' do
+      allow(sync).to receive(:query_terms).and_return(['ぼざろクリーチャー'])
+      allow(sync).to receive(:playlist_ids).and_return(['PL123'])
+      allow(sync).to receive(:sync_since).and_return(Time.zone.parse('2026-05-01 00:00:00'))
+
+      allow(client).to receive(:search_videos).with(
+        q: 'ぼざろクリーチャー',
+        published_after: Time.zone.parse('2026-05-01 00:00:00')
+      ).and_return({
+        'items' => [
+          {
+            'id' => {
+              'videoId' => 'search-video-1'
+            }
+          }
+        ]
+      })
+
+      allow(client).to receive(:playlist_items).with(
+        playlist_id: 'PL123',
+        page_token: nil
+      ).and_return({
+        'items' => [
+          {
+            'contentDetails' => {
+              'videoId' => 'playlist-video-1'
+            }
+          }
+        ],
+        'nextPageToken' => 'NEXT'
+      })
+
+      allow(client).to receive(:playlist_items).with(
+        playlist_id: 'PL123',
+        page_token: 'NEXT'
+      ).and_return({
+        'items' => [
+          {
+            'snippet' => {
+              'resourceId' => {
+                'videoId' => 'playlist-video-2'
+              }
+            }
+          }
+        ]
+      })
+
+      expect(client).to receive(:videos).with(
+        satisfy do |ids|
+          ids.sort == ['playlist-video-1', 'playlist-video-2', 'search-video-1']
+        end
+      ).and_return({ 'items' => [] })
+
+      sync.sync!
+    end
+
+    it 'creates a YouTube post with default tags and no_deerjikist when no deerjikist mapping exists' do
+      Tag.tagme
+      Tag.bot
+      Tag.youtube
+      Tag.video
+      Tag.no_deerjikist
+
+      allow(sync).to receive(:query_terms).and_return([])
+      allow(sync).to receive(:playlist_ids).and_return(['PL123'])
+
+      allow(client).to receive(:playlist_items).with(
+        playlist_id: 'PL123',
+        page_token: nil
+      ).and_return({
+        'items' => [
+          {
+            'contentDetails' => {
+              'videoId' => 'video-1'
+            }
+          }
+        ]
+      })
+
+      allow(client).to receive(:videos).with(['video-1']).and_return({
+        'items' => [
+          youtube_video_item(
+            id: 'video-1',
+            title: 'YouTube テスト動画',
+            channel_id: 'UC_NO_MAPPING'
+          )
+        ]
+      })
+
+      expect do
+        sync.sync!
+      end.to change(Post, :count).by(1)
+
+      post = Post.find_by!(url: 'https://www.youtube.com/watch?v=video-1')
+      tag_ids = post.tags.pluck(:id)
+
+      expect(post.title).to eq('YouTube テスト動画')
+      expect(post.uploaded_user_id).to be_nil
+      expect(post.original_created_from).to eq(Time.zone.parse('2026-05-01 12:34:00'))
+      expect(post.original_created_before).to eq(Time.zone.parse('2026-05-01 12:35:00'))
+
+      expect(tag_ids).to include(Tag.tagme.id)
+      expect(tag_ids).to include(Tag.bot.id)
+      expect(tag_ids).to include(Tag.youtube.id)
+      expect(tag_ids).to include(Tag.video.id)
+      expect(tag_ids).to include(Tag.no_deerjikist.id)
+
+      expect(PostVersionRecorder).to have_received(:record!).with(
+        post:,
+        event_type: :create,
+        created_by_user: nil
+      )
+    end
+
+    it 'uses deerjikist tag when channel id is mapped' do
+      Tag.tagme
+      Tag.bot
+      Tag.youtube
+      Tag.video
+      Tag.no_deerjikist
+
+      deerjikist_tag = Tag.find_or_create_by_tag_name!('テスト投稿者', category: :deerjikist)
+      Deerjikist.create!(
+        platform: 'youtube',
+        code: 'UC_MAPPED',
+        tag: deerjikist_tag
+      )
+
+      allow(sync).to receive(:query_terms).and_return([])
+      allow(sync).to receive(:playlist_ids).and_return(['PL123'])
+
+      allow(client).to receive(:playlist_items).with(
+        playlist_id: 'PL123',
+        page_token: nil
+      ).and_return({
+        'items' => [
+          {
+            'contentDetails' => {
+              'videoId' => 'video-1'
+            }
+          }
