require_relative "base/has_uuids"

module Uuids

  # Defines the +has_uuids+ model class helper.
  module Base
    extend ActiveSupport::Concern

    # Methods added to the ActiveRecord model.
    module ClassMethods

      private

      # The helper defines:
      #
      # +uuids+:: the +ActiveRecord+ association with a record's uuids.
      # +uuid+:: a virtual attribute that returns the first value of uuids.
      # <tt>uuid=</tt>:: new uuid setter.
      # <tt>uuids=</tt>:: uuids group setter.
      # <tt>by_uuid</tt>:: the +ActiveRecord+ relation scope.
      #
      # @example
      #   class City < ActiveRecord::Base
      #     include Uuids::Base
      #
      #     has_uuids
      #   end
      #
      #   city = City.create!
      #
      #   city.uuids.map(&:value)
      #   # => 51f50391-fcd2-4f69-aab7-6ef31b29c379
      #
      #   city.uuid
      #   # => 51f50391-fcd2-4f69-aab7-6ef31b29c379
      #
      #   city.uuid = "51f50391-fcd2-4f69-aab7-6ef31b29c379"
      #
      #   city.uuids = [
      #     "51f50391-fcd2-4f69-aab7-6ef31b29c379",
      #     "3ea8fd89-232f-4ed1-90b5-743da173cd7d"
      #   ]
      #
      #   City.by_uuid("51f50391-fcd2-4f69-aab7-6ef31b29c379").to_a == [city]
      #   # => true
      def has_uuids
        include Uuids::Base::HasUuids
        has_many_uuids
        after_initialize :add_default_uuid
        before_destroy   :prevent_destruction
        validates :uuids, presence: true, on: :update
      end

      # The helper defines both the getter and setter for object, associated
      # by uuid.
      #
      # @example
      #   class City < ActiveRecord::Base
      #     include Uuids::Base
      #
      #     belongs_by_uuid_to :state, class: State
      #   end
      #
      #   city = City.new
      #   city.state_uuid = "12345678-90ab-cdef-1234-567890abcdef"
      #
      #   city.state.class # => State
      #   city.state.uuid  # => "12345678-90ab-cdef-1234-567890abcdef"
      #
      #   city.state = State.new uuid: "fedcba98-7654-3210-fedc-ba9876543210"
      #   city.state.uuid  # => "fedcba98-7654-3210-fedc-ba9876543210"
      #
      # @param [String, Symbol] name The name of the attribute.
      # @param [Hash] options The options for the association.
      # @option options [Class] :class The model of the attribute.
      # @option options [String] :class_name The name of the attribute's model.
      def belongs_by_uuid_to(name, options = {})
        class_name = options[:class] || options[:class_name].constantize
        BelongsTo.add self, name, class_name
      end
    end

    private

    # Prevents the module usage outside an ActiveRecord model.
    def self.included(klass)
      unless klass.ancestors.include? ActiveRecord::Base
        fail TypeError.new("#{ klass.name } isn't an ActiveRecord model.")
      end
    end
  end
end