#171

#327

#327

#327

#327

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

#327

Co-authored-by: miteruzo <miteruzo@naver.com>
Reviewed-on: #342

backend/app/controllers/application_controller.rb

@@ -1,14 +1,16 @@
 class ApplicationController < ActionController::API
+  before_action :reject_banned_ip_address!
   before_action :authenticate_user
+  before_action :reject_banned_user!
 
-  def current_user
-    @current_user
-  end
+  def current_user = @current_user
 
   private
 
   def authenticate_user
     code = request.headers['X-Transfer-Code'] || request.headers['HTTP_X_TRANSFER_CODE']
+    return if code.blank?
+
     @current_user = User.find_by(inheritance_code: code)
   end
 
@@ -22,4 +24,17 @@ class ApplicationController < ActionController::API
       s.in?(['', '1', 'true', 'on', 'yes'])
     end
   end
+
+  def reject_banned_ip_address!
+    ip_address = IpAddress.find_by(ip_address: IPAddr.new(request.remote_ip).hton)
+    return unless ip_address&.banned?
+
+    head :forbidden
+  end
+
+  def reject_banned_user!
+    return unless current_user&.banned?
+
+    head :forbidden
+  end
 end

backend/app/controllers/nico_tags_controller.rb

@@ -33,7 +33,7 @@ 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,
+    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? }
 

backend/app/controllers/posts_controller.rb

@@ -44,7 +44,7 @@ class PostsController < ApplicationController
         filtered_posts
         .joins("LEFT JOIN (#{ pt_max_sql }) pt_max ON pt_max.post_id = posts.id")
         .reselect('posts.*', Arel.sql("#{ updated_at_all_sql } AS updated_at_all"))
-        .preload(tags: [:materials, { tag_name: :wiki_page }])
+        .preload(tags: [:deerjikists, :materials, { tag_name: :wiki_page }])
         .with_attached_thumbnail
 
     q = q.where('posts.url LIKE ?', "%#{ url }%") if url
@@ -95,7 +95,7 @@ class PostsController < ApplicationController
   end
 
   def random
-    post = filtered_posts.preload(tags: [:materials, { tag_name: :wiki_page }])
+    post = filtered_posts.preload(tags: [:deerjikists, :materials, { tag_name: :wiki_page }])
                          .order('RAND()')
                          .first
     return head :not_found unless post
@@ -104,12 +104,12 @@ class PostsController < ApplicationController
   end
 
   def show
-    post = Post.includes(tags: [:materials, { tag_name: :wiki_page }]).find_by(id: params[:id])
+    post = Post.includes(tags: [:deerjikists, :materials, { tag_name: :wiki_page }]).find_by(id: params[:id])
     return head :not_found unless post
 
     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
@@ -165,35 +173,76 @@ class PostsController < ApplicationController
     return head :unauthorized unless current_user
     return head :forbidden unless current_user.gte_member?
 
+    force = bool?(:force)
+    merge = bool?(:merge)
+    return head :bad_request if force && merge
+
+    base_version_no = parse_base_version_no
+    return head :bad_request if !(force) && !(base_version_no)
+
     title = params[:title].presence
     tag_names = params[:tags].to_s.split
     original_created_from = params[:original_created_from]
     original_created_before = params[:original_created_before]
+    parent_post_ids = parse_parent_post_ids
 
-    post = Post.find(params[:id].to_i)
+    post = nil
+    conflict_json = nil
 
     ApplicationRecord.transaction do
-      PostVersionRecorder.ensure_snapshot!(post, created_by_user: current_user)
+      post = Post.lock.find(params[:id].to_i)
 
-      post.update!(title:, original_created_from:, original_created_before:)
+      base_version = nil
+      base_snapshot = nil
+      current_snapshot = nil
+      unless force
+        base_version = post.post_versions.find_by!(version_no: base_version_no)
 
-      normalised_tags = Tag.normalise_tags(tag_names, with_tagme: false)
-      TagVersioning.record_tag_snapshots!(normalised_tags, created_by_user: current_user)
+        base_snapshot = post_snapshot_from_version(base_version)
+        current_snapshot = post_snapshot_from_record(post)
+      end
+      incoming_snapshot = post_incoming_snapshot(title:,
+                                                 original_created_from:,
+                                                 original_created_before:,
+                                                 tag_names:,
+                                                 parent_post_ids:)
 
-      tags = post.tags.nico.to_a + normalised_tags
-      tags = Tag.expand_parent_tags(tags)
-      sync_post_tags!(post, tags)
-      PostVersionRecorder.record!(post:, event_type: :update, created_by_user: current_user)
+      snapshot_to_apply =
+          if force || post.version_no == base_version_no || current_snapshot == base_snapshot
+            incoming_snapshot
+          else
+            changes = post_snapshot_changes(base_snapshot, current_snapshot, incoming_snapshot)
+            conflicts = changes.select { |change| change[:conflict] }
+
+            if merge && conflicts.empty?
+              merge_post_snapshots(base_snapshot, current_snapshot, incoming_snapshot)
+            else
+              conflict_json = post_conflict_json(post:,
+                                                 base_version_no:,
+                                                 base_snapshot:,
+                                                 current_snapshot:,
+                                                 incoming_snapshot:,
+                                                 changes:,
+                                                 conflicts:)
+              raise ActiveRecord::Rollback
+            end
           end
 
+      apply_post_snapshot!(post, snapshot_to_apply)
+    end
+
+    return render json: conflict_json, status: :conflict if conflict_json
+
     post.reload
-    json = post.as_json
+    json = PostRepr.base(post, current_user)
     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
@@ -211,7 +260,7 @@ class PostsController < ApplicationController
     pts = pts.where(post_id: id) if id.present?
     pts = pts.where(tag_id:) if tag_id.present?
     pts = pts.includes(:post, :created_user, :deleted_user,
-                       tag: [:materials, { tag_name: :wiki_page }])
+                       tag: [:deerjikists, :materials, { tag_name: :wiki_page }])
 
     events = []
     pts.each do |pt|
@@ -353,4 +402,242 @@ 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
+
+  def parse_base_version_no
+    version_no = Integer(params[:base_version_no], exception: false)
+    if version_no&.positive?
+      version_no
+    else
+      nil
+    end
+  end
+
+  def post_snapshot_from_version version
+    { title: version.title,
+      original_created_from: snapshot_time(version.original_created_from),
+      original_created_before: snapshot_time(version.original_created_before),
+      tag_names: editable_tag_names_from_version(version),
+      parent_post_ids: snapshot_parent_post_ids_from_version(version) }
+  end
+
+  def editable_tag_names_from_version version
+    version.tags.to_s.split.reject { |name| name.downcase.start_with?('nico:') }.sort
+  end
+
+  def post_snapshot_from_record post
+    { title: post.title,
+      original_created_from: snapshot_time(post.original_created_from),
+      original_created_before: snapshot_time(post.original_created_before),
+      tag_names: editable_tag_names_from_post(post),
+      parent_post_ids: post.parent_posts.order(:id).pluck(:id) }
+  end
+
+  def editable_tag_names_from_post post
+    post.tags.not_nico.joins(:tag_name).order('tag_names.name').pluck('tag_names.name')
+  end
+
+  def post_incoming_snapshot title:, original_created_from:, original_created_before:,
+                             tag_names:, parent_post_ids:
+    { title:,
+      original_created_from: snapshot_time(original_created_from),
+      original_created_before: snapshot_time(original_created_before),
+      tag_names: incoming_tag_names_for_snapshot(tag_names),
+      parent_post_ids: parent_post_ids.sort }
+  end
+
+  def snapshot_parent_post_ids_from_version version
+    if version.respond_to?(:parent_post_ids)
+      version.parent_post_ids.to_s.split.map { |id| id.to_i }.sort
+    elsif version.respond_to?(:parent_id) && version.parent_id
+      [version.parent_id]
+    else
+      []
+    end
+  end
+
+  def snapshot_time value
+    return nil if value.blank?
+
+    value = Time.zone.parse(value.to_s) if value in String
+    value&.in_time_zone&.iso8601(6)
+  rescue ArgumentError, TypeError
+    value.to_s
+  end
+
+  def incoming_tag_names_for_snapshot raw_tag_names
+    tags = Tag.normalise_tags!(raw_tag_names, with_tagme: false)
+
+    Tag.expand_parent_tags(tags).map(&:name).uniq.sort
+  end
+
+  def post_conflict_json post:, base_version_no:, base_snapshot:,
+                         current_snapshot:, incoming_snapshot:, changes:, conflicts:
+    { error: 'conflict',
+      message: '競合が発生しました．',
+      post_id: post.id,
+      base_version_no:,
+      current_version_no: post.version_no,
+      base: base_snapshot,
+      current: current_snapshot,
+      mine: incoming_snapshot,
+      changes:,
+      conflicts:,
+      mergeable: conflicts.empty? }
+  end
+
+  def post_snapshot_changes base_snapshot, current_snapshot, incoming_snapshot
+    [scalar_snapshot_change(:title, 'タイトル',
+                            base_snapshot, current_snapshot, incoming_snapshot),
+     scalar_snapshot_change(:original_created_from, 'オリジナルの作成日時（以降）',
+                            base_snapshot, current_snapshot, incoming_snapshot),
+     scalar_snapshot_change(:original_created_before, 'オリジナルの作成日時（より前）',
+                            base_snapshot, current_snapshot, incoming_snapshot),
+     set_snapshot_change(:tag_names, 'タグ',
+                         base_snapshot, current_snapshot, incoming_snapshot),
+     set_snapshot_change(:parent_post_ids, '親投稿',
+                         base_snapshot, current_snapshot, incoming_snapshot)].compact
+  end
+
+  def scalar_snapshot_change field, label, base_snapshot, current_snapshot, incoming_snapshot
+    base = base_snapshot[field]
+    current = current_snapshot[field]
+    mine = incoming_snapshot[field]
+
+    return nil if current == base && mine == base
+
+    { field:, label:, base:, current:, mine:,
+      changed_by_current: current != base,
+      changed_by_me: mine != base,
+      conflict: scalar_snapshot_conflict?(base, current, mine) }
+  end
+
+  def scalar_snapshot_conflict? base, current, mine
+    current != base && mine != base && current != mine
+  end
+
+  def set_snapshot_change field, label, base_snapshot, current_snapshot, incoming_snapshot
+    base = base_snapshot[field].to_a
+    current = current_snapshot[field].to_a
+    mine = incoming_snapshot[field].to_a
+
+    added_by_current = current - base
+    removed_by_current = base - current
+    added_by_me = mine - base
+    removed_by_me = base - mine
+
+    if (added_by_current.empty? &&
+        removed_by_current.empty? &&
+        added_by_me.empty? &&
+        removed_by_me.empty?)
+      return nil
+    end
+
+    { field:, label:, base:, current:, mine:, added_by_current:, removed_by_current:,
+      added_by_me:, removed_by_me:,
+      changed_by_current: added_by_current.present? || removed_by_current.present?,
+      changed_by_me: added_by_me.present? || removed_by_me.present?,
+      conflict: set_snapshot_conflict?(added_by_current:,
+                                       removed_by_current:,
+                                       added_by_me:,
+                                       removed_by_me:) }
+  end
+
+  def set_snapshot_conflict? added_by_current:, removed_by_current:,
+                             added_by_me:, removed_by_me:
+    (added_by_current & removed_by_me).present? || (removed_by_current & added_by_me).present?
+  end
+
+  def apply_post_snapshot! post, snapshot
+    PostVersionRecorder.ensure_snapshot!(post, created_by_user: current_user)
+
+    post.update!(title: snapshot[:title],
+                 original_created_from: snapshot[:original_created_from],
+                 original_created_before: snapshot[:original_created_before])
+
+    editable_tags = Tag.normalise_tags!(snapshot[:tag_names], with_tagme: false)
+    TagVersioning.record_tag_snapshots!(editable_tags, created_by_user: current_user)
+
+    readonly_tags = post.tags.nico.to_a
+
+    tags = readonly_tags + editable_tags
+    tags = Tag.expand_parent_tags(tags)
+
+    sync_post_tags!(post, tags)
+    sync_parent_posts!(post, snapshot[:parent_post_ids])
+
+    PostVersionRecorder.record!(post:, event_type: :update, created_by_user: current_user)
+  end
+
+  def merge_post_snapshots base_snapshot, current_snapshot, incoming_snapshot
+    [:title, :original_created_from, :original_created_before].map {
+      [_1, merge_scalar_snapshot_value(base_snapshot[_1],
+                                       current_snapshot[_1],
+                                       incoming_snapshot[_1])]
+    }.to_h.merge([:tag_names, :parent_post_ids].map {
+      [_1, merge_set_snapshot_value(base_snapshot[_1],
+                                    current_snapshot[_1],
+                                    incoming_snapshot[_1])]
+    }.to_h)
+  end
+
+  def merge_scalar_snapshot_value base, current, mine
+    return mine if current == base
+    return current if mine == base || current == mine
+
+    raise ArgumentError, '競合してゐる項目はマージできません．'
+  end
+
+  def merge_set_snapshot_value base, current, mine
+    base = base.to_a
+    current = current.to_a
+    mine = mine.to_a
+
+    added_by_current = current - base
+    removed_by_current = base - current
+    added_by_me = mine - base
+    removed_by_me = base - mine
+
+    merged = base + added_by_current + added_by_me
+    merged -= removed_by_current
+    merged -= removed_by_me
+
+    merged.uniq.sort
+  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
@@ -374,7 +403,7 @@ class TagsController < ApplicationController
   end
 
   def update_parent_tags! tag, parent_names
-    parent_tags = Tag.normalise_tags(parent_names, with_tagme: false,
+    parent_tags = Tag.normalise_tags!(parent_names, with_tagme: false,
                                                     with_no_deerjikist: false,
                                                     deny_nico: true)
 