+        ]
+      })
+
+      allow(client).to receive(:videos).with(['video-1']).and_return({
+        'items' => [
+          youtube_video_item(
+            id: 'video-1',
+            title: 'YouTube テスト動画',
+            channel_id: 'UC_MAPPED'
+          )
+        ]
+      })
+
+      sync.sync!
+
+      post = Post.find_by!(url: 'https://www.youtube.com/watch?v=video-1')
+      tag_ids = post.tags.pluck(:id)
+
+      expect(tag_ids).to include(deerjikist_tag.id)
+      expect(tag_ids).not_to include(Tag.no_deerjikist.id)
+    end
+
+    it 'removes no_deerjikist when deerjikist mapping is added later' do
+      Tag.no_deerjikist
+
+      post = Post.create!(
+        title: '旧タイトル',
+        url: 'https://www.youtube.com/watch?v=video-1',
+        uploaded_user_id: nil,
+        original_created_from: Time.zone.parse('2026-05-01 00:00:00'),
+        original_created_before: Time.zone.parse('2026-05-01 00:01:00')
+      )
+      PostTag.create!(post:, tag: Tag.no_deerjikist)
+
+      deerjikist_tag = Tag.find_or_create_by_tag_name!('後から判明した投稿者', category: :deerjikist)
+      Deerjikist.create!(
+        platform: 'youtube',
+        code: 'UC_MAPPED_LATER',
+        tag: deerjikist_tag
+      )
+
+      allow(sync).to receive(:query_terms).and_return([])
+      allow(sync).to receive(:playlist_ids).and_return(['PL123'])
+
+      allow(client).to receive(:playlist_items).with(
+        playlist_id: 'PL123',
+        page_token: nil
+      ).and_return({
+        'items' => [
+          {
+            'contentDetails' => {
+              'videoId' => 'video-1'
+            }
+          }
+        ]
+      })
+
+      allow(client).to receive(:videos).with(['video-1']).and_return({
+        'items' => [
+          youtube_video_item(
+            id: 'video-1',
+            title: '新タイトル',
+            channel_id: 'UC_MAPPED_LATER'
+          )
+        ]
+      })
+
+      sync.sync!
+
+      post.reload
+      tag_ids = post.tags.pluck(:id)
+
+      expect(post.title).to eq('新タイトル')
+      expect(tag_ids).to include(deerjikist_tag.id)
+      expect(tag_ids).not_to include(Tag.no_deerjikist.id)
+
+      expect(PostVersionRecorder).to have_received(:ensure_snapshot!).with(
+        post,
+        created_by_user: nil
+      )
+      expect(PostVersionRecorder).to have_received(:record!).with(
+        post:,
+        event_type: :update,
+        created_by_user: nil
+      )
+    end
+
+    it 'matches existing youtu.be URL and does not create duplicate post' do
+      post = Post.create!(
+        title: '旧タイトル',
+        url: 'https://youtu.be/video-1',
+        uploaded_user_id: nil,
+        original_created_from: Time.zone.parse('2026-05-01 00:00:00'),
+        original_created_before: Time.zone.parse('2026-05-01 00:01:00')
+      )
+
+      allow(sync).to receive(:query_terms).and_return([])
+      allow(sync).to receive(:playlist_ids).and_return(['PL123'])
+
+      allow(client).to receive(:playlist_items).with(
+        playlist_id: 'PL123',
+        page_token: nil
+      ).and_return({
+        'items' => [
+          {
+            'contentDetails' => {
+              'videoId' => 'video-1'
+            }
+          }
+        ]
+      })
+
+      allow(client).to receive(:videos).with(['video-1']).and_return({
+        'items' => [
+          youtube_video_item(
+            id: 'video-1',
+            title: '新タイトル',
+            channel_id: 'UC_NO_MAPPING'
+          )
+        ]
+      })
+
+      expect do
+        sync.sync!
+      end.not_to change(Post, :count)
+
+      expect(post.reload.title).to eq('新タイトル')
+    end
+  end
+
+  def youtube_video_item(id:, title:, channel_id:)
+    {
+      'id' => id,
+      'snippet' => {
+        'title' => title,
+        'channelId' => channel_id,
+        'publishedAt' => '2026-05-01T12:34:56Z',
+        'thumbnails' => {
+          'high' => {
+            'url' => "https://img.youtube.com/#{id}.jpg"
+          }
+        },
+        'tags' => ['tag-a', 'tag-b']
+      }
+    }
+  end
+end

