module ActiveSupport::Concern

def self.extended(base) #:nodoc:
  base.instance_variable_set(:@_dependencies, [])
end

def append_features(base)
  if base.instance_variable_defined?(:@_dependencies)
    base.instance_variable_get(:@_dependencies) << self
    return false
  else
    return false if base < self
    @_dependencies.each { |dep| base.include(dep) }
    super
    base.extend const_get(:ClassMethods) if const_defined?(:ClassMethods)
    base.class_eval(&@_included_block) if instance_variable_defined?(:@_included_block)
  end
end

def class_methods(&class_methods_module_definition)
  mod = const_defined?(:ClassMethods, false) ?
    const_get(:ClassMethods) :
    const_set(:ClassMethods, Module.new)
  mod.module_eval(&class_methods_module_definition)
end

def included(base = nil, &block)
  if base.nil?
    raise MultipleIncludedBlocks if instance_variable_defined?(:@_included_block)
    @_included_block = block
  else
    super
  end
end