@@ -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/controllers/users_controller.rb

@@ -1,9 +1,6 @@
 class UsersController < ApplicationController
   def create
-    return head :unprocessable_entity if request.remote_ip.blank?
-
     user = nil
-
     User.transaction do
       user = User.create!(inheritance_code: SecureRandom.uuid, role: :guest)
       attach_ip_address!(user)
@@ -17,8 +14,7 @@ class UsersController < ApplicationController
   def verify
     user = User.find_by(inheritance_code: params[:code])
     return render json: { valid: false } unless user
-
-    return head :unprocessable_entity if request.remote_ip.blank?
+    return head :forbidden if user.banned?
 
     attach_ip_address!(user)
 

backend/app/models/ip_address.rb

@@ -1,7 +1,10 @@
 class IpAddress < ApplicationRecord
   validates :ip_address, presence: true, length: { maximum: 16 }
-  validates :banned, inclusion: { in: [true, false] }
 
   has_many :user_ips, dependent: :destroy
   has_many :users, through: :user_ips
+
+  def banned? = banned_at.present?
+  def ban! = banned? || update!(banned_at: Time.current)
+  def unban! = update!(banned_at: nil)
 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
@@ -13,8 +12,24 @@ 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
 
+  attribute :version_no, :integer, default: 1
+
   before_validation :normalise_url
 
   validates :url, presence: true, uniqueness: true
@@ -22,17 +37,29 @@ 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? ?
+    super(options).merge(thumbnail: thumbnail.attached? ?
                                     Rails.application.routes.url_helpers.rails_blob_url(
                                         thumbnail, only_path: false) :
-                                      nil })
+                                    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

@@ -40,6 +40,8 @@ class Tag < ApplicationRecord
   belongs_to :tag_name
   delegate :wiki_page, to: :tag_name
 
+  attribute :version_no, :integer, default: 1
+
   delegate :name, to: :tag_name, allow_nil: true
   validates :tag_name, presence: true
 
@@ -79,6 +81,8 @@ 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)
@@ -86,7 +90,7 @@ class Tag < ApplicationRecord
   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,
+  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:') }

backend/app/models/user.rb

@@ -4,7 +4,6 @@ class User < ApplicationRecord
   validates :name, length: { maximum: 255 }
   validates :inheritance_code, presence: true, length: { maximum: 64 }
   validates :role, presence: true, inclusion: { in: roles.keys }
-  validates :banned, inclusion: { in: [true, false] }
 
   has_many :created_posts,
            class_name: 'Post', foreign_key: :uploaded_user_id, dependent: :nullify
@@ -19,5 +18,10 @@ class User < ApplicationRecord
            class_name: 'WikiPage', foreign_key: :updated_user_id, dependent: :nullify
 
   def viewed?(post) = user_post_views.exists?(post_id: post.id)
+
   def gte_member? = member? || admin?
+
+  def banned? = banned_at.present?
+  def ban! = banned? || update!(banned_at: Time.current)
+  def unban! = update!(banned_at: nil)
 end

backend/app/models/wiki_page.rb

@@ -15,6 +15,8 @@ class WikiPage < ApplicationRecord
 
   has_many :wiki_versions
 
+  attribute :version_no, :integer, default: 1
+
   belongs_to :tag_name
   validates :tag_name, presence: true
   validates :body, presence: true

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/version_recorder.rb

@@ -16,19 +16,20 @@ class VersionRecorder
       @record = record_class.unscoped.lock.find(@record.id)
       latest = latest_version
 
-      if !(latest) && @event_type != 'create'
-        raise "#{ version_class.name } first event must be create"
-      end
-
-      if @event_type == 'create' && latest
-        raise "#{ version_class.name } create event already exists"
-      end
+      validate_version_sequence!(latest)
 
       attrs = snapshot_attributes
 
-      return latest if @event_type == 'update' && latest && same_snapshot?(latest, attrs)
+      if @event_type == 'update' && latest && same_snapshot?(latest, attrs)
+        return latest
+      end
 
-      version_class.create!(base_attributes(latest).merge(record_key => @record).merge(attrs))
+      version = version_class.create!(
+          base_attributes(latest).merge(record_key => @record).merge(attrs))
+
+      update_record_version_no!(version.version_no)
+
+      version
     end
   end
 
@@ -45,7 +46,31 @@ class VersionRecorder
       created_by_user: @created_by_user }
   end
 
-  def same_snapshot?(version, attrs) = attrs.all? { |k, v| version.public_send(k) == v }
+  def update_record_version_no! version_no
+    @record.update_columns(version_no:)
+    @record.version_no = version_no
+  end
+
+  def validate_version_sequence! latest
+    if !(latest) && @event_type != 'create'
+      raise "#{ version_class.name } first event must be create"
+    end
+
+    if @event_type == 'create' && latest
+      raise "#{ version_class.name } create event already exists"
+    end
+
+    return unless latest
+
+    if @record.version_no != latest.version_no
+      raise ("#{ record_class.name }##{ @record.id } version_no is #{ @record.version_no }, " +
+             "but latest #{ version_class.name } version_no is #{ latest.version_no }")
+    end
+  end
+
+  def same_snapshot? version, attrs
+    attrs.all? { |k, v| version.public_send(k) == v }
+  end
 
   def validate_event_type!
     return if EVENT_TYPES.include?(@event_type)

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/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/db/migrate/20260501153900_rename_banned_to_banned_at_in_users_and_ip_addresses.rb

@@ -0,0 +1,16 @@
+class RenameBannedToBannedAtInUsersAndIpAddresses < ActiveRecord::Migration[8.0]
+  def up
+    [:users, :ip_addresses].each do
+      add_column _1, :banned_at, :datetime, after: :banned
+      add_index _1, :banned_at
+      remove_column _1, :banned
+    end
+  end
+
+  def down
+    [:ip_addresses, :users].each do
+      add_column _1, :banned, :boolean, null: false, default: false, after: :banned_at
+      remove_column _1, :banned_at
+    end
+  end
+end

backend/db/migrate/20260507124000_add_version_no_to_posts.rb

@@ -0,0 +1,27 @@
+class AddVersionNoToPosts < ActiveRecord::Migration[8.0]
+  def up
+    add_column :posts, :version_no, :integer
+
+    execute <<~SQL
+      UPDATE
+        posts
+      SET
+        version_no = (
+          SELECT
+            MAX(version_no)
+          FROM
+            post_versions
+          WHERE
+            post_id = posts.id)
+    SQL
+
+    change_column_null :posts, :version_no, false
+
+    add_check_constraint :posts, 'version_no > 0', name: 'chk_posts_version_no_positive'
+  end
+
+  def down
+    remove_check_constraint :posts, name: 'chk_posts_version_no_positive'
+    remove_column :posts, :version_no
+  end
+end

backend/db/migrate/20260507211600_add_version_no_to_tags.rb

@@ -0,0 +1,37 @@
+class AddVersionNoToTags < ActiveRecord::Migration[8.0]
+  def up
+    add_column :tags, :version_no, :integer
+
+    execute <<~SQL
+      UPDATE
+        tags
+      SET
+        version_no = (
+          CASE category
+          WHEN 'nico' THEN
+            (SELECT
+               MAX(version_no)
+             FROM
+               nico_tag_versions
+             WHERE
+               tag_id = tags.id)
+          ELSE
+            (SELECT
+               MAX(version_no)
+             FROM
+               tag_versions
+             WHERE
+               tag_id = tags.id)
+          END)
+    SQL
+
+    change_column_null :tags, :version_no, false
+
+    add_check_constraint :tags, 'version_no > 0', name: 'chk_tags_version_no_positive'
+  end
+
+  def down
+    remove_check_constraint :tags, name: 'chk_tags_version_no_positive'
+    remove_column :tags, :version_no
+  end
+end

backend/db/migrate/20260507213300_add_version_no_to_wiki_pages.rb

@@ -0,0 +1,27 @@
+class AddVersionNoToWikiPages < ActiveRecord::Migration[8.0]
+  def up
+    add_column :wiki_pages, :version_no, :integer
+
+    execute <<~SQL
+      UPDATE
+        wiki_pages
+      SET
+        version_no = (
+          SELECT
+            MAX(version_no)
+          FROM
+            wiki_versions
+          WHERE
+            wiki_page_id = wiki_pages.id)
+    SQL
+
+    change_column_null :wiki_pages, :version_no, false
+
+    add_check_constraint :wiki_pages, 'version_no > 0', name: 'chk_wiki_pages_version_no_positive'
+  end
+
+  def down
+    remove_check_constraint :wiki_pages, name: 'chk_wiki_pages_version_no_positive'
+    remove_column :wiki_pages, :version_no
+  end
+end

backend/db/schema.rb

@@ -10,7 +10,7 @@
 #
 # It's strongly recommended that you check this file into your version control system.
 
-ActiveRecord::Schema[8.0].define(version: 2026_04_26_120600) do
+ActiveRecord::Schema[8.0].define(version: 2026_05_07_213300) do
   create_table "active_storage_attachments", charset: "utf8mb4", collation: "utf8mb4_0900_ai_ci", force: :cascade do |t|
     t.string "name", null: false
     t.string "record_type", null: false
@@ -50,9 +50,10 @@ ActiveRecord::Schema[8.0].define(version: 2026_04_26_120600) do
 
   create_table "ip_addresses", charset: "utf8mb4", collation: "utf8mb4_0900_ai_ci", force: :cascade do |t|
     t.binary "ip_address", limit: 16, null: false
-    t.boolean "banned", default: false, null: false
+    t.datetime "banned_at"
     t.datetime "created_at", null: false
     t.datetime "updated_at", null: false
+    t.index ["banned_at"], name: "index_ip_addresses_on_banned_at"
     t.index ["ip_address"], name: "index_ip_addresses_on_ip_address", unique: true
   end
 
@@ -119,6 +120,15 @@ ActiveRecord::Schema[8.0].define(version: 2026_04_26_120600) do
     t.check_constraint "`version_no` > 0", name: "nico_tag_versions_version_no_positive"
   end
 
+  create_table "post_implications", primary_key: ["post_id", "parent_post_id"], charset: "utf8mb4", collation: "utf8mb4_0900_ai_ci", force: :cascade do |t|
+    t.bigint "post_id", null: false
+    t.bigint "parent_post_id", null: false
+    t.datetime "created_at", null: false
+    t.datetime "updated_at", null: false
+    t.index ["parent_post_id"], name: "index_post_implications_on_parent_post_id"
+    t.check_constraint "`post_id` <> `parent_post_id`", name: "chk_post_implications_no_self"
+  end
+
   create_table "post_similarities", primary_key: ["post_id", "target_post_id"], charset: "utf8mb4", collation: "utf8mb4_0900_ai_ci", force: :cascade do |t|
     t.bigint "post_id", null: false
     t.bigint "target_post_id", null: false
@@ -155,13 +165,12 @@ ActiveRecord::Schema[8.0].define(version: 2026_04_26_120600) do
     t.string "url", limit: 768, null: false
     t.string "thumbnail_base", limit: 2000
     t.text "tags", null: false
-    t.bigint "parent_id"
+    t.text "parent_post_ids", null: false
     t.datetime "original_created_from"
     t.datetime "original_created_before"
     t.datetime "created_at", null: false
     t.bigint "created_by_user_id"
     t.index ["created_by_user_id"], name: "index_post_versions_on_created_by_user_id"
-    t.index ["parent_id"], name: "index_post_versions_on_parent_id"
     t.index ["post_id", "version_no"], name: "index_post_versions_on_post_id_and_version_no", unique: true
     t.index ["post_id"], name: "index_post_versions_on_post_id"
     t.check_constraint "`event_type` in (_utf8mb4'create',_utf8mb4'update',_utf8mb4'discard',_utf8mb4'restore')", name: "post_versions_event_type_valid"
@@ -172,15 +181,15 @@ ActiveRecord::Schema[8.0].define(version: 2026_04_26_120600) do
     t.string "title"
     t.string "url", limit: 768, null: false
     t.string "thumbnail_base", limit: 2000
-    t.bigint "parent_id"
     t.bigint "uploaded_user_id"
     t.datetime "created_at", null: false
     t.datetime "original_created_from"
     t.datetime "original_created_before"
     t.datetime "updated_at", null: false
-    t.index ["parent_id"], name: "index_posts_on_parent_id"
+    t.integer "version_no", null: false
     t.index ["uploaded_user_id"], name: "index_posts_on_uploaded_user_id"
     t.index ["url"], name: "index_posts_on_url", unique: true
+    t.check_constraint "`version_no` > 0", name: "chk_posts_version_no_positive"
   end
 