backend/spec/services/youtube/video_item_spec.rb

@@ -0,0 +1,93 @@
+require 'rails_helper'
+
+RSpec.describe Youtube::VideoItem do
+  describe '#initialize' do
+    it 'extracts fields from YouTube video API item' do
+      item = {
+        'id' => 'video-1',
+        'snippet' => {
+          'title' => 'テスト動画',
+          'channelId' => 'UC123',
+          'publishedAt' => '2026-05-01T12:34:56Z',
+          'tags' => ['tag-a', 'tag-b'],
+          'thumbnails' => {
+            'high' => {
+              'url' => 'https://img.youtube.com/high.jpg'
+            },
+            'medium' => {
+              'url' => 'https://img.youtube.com/medium.jpg'
+            }
+          }
+        }
+      }
+
+      video = described_class.new(item)
+
+      expect(video.id).to eq('video-1')
+      expect(video.title).to eq('テスト動画')
+      expect(video.channel_id).to eq('UC123')
+      expect(video.published_at).to eq(Time.iso8601('2026-05-01T12:34:56Z'))
+      expect(video.thumbnail_url).to eq('https://img.youtube.com/high.jpg')
+      expect(video.raw_tags).to eq(['tag-a', 'tag-b'])
+      expect(video.url).to eq('https://www.youtube.com/watch?v=video-1')
+    end
+
+    it 'uses highest priority thumbnail' do
+      item = {
+        'id' => 'video-1',
+        'snippet' => {
+          'title' => 'テスト動画',
+          'channelId' => 'UC123',
+          'publishedAt' => '2026-05-01T12:34:56Z',
+          'thumbnails' => {
+            'default' => {
+              'url' => 'https://img.youtube.com/default.jpg'
+            },
+            'standard' => {
+              'url' => 'https://img.youtube.com/standard.jpg'
+            },
+            'maxres' => {
+              'url' => 'https://img.youtube.com/maxres.jpg'
+            }
+          }
+        }
+      }
+
+      video = described_class.new(item)
+
+      expect(video.thumbnail_url).to eq('https://img.youtube.com/maxres.jpg')
+    end
+
+    it 'falls back to empty raw tags' do
+      item = {
+        'id' => 'video-1',
+        'snippet' => {
+          'title' => 'テスト動画',
+          'channelId' => 'UC123',
+          'publishedAt' => '2026-05-01T12:34:56Z',
+          'thumbnails' => {}
+        }
+      }
+
+      video = described_class.new(item)
+
+      expect(video.raw_tags).to eq([])
+    end
+
+    it 'returns nil thumbnail when no thumbnail exists' do
+      item = {
+        'id' => 'video-1',
+        'snippet' => {
+          'title' => 'テスト動画',
+          'channelId' => 'UC123',
+          'publishedAt' => '2026-05-01T12:34:56Z',
+          'thumbnails' => {}
+        }
+      }
+
+      video = described_class.new(item)
+
+      expect(video.thumbnail_url).to be_nil
+    end
+  end
+end

backend/spec/tasks/nico_sync_spec.rb

@@ -104,7 +104,7 @@ RSpec.describe "nico:sync" do
       url: post.url,
       thumbnail_base: post.thumbnail_base,
       tags: snapshot_tags(post),
-      parent: post.parent,
+      parent_post_ids: post.snapshot_parent_post_ids.join(' '),
       original_created_from: post.original_created_from,
       original_created_before: post.original_created_before,
       created_at: Time.current,

backend/spec/tasks/post_sync_spec.rb

@@ -0,0 +1,25 @@
+require 'rails_helper'
+require 'rake'
+
+RSpec.describe 'post:sync' do
+  around do |example|
+    original_application = Rake.application
+    Rake.application = Rake::Application.new
+
+    Rake::Task.define_task(:environment)
+    load Rails.root.join('lib/tasks/sync_posts.rake')
+
+    example.run
+  ensure
+    Rake.application = original_application
+  end
+
+  it 'runs Youtube::Sync' do
+    sync = instance_double(Youtube::Sync)
+
+    expect(Youtube::Sync).to receive(:new).once.and_return(sync)
+    expect(sync).to receive(:sync!).once
+
+    Rake::Task['post:sync'].invoke
+  end
+end

frontend/src/App.tsx

@@ -10,6 +10,7 @@ import RouteBlockerOverlay from '@/components/RouteBlockerOverlay'
 import TopNav from '@/components/TopNav'
 import { Toaster } from '@/components/ui/toaster'
 import { apiPost, isApiError } from '@/lib/api'
+import DeerjikistDetailPage from '@/pages/deerjikists/DeerjikistDetailPage'
 import MaterialBasePage from '@/pages/materials/MaterialBasePage'
 import MaterialDetailPage from '@/pages/materials/MaterialDetailPage'
 import MaterialListPage from '@/pages/materials/MaterialListPage'
@@ -58,6 +59,7 @@ const RouteTransitionWrapper = ({ user, setUser }: {
 	  <Route path="/posts/changes" element={<PostHistoryPage/>}/>
 	  <Route path="/tags" element={<TagListPage/>}/>
 	  <Route path="/tags/:id" element={<TagDetailPage/>}/>
+	  <Route path="/tags/:id/deerjikists" element={<DeerjikistDetailPage/>}/>
 	  <Route path="/tags/nico" element={<NicoTagListPage user={user}/>}/>
 	  <Route path="/tags/changes" element={<TagHistoryPage/>}/>
 	  <Route path="/theatres/:id" element={<TheatreDetailPage/>}/>

