# encoding: utf-8
require_relative "base"

module Hexx
  module Helpers

    # @api hide
    # Coerces class attribute getter and setter with given type.
    #
    # @example
    #   Coercion.add MyClass, :name, Multibyte::Chars
    #   object = MyClass.new
    #
    #   object.name = "Ivo"
    #   object.name
    #   # => #<Multibyte::Chars @wrapped_string="Ivo" >
    class Coercion < Base

      # @api hide
      # @!scope class
      # @!method add(target, name, type)
      # Reloads the Base class initializer by adding the type of the attribute
      # to coerce with.
      #
      # @example (see Hexx::Helpers::Coercion)
      # @param  (see Hexx::Helpers::Base.add)
      # @param  [Module] type The type of the attribute.
      # @raise  (see Hexx::Helpers::Coercion#validate)
      # @return [Hexx::Helpers::Coercion] the coercion object.
      def initialize(target, name, type)
        super target, name
        @type = type
      end

      # @!attribute type
      # The type to coerce the attribute with
      # @return [Class] the type of the attribute
      attr_accessor :type

      # @api hide
      # Validates parameters of the coercion declaration.
      #
      # Adds validation of the coercion type to the
      # {Hexx::Helper::Base#validate}.
      #
      # @raise  (see Hexx::Helpers::Base.validate)
      # @raise  (see Hexx::Helpers::Coercion#check_type)
      # @return [Hexx::Helpers::Coercion] +self+
      def validate
        check_type
        super
      end

      private

      # @api hide
      # The definition of the coerced attribute getter.
      # To be reloaded for ActiveRecord models.
      def getter
        "def #{ name }=(value);
           @#{ name } = #{ type.name }.new(value);
         end"
      end

      # @api hide
      # The definition of the coerced attribute setter.
      # To be reloaded for ActiveRecord models.
      def setter
        "def #{ name };
           #{ type.name }.new(@#{ name });
         end"
      end

      # @api hide
      # @raise [TypeError] if type is not a class
      def check_type
        return if type.is_a? Class
        fail TypeError.new "#{ type.inspect } is not a class"
      end
    end
  end
end