   create_table "settings", charset: "utf8mb4", collation: "utf8mb4_0900_ai_ci", force: :cascade do |t|
@@ -255,8 +264,10 @@ ActiveRecord::Schema[8.0].define(version: 2026_04_26_120600) do
     t.datetime "updated_at", null: false
     t.integer "post_count", default: 0, null: false
     t.datetime "discarded_at"
+    t.integer "version_no", null: false
     t.index ["discarded_at"], name: "index_tags_on_discarded_at"
     t.index ["tag_name_id"], name: "index_tags_on_tag_name_id", unique: true
+    t.check_constraint "`version_no` > 0", name: "chk_tags_version_no_positive"
   end
 
   create_table "theatre_comments", primary_key: ["theatre_id", "no"], charset: "utf8mb4", collation: "utf8mb4_0900_ai_ci", force: :cascade do |t|
@@ -326,9 +337,10 @@ ActiveRecord::Schema[8.0].define(version: 2026_04_26_120600) do
     t.string "name"
     t.string "inheritance_code", limit: 64, null: false
     t.string "role", null: false
-    t.boolean "banned", default: false, null: false
+    t.datetime "banned_at"
     t.datetime "created_at", null: false
     t.datetime "updated_at", null: false
+    t.index ["banned_at"], name: "index_users_on_banned_at"
   end
 
   create_table "wiki_assets", charset: "utf8mb4", collation: "utf8mb4_0900_ai_ci", force: :cascade do |t|
@@ -361,10 +373,12 @@ ActiveRecord::Schema[8.0].define(version: 2026_04_26_120600) do
     t.datetime "updated_at", null: false
     t.datetime "discarded_at"
     t.integer "next_asset_no", default: 1, null: false
+    t.integer "version_no", null: false
     t.index ["created_user_id"], name: "index_wiki_pages_on_created_user_id"
     t.index ["discarded_at"], name: "index_wiki_pages_on_discarded_at"
     t.index ["tag_name_id"], name: "index_wiki_pages_on_tag_name_id", unique: true
     t.index ["updated_user_id"], name: "index_wiki_pages_on_updated_user_id"
+    t.check_constraint "`version_no` > 0", name: "chk_wiki_pages_version_no_positive"
   end
 
   create_table "wiki_revision_lines", charset: "utf8mb4", collation: "utf8mb4_0900_ai_ci", force: :cascade do |t|
@@ -428,6 +442,8 @@ ActiveRecord::Schema[8.0].define(version: 2026_04_26_120600) do
   add_foreign_key "nico_tag_relations", "tags", column: "nico_tag_id"
   add_foreign_key "nico_tag_versions", "tags"
   add_foreign_key "nico_tag_versions", "users", column: "created_by_user_id"
+  add_foreign_key "post_implications", "posts"
+  add_foreign_key "post_implications", "posts", column: "parent_post_id"
   add_foreign_key "post_similarities", "posts"
   add_foreign_key "post_similarities", "posts", column: "target_post_id"
   add_foreign_key "post_tags", "posts"
@@ -435,9 +451,7 @@ ActiveRecord::Schema[8.0].define(version: 2026_04_26_120600) do
   add_foreign_key "post_tags", "users", column: "created_user_id"
   add_foreign_key "post_tags", "users", column: "deleted_user_id"
   add_foreign_key "post_versions", "posts"
-  add_foreign_key "post_versions", "posts", column: "parent_id"
   add_foreign_key "post_versions", "users", column: "created_by_user_id"
-  add_foreign_key "posts", "posts", column: "parent_id"
   add_foreign_key "posts", "users", column: "uploaded_user_id"
   add_foreign_key "settings", "users"
   add_foreign_key "tag_implications", "tags"

backend/spec/factories/ip_addresses.rb

@@ -0,0 +1,10 @@
+FactoryBot.define do
+  factory :ip_address do
+    ip_address { IPAddr.new('203.0.113.10').hton }
+    banned_at { nil }
+
+    trait :banned do
+      banned_at { Time.current }
+    end
+  end
+end

backend/spec/factories/users.rb

@@ -1,15 +1,24 @@
 FactoryBot.define do
   factory :user do
-    name { "test-user" }
+    name { nil }
     inheritance_code { SecureRandom.uuid }
-    role { "guest" }
+    role { 'guest' }
+    banned_at { nil }
+
+    trait :guest do
+      role { 'guest' }
+    end
 
     trait :member do
-      role { "member" }
+      role { 'member' }
     end
 
     trait :admin do
       role { 'admin' }
     end
+
+    trait :banned do
+      banned_at { Time.current }
+    end
   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

@@ -10,11 +10,53 @@ RSpec.describe 'Posts API', type: :request do
     allow_any_instance_of(Post).to receive(:resized_thumbnail!).and_return(true)
   end
 
+  def create_nico_tag!(name)
+    Tag.find_or_create_by_tag_name!(name, category: :nico)
+  end
+
   def dummy_upload
     # 中身は何でもいい（加工処理はスタブしてる）
     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)
+    version =
+        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)
+
+    post.update_columns(version_no: version.version_no) if post.has_attribute?(:version_no)
+    post.version_no = version.version_no if post.respond_to?(:version_no=)
+
+    version
+  end
+
+  def post_update_params(post, params = { })
+    base_version =
+        post.post_versions.order(version_no: :desc).first ||
+        create_post_version_for!(post.reload)
+
+    post_write_params({ base_version_no: base_version.version_no }.merge(params))
+  end
+
   let!(:tag_name) { TagName.create!(name: 'spec_tag') }
   let!(:tag)      { Tag.create!(tag_name: tag_name, category: :general) }
 
@@ -457,6 +499,65 @@ 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 +576,28 @@ 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 +611,12 @@ 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 +637,14 @@ RSpec.describe 'Posts API', type: :request do
       it 'return 400' do
         sign_in_as(member)
 
-        post '/posts', params: {
+        post '/posts', params: post_write_params(
           title: 'new post',
-            url: 'https://example.com/nico_tag',
+          url: 'https://example.com/nico-tag-post',
           tags: 'nico:nico_tag',
-            thumbnail: dummy_upload }
+          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 +652,11 @@ 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
@@ -561,16 +666,156 @@ 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: 'ぼざクリタグ広場',
             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
     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
 
   describe 'PUT /posts/:id' do
@@ -578,33 +823,33 @@ 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_update_params(
+          post_record, 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_update_params(
+          post_record, title: 'updated', tags: 'spec_tag')
       expect(response).to have_http_status(:forbidden)
     end
 
     it '200 and updates title + resync tags when member' do
       sign_in_as(member)
 
-      # 追加で別タグも作って、更新時に入れ替わることを見る
       tn2 = TagName.create!(name: 'spec_tag_2')
       Tag.create!(tag_name: tn2, category: :general)
 
-      put "/posts/#{post_record.id}", params: {
+      put "/posts/#{post_record.id}", params: post_update_params(
+          post_record,
           title: 'updated title',
-        tags: 'spec_tag_2'
-      }
+          tags: 'spec_tag_2')
 
       expect(response).to have_http_status(:ok)
       expect(json).to have_key('tags')
       expect(json['tags']).to be_an(Array)
 
-      # show と同様、update 後レスポンスもツリー形式
       names = json['tags'].map { |n| n['name'] }
       expect(names).to include('spec_tag_2')
     end
@@ -619,12 +864,402 @@ 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_update_params(
+            post_record,
             title: 'updated title',
-            tags: 'nico:nico_tag' }
+            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_update_params(
+            post_record,
+            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_update_params(
+          post_record,
+          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_update_params(
+          post_record,
+          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)
+
+        base_version = create_post_version_for!(post_record.reload)
+
+        put "/posts/#{post_record.id}", params: {
+            base_version_no: base_version.version_no,
+            title: 'updated title',
+            tags: 'spec_tag' }
+
+        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_update_params(
+          post_record,
+          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_update_params(
+          post_record,
+          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_update_params(
+          post_record,
+          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
+
+    context 'with optimistic locking' do
+      let!(:no_deerjikist_tag) { Tag.no_deerjikist }
+
+      before do
+        PostTag.create!(post: post_record, tag: no_deerjikist_tag)
+      end
+
+      it '400 when base_version_no is missing without force' do
+        sign_in_as(member)
+
+        put "/posts/#{post_record.id}", params: post_write_params(
+            title: 'updated title',
+            tags: 'spec_tag')
 
         expect(response).to have_http_status(:bad_request)
       end
+
+      it '400 when force and merge are both true' do
+        sign_in_as(member)
+
+        put "/posts/#{post_record.id}", params: post_write_params(
+            title: 'updated title',
+            tags: 'spec_tag',
+            force: '1',
+            merge: '1')
+
+        expect(response).to have_http_status(:bad_request)
+      end
+
+      it '409 when scalar fields are changed both by current and incoming updates' do
+        sign_in_as(member)
+
+        base_version = create_post_version_for!(post_record.reload)
+
+        post_record.update!(title: 'updated by other user')
+        PostVersionRecorder.record!(
+            post: post_record.reload,
+            event_type: :update,
+            created_by_user: member)
+
+        put "/posts/#{post_record.id}", params: post_write_params(
+            base_version_no: base_version.version_no,
+            title: 'updated by me',
+            tags: "spec_tag #{Tag.no_deerjikist.name}")
+
+        expect(response).to have_http_status(:conflict)
+
+        expect(json.fetch('error')).to eq('conflict')
+        expect(json.fetch('base_version_no')).to eq(base_version.version_no)
+        expect(json.fetch('current_version_no')).to eq(2)
+        expect(json.fetch('mergeable')).to be(false)
+
+        conflict_fields = json.fetch('conflicts').map { |change| change.fetch('field') }
+        expect(conflict_fields).to include('title')
+
+        expect(post_record.reload.title).to eq('updated by other user')
+      end
+
+      it 'returns 409 with mergeable true when stale tag changes do not conflict but merge is not requested' do
+        sign_in_as(member)
+
+        base_version = create_post_version_for!(post_record.reload)
+
+        current_tag = Tag.find_or_create_by_tag_name!('current_added_tag', category: :general)
+        PostTag.create!(post: post_record, tag: current_tag, created_user: member)
+
+        PostVersionRecorder.record!(
+            post: post_record.reload,
+            event_type: :update,
+            created_by_user: member)
+
+        put "/posts/#{post_record.id}", params: post_write_params(
+            base_version_no: base_version.version_no,
+            title: post_record.title,
+            tags: "spec_tag #{Tag.no_deerjikist.name} incoming_added_tag")
+
+        expect(response).to have_http_status(:conflict)
+
+        expect(json.fetch('mergeable')).to be(true)
+
+        tag_change = json.fetch('changes').find { |change| change.fetch('field') == 'tag_names' }
+        expect(tag_change).to be_present
+        expect(tag_change.fetch('conflict')).to be(false)
+        expect(tag_change.fetch('added_by_current')).to include('current_added_tag')
+        expect(tag_change.fetch('added_by_me')).to include('incoming_added_tag')
+      end
+
+      it 'merges non-conflicting stale tag changes when merge is true' do
+        sign_in_as(member)
+
+        base_version = create_post_version_for!(post_record.reload)
+
+        current_tag = Tag.find_or_create_by_tag_name!('current_merge_tag', category: :general)
+        PostTag.create!(post: post_record, tag: current_tag, created_user: member)
+
+        PostVersionRecorder.record!(
+            post: post_record.reload,
+            event_type: :update,
+            created_by_user: member)
+
+        put "/posts/#{post_record.id}", params: post_write_params(
+            base_version_no: base_version.version_no,
+            title: post_record.title,
+            tags: "spec_tag #{Tag.no_deerjikist.name} incoming_merge_tag",
+            merge: '1')
+
+        expect(response).to have_http_status(:ok)
+
+        names = post_record.reload.tags.map(&:name)
+
+        expect(names).to include('spec_tag')
+        expect(names).to include(Tag.no_deerjikist.name)
+        expect(names).to include('current_merge_tag')
+        expect(names).to include('incoming_merge_tag')
+      end
+
+      it 'does not conflict when only nico tags changed after the base version' do
+        sign_in_as(member)
+
+        base_version = create_post_version_for!(post_record.reload)
+
+        nico_tag = create_nico_tag!('nico:optimistic_lock_nico')
+        PostTag.create!(post: post_record, tag: nico_tag, created_user: member)
+
+        PostVersionRecorder.record!(
+            post: post_record.reload,
+            event_type: :update,
+            created_by_user: member)
+
+        expect(post_record.reload.version_no).to eq(2)
+
+        put "/posts/#{post_record.id}", params: post_write_params(
+            base_version_no: base_version.version_no,
+            title: post_record.title,
+            tags: "spec_tag #{ Tag.no_deerjikist.name }")
+
+        expect(response).to have_http_status(:ok)
+
+        names = post_record.reload.tags.map(&:name)
+
+        expect(names).to include('spec_tag')
+        expect(names).to include(Tag.no_deerjikist.name)
+        expect(names).to include(nico_tag.name)
+      end
+
+      it 'keeps nico tags even when they are not included in PUT tags' do
+        sign_in_as(member)
+
+        nico_tag = create_nico_tag!('nico:readonly_update_nico')
+        PostTag.create!(post: post_record, tag: nico_tag, created_user: member)
+
+        base_version = create_post_version_for!(post_record.reload)
+
+        put "/posts/#{post_record.id}", params: post_write_params(
+            base_version_no: base_version.version_no,
+            title: 'updated title',
+            tags: "spec_tag #{ Tag.no_deerjikist.name }")
+
+        expect(response).to have_http_status(:ok)
+
+        names = post_record.reload.tags.map(&:name)
+
+        expect(names).to include('spec_tag')
+        expect(names).to include(Tag.no_deerjikist.name)
+        expect(names).to include(nico_tag.name)
+      end
+
+      it 'allows non-nico tags linked from nico tags to be removed by normal post update' do
+        sign_in_as(member)
+
+        nico_tag = create_nico_tag!('nico:relation_source')
+        linked_tag = Tag.find_or_create_by_tag_name!('relation_linked_tag', category: :general)
+
+        NicoTagRelation.create!(nico_tag:, tag: linked_tag)
+        PostTag.create!(post: post_record, tag: nico_tag, created_user: member)
+        PostTag.create!(post: post_record, tag: linked_tag, created_user: member)
+
+        base_version = create_post_version_for!(post_record.reload)
+
+        put "/posts/#{post_record.id}", params: post_write_params(
+            base_version_no: base_version.version_no,
+            title: post_record.title,
+            tags: "spec_tag #{ Tag.no_deerjikist.name }")
+
+        expect(response).to have_http_status(:ok)
+
+        names = post_record.reload.tags.map(&:name)
+
+        expect(names).to include(nico_tag.name)
+        expect(names).to include('spec_tag')
+        expect(names).to include(Tag.no_deerjikist.name)
+        expect(names).not_to include(linked_tag.name)
+      end
+
+      it 'force-updates stale posts without base_version_no' do
+        sign_in_as(member)
+
+        create_post_version_for!(post_record.reload)
+
+        post_record.update!(title: 'updated by other user')
+        PostVersionRecorder.record!(
+            post: post_record.reload,
+            event_type: :update,
+            created_by_user: member)
+
+        put "/posts/#{post_record.id}", params: post_write_params(
+            title: 'forced title',
+            tags: "spec_tag #{Tag.no_deerjikist.name}",
+            force: '1')
+
+        expect(response).to have_http_status(:ok)
+        expect(post_record.reload.title).to eq('forced title')
+      end
     end
   end
 