frontend/src/components/PostEditForm.tsx

@@ -4,6 +4,7 @@ import PostFormTagsArea from '@/components/PostFormTagsArea'
 import PostOriginalCreatedTimeField from '@/components/PostOriginalCreatedTimeField'
 import Label from '@/components/common/Label'
 import { Button } from '@/components/ui/button'
+import { toast } from '@/components/ui/use-toast'
 import { apiPut } from '@/lib/api'
 
 import type { FC } from 'react'
@@ -35,20 +36,34 @@ export default (({ post, onSave }: Props) => {
       useState<string | null> (post.originalCreatedBefore)
   const [originalCreatedFrom, setOriginalCreatedFrom] =
       useState<string | null> (post.originalCreatedFrom)
-  const [title, setTitle] = useState (post.title)
+  const [parentPostIds, setParentPostIds] =
+      useState ((post.parentPosts ?? []).map (p => p.id).join (' '))
   const [tags, setTags] = useState<string> ('')
+  const [title, setTitle] = useState (post.title)
 
   const handleSubmit = async () => {
-    const data = await apiPut<Post> (
-	`/posts/${ post.id }`,
-	{ title, tags, original_created_from: originalCreatedFrom,
-	  original_created_before: originalCreatedBefore },
-	{ headers: { 'Content-Type': 'multipart/form-data' } })
-    onSave ({ ...post,
-	      title:                  data.title,
-	      tags:                   data.tags,
-	      originalCreatedFrom:    data.originalCreatedFrom,
-	      originalCreatedBefore:  data.originalCreatedBefore } as Post)
+    try
+    {
+      const data = await apiPut<Post> (
+	  `/posts/${ post.id }`,
+	  { title, tags, parent_post_ids: parentPostIds,
+	    original_created_from: originalCreatedFrom,
+	    original_created_before: originalCreatedBefore },
+	  { headers: { 'Content-Type': 'multipart/form-data' } })
+      onSave ({ ...post,
+		title:                  data.title,
+		tags:                   data.tags,
+		parentPosts:            data.parentPosts,
+		childPosts:             data.childPosts,
+		siblingPosts:           data.siblingPosts,
+		originalCreatedFrom:    data.originalCreatedFrom,
+		originalCreatedBefore:  data.originalCreatedBefore } as Post)
+      toast ({ description: '更新しました．' })
+    }
+    catch
+    {
+      toast ({ description: '更新はできなかったよ……' })
+    }
   }
 
   useEffect (() => {
@@ -66,6 +81,16 @@ export default (({ post, onSave }: Props) => {
 		 onChange={ev => setTitle (ev.target.value)}/>
 	</div>
 
+	{/* 親投稿 */}
+	<div>
+	  <Label>親投稿</Label>
+	  <input
+	      type="text"
+	      value={parentPostIds}
+	      onChange={e => setParentPostIds (e.target.value)}
+	      className="w-full border p-2 rounded"/>
+	</div>
+
 	{/* タグ */}
 	<PostFormTagsArea tags={tags} setTags={setTags}/>
 

frontend/src/components/PostList.tsx

@@ -3,6 +3,7 @@ import { useRef } from 'react'
 import { useLocation } from 'react-router-dom'
 
 import PrefetchLink from '@/components/PrefetchLink'
+import { cn } from '@/lib/utils'
 import { useSharedTransitionStore } from '@/stores/sharedTransitionStore'
 
 import type { FC, MouseEvent } from 'react'
@@ -39,8 +40,10 @@ export default (({ posts, onClick }: Props) => {
 		<motion.div
 		    ref={cardRef}
 		    layoutId={layoutId}
-		    className="w-full h-full overflow-hidden rounded-xl shadow
-			       transform-gpu will-change-transform"
+		    className={cn ('w-full h-full overflow-hidden rounded-xl shadow',
+				   'transform-gpu will-change-transform',
+				   (post.childPosts ?? []).length > 0 && 'outline-4 outline-green-500',
+				   (post.parentPosts ?? []).length > 0 && 'ring-4 ring-yellow-500')}
 		    whileHover={{ scale: 1.02 }}
 		    onLayoutAnimationStart={() => {
 		      if (!(cardRef.current))

