#77

backend/app/models/nico_tag_relation.rb

@@ -1,6 +1,6 @@
 class NicoTagRelation < ApplicationRecord
-  belongs_to :nico_tag, class_name: 'Tag', foreign_key: 'nico_tag_id'
-  belongs_to :tag, class_name: 'Tag', foreign_key: 'tag_id'
+  belongs_to :nico_tag, class_name: 'Tag'
+  belongs_to :tag, class_name: 'Tag'
 
   validates :nico_tag_id, presence: true
   validates :tag_id, presence: true
@@ -14,4 +14,10 @@ class NicoTagRelation < ApplicationRecord
       errors.add :nico_tag_id, 'タグのカテゴリがニコニコである必要があります．'
     end
   end
+
+  def tag_mustnt_be_nico
+    if tag && tag.category == 'nico'
+      errors.add :tag_id, '連携先タグのカテゴリはニコニコであってはなりません．'
+    end
+  end
 end

backend/app/models/tag.rb

@@ -2,7 +2,14 @@ class Tag < ApplicationRecord
   has_many :post_tags, dependent: :destroy
   has_many :posts, through: :post_tags
   has_many :tag_aliases, dependent: :destroy
-  has_many :wiki_pages, dependent: :nullify
+
+  has_many :nico_tag_relations, foreign_key: :nico_tag_id, dependent: :destroy
+  has_many :linked_tags, through: :nico_tag_relations, source: :tag
+
+  has_many :reversed_nico_tag_relations, class_name: 'NicoTagRelation',
+                                         foreign_key: :tag_id,
+                                         dependent: :destroy
+  has_many :linked_nico_tags, through: :reversed_nico_tag_relations, source: :nico_tag
 
   enum :category, { deerjikist:  'deerjikist',
                     meme:        'meme',
@@ -17,7 +24,7 @@ class Tag < ApplicationRecord
 
   validate :nico_tag_name_must_start_with_nico
 
-  scope :nico_tags, -> { where category: :nico }
+  scope :nico_tags, -> { where(category: :nico) }
 
   def self.tagme
     @tagme ||= Tag.find_or_initialize_by(name: 'タグ希望') do |tag|
@@ -34,7 +41,8 @@ class Tag < ApplicationRecord
   private
 
   def nico_tag_name_must_start_with_nico
-    if category == 'nico' && name&.[](0, 5) != 'nico:'
+    if ((category == 'nico' && name&.[](0, 5) != 'nico:') || 
+        (category != 'nico' && name&.[](0, 5) == 'nico:'))
       errors.add :name, 'ニコニコ・タグの命名規則に反してゐます．'
     end
   end