require 'active_support/core_ext/class/attribute'

module ActionController
  # ActionController::Metal provides a way to get a valid Rack application from a controller.
  #
  # In AbstractController, dispatching is triggered directly by calling #process on a new controller.
  # ActionController::Metal provides an #action method that returns a valid Rack application for a
  # given action. Other rack builders, such as Rack::Builder, Rack::URLMap, and the Rails router,
  # can dispatch directly to the action returned by FooController.action(:index).
  class Metal < AbstractController::Base
    abstract!

    # :api: public
    attr_internal :params, :env

    # Returns the last part of the controller's name, underscored, without the ending
    # "Controller". For instance, MyApp::MyPostsController would return "my_posts" for
    # controller_name
    #
    # ==== Returns
    # String
    def self.controller_name
      @controller_name ||= controller_path.split("/").last
    end

    # Delegates to the class' #controller_name
    def controller_name
      self.class.controller_name
    end

    # The details below can be overridden to support a specific
    # Request and Response object. The default ActionController::Base
    # implementation includes RackDelegation, which makes a request
    # and response object available. You might wish to control the
    # environment and response manually for performance reasons.

    attr_internal :status, :headers, :content_type, :response

    def initialize(*)
      @_headers = {}
      super
    end

    # Basic implementations for content_type=, location=, and headers are
    # provided to reduce the dependency on the RackDelegation module
    # in Renderer and Redirector.

    def content_type=(type)
      headers["Content-Type"] = type.to_s
    end

    def location=(url)
      headers["Location"] = url
    end

    def status=(status)
      @_status = Rack::Utils.status_code(status)
    end

    # :api: private
    def dispatch(name, env)
      @_env = env
      @_env['action_controller.instance'] = self
      process(name)
      to_a
    end

    # :api: private
    def to_a
      response ? response.to_a : [status, headers, response_body]
    end

    class ActionEndpoint
      @@endpoints = Hash.new {|h,k| h[k] = Hash.new {|sh,sk| sh[sk] = {} } }

      def self.for(controller, action, stack)
        @@endpoints[controller][action][stack] ||= begin
          endpoint = new(controller, action)
          stack.build(endpoint)
        end
      end

      def initialize(controller, action)
        @controller, @action = controller, action
        @_formats = [Mime::HTML]
      end

      def call(env)
        @controller.new.dispatch(@action, env)
      end
    end

    class_attribute :middleware_stack
    self.middleware_stack = ActionDispatch::MiddlewareStack.new

    def self.inherited(base)
      self.middleware_stack = base.middleware_stack.dup
    end

    def self.use(*args)
      middleware_stack.use(*args)
    end

    def self.middleware
      middleware_stack
    end

    def self.call(env)
      action(env['action_dispatch.request.path_parameters'][:action]).call(env)
    end

    # Return a rack endpoint for the given action. Memoize the endpoint, so
    # multiple calls into MyController.action will return the same object
    # for the same action.
    #
    # ==== Parameters
    # action<#to_s>:: An action name
    #
    # ==== Returns
    # Proc:: A rack application
    def self.action(name)
      ActionEndpoint.for(self, name, middleware_stack)
    end
  end
end