frontend/src/components/TagLink.tsx

@@ -45,9 +45,9 @@ export default (({ tag,
       <>
 	{(linkFlg && withWiki) && (
 	    <span className="mr-1">
-	      {(tag.materialId != null || tag.hasWiki)
+	      {(tag.materialId != null || tag.hasWiki || tag.hasDeerjikists)
 	       ? (
-		  tag.materialId == null
+		  tag.materialId == null && !(tag.hasDeerjikists)
 		  ? (
 		      <PrefetchLink
 			  to={`/wiki/${ encodeURIComponent (tag.name) }`}
@@ -55,11 +55,19 @@ export default (({ tag,
 			?
 		      </PrefetchLink>)
 		  : (
-		      <PrefetchLink
-			  to={`/materials/${ tag.materialId }`}
-			  className={linkClass}>
-			?
-		      </PrefetchLink>))
+		      tag.materialId != null
+		      ? (
+			  <PrefetchLink
+			      to={`/materials/${ tag.materialId }`}
+			      className={linkClass}>
+			    ?
+			  </PrefetchLink>)
+		      : (
+			  <PrefetchLink
+			      to={`/tags/${ tag.id }/deerjikists`}
+			      className={linkClass}>
+			    ?
+			  </PrefetchLink>)))
 	       : (
 		  ['character', 'material'].includes (tag.category)
 		  ? (
@@ -71,13 +79,23 @@ export default (({ tag,
 			!
 		      </PrefetchLink>)
 		  : (
-		      <PrefetchLink
-			  to={`/wiki/${ encodeURIComponent (tag.name) }`}
-			  className="animate-[wiki-blink_.25s_steps(2,end)_infinite]
-				     dark:animate-[wiki-blink-dark_.25s_steps(2,end)_infinite]"
-			  title={`${ tag.name } Wiki が存在しません．`}>
-			!
-		      </PrefetchLink>))}
+		      tag.category === 'deerjikist'
+		      ? (
+			  <PrefetchLink
+			      to={`/tags/${ tag.id }/deerjikists`}
+			      className="animate-[wiki-blink_.25s_steps(2,end)_infinite]
+					 dark:animate-[wiki-blink-dark_.25s_steps(2,end)_infinite]"
+			      title={`${ tag.name } に関する情報が存在しません．`}>
+			    !
+			  </PrefetchLink>)
+		      : (
+			  <PrefetchLink
+			      to={`/wiki/${ encodeURIComponent (tag.name) }`}
+			      className="animate-[wiki-blink_.25s_steps(2,end)_infinite]
+					 dark:animate-[wiki-blink-dark_.25s_steps(2,end)_infinite]"
+			      title={`${ tag.name } Wiki が存在しません．`}>
+			    !
+			  </PrefetchLink>)))}
 	    </span>)}
 	{nestLevel > 0 && (
 	    <span

frontend/src/consts.ts

@@ -1,4 +1,4 @@
-import type { Category } from 'types'
+import type { Category, Platform } from 'types'
 
 export const LIGHT_COLOUR_SHADE = 800
 export const DARK_COLOUR_SHADE = 300
@@ -31,6 +31,11 @@ export const FETCH_POSTS_ORDER_FIELDS = [
     'updated_at',
     ] as const
 
+export const PLATFORMS = ['nico', 'youtube'] as const
+
+export const PLATFORM_NAMES: Record<Platform, string> =
+    { nico: 'ニコニコ', youtube: 'YouTube' } as const
+
 export const TAG_COLOUR = {
     deerjikist: 'rose',
     meme:       'purple',

frontend/src/lib/queryKeys.ts

@@ -9,11 +9,12 @@ export const postsKeys = {
 		  ['posts', 'changes', p] as const }
 
 export const tagsKeys = {
-    root:     ['tags'] as const,
-    index:    (p: FetchTagsParams) => ['tags', 'index', p] as const,
-    show:     (name: string) => ['tags', name] as const,
-    changes:  (p: { id?: string; page: number; limit: number }) =>
-		  ['tags', 'changes', p] as const }
+    root:         ['tags'] as const,
+    index:        (p: FetchTagsParams) => ['tags', 'index', p] as const,
+    show:         (name: string) => ['tags', name] as const,
+    changes:      (p: { id?: string; page: number; limit: number }) =>
+		      ['tags', 'changes', p] as const,
+    deerjikists:  (id: string) => ['tags', 'deerjikists', id] as const }
 
 export const wikiKeys = {
     root:   ['wiki'] as const,

frontend/src/lib/tags.ts

@@ -1,6 +1,6 @@
 import { apiGet } from '@/lib/api'
 