@@ -773,20 +1408,20 @@ 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 +1650,15 @@ 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: {
+        post '/posts', params: post_write_params(
             title: 'versioned post',
             url: 'https://example.com/versioned-post',
             tags: 'spec_tag',
-          thumbnail: dummy_upload
-        }
+            thumbnail: dummy_upload)
       end.to change(PostVersion, :count).by(1)
 
       expect(response).to have_http_status(:created)
@@ -1058,16 +1675,16 @@ RSpec.describe 'Posts API', type: :request do
 
     it 'creates next version on PUT /posts/:id when snapshot changes' do
       sign_in_as(member)
-      create_post_version_for!(post_record)
+      base_version = create_post_version_for!(post_record)
 
       tag_name2 = TagName.create!(name: 'spec_tag_2')
       Tag.create!(tag_name: tag_name2, category: :general)
 
       expect do
-        put "/posts/#{post_record.id}", params: {
+        put "/posts/#{post_record.id}", params: post_write_params(
+            base_version_no: base_version.version_no,
             title: 'updated title',
-          tags: 'spec_tag_2'
-        }
+            tags: 'spec_tag_2')
       end.to change(PostVersion, :count).by(1)
 
       expect(response).to have_http_status(:ok)
@@ -1084,14 +1701,15 @@ RSpec.describe 'Posts API', type: :request do
       sign_in_as(member)
 
       PostTag.create!(post: post_record, tag: Tag.no_deerjikist)
-      create_post_version_for!(post_record.reload)
+      base_version = create_post_version_for!(post_record.reload)
 
       expect {
-        put "/posts/#{post_record.id}", params: {
+        put "/posts/#{post_record.id}", params: post_write_params(
+            base_version_no: base_version.version_no,
             title: post_record.title,
-          tags: 'spec_tag'
-        }
+            tags: 'spec_tag')
       }.not_to change(PostVersion, :count)
+
       expect(response).to have_http_status(:ok)
 
       version = post_record.reload.post_versions.order(:version_no).last
@@ -1104,12 +1722,11 @@ RSpec.describe 'Posts API', type: :request do
       sign_in_as(member)
 
       expect do
-        post '/posts', params: {
+        post '/posts', params: post_write_params(
             title: 'invalid post',
             url: 'ぼざクリタグ広場',
             tags: 'spec_tag',
-          thumbnail: dummy_upload
-        }
+            thumbnail: dummy_upload)
       end.not_to change(PostVersion, :count)
 
       expect(response).to have_http_status(:unprocessable_entity)
@@ -1117,15 +1734,15 @@ RSpec.describe 'Posts API', type: :request do
 
     it 'does not create a version when PUT /posts/:id is invalid' do
       sign_in_as(member)
-      create_post_version_for!(post_record)
+      base_version = create_post_version_for!(post_record)
 
       expect do
-        put "/posts/#{post_record.id}", params: {
+        put "/posts/#{post_record.id}", params: post_write_params(
+            base_version_no: base_version.version_no,
             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
-        }
+            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)
@@ -1135,48 +1752,22 @@ RSpec.describe 'Posts API', type: :request do
   describe 'tag versioning from post write actions' do
     let(:member) { create(:user, :member) }
 
-    it 'creates tag snapshot for normalised tags on POST /posts' 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
-        }
-      }.to change { tag.reload.tag_versions.count }.by(1)
-
-      expect(response).to have_http_status(:created)
-
-      version = tag.reload.tag_versions.order(:version_no).last
-      expect(version.version_no).to eq(1)
-      expect(version.event_type).to eq('create')
-      expect(version.name).to eq('spec_tag')
-      expect(version.category).to eq('general')
-      expect(version.created_by_user_id).to eq(member.id)
-    end
-
     it 'creates tag snapshot for normalised tags on PUT /posts/:id' do
       sign_in_as(member)
 
+      base_version = create_post_version_for!(post_record.reload)
+
       tag_name2 = TagName.create!(name: 'spec_tag_2')
       tag2 = Tag.create!(tag_name: tag_name2, category: :general)
 
       expect {
-        put "/posts/#{post_record.id}", params: {
+        put "/posts/#{post_record.id}", params: post_write_params(
+            base_version_no: base_version.version_no,
             title: 'updated title',
-          tags: 'spec_tag_2'
-        }
+            tags: 'spec_tag_2')
       }.to change { tag2.reload.tag_versions.count }.by(1)
 
-      expect(response).to have_http_status(:ok)
-
-      version = tag2.reload.tag_versions.order(:version_no).last
-      expect(version.version_no).to eq(1)
-      expect(version.event_type).to eq('create')
-      expect(version.name).to eq('spec_tag_2')
-      expect(version.created_by_user_id).to eq(member.id)
+      expect(response).to have_http_status(:ok), response.body
     end
   end
 end

backend/spec/requests/tag_versions_spec.rb

@@ -26,6 +26,7 @@ RSpec.describe 'TagVersions API', type: :request do
     created_by_user:,
     created_at:
   )
+    version =
         TagVersion.create!(
             tag: tag,
             version_no: version_no,
@@ -35,8 +36,12 @@ RSpec.describe 'TagVersions API', type: :request do
             aliases: Array(aliases).join(' '),
             parent_tag_ids: Array(parent_tags).map(&:id).join(' '),
             created_by_user: created_by_user,
-      created_at: created_at
-    )
+            created_at: created_at)
+
+    tag.update_columns(version_no: version_no) if tag.has_attribute?(:version_no)
+    tag.version_no = version_no if tag.respond_to?(:version_no=)
+
+    version
   end
 
   let!(:v1) do

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
 
@@ -34,14 +46,24 @@ 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(
+        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],
           )
@@ -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(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(platform1)
-        expect(json[0]['code']).to eq(code1)
+          expect(json[0]['platform']).to eq('youtube')
+          expect(json[0]['code']).to eq(channel_id)
+        end
       end
     end
   end

backend/spec/requests/users_spec.rb

@@ -1,109 +1,266 @@
-require "rails_helper"
+require 'rails_helper'
+
+RSpec.describe 'Users', type: :request do
+  let(:remote_ip) { '203.0.113.10' }
+
+  before do
+    allow_any_instance_of(ActionDispatch::Request)
+      .to receive(:remote_ip)
+      .and_return(remote_ip)
+  end
+
+  def auth_headers(user)
+    { 'X-Transfer-Code' => user.inheritance_code }
+  end
+
+  describe 'POST /users' do
+    it 'creates guest user, IpAddress and UserIp, and returns code' do
+      expect {
+        post '/users'
+      }.to change(User, :count).by(1)
+        .and change(IpAddress, :count).by(1)
+        .and change(UserIp, :count).by(1)
 
-RSpec.describe "Users", type: :request do
-  describe "POST /users" do
-    it "creates guest user and returns code" do
-      post "/users"
       expect(response).to have_http_status(:created)
-      expect(json["code"]).to be_present
-      expect(json["user"]["role"]).to eq("guest")
+      expect(json['code']).to be_present
+      expect(json['user']['role']).to eq('guest')
+
+      user = User.last
+      ip_address = IpAddress.find_by(ip_address: IPAddr.new(remote_ip).hton)
+
+      expect(user.role).to eq('guest')
+      expect(ip_address).to be_present
+      expect(UserIp.exists?(user:, ip_address:)).to eq(true)
+    end
+
+    it 'returns 403 and does not create user when current IP address is banned' do
+      IpAddress.create!(
+        ip_address: IPAddr.new(remote_ip).hton,
+        banned_at: Time.current
+      )
+
+      expect {
+        post '/users'
+      }.not_to change(User, :count)
+
+      expect(response).to have_http_status(:forbidden)
+      expect(UserIp.count).to eq(0)
     end
   end
 
-  describe "POST /users/code/renew" do
-    it "returns 401 when not logged in" do
-      sign_out
-      post "/users/code/renew"
-      expect(response).to have_http_status(:unauthorized)
-    end
-  end
+  describe 'POST /users/code/renew' do
+    it 'returns 401 when not logged in' do
+      post '/users/code/renew'
 
-  describe "PUT /users/:id" do
-    let(:user) { create(:user, name: "old-name", role: "guest") }
-
-    it "returns 401 when current_user id mismatch" do
-      sign_in_as(create(:user))
-      put "/users/#{user.id}", params: { name: "new-name" }
       expect(response).to have_http_status(:unauthorized)
     end
 
-    it "returns 400 when name is blank" do
-      sign_in_as(user)
-      put "/users/#{user.id}", params: { name: "   " }
+    it 'returns 403 when current user is banned' do
+      user = create(:user, :banned)
+
+      post '/users/code/renew', headers: auth_headers(user)
+
+      expect(response).to have_http_status(:forbidden)
+    end
+
+    it 'returns 403 when current IP address is banned' do
+      user = create(:user)
+
+      IpAddress.create!(
+        ip_address: IPAddr.new(remote_ip).hton,
+        banned_at: Time.current
+      )
+
+      post '/users/code/renew', headers: auth_headers(user)
+
+      expect(response).to have_http_status(:forbidden)
+    end
+  end
+
+  describe 'PUT /users/:id' do
+    let(:user) { create(:user, name: 'old-name', role: 'guest') }
+
+    it 'returns 401 when current_user id mismatch' do
+      other_user = create(:user)
+
+      put "/users/#{user.id}",
+          params: { name: 'new-name' },
+          headers: auth_headers(other_user)
+
+      expect(response).to have_http_status(:unauthorized)
+    end
+
+    it 'returns 400 when name is blank' do
+      put "/users/#{user.id}",
+          params: { name: '   ' },
+          headers: auth_headers(user)
+
       expect(response).to have_http_status(:bad_request)
     end
 
