app/models/category.rb

class Category < ApplicationRecord
  belongs_to :parent, class_name: "Category", optional: true
  has_many :children, class_name: "Category", foreign_key: "parent_id", dependent: :destroy
  has_many :auctions, dependent: :restrict_with_error
  has_many :user_expert_categories, dependent: :destroy
  has_many :experts, through: :user_expert_categories, source: :user

  validates :name, presence: true, uniqueness: true

  # Ransack configuration for Active Admin
  def self.ransackable_attributes(auth_object = nil)
    [ "id", "name", "description", "parent_id", "created_at", "updated_at" ]
  end

  def self.ransackable_associations(auth_object = nil)
    [ "parent", "children", "auctions", "experts", "user_expert_categories" ]
  end
end