-import type { FetchTagsParams, Tag, TagVersion } from '@/types'
+import type { Deerjikist, FetchTagsParams, Tag, TagVersion } from '@/types'
 
 
 export const fetchTags = async (
@@ -56,3 +56,9 @@ export const fetchTagChanges = async (
     versions: TagVersion[]
     count:    number }> =>
 	await apiGet ('/tags/versions', { params: { ...(id && { id }), page, limit } })
+
+
+export const fetchDeerjikistsByTag = async (
+    id: string,
+): Promise<{ tag: Tag; deerjikists: Deerjikist[]}> =>
+    await apiGet (`/tags/${ id }/deerjikists`)

frontend/src/pages/deerjikists/DeerjikistDetailPage.tsx

@@ -0,0 +1,155 @@
+import { useQuery, useQueryClient } from '@tanstack/react-query'
+import { useEffect, useState } from 'react'
+import { useParams } from 'react-router-dom'
+
+import TagLink from '@/components/TagLink'
+import Label from '@/components/common/Label'
+import PageTitle from '@/components/common/PageTitle'
+import MainArea from '@/components/layout/MainArea'
+import { toast } from '@/components/ui/use-toast'
+import { PLATFORM_NAMES, PLATFORMS } from '@/consts'
+import { apiPut } from '@/lib/api'
+import { tagsKeys } from '@/lib/queryKeys'
+import { fetchDeerjikistsByTag } from '@/lib/tags'
+import { cn } from '@/lib/utils'
+
+import type { FC, FormEvent } from 'react'
+
+import type { Deerjikist, Platform } from '@/types'
+
+
+export default (() => {
+  const { id } = useParams ()
+  const tagId = String (id ?? '')
+  const tagKey = tagsKeys.deerjikists (tagId)
+
+  const { data: qData, isLoading: loading } =
+      useQuery ({ queryKey: tagKey, queryFn: () => fetchDeerjikistsByTag (tagId) })
+  const tag = qData?.tag
+  const deerjikists = qData?.deerjikists ?? []
+
+  const [data, setData] =
+      useState<(Omit<Deerjikist, 'platform'> & { platform: Platform | null })[]> ([])
+  const [disabled, setDisabled] = useState (true)
+
+  const qc = useQueryClient ()
+
+  const handleSubmit = async (e: FormEvent) => {
+    e.preventDefault ()
+
+    try
+    {
+      setDisabled (true)
+
+      setData (await apiPut<Deerjikist[]> (`/tags/${ id }/deerjikists`, data))
+      qc.invalidateQueries ({ queryKey: tagsKeys.root })
+
+      toast ({ description: '更新しました．' })
+    }
+    catch
+    {
+      toast ({ title: '更新失敗', description: '入力内容を確認してください．' })
+    }
+    finally
+    {
+      setDisabled (false)
+    }
+  }
+
+  useEffect (() => {
+    if (!(tag))
+      {
+	setDisabled (true)
+	return
+      }
+
+    setData (deerjikists)
+    setDisabled (false)
+  }, [tag, deerjikists])
+
+  return (
+      <MainArea>
+	{(loading || !(tag)) ? 'Loading...' : (
+	    <div className="max-w-xl">
+	      <PageTitle>
+		<TagLink tag={tag} withWiki={false} withCount={false}/>
+	      </PageTitle>
+
+	      <form onSubmit={handleSubmit} className="my-4 space-y-2">
+		{data.map ((datum, i) => (
+		    <fieldset key={i} className="min-w-0 rounded-lg border border-gray-300
+						 dark:border-gray-700 p-4">
+		      <legend className="px-2 text-sm font-semibold text-gray-700
+					 dark:text-gray-300">
+			<button
+			    type="button"
+			    disabled={disabled}
+			    onClick={() => setData (prev => [...prev.slice (0, i),
+							     ...prev.slice (i + 1)])}>
+			  #{i + 1}
+			</button>
+		      </legend>
+
+		      {/* プラットフォーム */}
+		      <div>
+			<Label>プラットフォーム</Label>
+			<select
+			    className="w-full border p-2 rounded"
+			    disabled={disabled}
+			    value={datum.platform ?? ''}
+			    onChange={e => setData (prev => {
+			      const rtn = [...prev]
+			      rtn[i] = { ...rtn[i],
+					 platform: (e.target.value || null) as Platform | null }
+			      return rtn
+			    })}>
+			  <option value="">&nbsp;</option>
+			  {PLATFORMS.map (p => (
+			      <option key={p} value={p}>
+				{PLATFORM_NAMES[p]}
+			      </option>))}
+			</select>
+		      </div>
+
+		      {/* コード */}
+		      <div>
+			<Label>コード</Label>
+			<input
+			    type="text"
+			    disabled={disabled}
+			    className="w-full border p-2 rounded"
+			    value={datum.code}
+			    onChange={e => setData (prev => {
+			      const rtn = [...prev]
+			      rtn[i] = { ...rtn[i], code: e.target.value }
+			      return rtn
+			    })}/>
+		      </div>
+		    </fieldset>
+		))}
+
+		<div className="py-3">
+		  <button
+		      type="button"
+		      disabled={disabled}
+		      onClick={() => setData (prev => [...prev, { platform: null, code: '' }])}>
+		    +
+		  </button>
+		</div>
+
+		<div className="py-3">
+		  <button
+		      type="submit"
+		      disabled={disabled}
+		      className={cn ('px-4 py-2 rounded',
+				     (disabled
+				      ? 'text-gray-300 bg-gray-500'
+				      : 'text-white bg-blue-500'))}>
+		    更新
+		  </button>
+		</div>
+	      </form>
+	    </div>
+	)}
+      </MainArea>)
+}) satisfies FC

