class ActionController::MiddlewareStack

def build(action, app = nil, &block)
  action = action.to_s
  middlewares.reverse.inject(app || block) do |a, middleware|
    middleware.valid?(action) ? middleware.build(a) : a
  end
end

def build_middleware(klass, args, block)
  options = args.extract_options!
  only   = Array(options.delete(:only)).map(&:to_s)
  except = Array(options.delete(:except)).map(&:to_s)
  args << options unless options.empty?
  strategy = NULL
  list     = nil
  if only.any?
    strategy = INCLUDE
    list     = only
  elsif except.any?
    strategy = EXCLUDE
    list     = except
  end
  Middleware.new(klass, args, list, strategy, block)
end