# encoding: utf-8

module Assertion

  module DSL

    # Provides methods to build assertions and guards
    #
    module Builder

      # Builds the subclass of `Assertion::Base` with predefined `attributes`
      # and implementation of the `#check` method.
      #
      # @example
      #   IsMan = Assertion.about :age, :gender do
      #     (age >= 18) && (gender == :male)
      #   end
      #
      #   # This is the same as:
      #   class IsMan < Assertion::Base
      #     attribute :age, :gender
      #
      #     def check
      #       (age >= 18) && (gender == :male)
      #     end
      #   end
      #
      # @param [Symbol, Array<Symbol>] attributes
      #   The list of attributes for the new assertion
      # @param [Proc] block
      #   The content for the `check` method
      #
      # @return [Class] The specific assertion class
      #
      def about(*attributes, &block)
        __build__(Base, attributes, :check, &block)
      end

      # Builds the subclass of `Assertion::Guard` with given attribute
      # (alias for the `object`) and implementation of the `#state` method.
      #
      # @example
      #   VoterOnly = Assertion.guards :user do
      #     IsAdult[user.attributes] & IsCitizen[user.attributes]
      #   end
      #
      #   # This is the same as:
      #   class VoterOnly < Assertion::Guard
      #     alias_method :user, :object
      #
      #     def state
      #       IsAdult[user.attributes] & IsCitizen[user.attributes]
      #     end
      #   end
      #
      # @param [Symbol] attribute
      #   The alias for the `object` attribute
      # @param [Proc] block
      #   The content for the `state` method
      #
      # @return [Class] The specific guard class
      #
      def guards(attribute = nil, &block)
        __build__(Guard, attribute, :state, &block)
      end

      private

      def __build__(type, attributes, name, &block)
        klass = Class.new(type)
        klass.public_send(:attribute, attributes) if attributes
        klass.__send__(:define_method, name, &block) if block_given?

        klass
      end

    end # module Builder

  end # module DSL

end # module Assertion