frontend/src/pages/posts/PostDetailPage.tsx

@@ -21,7 +21,7 @@ import ServiceUnavailable from '@/pages/ServiceUnavailable'
 
 import type { FC } from 'react'
 
-import type { NiconicoViewerHandle, User } from '@/types'
+import type { NiconicoViewerHandle, Post, User } from '@/types'
 
 type Props = { user: User | null }
 
@@ -108,6 +108,34 @@ export default (({ user }: Props) => {
 	  {post
 	   ? (
 	      <>
+		{(post.childPosts ?? []).length > 0 && (
+		    <div className="mb-4 bg-green-200 dark:bg-green-800 text-sm p-2 rounded-md">
+		      <p>この投稿には {post.childPosts!.length} 件の子投稿があります．</p>
+		      <PostList posts={[{ ...post, childPosts: [{ } as Post] },
+					...post.childPosts!.map (p => ({
+					    ...p, parentPosts: [{ } as Post] }))]}/>
+		    </div>
+		)}
+		{(post.parentPosts ?? []).map (pp => {
+		  const siblings = post.siblingPosts?.[String (pp.id) as `${ number }`]
+		  if (!(siblings))
+		    return
+
+		  return (
+		      <div
+			  key={pp.id}
+			  className="mb-4 bg-yellow-200 dark:bg-yellow-800 text-sm p-2 rounded-md">
+			<p>
+			  この投稿には 1 件の親投稿{
+			      siblings.length > 1
+			      && `と ${ siblings.length - 1 } 件の姉妹投稿`}があります．
+			</p>
+			<PostList posts={[{ ...pp, childPosts: [{ } as Post] },
+					  ...siblings.map (p => ({
+					      ...p, parentPosts: [{ } as Post] }))]}/>
+		      </div>)
+		})}
+
 		{(post.thumbnail || post.thumbnailBase) && (
 		    <motion.div
 			layoutId={`page-${ id }`}
@@ -146,7 +174,6 @@ export default (({ user }: Props) => {
 					       (prev: any) => newPost ?? prev)
 			      qc.invalidateQueries ({ queryKey: postsKeys.root })
 			      qc.invalidateQueries ({ queryKey: tagsKeys.root })
-			      toast ({ description: '更新しました．' })
 			    }}/>
 		      </Tab>)}
 		</TabGroup>

frontend/src/pages/posts/PostHistoryPage.tsx

@@ -95,6 +95,8 @@ export default (() => {
 		    <col className="w-96"/>
 		    {/* タグ */}
 		    <col className="w-[48rem]"/>
+		    {/* TODO: 親投稿 */}
+		    {/* <col className="w-[48rem]"/> */}
 		    {/* オリジナルの投稿日時 */}
 		    <col className="w-96"/>
 		    {/* 更新日時 */}
@@ -110,6 +112,8 @@ export default (() => {
 		      <th className="p-2 text-left">タイトル</th>
 		      <th className="p-2 text-left">URL</th>
 		      <th className="p-2 text-left">タグ</th>
+		      {/* TODO: 親投稿の履歴 */}
+		      {/* <th className="p-2 text-left">親投稿</th> */}
 		      <th className="p-2 text-left">オリジナルの投稿日時</th>
 		      <th className="p-2 text-left">更新日時</th>
 		      <th className="p-2"/>
@@ -180,6 +184,29 @@ export default (() => {
 					    {tag.name}
 					  </span>))))}
 			    </td>
+			    {/* TODO: 親投稿の履歴 */}
+			    {/* <td className="p-2">
+			      {change.parentPosts.map ((pp, i) => (
+				  pp.type === 'added'
+				  ? (
+				      <ins
+					  key={i}
+					  className="mr-2 text-green-600 dark:text-green-400">
+					{pp.title}
+				      </ins>)
+				  : (
+				      pp.type === 'removed'
+				      ? (
+					  <del
+					      key={i}
+					      className="mr-2 text-red-600 dark:text-red-400">
+					    {pp.title}
+					  </del>)
+				      : (
+					  <span key={i} className="mr-2">
+					    {pp.title}
+					  </span>))))}
+			    </td> */}
 			    <td className="p-2">
 			      {change.versionNo === 1
 			       ? originalCreatedAtString (change.originalCreatedFrom.current,
@@ -225,6 +252,11 @@ export default (() => {
 						  .map (t => t.name)
 						  .filter (t => t.slice (0, 5) !== 'nico:')
 						  .join (' '),
+					    parent_post_ids:
+						(change.parentPosts ?? [])
+						.filter (p => p.type !== 'removed')
+						.map (p => p.id)
+						.join (' '),
 					    original_created_from:
 						change.originalCreatedFrom.current,
 					    original_created_before:

