# encoding: utf-8

module ServiceObjects

  module Helpers

    # Features for service parameters declaration
    #
    # @note
    #   A target class should be **extended** by the module
    module Parameterized

      # Whitelists {.new} options assigned to params
      #
      # Mutates the current class by adding the corresponding attribute
      # for every parameter.
      #
      # @example Whitelists options
      #   class AddFoo
      #     extend ServiceObjects::Helpers::Parameterized
      #
      #     allows_params :foo
      #   end
      #
      #   service = AddFoo.new foo: "foo", bar: "baz"
      #   service.params # => { foo: "foo" }
      #
      # @example Adds attributes as aliases to corresponding params
      #   class AddFoo
      #     extend ServiceObjects::Helpers::Parameterized
      #
      #     allows_params :foo
      #   end
      #
      #   service = AddFoo.new foo: "foo"
      #   service.foo           # => "foo"
      #
      #   service.params[:foo] = "bar"
      #   service.foo           # => "bar"
      #
      #   service.foo = "baz"
      #   service.foo           # => "baz"
      #   service.params[:foo]  # => "baz"
      #
      # @param [Array<#to_sym>] list
      #
      # @return [Array<Symbol>]
      #   the list of arguments
      def allows_params(*list)
        @whitelist = list.flatten.map(&:to_sym).freeze
        __attr_params__

        whitelist
      end

      private

      # @!parse include ServiceObjects::Helpers::Parameters
      def self.extended(klass)
        klass.include Parameters
        super
      end

      def __attr_params__
        whitelist.each(&method(:__attr_param_accessor__))
      end

      def __attr_param_accessor__(name)
        __attr_param_reader__ name
        __attr_param_writer__ name
      end

      def __attr_param_reader__(name)
        define_method(name) { params[name] }
      end

      def __attr_param_writer__(name)
        define_method("#{ name }=") { |value| params[name] = value }
      end

    end # module Parameters

  end # module Helpers

end # module ServiceObjects