#425

backend/app/services/tag_group_operation.rb

@@ -27,6 +27,8 @@ class TagGroupOperation
       group.lock!
       old_name = group.name
       attributes = prepare!(group:, name:, description:, members:, placements:)
+      next [group, nil] if unchanged?(group, attributes)
+
       group.update!(name: attributes.fetch(:name),
                     description: attributes.fetch(:description),
                     version_no: group.version_no + 1,
@@ -66,6 +68,49 @@ class TagGroupOperation
   end
   private_class_method :prepare!
 
+  def self.unchanged?(group, attributes)
+    unless (group.name_in_database == attributes.fetch(:name) &&
+            group.description_in_database == attributes.fetch(:description))
+      return false
+    end
+
+    members = TagGroupTag.where(tag_group_id: group.id).pluck(:tag_id)
+        .map { { 'tag_id' => _1 } }
+    members.concat(TagGroupGroup.where(tag_group_id: group.id)
+        .pluck(:child_tag_group_id).map { { 'tag_group_id' => _1 } })
+    requested_members = attributes.fetch(:members).map do |member|
+      member.except('version_no')
+    end
+    return false unless members.to_set == requested_members.to_set
+
+    rows = TagGroupPlacement.where(tag_group_id: group.id).order(:position)
+        .group_by(&:parent_position)
+    build = lambda do |parent_position|
+      rows.fetch(parent_position, []).map do |row|
+        node = if row.tag_id
+          { 'tag_id' => row.tag_id }
+        elsif row.child_tag_group_id
+          { 'tag_group_id' => row.child_tag_group_id }
+        else
+          { 'section_name' => row.section_name, 'description' => row.description }
+        end
+        node.merge('children' => build.call(row.position))
+      end
+    end
+    build.call(nil) == comparable_placements(attributes.fetch(:placements))
+  end
+  private_class_method :unchanged?
+
+  def self.comparable_placements(nodes)
+    nodes.map do |node|
+      result = node.dup
+      result['description'] = node['description'] if node.key?('section_name')
+      result['children'] = comparable_placements(node.fetch('children'))
+      result
+    end
+  end
+  private_class_method :comparable_placements
+
   def self.normalize_members(record, members)
     invalid!(record, :members, 'members は配列で指定してください．') unless members.is_a?(Array)