# = Class Extension
#
# Normally when including modules, class/module methods are not
# extended. To achieve this behavior requires some clever
# Ruby Karate. Instead class_extension provides an easy to use
# and clean solution. Simply place the extending class methods
# in a block of the special module method #class_extension.
#
#   module Mix
#     def inst_meth
#       puts 'inst_meth'
#     end
#
#     class_extend do
#       def class_meth
#         "Class Method!"
#       end
#     end
#   end
#
#   class X
#     include Mix
#   end
#
#   X.class_meth  #=> "Class Method!"
#
# == History
#
# Thanks to Trans, Nobu and Ulysses for their original on this concept.
#
# == Authors
#
# * Daniel Schierbeck
# * Thomas Sawyer
# * Nobu Nakada
# * Ulysses
#
# == Copying
#
# Copyright (c) 2006 Daniel Schierbeck
#
# Ruby License
#
# This module is free software. You may use, modify, and/or redistribute this
# software under the same terms as Ruby.
#
# This program is distributed in the hope that it will be useful, but WITHOUT
# ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
# FOR A PARTICULAR PURPOSE.

#
class Module

  alias_method :append_features_without_class_extension, :append_features

  # Normally when including modules, class/module methods are not
  # extended. To achieve this behavior requires some clever
  # Ruby Karate. Instead #class_extend provides an easy to use
  # and clean solution. Simply place the extending class methods
  # in a block of the special module method #class_extend.
  #
  #   module Mix
  #     def inst_meth
  #       puts 'inst_meth'
  #     end
  #
  #     class_extend do
  #       def class_meth
  #         "Class Method!"
  #       end
  #     end
  #   end
  #
  #   class X
  #     include Mix
  #   end
  #
  #   X.class_meth  #=> "Class Method!"
  #
  # NOTE: This old #class_extension version of this method
  # did not extend the containing class automatically --it had
  # to be done by hand. With #class_extend, that is no longer
  # the case.
  #
  def class_extend(*mods, &block)
    @class_extension ||= Module.new do
      def self.append_features(mod)
        append_features_without_class_extension(mod)
      end
    end
    @class_extension.__send__(:include, *mods)
    @class_extension.module_eval(&block) if block_given?
    extend(@class_extension)  # extend this module too
    @class_extension
  end

  # TODO: DEPRECATE
  alias_method :class_extension, :class_extend

  #private :class_extend

  # Override +append_features+ to handle class-inheritable extensions.
  def append_features(mod)
    append_features_without_class_extension(mod)
    mod.extend(class_extend)
    if mod.instance_of? Module
      mod.__send__(:class_extend).__send__(:include, class_extend)
    end
  end

end

class Class
  # For Class, #class_extend is the same as class_eval.
  # The alternative is to "undef_method :class_extend",
  # but this seems uneccessarily limited.
  #
  def class_extend(*mods, &block)
    m = Module.new
    m.__send__(:include, *mods)
    m.module_eval(&block)
    extend(m)
    m
  end
end