-    it "updates name and returns 201 with user slice" do
-      sign_in_as(user)
-      put "/users/#{user.id}", params: { name: "new-name" }
+    it 'updates name and returns user slice' do
+      put "/users/#{user.id}",
+          params: { name: 'new-name' },
+          headers: auth_headers(user)
 
       expect(response).to have_http_status(:ok)
-      expect(json["id"]).to eq(user.id)
-      expect(json["name"]).to eq("new-name")
+      expect(json['id']).to eq(user.id)
+      expect(json['name']).to eq('new-name')
 
       user.reload
-      expect(user.name).to eq("new-name")
+      expect(user.name).to eq('new-name')
+    end
+
+    it 'returns 403 when current user is banned' do
+      user.update!(banned_at: Time.current)
+
+      put "/users/#{user.id}",
+          params: { name: 'new-name' },
+          headers: auth_headers(user)
+
+      expect(response).to have_http_status(:forbidden)
+
+      user.reload
+      expect(user.name).to eq('old-name')
+    end
+
+    it 'returns 403 when current IP address is banned' do
+      IpAddress.create!(
+        ip_address: IPAddr.new(remote_ip).hton,
+        banned_at: Time.current
+      )
+
+      put "/users/#{user.id}",
+          params: { name: 'new-name' },
+          headers: auth_headers(user)
+
+      expect(response).to have_http_status(:forbidden)
+
+      user.reload
+      expect(user.name).to eq('old-name')
     end
   end
 
-  describe "POST /users/verify" do
-    it "returns valid:false when code not found" do
-      post "/users/verify", params: { code: "nope" }
+  describe 'POST /users/verify' do
+    it 'returns valid:false when code not found' do
+      post '/users/verify', params: { code: 'nope' }
+
       expect(response).to have_http_status(:ok)
-      expect(json["valid"]).to eq(false)
+      expect(json['valid']).to eq(false)
     end
 
-    it "creates IpAddress and UserIp, and returns valid:true with user slice" do
-      user = create(:user, inheritance_code: SecureRandom.uuid, role: "guest")
+    it 'returns 403 when current IP address is banned' do
+      user = create(:user, inheritance_code: SecureRandom.uuid, role: 'guest')
 
-      # request.remote_ip を固定
-      allow_any_instance_of(ActionDispatch::Request).to receive(:remote_ip).and_return("203.0.113.10")
+      IpAddress.create!(
+        ip_address: IPAddr.new(remote_ip).hton,
+        banned_at: Time.current
+      )
 
       expect {
-        post "/users/verify", params: { code: user.inheritance_code }
+        post '/users/verify', params: { code: user.inheritance_code }
+      }.not_to change(UserIp, :count)
+
+      expect(response).to have_http_status(:forbidden)
+    end
+
+    it 'returns 403 when verified user is banned' do
+      user = create(
+        :user,
+        :banned,
+        inheritance_code: SecureRandom.uuid,
+        role: 'guest'
+      )
+
+      expect {
+        post '/users/verify', params: { code: user.inheritance_code }
+      }.not_to change(UserIp, :count)
+
+      expect(response).to have_http_status(:forbidden)
+    end
+
+    it 'creates IpAddress and UserIp, and returns valid:true with user slice' do
+      user = create(:user, inheritance_code: SecureRandom.uuid, role: 'guest')
+
+      expect {
+        post '/users/verify', params: { code: user.inheritance_code }
       }.to change(UserIp, :count).by(1)
+        .and change(IpAddress, :count).by(1)
 
       expect(response).to have_http_status(:ok)
-      expect(json["valid"]).to eq(true)
-      expect(json["user"]["id"]).to eq(user.id)
-      expect(json["user"]["inheritance_code"]).to eq(user.inheritance_code)
-      expect(json["user"]["role"]).to eq("guest")
+      expect(json['valid']).to eq(true)
+      expect(json['user']['id']).to eq(user.id)
+      expect(json['user']['inheritance_code']).to eq(user.inheritance_code)
+      expect(json['user']['role']).to eq('guest')
 
-      # ついでに IpAddress もできてることを確認（ipの保存形式がバイナリでも count で見れる）
-      expect(IpAddress.count).to be >= 1
+      ip_address = IpAddress.find_by(ip_address: IPAddr.new(remote_ip).hton)
+      expect(ip_address).to be_present
+      expect(UserIp.exists?(user:, ip_address:)).to eq(true)
     end
 
-    it "is idempotent for same user+ip (does not create duplicate UserIp)" do
-      user = create(:user, inheritance_code: SecureRandom.uuid, role: "guest")
-      allow_any_instance_of(ActionDispatch::Request).to receive(:remote_ip).and_return("203.0.113.10")
+    it 'is idempotent for same user and same IP address' do
+      user = create(:user, inheritance_code: SecureRandom.uuid, role: 'guest')
 
-      post "/users/verify", params: { code: user.inheritance_code }
+      post '/users/verify', params: { code: user.inheritance_code }
       expect(response).to have_http_status(:ok)
 
       expect {
-        post "/users/verify", params: { code: user.inheritance_code }
+        post '/users/verify', params: { code: user.inheritance_code }
       }.not_to change(UserIp, :count)
 
       expect(response).to have_http_status(:ok)
-      expect(json["valid"]).to eq(true)
+      expect(json['valid']).to eq(true)
+    end
+
+    it 'creates another UserIp for same user and different IP address' do
+      user = create(:user, inheritance_code: SecureRandom.uuid, role: 'guest')
+
+      post '/users/verify', params: { code: user.inheritance_code }
+      expect(response).to have_http_status(:ok)
+
+      allow_any_instance_of(ActionDispatch::Request)
+        .to receive(:remote_ip)
+        .and_return('203.0.113.11')
+
+      expect {
+        post '/users/verify', params: { code: user.inheritance_code }
+      }.to change(UserIp, :count).by(1)
+
+      expect(response).to have_http_status(:ok)
+      expect(json['valid']).to eq(true)
     end
   end
 
-  describe "GET /users/me" do
-    it "returns 404 when code not found" do
-      get "/users/me", params: { code: "nope" }
+  describe 'GET /users/me' do
+    it 'returns 404 when code not found' do
+      get '/users/me', params: { code: 'nope' }
+
       expect(response).to have_http_status(:not_found)
     end
 
-    it "returns user slice when found" do
-      user = create(:user, inheritance_code: SecureRandom.uuid, name: "me", role: "guest")
-      get "/users/me", params: { code: user.inheritance_code }
+    it 'returns user slice when found' do
+      user = create(:user, inheritance_code: SecureRandom.uuid, name: 'me', role: 'guest')
+
+      get '/users/me', params: { code: user.inheritance_code }
 
       expect(response).to have_http_status(:ok)
-      expect(json["id"]).to eq(user.id)
-      expect(json["name"]).to eq("me")
-      expect(json["inheritance_code"]).to eq(user.inheritance_code)
-      expect(json["role"]).to eq("guest")
+      expect(json['id']).to eq(user.id)
+      expect(json['name']).to eq('me')
+      expect(json['inheritance_code']).to eq(user.inheritance_code)
+      expect(json['role']).to eq('guest')
+    end
+
+    it 'returns 403 when current IP address is banned' do
+      user = create(:user, inheritance_code: SecureRandom.uuid)
+
+      IpAddress.create!(
+        ip_address: IPAddr.new(remote_ip).hton,
+        banned_at: Time.current
+      )
+
+      get '/users/me', params: { code: user.inheritance_code }
+
+      expect(response).to have_http_status(:forbidden)
     end
   end
 end

backend/spec/services/version_recorder_spec.rb

@@ -0,0 +1,85 @@
+require 'rails_helper'
+
+RSpec.describe VersionRecorder do
+  let(:member) { create(:user, :member) }
+
+  let(:post_record) do
+    Post.create!(
+        title: 'version recorder post',
+        url: 'https://example.com/version-recorder-post')
+  end
+
+  it 'updates record version_no when creating the first version' do
+    version =
+        PostVersionRecorder.record!(
+            post: post_record,
+            event_type: :create,
+            created_by_user: member)
+
+    expect(version.version_no).to eq(1)
+    expect(post_record.reload.version_no).to eq(1)
+  end
+
+  it 'updates record version_no when creating the next version' do
+    PostVersionRecorder.record!(
+        post: post_record,
+        event_type: :create,
+        created_by_user: member)
+
+    post_record.update!(title: 'updated version recorder post')
+
+    version =
+        PostVersionRecorder.record!(
+            post: post_record.reload,
+            event_type: :update,
+            created_by_user: member)
+
+    expect(version.version_no).to eq(2)
+    expect(post_record.reload.version_no).to eq(2)
+  end
+
+  it 'does not create a new version or advance version_no when snapshot is unchanged' do
+    first =
+        PostVersionRecorder.record!(
+            post: post_record,
+            event_type: :create,
+            created_by_user: member)
+
+    expect {
+      version =
+          PostVersionRecorder.record!(
+              post: post_record.reload,
+              event_type: :update,
+              created_by_user: member)
+
+      expect(version).to eq(first)
+    }.not_to change(PostVersion, :count)
+
+    expect(post_record.reload.version_no).to eq(1)
+  end
+
+  it 'raises when record version_no is older than the latest version' do
+    PostVersionRecorder.record!(
+        post: post_record,
+        event_type: :create,
+        created_by_user: member)
+
+    post_record.update!(title: 'updated once')
+
+    PostVersionRecorder.record!(
+        post: post_record.reload,
+        event_type: :update,
+        created_by_user: member)
+
+    post_record.update_columns(version_no: 1)
+
+    post_record.update!(title: 'updated with stale version_no')
+
+    expect {
+      PostVersionRecorder.record!(
+          post: post_record.reload,
+          event_type: :update,
+          created_by_user: member)
+    }.to raise_error(RuntimeError, /version_no/)
+  end
+end

backend/spec/support/test_records.rb

@@ -2,14 +2,12 @@ module TestRecords
   def create_member_user!
     User.create!(name: 'spec user',
                  inheritance_code: SecureRandom.hex(16),
-                 role: 'member',
-                 banned: false)
+                 role: 'member')
   end
 
   def create_admin_user!
     User.create!(name: 'spec admin',
                  inheritance_code: SecureRandom.hex(16),
-                 role: 'admin',
-                 banned: false)
+                 role: 'admin')
   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,

frontend/src/App.tsx

@@ -8,8 +8,10 @@ import { BrowserRouter,
 
 import RouteBlockerOverlay from '@/components/RouteBlockerOverlay'
 import TopNav from '@/components/TopNav'
+import DialogueProvider from '@/components/dialogues/DialogueProvider'
 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 +60,7 @@ 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/>}/>
@@ -136,7 +139,9 @@ export default (() => {
   return (
       <>
 	<RouteBlockerOverlay/>
+
 	<BrowserRouter>
+	  <DialogueProvider>
 	    <LayoutGroup>
 	      <motion.div
 		  layout="position"
@@ -146,7 +151,9 @@ export default (() => {
 		<RouteTransitionWrapper user={user} setUser={setUser}/>
 	      </motion.div>
 	    </LayoutGroup>
+
 	    <Toaster/>
+	  </DialogueProvider>
 	</BrowserRouter>
       </>)
 }) satisfies FC

frontend/src/components/PostEditForm.tsx

@@ -3,10 +3,12 @@ import { useEffect, useState } from 'react'
 import PostFormTagsArea from '@/components/PostFormTagsArea'
 import PostOriginalCreatedTimeField from '@/components/PostOriginalCreatedTimeField'
 import Label from '@/components/common/Label'
+import { useDialogue } from '@/components/dialogues/DialogueProvider'
 import { Button } from '@/components/ui/button'
-import { apiPut } from '@/lib/api'
+import { toast } from '@/components/ui/use-toast'
+import { updatePost } from '@/lib/posts'
 
-import type { FC } from 'react'
+import type { FC, FormEvent } from 'react'
 
 import type { Post, Tag } from '@/types'
 
