投稿に対する履歴（#264） (#307)

Merge branch 'main' into feature/264

#264

#264

#264

#264

Co-authored-by: miteruzo <miteruzo@naver.com>
Reviewed-on: #307

backend/app/models/post_version.rb

@@ -0,0 +1,38 @@
+class PostVersion < ApplicationRecord
+  before_update do
+    raise ActiveRecord::ReadOnlyRecord, '版は更新できません．'
+  end
+
+  before_destroy do
+    raise ActiveRecord::ReadOnlyRecord, '版は削除できません．'
+  end
+
+  belongs_to :post
+  belongs_to :parent, class_name: 'Post', optional: true
+  belongs_to :created_by_user, class_name: 'User', optional: true
+
+  enum :event_type, { create: 'create',
+                      update: 'update',
+                      discard: 'discard',
+                      restore: 'restore' }, prefix: true, validate: true
+
+  validates :version_no, presence: true, numericality: { only_integer: true, greater_than: 0 }
+  validates :event_type, presence: true, inclusion: { in: event_types.keys }
+  validates :url, presence: true
+
+  validate :validate_original_created_range
+
+  scope :chronological, -> { order(:version_no, :id) }
+
+  private
+
+  def validate_original_created_range
+    f = original_created_from
+    b = original_created_before
+    return if f.blank? || b.blank?
+
+    if f >= b
+      errors.add :original_created_before, 'オリジナルの作成日時の順番がをかしぃです．'
+    end
+  end
+end