module Leafable
  extend ActiveSupport::Concern

  TYPES = %w[ Page Section Picture ]

  included do
    has_one :leaf, as: :leafable, inverse_of: :leafable, touch: true
    has_one :book, through: :leaf

    delegate :title, to: :leaf
  end

  class_methods do
    def leafable_name
      @leafable_name ||= ActiveModel::Name.new(self).singular.inquiry
    end
  end

  def leafable_name
    self.class.leafable_name
  end
end