feat: 上位タグ（#64） (#173)

#64 おそらく完成

Merge remote-tracking branch 'origin/main' into feature/064

#64 バックエンドぼちぼち

Co-authored-by: miteruzo <miteruzo@naver.com>
Reviewed-on: #173

backend/app/controllers/posts_controller.rb

@@ -52,9 +52,12 @@ class PostsController < ApplicationController
 
     viewed = current_user&.viewed?(post) || false
 
-    render json: (post
-                  .as_json(include: { tags: { only: [:id, :name, :category, :post_count] } })
-                  .merge(related: post.related(limit: 20), viewed:))
+    json = post.as_json
+    json['tags'] = build_tag_tree_for(post.tags)
+    json['related'] = post.related(limit: 20)
+    json['viewed'] = viewed
+
+    render json:
   end
 
   # POST /posts
@@ -78,6 +81,7 @@ class PostsController < ApplicationController
     if post.save
       post.resized_thumbnail!
       post.tags = Tag.normalise_tags(tag_names)
+      post.tags = Tag.expand_parent_tags(post.tags)
       render json: post.as_json(include: { tags: { only: [:id, :name, :category, :post_count] } }),
              status: :created
     else
@@ -112,9 +116,11 @@ class PostsController < ApplicationController
     post = Post.find(params[:id].to_i)
     tags = post.tags.where(category: 'nico').to_a +
            Tag.normalise_tags(tag_names, with_tagme: false)
+    tags = Tag.expand_parent_tags(tags)
     if post.update(title:, tags:, original_created_from:, original_created_before:)
-      render json: post.as_json(include: { tags: { only: [:id, :name, :category, :post_count] } }),
-             status: :ok
+      json = post.as_json
+      json['tags'] = build_tag_tree_for(post.tags)
+      render json:, status: :ok
     else
       render json: post.errors, status: :unprocessable_entity
     end
@@ -143,4 +149,46 @@ class PostsController < ApplicationController
     end
     posts.distinct
   end
+
+  def build_tag_tree_for tags
+    tags = tags.to_a
+    tag_ids = tags.map(&:id)
+
+    implications = TagImplication.where(parent_tag_id: tag_ids, tag_id: tag_ids)
+
+    children_ids_by_parent = Hash.new { |h, k| h[k] = [] }
+    implications.each do |imp|
+      children_ids_by_parent[imp.parent_tag_id] << imp.tag_id
+    end
+
+    child_ids = children_ids_by_parent.values.flatten.uniq
+
+    root_ids = tag_ids - child_ids
+
+    tags_by_id = tags.index_by(&:id)
+
+    memo = { }
+
+    build_node = -> tag_id, path do
+      tag = tags_by_id[tag_id]
+      return nil unless tag
+
+      if path.include?(tag_id)
+        return tag.as_json(only: [:id, :name, :category, :post_count]).merge(children: [])
+      end
+
+      if memo.key?(tag_id)
+        return memo[tag_id]
+      end
+
+      new_path = path + [tag_id]
+      child_ids = children_ids_by_parent[tag_id] || []
+
+      children = child_ids.filter_map { |cid| build_node.(cid, new_path) }
+
+      memo[tag_id] = tag.as_json(only: [:id, :name, :category, :post_count]).merge(children:)
+    end
+
+    root_ids.filter_map { |id| build_node.call(id, []) }
+  end
 end

backend/app/models/tag.rb

@@ -11,6 +11,14 @@ class Tag < ApplicationRecord
                                          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
+
+  has_many :reversed_tag_implications, class_name: 'TagImplication',
+                                       foreign_key: :tag_id,
+                                       dependent: :destroy
+  has_many :parents, through: :reversed_tag_implications, source: :parent_tag
+
   enum :category, { deerjikist:  'deerjikist',
                     meme:        'meme',
                     character:   'character',
@@ -61,6 +69,29 @@ class Tag < ApplicationRecord
     tags.uniq
   end
 
+  def self.expand_parent_tags tags
+    return [] if tags.blank?
+
+    seen = Set.new
+    result = []
+    stack = tags.compact.dup
+
+    until stack.empty?
+      tag = stack.pop
+      next unless tag
+
+      tag.parents.each do |parent|
+        next if seen.include?(parent.id)
+
+        seen << parent.id
+        result << parent
+        stack << parent
+      end
+    end
+
+    (result + tags).uniq { |t| t.id }
+  end
+
   private
 
   def nico_tag_name_must_start_with_nico

backend/app/models/tag_implication.rb

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