Add circle editor

app/models/circle_account.rb

@@ -0,0 +1,39 @@
+# frozen_string_literal: true
+
+# == Schema Information
+#
+# Table name: circle_accounts
+#
+#  id         :bigint(8)        not null, primary key
+#  circle_id  :bigint(8)
+#  account_id :bigint(8)        not null
+#  follow_id  :bigint(8)        not null
+#  created_at :datetime         not null
+#  updated_at :datetime         not null
+#
+
+class CircleAccount < ApplicationRecord
+  belongs_to :circle
+  belongs_to :account
+  belongs_to :follow
+
+  validates :account_id, uniqueness: { scope: :circle_id }
+  validate :validate_relationship
+
+  before_validation :set_follow
+
+  private
+
+  def set_follow
+    return if circle.account_id == account.id
+
+    self.follow = Follow.find_by!(account_id: account.id, target_account_id: circle.account_id)
+  end
+
+  def validate_relationship
+    return if circle.account_id == account_id
+
+    errors.add(:account_id, 'follow relationship missing') if follow_id.nil?
+    errors.add(:follow, 'mismatched accounts') if follow_id.present? && follow.account_id != account_id
+  end
+end