#419

backend/app/controllers/tags_controller.rb

@@ -166,7 +166,7 @@ class TagsController < ApplicationController
 
     rows =
         (internal_rows + external_rows)
-        .sort_by { |row| [-row[:post_count], row[:name]] }
+        .sort_by { |row| [-row['post_count'], row['name']] }
         .first(20)
 
     render json: rows

backend/app/models/external_tag.rb

@@ -6,8 +6,13 @@ class ExternalTag < ApplicationRecord
   has_many :posts, through: :post_external_tags
 
   has_many :nico_tag_versions, foreign_key: :tag_id, inverse_of: :external_tag
-  has_many :nico_tag_relations, foreign_key: :tag_id, dependent: :destroy
-  has_many :linked_tags, through: :nico_tag_relations, source: :nico_tag
+
+  has_many :nico_tag_relations,
+           foreign_key: :nico_tag_id,
+           inverse_of: :nico_tag,
+           dependent: :destroy
+
+  has_many :linked_tags, through: :nico_tag_relations, source: :tag
 
   def snapshot_linked_tag_names
     linked_tags.joins(:tag_name).order('tag_names.name').pluck('tag_names.name')

backend/app/models/nico_tag_relation.rb

@@ -1,6 +1,9 @@
 class NicoTagRelation < ApplicationRecord
-  belongs_to :nico_tag, class_name: 'Tag'
-  belongs_to :tag, class_name: 'Tag'
+  belongs_to :nico_tag,
+             class_name: 'ExternalTag',
+             foreign_key: :nico_tag_id,
+             inverse_of: :nico_tag_relations
+  belongs_to :tag, class_name: 'Tag', foreign_key: :tag_id
 
   validates :nico_tag_id, presence: true
   validates :tag_id, presence: true

backend/app/models/tag.rb

@@ -28,8 +28,11 @@ class Tag < ApplicationRecord
   has_many :post_tags, inverse_of: :tag
   has_many :posts, through: :post_tags
 
-  has_many :nico_tag_relations, foreign_key: :nico_tag_id, dependent: :destroy
-  has_many :linked_tags, through: :nico_tag_relations, source: :tag
+  has_many :reversed_nico_tag_relations,
+           class_name: 'NicoTagRelation',
+           foreign_key: :nico_tag_id,
+           dependent: :destroy
+  has_many :linked_nico_tags, through: :reversed_nico_tag_relations, source: :nico_tag
 
   has_many :tag_implications, foreign_key: :parent_tag_id, dependent: :destroy
   has_many :children, through: :tag_implications, source: :tag

backend/app/services/nico_tag_version_recorder.rb

@@ -1,20 +1,22 @@
 class NicoTagVersionRecorder < VersionRecorder
-  def self.record! tag:, event_type:, created_by_user:
-    new(tag:, event_type:, created_by_user:).record!
+  def self.record! external_tag:, event_type:, created_by_user:
+    new(external_tag:, event_type:, created_by_user:).record!
   end
 
-  def initialize tag:, event_type:, created_by_user:
-    super(record: tag, event_type:, created_by_user:)
+  def initialize external_tag:, event_type:, created_by_user:
+    super(record: external_tag, event_type:, created_by_user:)
   end
 
   private
 
   def version_class = NicoTagVersion
   def version_association = :nico_tag_versions
-  def record_key = :tag
+  def record_key = :external_tag
 
   def snapshot_attributes
     { name: "#{ @record.platform }:#{ @record.name }",
       linked_tags: @record.snapshot_linked_tag_names.join(' ') }
   end
+
+  def tracks_version_no_on_record? = false
 end

backend/app/services/version_recorder.rb

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