#90

backend/app/controllers/nico_tags_controller.rb

@@ -1,26 +1,69 @@
 class NicoTagsController < ApplicationController
   def index
-    limit = (params[:limit] || 20).to_i
-    cursor = params[:cursor].presence
+    name = params[:name].presence
+    linked_tag = params[:linked_tag].presence
+    link_status = params[:link_status].presence
+    order = params[:order].to_s.split(':', 2).map(&:strip)
+    order[0] = 'updated_at' unless order[0].in?(['name', 'created_at', 'updated_at'])
+    unless order[1].in?(['asc', 'desc'])
+      order[1] = order[0] == 'name' ? 'asc' : 'desc'
+    end
+    page = (params[:page].presence || 1).to_i
+    limit = (params[:limit].presence || 20).to_i
+
+    page = 1 if page < 1
+    limit = 1 if limit < 1
+
+    post_tag_max_sql =
+        PostTag
+        .select('tag_id, MAX(created_at) AS max_created_at')
+        .group('tag_id')
+        .to_sql
 
     q = Tag.nico_tags
+           .joins(:tag_name)
+           .joins("LEFT JOIN (#{ post_tag_max_sql }) post_tag_max " \
+                  'ON post_tag_max.tag_id = tags.id')
            .includes(:tag_name, tag_name: :wiki_page, linked_tags: { tag_name: :wiki_page })
-           .order(updated_at: :desc)
-    q = q.where('tags.updated_at < ?', Time.iso8601(cursor)) if cursor
-
-    tags = q.limit(limit + 1).to_a
-
-    next_cursor = nil
-    if tags.size > limit
-      next_cursor = tags.last.updated_at.iso8601(6)
-      tags = tags.first(limit)
+    q = q.where('tag_names.name LIKE ?', "%#{ name }%") if name
+    if linked_tag
+      linked_tag_ids =
+        Tag
+        .joins(:tag_name)
+        .where('tag_names.name LIKE ?', "%#{ linked_tag }%")
+        .pluck(:id)
+      linked_nico_tag_ids = NicoTagRelation.where(tag_id: linked_tag_ids).pluck(:nico_tag_id)
+      q = q.where(id: linked_nico_tag_ids)
+    end
+    if link_status.in?(['linked', 'unlinked'])
+      exists_sql =
+          'EXISTS (SELECT 1 FROM nico_tag_relations ' \
+          'WHERE nico_tag_relations.nico_tag_id = tags.id)'
+      q = link_status == 'linked' ? q.where(exists_sql) : q.where("NOT #{ exists_sql }")
     end
 
+    count = q.count
+    sort_sql =
+        case order[0]
+        when 'name'
+          'tag_names.name'
+        when 'updated_at'
+          'post_tag_max.max_created_at'
+        else
+          "tags.#{ order[0] }"
+        end
+    tags = q.reselect('tags.*',
+                      Arel.sql('post_tag_max.max_created_at AS recent_post_tag_created_at'))
+            .order(Arel.sql("#{ sort_sql } #{ order[1] }, tags.id #{ order[1] }"))
+            .limit(limit)
+            .offset((page - 1) * limit)
+            .to_a
+
     render json: { tags: tags.map { |tag|
-      TagRepr.base(tag).merge(linked_tags: tag.linked_tags.map { |lt|
-        TagRepr.base(lt)
-      })
-    }, next_cursor: }
+      TagRepr.base(tag).merge(
+          recent_post_tag_created_at: tag.recent_post_tag_created_at,
+          linked_tags: tag.linked_tags.map { |lt| TagRepr.base(lt) })
+    }, count: }
   end
 
   def update