@@ -31,24 +33,86 @@ type Props = { post:    Post
 
 
 export default (({ post, onSave }: Props) => {
+  const [disabled, setDisabled] = useState (false)
   const [originalCreatedBefore, setOriginalCreatedBefore] =
       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' } })
+  const dialogue = useDialogue ()
+
+  const update = async (...args: Parameters<typeof updatePost>) => {
+    try
+    {
+      const data = await updatePost (...args)
       onSave ({ ...post,
+		versionNo:              data.versionNo,
 		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 (e)
+    {
+      const response = (e as any)?.response
+
+      if (response?.status !== 409)
+	{
+	  toast ({ description: '更新はできなかったよ……' })
+	  return
+	}
+
+      const action = await dialogue.choice ({
+	  title: '競合が発生しました．',
+	  description: (
+	      <div>
+		<p>ほかの耕作員が先に更新してゐます．</p>
+		<p>現在の変更をどう扱ひますか?</p>
+	      </div>),
+	  choices: [...(response?.data?.mergeable ? [{ value: 'merge', label: '差分をマージ' }] : []),
+		    { value: 'overwrite', label: '強制上書き', variant: 'danger' }] })
+
+      if (action === 'merge')
+	{
+	  // TODO: 差分 UI
+	  await update ({ id: post.id, title, tags, parentPostIds,
+			  originalCreatedFrom, originalCreatedBefore },
+			{ baseVersionNo: post.versionNo, merge: true })
+	  return
+	}
+
+      if (action === 'overwrite')
+	{
+	  await update ({ id: post.id, title, tags, parentPostIds,
+			  originalCreatedFrom, originalCreatedBefore },
+			{ baseVersionNo: post.versionNo, force: true })
+	  return
+	}
+    }
+  }
+
+  const handleSubmit = async (e: FormEvent) => {
+    e.preventDefault ()
+
+    setDisabled (true)
+    try
+    {
+      await update ({ id: post.id, title, tags, parentPostIds,
+		      originalCreatedFrom, originalCreatedBefore },
+		    { baseVersionNo: post.versionNo })
+    }
+    finally
+    {
+      setDisabled (false)
+    }
   }
 
   useEffect (() => {
@@ -56,30 +120,48 @@ export default (({ post, onSave }: Props) => {
   }, [post])
 
   return (
-      <div className="max-w-xl pt-2 space-y-4">
+      <form onSubmit={handleSubmit} className="max-w-xl pt-2 space-y-4">
 	{/* タイトル */}
 	<div>
 	  <Label>タイトル</Label>
-	  <input type="text"
+	  <input
+	      type="text"
+	      disabled={disabled}
 	      className="w-full border rounded p-2"
 	      value={title ?? ''}
 	      onChange={ev => setTitle (ev.target.value)}/>
 	</div>
 
+	{/* 親投稿 */}
+	<div>
+	  <Label>親投稿</Label>
+	  <input
+	      type="text"
+	      disabled={disabled}
+	      value={parentPostIds}
+	      onChange={e => setParentPostIds (e.target.value)}
+	      className="w-full border p-2 rounded"/>
+	</div>
+
 	{/* タグ */}
-	<PostFormTagsArea tags={tags} setTags={setTags}/>
+	<PostFormTagsArea
+	    disabled={disabled}
+	    tags={tags}
+	    setTags={setTags}/>
 
 	{/* オリジナルの作成日時 */}
 	<PostOriginalCreatedTimeField
+	    disabled={disabled}
 	    originalCreatedFrom={originalCreatedFrom}
 	    setOriginalCreatedFrom={setOriginalCreatedFrom}
 	    originalCreatedBefore={originalCreatedBefore}
 	    setOriginalCreatedBefore={setOriginalCreatedBefore}/>
 
 	{/* 送信 */}
-	<Button onClick={handleSubmit}
-		className="px-4 py-2 bg-blue-600 text-white rounded disabled:bg-gray-400">
+	<Button
+	    type="submit"
+	    disabled={disabled}>
 	  更新
 	</Button>
-      </div>)
+      </form>)
 }) satisfies FC<Props>

frontend/src/components/PostEmbed.tsx

@@ -3,6 +3,7 @@ import YoutubeEmbed from 'react-youtube'
 
 import NicoViewer from '@/components/NicoViewer'
 import TwitterEmbed from '@/components/TwitterEmbed'
+import { useDialogue } from '@/components/dialogues/DialogueProvider'
 
 import type { FC, RefObject } from 'react'
 
@@ -16,6 +17,8 @@ type Props = {
 
 
 export default (({ ref, post, onLoadComplete, onMetadataChange }: Props) => {
+  const dialogue = useDialogue ()
+
   const url = new URL (post.url)
 
   switch (url.hostname.split ('.').slice (-2).join ('.'))
@@ -82,12 +85,17 @@ export default (({ ref, post, onLoadComplete, onMetadataChange }: Props) => {
 		height={360}/>)
 	 : (
 	    <div>
-	      <a href="#" onClick={e => {
+	      <a href="#" onClick={async e => {
 		e.preventDefault ()
-		setFramed (confirm ('未確認の外部ページを表示します。\n'
-				    + '悪意のあるスクリプトが実行される可能性があります。\n'
-				    + '表示しますか?'))
-		return
+
+		setFramed (await dialogue.confirm ({
+		    title: '未確認の外部ページを表示します。',
+		    description: (
+			<div>
+			  <p>悪意のあるスクリプトが実行される可能性があります。</p>
+			  <p>表示しますか?</p>
+			</div>),
+		    confirmText: '表示' }))
 	      }}>
 		外部ページを表示
 	      </a>

frontend/src/components/PostFormTagsArea.tsx

@@ -7,7 +7,7 @@ import Label from '@/components/common/Label'
 import TextArea from '@/components/common/TextArea'
 import { apiGet } from '@/lib/api'
 
-import type { FC, SyntheticEvent } from 'react'
+import type { ComponentPropsWithoutRef, FC, SyntheticEvent } from 'react'
 
 import type { Tag } from '@/types'
 
@@ -31,12 +31,12 @@ const replaceToken = (value: string, start: number, end: number, text: string) =
     `${ value.slice (0, start) }${ text }${ value.slice (end) }`
 
 
-type Props = {
+type Props = Omit<ComponentPropsWithoutRef<'textarea'>, 'value' | 'onChange' | 'onBlur'> & {
     tags:     string
     setTags:  (tags: string) => void }
 
 
-export default (({ tags, setTags }: Props) => {
+export default (({ tags, setTags, ...rest }: Props) => {
   const ref = useRef<HTMLTextAreaElement> (null)
 
   const [bounds, setBounds] = useState<{ start: number; end: number }> ({ start: 0, end: 0 })
@@ -76,6 +76,7 @@ export default (({ tags, setTags }: Props) => {
       <div className="relative w-full">
 	<Label>タグ</Label>
 	<TextArea
+	    {...rest}
 	    ref={ref}
 	    value={tags}
 	    onChange={ev => setTags (ev.target.value)}

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 && 'ring-4 ring-green-500',
+				   (post.parentPosts ?? []).length > 0 && 'ring-4 ring-yellow-500')}
 		    whileHover={{ scale: 1.02 }}
 		    onLayoutAnimationStart={() => {
 		      if (!(cardRef.current))

frontend/src/components/PostOriginalCreatedTimeField.tsx

@@ -5,13 +5,15 @@ import { Button } from '@/components/ui/button'
 import type { FC } from 'react'
 
 type Props = {
+    disabled?:                boolean
     originalCreatedFrom:      string | null
     setOriginalCreatedFrom:   (x: string | null) => void
     originalCreatedBefore:    string | null
     setOriginalCreatedBefore: (x: string | null) => void }
 
 
-export default (({ originalCreatedFrom,
+export default (({ disabled,
+		   originalCreatedFrom,
 		   setOriginalCreatedFrom,
 		   originalCreatedBefore,
 		   setOriginalCreatedBefore }: Props) => (
@@ -21,6 +23,7 @@ export default (({ originalCreatedFrom,
 	<div className="w-80">
 	  <DateTimeField
 	      className="mr-2"
+	      disabled={disabled ?? false}
 	      value={originalCreatedFrom ?? undefined}
 	      onChange={setOriginalCreatedFrom}
 	      onBlur={ev => {
@@ -40,6 +43,7 @@ export default (({ originalCreatedFrom,
 	<div>
 	  <Button
 	      className="bg-gray-600 text-white rounded"
+	      disabled={disabled}
 	      onClick={() => {
 		setOriginalCreatedFrom (null)
 	      }}>
@@ -51,6 +55,7 @@ export default (({ originalCreatedFrom,
 	<div className="w-80">
 	  <DateTimeField
 	      className="mr-2"
+	      disabled={disabled}
 	      value={originalCreatedBefore ?? undefined}
 	      onChange={setOriginalCreatedBefore}/>
 	  より前
@@ -58,6 +63,7 @@ export default (({ originalCreatedFrom,
 	<div>
 	  <Button
 	      className="bg-gray-600 text-white rounded"
+	      disabled={disabled}
 	      onClick={() => {
 		setOriginalCreatedBefore (null)
 	      }}>

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/${ encodeURIComponent (tag.name) }`}
@@ -55,11 +55,19 @@ export default (({ tag,
 			?
 		      </PrefetchLink>)
 		  : (
+		      tag.materialId != null
+		      ? (
 			  <PrefetchLink
 			      to={`/materials/${ tag.materialId }`}
 			      className={linkClass}>
 			    ?
-		      </PrefetchLink>))
+			  </PrefetchLink>)
+		      : (
+			  <PrefetchLink
+			      to={`/tags/${ tag.id }/deerjikists`}
+			      className={linkClass}>
+			    ?
+			  </PrefetchLink>)))
 	       : (
 		  ['character', 'material'].includes (tag.category)
 		  ? (
@@ -70,6 +78,16 @@ export default (({ tag,
 			  title={`${ tag.name } 素材情報が存在しません．`}>
 			!
 		      </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/${ encodeURIComponent (tag.name) }`}
@@ -77,7 +95,7 @@ export default (({ tag,
 					 dark:animate-[wiki-blink-dark_.25s_steps(2,end)_infinite]"
 			      title={`${ tag.name } Wiki が存在しません．`}>
 			    !
-		      </PrefetchLink>))}
+			  </PrefetchLink>)))}
 	    </span>)}
 	{nestLevel > 0 && (
 	    <span

frontend/src/components/TopNav.tsx

@@ -36,12 +36,12 @@ export const menuOutline = ({ tag, wikiId, user, pathName }: {
 	  { name: '一覧', to: '/posts' },
 	  { name: '検索', to: '/posts/search' },
 	  { name: '追加', to: '/posts/new' },
-	  { name: '履歴', to: '/posts/changes' },
+	  { name: '全体履歴', to: '/posts/changes' },
 	  { name: 'ヘルプ', to: '/wiki/ヘルプ:広場' }] },
       { name: 'タグ', to: '/tags', subMenu: [
 	  { name: 'マスタ', to: '/tags' },
 	  { name: 'ニコニコ連携', to: '/tags/nico' },
-	  { name: '履歴', to: '/tags/changes' },
+	  { name: '全体履歴', to: '/tags/changes' },
 	  { name: 'ヘルプ', to: '/wiki/ヘルプ:タグ' },
 	  { component: <Separator/>, visible: tagFlg },
 	  { name: `広場 (${ postCount || 0 })`,
@@ -53,7 +53,7 @@ export const menuOutline = ({ tag, wikiId, user, pathName }: {
 	  { name: '一覧', to: '/materials' },
 	  { name: '検索', to: '/materials/search', visible: false }, 
 	  { name: '追加', to: '/materials/new' },
-	  { name: '履歴', to: '/materials/changes', visible: false },
+	  { name: '全体履歴', to: '/materials/changes', visible: false },
 	  { name: 'ヘルプ', to: '/wiki/ヘルプ:素材集' }] },
       { name: '上映会', to: '/theatres/1', base: '/theatres', subMenu: [
 	  { name: <>第&thinsp;1&thinsp;会場</>, to: '/theatres/1' },

frontend/src/components/common/DateTimeField.tsx

@@ -2,7 +2,7 @@ import { useEffect, useState } from 'react'
 
 import { cn } from '@/lib/utils'
 
-import type { FC, FocusEvent } from 'react'
+import type { ComponentPropsWithoutRef, FC, FocusEvent } from 'react'
 
 
 const pad = (n: number): string => n.toString ().padStart (2, '0')
@@ -18,14 +18,14 @@ const toDateTimeLocalValue = (d: Date) => {
 }
 
 
-type Props = {
+type Props = Omit<ComponentPropsWithoutRef<'input'>, 'onChange'> & {
     value?:     string
     onChange?:  (isoUTC: string | null) => void
     className?: string
     onBlur?:    (ev: FocusEvent<HTMLInputElement>) => void }
 
