module Celluloid
  module IO
    # An alternative implementation of Celluloid::Mailbox using Wakers
    class Mailbox < Celluloid::Mailbox
      attr_reader :reactor, :waker

      def initialize
        @messages = []
        @lock  = Mutex.new
        @waker = Waker.new
        @reactor = Reactor.new(@waker)
      end

      # Add a message to the Mailbox
      def <<(message)
        @lock.synchronize do
          @messages << message
          @waker.signal
        end
        nil
      rescue DeadWakerError
        raise MailboxError, "dead recipient"
      end

      # Add a high-priority system event to the Mailbox
      def system_event(event)
        @lock.synchronize do
          @messages.unshift event

          begin
            @waker.signal
          rescue DeadWakerError
            # Silently fail if messages are sent to dead actors
          end
        end
        nil
      end

      # Receive a message from the Mailbox
      def receive(timeout = nil, &block)
        message = nil

        begin
          if timeout
             now = Time.now
             wait_until ||= now + timeout
             wait_interval = wait_until - now
             return if wait_interval < 0
           else
             wait_interval = nil
           end

          @reactor.run_once(wait_interval) do
            @waker.wait
            message = next_message(&block)
          end
        end until message

        message
      rescue IOError, DeadWakerError
        shutdown # force shutdown of the mailbox
        raise MailboxShutdown, "mailbox shutdown called during receive"
      end

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