feat: 耕作履歴ページ作成（#112） (#177)

#112 現在ページの表示を太く

#112 完了

Co-authored-by: miteruzo <miteruzo@naver.com>
Reviewed-on: #177

backend/app/controllers/posts_controller.rb

@@ -1,4 +1,6 @@
 class PostsController < ApplicationController
+  Event = Struct.new(:post, :tag, :user, :change_type, :timestamp, keyword_init: true)
+
   # GET /posts
   def index
     limit = params[:limit].presence&.to_i
@@ -128,6 +130,44 @@ class PostsController < ApplicationController
   def destroy
   end
 
+  def changes
+    id = params[:id]
+    page = (params[:page].presence || 1).to_i
+    limit = (params[:limit].presence || 20).to_i
+
+    page = 1 if page < 1
+    limit = 1 if limit < 1
+
+    offset = (page - 1) * limit
+
+    pts = PostTag.with_discarded
+    pts = pts.where(post_id: id) if id.present?
+    pts = pts.includes(:post, :tag, :created_user, :deleted_user)
+
+    events = []
+    pts.each do |pt|
+      events << Event.new(
+          post:         pt.post,
+          tag:          pt.tag,
+          user:         pt.created_user && { id: pt.created_user.id, name: pt.created_user.name },
+          change_type:  'add',
+          timestamp:    pt.created_at)
+
+      if pt.discarded_at
+        events << Event.new(
+            post:         pt.post,
+            tag:          pt.tag,
+            user:         pt.deleted_user && { id: pt.deleted_user.id, name: pt.deleted_user.name },
+            change_type:  'remove',
+            timestamp:    pt.discarded_at)
+      end
+    end
+    events.sort_by!(&:timestamp)
+    events.reverse!
+
+    render json: { changes: events.slice(offset, limit).as_json, count: events.size }
+  end
+
   private
 
   def filtered_posts