module Celluloid
  class Mailbox
    # An alternative implementation of Celluloid::Mailbox using Reactor
    class Evented < Celluloid::Mailbox
      attr_reader :reactor

      def initialize(reactor_class)
        super()
        # @condition won't be used in the class.
        @reactor = reactor_class.new
      end

      # Add a message to the Mailbox
      def <<(message)
        @mutex.lock
        begin
          if mailbox_full || @dead
            dead_letter(message)
            return
          end
          if message.is_a?(SystemEvent)
            # SystemEvents are high priority messages so they get added to the
            # head of our message queue instead of the end
            @messages.unshift message
          else
            @messages << message
          end
        ensure
          begin
            @mutex.unlock
          rescue
            nil
          end
        end
        begin
          current_actor = Thread.current[:celluloid_actor]
          @reactor.wakeup unless current_actor && current_actor.mailbox == self
        rescue => ex
          Internals::Logger.crash "reactor crashed", ex
          dead_letter(message)
        end
        nil
      end

      # Receive a message from the Mailbox
      def check(timeout = nil, &block)
        # Get a message if it is available and process it immediately if possible:
        if message = next_message(block)
          return message
        end

        # ... otherwise, run the reactor once, either blocking or will return
        # after the given timeout:
        @reactor.run_once(timeout)

        # No message was received:
        nil
      end

      # Obtain the next message from the mailbox that matches the given block
      def next_message(block)
        @mutex.lock
        begin
          super(&block)
        ensure
          begin
            @mutex.unlock
          rescue
            nil
          end
        end
      end

      # Cleanup any IO objects this Mailbox may be using
      def shutdown
        super do
          @reactor.shutdown
        end
      end
    end
  end
end