frontend/src/pages/posts/PostNewPage.tsx

@@ -29,6 +29,7 @@ export default (({ user }: Props) => {
 
   const [originalCreatedBefore, setOriginalCreatedBefore] = useState<string | null> (null)
   const [originalCreatedFrom, setOriginalCreatedFrom] = useState<string | null> (null)
+  const [parentPostIds, setParentPostIds] = useState ('')
   const [tags, setTags] = useState ('')
   const [thumbnailAutoFlg, setThumbnailAutoFlg] = useState (true)
   const [thumbnailFile, setThumbnailFile] = useState<File | null> (null)
@@ -46,6 +47,7 @@ export default (({ user }: Props) => {
     formData.append ('title', title)
     formData.append ('url', url)
     formData.append ('tags', tags)
+    formData.append ('parent_post_ids', parentPostIds)
     if (thumbnailFile)
       formData.append ('thumbnail', thumbnailFile)
     if (originalCreatedFrom)
@@ -177,6 +179,16 @@ export default (({ user }: Props) => {
 		     className="mt-2 max-h-48 rounded border"/>)}
 	  </div>
 
+	  {/* 親投稿 */}
+	  <div>
+	    <Label>親投稿</Label>
+	    <input
+		type="text"
+		value={parentPostIds}
+		onChange={e => setParentPostIds (e.target.value)}
+		className="w-full border p-2 rounded"/>
+	  </div>
+
 	  {/* タグ */}
 	  <PostFormTagsArea tags={tags} setTags={setTags}/>
 

frontend/src/types.ts

@@ -1,5 +1,6 @@
 import { CATEGORIES,
 	 FETCH_POSTS_ORDER_FIELDS,
+	 PLATFORMS,
 	 USER_ROLES,
 	 ViewFlagBehavior } from '@/consts'
 
@@ -7,6 +8,8 @@ import type { ReactNode } from 'react'
 
 export type Category = typeof CATEGORIES[number]
 
+export type Deerjikist = { platform: Platform; code: string }
+
 export type FetchPostsOrder = `${ FetchPostsOrderField }:${ 'asc' | 'desc' }`
 
 export type FetchPostsOrderField = typeof FETCH_POSTS_ORDER_FIELDS[number]
@@ -114,6 +117,8 @@ export type NiconicoViewerHandle = {
     showComments: () => void
     hideComments: () => void }
 
+export type Platform = typeof PLATFORMS[number]
+
 export type Post = {
     id:                     number
     url:                    string
@@ -121,6 +126,9 @@ export type Post = {
     thumbnail:              string | null
     thumbnailBase:          string | null
     tags:                   Tag[]
+    parentPosts?:           Post[]
+    childPosts?:            Post[]
+    siblingPosts?:          Record<`${ number }`, Post[]>
     viewed:                 boolean
     related:                Post[]
     originalCreatedFrom:    string | null
@@ -144,7 +152,11 @@ export type PostVersion = {
     url:                    { current: string; prev: string | null }
     thumbnail:              { current: string | null; prev: string | null }
     thumbnailBase:          { current: string | null; prev: string | null }
-    tags:                   { name: string; type: 'context' | 'added' | 'removed' }[]
+    tags:                   { name: string
+			      type: 'context' | 'added' | 'removed' }[]
+    parentPosts:            { id: number
+			      title: string
+			      type: 'context' | 'added' | 'removed' }[]
     originalCreatedFrom:    { current: string | null; prev: string | null }
     originalCreatedBefore:  { current: string | null; prev: string | null }
     createdAt:              string
@@ -171,7 +183,8 @@ export type Tag = {
     createdAt:      string
     updatedAt:      string
     hasWiki:        boolean
-    materialId:     number
+    materialId:     number | null
+    hasDeerjikists: boolean
     children?:      Tag[]
     matchedAlias?:  string | null }