 
-export default (({ value, onChange, className, onBlur }: Props) => {
+export default (({ value, onChange, className, onBlur, ...rest }: Props) => {
   const [local, setLocal] = useState ('')
 
   useEffect (() => {
@@ -34,6 +34,7 @@ export default (({ value, onChange, className, onBlur }: Props) => {
 
   return (
       <input
+	  {...rest}
 	  className={cn ('border rounded p-2', className)}
 	  type="datetime-local"
 	  value={local}

frontend/src/components/dialogues/DialogueProvider.tsx

@@ -0,0 +1,187 @@
+import { createContext, useCallback, useContext, useMemo, useState } from 'react'
+
+import { Button } from '@/components/ui/button'
+import { Dialog,
+	 DialogContent,
+	 DialogDescription,
+	 DialogFooter,
+	 DialogHeader,
+	 DialogTitle } from '@/components/ui/dialog'
+
+import type { FC, ReactNode } from 'react'
+
+type DialogueVariant = 'default' | 'danger'
+
+type ConfirmOptions = { title:        string
+			description?: ReactNode
+			confirmText?: string
+			cancelText?:  string
+			variant?:     DialogueVariant }
+
+type AlertOptions = { title:        string
+		      description?: ReactNode
+		      okText?:      string }
+
+type Choice<T extends string> = { value:    T
+				  label:    string
+				  variant?: DialogueVariant }
+
+type ChoiceOptions<T extends string> = { title:         string
+					 description?:  ReactNode
+					 choices:       Choice<T>[]
+					 cancelText?:   string }
+
+type DialogueRequest =
+    | { id:       number
+	kind:     'confirm'
+	options:  ConfirmOptions
+	resolve:  (value: boolean) => void }
+    | { id:       number
+	kind:     'alert'
+	options:  AlertOptions
+	resolve:  () => void }
+    | { id:       number
+	kind:     'choice'
+	options:  ChoiceOptions<string>
+	resolve:  (value: string | null) => void }
+
+type DialogueAPI =
+    { confirm:  (options: ConfirmOptions) => Promise<boolean>
+      alert:    (options: AlertOptions) => Promise<void>
+      choice:   <T extends string> (options: ChoiceOptions<T>) => Promise<T | null> }
+
+const DialogueContext = createContext<DialogueAPI | null> (null)
+
+let nextDialogueId = 1
+
+type Props = { children: ReactNode }
+
+
+export default (({ children }: Props) => {
+  const [queue, setQueue] = useState<DialogueRequest[]> ([])
+
+  const push = useCallback ((request: Omit<DialogueRequest, 'id'>) => {
+    const id = nextDialogueId
+    ++nextDialogueId
+
+    setQueue (q => [...q, { ...request, id } as DialogueRequest])
+  }, [])
+
+  const closeActive = useCallback ((result?: unknown) => {
+    setQueue (q => {
+      const [active, ...rest] = q
+
+      if (!(active))
+	return rest
+
+      switch (active.kind)
+      {
+      case 'confirm':
+	active.resolve (Boolean (result))
+	break
+
+      case 'alert':
+	active.resolve ()
+	break
+
+      case 'choice':
+	active.resolve ((result ?? null) as string | null)
+	break
+      }
+
+      return rest
+    })
+  }, [])
+
+  const api = useMemo<DialogueAPI> (() => ({
+      confirm: options => new Promise<boolean> (resolve => {
+	push ({ kind: 'confirm', options, resolve })
+      }),
+      alert: options => new Promise<void> (resolve => {
+	push ({ kind: 'alert', options, resolve })
+      }),
+      choice: options => new Promise (resolve => {
+	push ({ kind: 'choice',
+		options: options as ChoiceOptions<string>,
+		resolve: resolve as (value: string | null) => void })
+      }) }), [push])
+
+  const active = queue[0]
+
+  return (
+      <DialogueContext.Provider value={api}>
+	{children}
+
+	<Dialog
+	    open={Boolean (active)}
+	    onOpenChange={open => {
+	      if (!(open))
+		closeActive (active?.kind !== 'confirm' && null)
+	    }}>
+	  {active && (
+	      <DialogContent className="px-6 pb-6 pt-7">
+		<DialogHeader className="pl-8">
+		  <DialogTitle>{active.options.title}</DialogTitle>
+
+		  {active.options.description && (
+		      <DialogDescription asChild>
+			<div>{active.options.description}</div>
+		      </DialogDescription>)}
+		</DialogHeader>
+
+		<DialogFooter>
+		  {active.kind === 'confirm' && (
+		      <>
+			<Button
+			    variant="outline"
+			    onClick={() => closeActive (false)}>
+			  {active.options.cancelText ?? '取消'}
+			</Button>
+
+			<Button
+			    variant={(active.options.variant === 'danger')
+				     ? 'destructive'
+				     : 'default'}
+			    onClick={() => closeActive (true)}>
+			  {active.options.confirmText ?? '確定'}
+			</Button>
+		      </>)}
+
+		  {active.kind === 'alert' && (
+		      <Button onClick={() => closeActive ()}>
+			{active.options.okText ?? '確定'}
+		      </Button>)}
+
+		  {active.kind === 'choice' && (
+		      <>
+			<Button
+			    variant="outline"
+			    onClick={() => closeActive (null)}>
+			  {active.options.cancelText ?? '取消'}
+			</Button>
+
+			{active.options.choices.map (choice => (
+			    <Button
+				key={choice.value}
+				variant={(choice.variant === 'danger')
+					 ? 'destructive'
+					 : 'default'}
+				onClick={() => closeActive (choice.value)}>
+			      {choice.label}
+			    </Button>))}
+		      </>)}
+		</DialogFooter>
+	      </DialogContent>)}
+	</Dialog>
+      </DialogueContext.Provider>)
+}) satisfies FC<Props>
+
+
+export const useDialogue = () => {
+  const dialogue = useContext (DialogueContext)
+
+  if (!(dialogue))
+    throw new Error ('useDialogue must be used inside DialogueProvider')
+
+  return dialogue
+}

frontend/src/components/ui/button.tsx

@@ -4,34 +4,47 @@ import { cva, type VariantProps } from "class-variance-authority"
 
 import { cn } from "@/lib/utils"
 
-const buttonVariants = cva(
-  "inline-flex items-center justify-center gap-2 whitespace-nowrap rounded-md text-sm font-medium ring-offset-background transition-colors focus-visible:outline-none focus-visible:ring-2 focus-visible:ring-ring focus-visible:ring-offset-2 disabled:pointer-events-none disabled:opacity-50 [&_svg]:pointer-events-none [&_svg]:size-4 [&_svg]:shrink-0",
+const buttonVariants = cva (
+  [
+    'inline-flex items-center justify-center gap-2 whitespace-nowrap',
+    'rounded-md text-sm font-medium transition-colors',
+    'focus-visible:outline-none focus-visible:ring-2 focus-visible:ring-slate-400',
+    'disabled:pointer-events-none disabled:opacity-50',
+    '[&_svg]:pointer-events-none [&_svg]:size-4 [&_svg]:shrink-0',
+  ].join (' '),
   {
     variants: {
       variant: {
-        default: "bg-primary text-primary-foreground hover:bg-primary/90",
+        default:
+          'bg-slate-900 text-white hover:bg-slate-700 dark:bg-slate-100 dark:text-slate-900 dark:hover:bg-slate-300',
+
         destructive:
-          "bg-destructive text-destructive-foreground hover:bg-destructive/90",
+          'bg-red-600 text-white hover:bg-red-700 dark:bg-red-700 dark:hover:bg-red-600',
+
         outline:
-          "border border-input bg-background hover:bg-accent hover:text-accent-foreground",
+          'border border-slate-300 bg-white text-slate-900 hover:bg-slate-100 dark:border-slate-700 dark:bg-slate-900 dark:text-slate-100 dark:hover:bg-slate-800',
+
         secondary:
-          "bg-secondary text-secondary-foreground hover:bg-secondary/80",
-        ghost: "hover:bg-accent hover:text-accent-foreground",
-        link: "text-primary underline-offset-4 hover:underline",
+          'bg-slate-100 text-slate-900 hover:bg-slate-200 dark:bg-slate-800 dark:text-slate-100 dark:hover:bg-slate-700',
+
+        ghost:
+          'text-slate-900 hover:bg-slate-100 dark:text-slate-100 dark:hover:bg-slate-800',
+
+        link:
+          'text-blue-700 underline-offset-4 hover:underline dark:text-blue-300',
       },
       size: {
-        default: "h-10 px-4 py-2",
-        sm: "h-9 rounded-md px-3",
-        lg: "h-11 rounded-md px-8",
-        icon: "h-10 w-10",
+        default: 'h-10 px-4 py-2',
+        sm:      'h-9 rounded-md px-3',
+        lg:      'h-11 rounded-md px-8',
+        icon:    'h-10 w-10',
       },
     },
     defaultVariants: {
-      variant: "default",
-      size: "default",
+      variant: 'default',
+      size:    'default',
     },
-  }
-)
+  })
 
 export interface ButtonProps
   extends React.ButtonHTMLAttributes<HTMLButtonElement>,

frontend/src/components/ui/dialog.tsx

@@ -37,25 +37,29 @@ const DialogContent = React.forwardRef<
     <DialogOverlay />
     <DialogPrimitive.Content
       ref={ref}
-      className={cn(
-	  'fixed left-[50%] top-[50%] z-50 w-[90%] grid max-w-lg',
+      className={cn (
+	  'fixed left-[50%] top-[50%] z-50 grid w-[calc(100%-2rem)] max-w-lg',
 	  'translate-x-[-50%] translate-y-[-50%]',
-	  'gap-4 border bg-gray-300/80 dark:bg-gray-700/80',
-	  'p-6 shadow-lg duration-200',
+	  'gap-5 rounded-2xl border border-border',
+	  'bg-background p-6 text-foreground shadow-2xl',
+	  'duration-200',
 	  'data-[state=open]:animate-in data-[state=closed]:animate-out',
 	  'data-[state=closed]:fade-out-0 data-[state=open]:fade-in-0',
 	  'data-[state=closed]:zoom-out-95 data-[state=open]:zoom-in-95',
-	  'data-[state=closed]:slide-out-to-left-1/2',
-	  'data-[state=closed]:slide-out-to-top-[48%]',
-	  'data-[state=open]:slide-in-from-left-1/2',
-	  'data-[state=open]:slide-in-from-top-[48%] rounded-lg',
 	  className)}
       {...props}
     >
       {children}
-      <DialogPrimitive.Close className="absolute right-4 top-4 bg-red-500 rounded-sm opacity-70 ring-offset-background transition-opacity hover:opacity-100 focus:outline-none focus:ring-2 focus:ring-ring focus:ring-offset-2 disabled:pointer-events-none data-[state=open]:bg-accent data-[state=open]:text-muted-foreground">
-        <X className="h-3 w-3" />
-        <span className="sr-only">Close</span>
+
+      <DialogPrimitive.Close
+	  className={cn (
+	      'absolute left-4 top-4 rounded-full p-1',
+	      'text-slate-500 transition-colors',
+	      'hover:bg-slate-200 hover:text-slate-900',
+	      'dark:text-slate-400 dark:hover:bg-slate-700 dark:hover:text-slate-50',
+	      'focus:outline-none focus:ring-2 focus:ring-slate-400')}>
+	<X className="h-4 w-4"/>
+	<span className="sr-only">閉ぢる</span>
       </DialogPrimitive.Close>
     </DialogPrimitive.Content>
   </DialogPortal>

frontend/src/components/users/InheritDialogue.tsx

@@ -1,8 +1,11 @@
 import { useState } from 'react'
 
+import { useDialogue } from '@/components/dialogues/DialogueProvider'
 import { Button } from '@/components/ui/button'
 import { Dialog,
 	 DialogContent,
+	 DialogDescription,
+	 DialogHeader,
 	 DialogTitle } from '@/components/ui/dialog'
 import { Input } from '@/components/ui/input'
 import { toast } from '@/components/ui/use-toast'
@@ -16,10 +19,16 @@ type Props = { visible:         boolean
 
 
 export default ({ visible, onVisibleChange, setUser }: Props) => {
+  const dialogue = useDialogue ()
+
   const [inputCode, setInputCode] = useState ('')
 
   const handleTransfer = async () => {
-    if (!(confirm ('引継ぎを行ってもよろしいですか?\n現在のアカウントからはログアウトされます．')))
+    if (!(await dialogue.confirm ({
+	title: '引継ぎを行ってもよろしいですか?',
+	description: '現在のアカウントからはログアウトされます．',
+	confirmText: '引継ぐ',
+	variant: 'danger' })))
       return
 
     try
@@ -44,14 +53,18 @@ export default ({ visible, onVisibleChange, setUser }: Props) => {
 
   return (
       <Dialog open={visible} onOpenChange={onVisibleChange}>
-	<DialogContent>
+	<DialogContent className="px-6 pp-6 pt-7">
+	  <DialogHeader className="pl-8">
 	    <DialogTitle>ほかのブラウザから引継ぐ</DialogTitle>
+	    <DialogDescription asChild>
 	      <div className="flex gap-2">
 		<Input placeholder="引継ぎコードを入力"
 		       value={inputCode}
 		       onChange={ev => setInputCode (ev.target.value)}/>
 		<Button onClick={handleTransfer}>引継ぐ</Button>
 	      </div>
+	    </DialogDescription>
+	  </DialogHeader>
 	</DialogContent>
       </Dialog>)
 }

frontend/src/components/users/UserCodeDialogue.tsx

@@ -1,6 +1,10 @@
+import { useDialogue } from '@/components/dialogues/DialogueProvider'
 import { Button } from '@/components/ui/button'
 import { Dialog,
 	 DialogContent,
+	 DialogDescription,
+	 DialogFooter,
+	 DialogHeader,
 	 DialogTitle } from '@/components/ui/dialog'
 import { toast } from '@/components/ui/use-toast'
 import { apiPost } from '@/lib/api'
@@ -14,11 +18,20 @@ type Props = { visible:         boolean
 
 
 export default ({ visible, onVisibleChange, user, setUser }: Props) => {
+  const dialogue = useDialogue ()
+
   const handleChange = async () => {
     if (!(user))
       return
 
-    if (!(confirm ('引継ぎコードを再発行しますか?\n再発行するとほかのブラウザからはログアウトされます．')))
+    if (!(await dialogue.confirm ({
+	title: '引継ぎコードを再発行しますか?',
+	description: (
+	    <div>
+	      <p>再発行するとほかのブラウザからはログアウトされます．</p>
+	    </div>),
+	confirmText: '再発行',
+	variant: 'danger' })))
       return
 
     const data = await apiPost<{ code: string }> ('/users/code/renew', { },
@@ -33,21 +46,26 @@ export default ({ visible, onVisibleChange, user, setUser }: Props) => {
 
   return (
       <Dialog open={visible} onOpenChange={onVisibleChange}>
-	<DialogContent>
+	<DialogContent className="px-6 pb-6 pt-7">
+	  <DialogHeader className="pl-8">
 	    <DialogTitle>引継ぎコード</DialogTitle>
+
+	    <DialogDescription asChild>
 	      <div>
 		<p>あなたの引継ぎコードはこちらです：</p>
 		<div className="m-2">{user?.inheritanceCode}</div>
-	    <p className="mt-1 text-sm text-red-500">
+		<p className="mt-1 text-sm text-destructive">
 		  このコードはほかの人には教えないでください!
 		</p>
-	    <div className="my-4">
-	      <Button onClick={handleChange}
-		      className="px-4 py-2 bg-red-600 text-white rounded disabled:bg-gray-400">
+	      </div>
+	    </DialogDescription>
+	  </DialogHeader>
+
+	  <DialogFooter>
+	    <Button onClick={handleChange} variant="destructive">
 	      引継ぎコード再発行
 	    </Button>
-	    </div>
-	  </div>
+	  </DialogFooter>
 	</DialogContent>
       </Dialog>)
 }

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/index.css

@@ -6,6 +6,56 @@
 
 @layer base
 {
+  :root
+  {
+    --background: 0 0% 100%;
+    --foreground: 222.2 84% 4.9%;
+
+    --primary: 222.2 47.4% 11.2%;
+    --primary-foreground: 210 40% 98%;
+
+    --secondary: 210 40% 96.1%;
+    --secondary-foreground: 222.2 47.4% 11.2%;
+
+    --destructive: 0 72.2% 50.6%;
+    --destructive-foreground: 210 40% 98%;
+
+    --muted: 210 40% 96.1%;
+    --muted-foreground: 215.4 16.3% 46.9%;
+
+    --accent: 210 40% 96.1%;
+    --accent-foreground: 222.2 47.4% 11.2%;
+
+    --border: 214.3 31.8% 91.4%;
+    --input: 214.3 31.8% 91.4%;
+    --ring: 222.2 84% 4.9%;
+  }
+
+  .dark
+  {
+    --background: 222.2 84% 4.9%;
+    --foreground: 210 40% 98%;
+
+    --primary: 210 40% 98%;
+    --primary-foreground: 222.2 47.4% 11.2%;
+
+    --secondary: 217.2 32.6% 17.5%;
+    --secondary-foreground: 210 40% 98%;
+
+    --destructive: 0 62.8% 45%;
+    --destructive-foreground: 210 40% 98%;
+
+    --muted: 217.2 32.6% 17.5%;
+    --muted-foreground: 215 20.2% 65.1%;
+
+    --accent: 217.2 32.6% 17.5%;
+    --accent-foreground: 210 40% 98%;
+
+    --border: 217.2 32.6% 17.5%;
+    --input: 217.2 32.6% 17.5%;
+    --ring: 212.7 26.8% 83.9%;
+  }
+
   body
   {
     @apply overflow-x-clip;
@@ -54,34 +104,6 @@ body
   min-height: 100dvh;
 }
 
-h1
-{
-  font-size: 3.2em;
-  line-height: 1.1;
-}
-
-button
-{
-  border-radius: 8px;
-  border: 1px solid transparent;
-  padding: 0.6em 1.2em;
-  font-size: 1em;
-  font-weight: 500;
-  font-family: inherit;
-  background-color: #1a1a1a;
-  cursor: pointer;
-  transition: border-color 0.25s;
-}
-button:hover
-{
-  border-color: #646cff;
-}
-button:focus,
-button:focus-visible
-{
-  outline: 4px auto -webkit-focus-ring-color;
-}
-
 @media (prefers-color-scheme: light)
 {
   :root

frontend/src/lib/posts.ts

@@ -1,4 +1,4 @@
-import { apiDelete, apiGet, apiPost } from '@/lib/api'
+import { apiDelete, apiGet, apiPost, apiPut } from '@/lib/api'
 
 import type { FetchPostsParams, Post, PostVersion } from '@/types'
 
@@ -42,6 +42,30 @@ export const fetchPostChanges = async (
 						     page, limit } })
 
 
+export const updatePost = async (
+    post: { id:                     number
+	    title:                  string | null
+	    tags:                   string
+	    parentPostIds:          string
+	    originalCreatedFrom:    string | null
+	    originalCreatedBefore:  string | null },
+    { baseVersionNo, force, merge }: {
+	baseVersionNo?: number
+	force?:         boolean
+	merge?:         boolean }
+) =>
+    await apiPut<Post> (
+	`/posts/${ post.id }`,
+	{ title: post.title,
+	  tags: post.tags,
+	  parent_post_ids: post.parentPostIds,
+	  original_created_from: post.originalCreatedFrom,
+	  original_created_before: post.originalCreatedBefore },
+	{ params: { ...(baseVersionNo && { base_version_no: String (baseVersionNo) }),
+	            force: force ? '1' : '0',
+		    merge: merge ? '1' : '0' } })
+
+
 export const toggleViewedFlg = async (id: string, viewed: boolean): Promise<void> => {
   await (viewed ? apiPost : apiDelete) (`/posts/${ id }/viewed`)
 }

frontend/src/lib/queryKeys.ts

@@ -13,7 +13,8 @@ export const tagsKeys = {
     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 }
+		      ['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

@@ -8,16 +8,18 @@ import TagLink from '@/components/TagLink'
 import PrefetchLink from '@/components/PrefetchLink'
 import PageTitle from '@/components/common/PageTitle'
 import Pagination from '@/components/common/Pagination'
+import { useDialogue } from '@/components/dialogues/DialogueProvider'
 import MainArea from '@/components/layout/MainArea'
 import { toast } from '@/components/ui/use-toast'
 import { SITE_TITLE } from '@/config'
-import { apiPut } from '@/lib/api'
-import { fetchPostChanges } from '@/lib/posts'
+import { fetchPostChanges, updatePost } from '@/lib/posts'
 import { postsKeys, tagsKeys } from '@/lib/queryKeys'
 import { fetchTag } from '@/lib/tags'
 import { cn, dateString, originalCreatedAtString } from '@/lib/utils'
 
-import type { FC } from 'react'
+import type { FC, MouseEvent } from 'react'
+
+import type { PostVersion } from '@/types'
 
 
 const renderDiff = (diff: { current: string | null; prev: string | null }) => (
@@ -34,6 +36,8 @@ const renderDiff = (diff: { current: string | null; prev: string | null }) => (
 
 
 export default (() => {
+  const dialogue = useDialogue ()
+
   const location = useLocation ()
   const query = new URLSearchParams (location.search)
   const id = query.get ('id')
@@ -62,6 +66,48 @@ export default (() => {
 
   const qc = useQueryClient ()
 
+  const handleRevert = async (e: MouseEvent<HTMLAnchorElement>, change: PostVersion) => {
+    e.preventDefault ()
+
+    if (!(await dialogue.confirm ({
+	title: '差戻の確認',
+	description: `『${ change.title.current || change.url.current }』を版 ${
+	    change.versionNo } に差戻します．\nよろしいですか?`,
+	confirmText: '差戻' })))
+      return
+
+    try
+    {
+      const id = change.postId
+      const title = change.title.current
+      const tags =
+	  change.tags
+	  .filter (t => t.type !== 'removed')
+	  .map (t => t.name)
+	  .filter (t => t.slice (0, 5) !== 'nico:')
+	  .join (' ')
+      const parentPostIds =
+	  (change.parentPosts ?? [])
+	  .filter (p => p.type !== 'removed')
+	  .map (p => p.id)
+	  .join (' ')
+      const originalCreatedFrom = change.originalCreatedFrom.current
+      const originalCreatedBefore = change.originalCreatedBefore.current
+      await updatePost ({ id, title, tags, parentPostIds,
+			  originalCreatedFrom, originalCreatedBefore },
+		        { force: true })
+
+      qc.invalidateQueries ({ queryKey: postsKeys.root })
+      qc.invalidateQueries ({ queryKey: tagsKeys.root })
+
+      toast ({ description: '差戻しました．' })
+    }
+    catch
+    {
+      toast ({ description: '差戻に失敗……' })
+    }
+  }
+
   useEffect (() => {
     document.querySelector ('table')?.scrollIntoView ({ behavior: 'smooth' })
   }, [location.search])
@@ -95,6 +141,8 @@ 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 +158,8 @@ 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 +230,29 @@ 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,
@@ -204,41 +277,7 @@ export default (() => {
 			      {dateString (change.createdAt)}
 			    </td>
 			    <td className="p-2">
-			      <a
-				  href="#"
-				  onClick={async e => {
-				    e.preventDefault ()
-
-				    if (!(confirm (
-					`『${ change.title.current
-					      || change.url.current }』を版 ${
-					change.versionNo } に差戻します．\nよろしいですか?`)))
-				      return
-
-				    try
-				    {
-				      await apiPut (
-					  `/posts/${ change.postId }`,
-					  { title: change.title.current,
-					    tags: change.tags
-						  .filter (t => t.type !== 'removed')
-						  .map (t => t.name)
-						  .filter (t => t.slice (0, 5) !== 'nico:')
-						  .join (' '),
-					    original_created_from:
-						change.originalCreatedFrom.current,
-					    original_created_before:
-						change.originalCreatedBefore.current })
-
-				      qc.invalidateQueries ({ queryKey: postsKeys.root })
-				      qc.invalidateQueries ({ queryKey: tagsKeys.root })
-				      toast ({ description: '差戻しました．' })
-				    }
-				    catch
-				    {
-				      toast ({ description: '差戻に失敗……' })
-				    }
-				  }}>
+			      <a href="#" onClick={async e => await handleRevert (e, change)}>
 				復元
 			      </a>
 			    </td>

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]
@@ -114,13 +117,19 @@ export type NiconicoViewerHandle = {
     showComments: () => void
     hideComments: () => void }
 
+export type Platform = typeof PLATFORMS[number]
+
 export type Post = {
     id:                     number
+    versionNo:              number
     url:                    string
     title:                  string | null
     thumbnail:              string | null
     thumbnailBase:          string | null
     tags:                   Tag[]
+    parentPosts?:           Post[]
+    childPosts?:            Post[]
+    siblingPosts?:          Record<`${ number }`, Post[]>
     viewed:                 boolean
     related:                Post[]
     originalCreatedFrom:    string | null
@@ -138,13 +147,18 @@ export type PostTagChange = {
 
 export type PostVersion = {
     postId:                 number
+    latestVersionNo:        number
     versionNo:              number
     eventType:              'create' | 'update' | 'discard' | 'restore'
     title:                  { current: string | null; prev: string | null }
     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 +185,8 @@ export type Tag = {
     createdAt:      string
     updatedAt:      string
     hasWiki:        boolean
-    materialId:     number
+    materialId:     number | null
+    hasDeerjikists: boolean
     children?:      Tag[]
     matchedAlias?:  string | null }
 

frontend/tailwind.config.js

@@ -19,7 +19,22 @@ export default {
 		'rainbow-scroll': 'rainbow-scroll .25s linear infinite' },
 	    colors: {
 		red: { 925: '#5f1414',
-		       975: '#230505' } },
+		       975: '#230505' },
+		border: 'hsl(var(--border))',
+		input: 'hsl(var(--input))',
+		ring: 'hsl(var(--ring))',
+		background: 'hsl(var(--background))',
+		foreground: 'hsl(var(--foreground))',
+		primary: { DEFAULT: 'hsl(var(--primary))',
+			   foreground: 'hsl(var(--primary-foreground))' },
+		secondary: { DEFAULT: 'hsl(var(--secondary))',
+			     foreground: 'hsl(var(--secondary-foreground))' },
+		destructive: { DEFAULT: 'hsl(var(--destructive))',
+			       foreground: 'hsl(var(--destructive-foreground))' },
+		muted: { DEFAULT: 'hsl(var(--muted))',
+			 foreground: 'hsl(var(--muted-foreground))' },
+		accent: { DEFAULT: 'hsl(var(--accent))',
+			  foreground: 'hsl(var(--accent-foreground))' } },
 	    keyframes: {
 		'rainbow-scroll': {
 		    '0%':   { backgroundPosition: '0% 50%' },