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# -*- encoding: binary -*-
require 'eventmachine'
EM::VERSION >= '0.12.10' or abort 'eventmachine 0.12.10 is required'
require 'rainbows/ev_core'

# Implements a basic single-threaded event model with
# {EventMachine}[http://rubyeventmachine.com/].  It is capable of
# handling thousands of simultaneous client connections, but with only
# a single-threaded app dispatch.  It is suited for slow clients,
# and can work with slow applications via asynchronous libraries such as
# {async_sinatra}[http://github.com/raggi/async_sinatra],
# {Cramp}[http://m.onkey.org/2010/1/7/introducing-cramp],
# and {rack-fiber_pool}[http://github.com/mperham/rack-fiber_pool].
#
# It does not require your Rack application to be thread-safe,
# reentrancy is only required for the DevFdResponse body
# generator.
#
# Compatibility: Whatever \EventMachine ~> 0.12.10 and Unicorn both
# support, currently Ruby 1.8/1.9.
#
# This model is compatible with users of "async.callback" in the Rack
# environment such as
# {async_sinatra}[http://github.com/raggi/async_sinatra].
#
# For a complete asynchronous framework,
# {Cramp}[http://m.onkey.org/2010/1/7/introducing-cramp] is fully
# supported when using this concurrency model.
#
# This model is fully-compatible with
# {rack-fiber_pool}[http://github.com/mperham/rack-fiber_pool]
# which allows each request to run inside its own \Fiber after
# all request processing is complete.
#
# Merb (and other frameworks/apps) supporting +deferred?+ execution as
# documented at http://brainspl.at/articles/2008/04/18/deferred-requests-with-merb-ebb-and-thin
# will also get the ability to conditionally defer request processing
# to a separate thread.
#
# This model does not implement as streaming "rack.input" which allows
# the Rack application to process data as it arrives.  This means
# "rack.input" will be fully buffered in memory or to a temporary file
# before the application is entered.
module Rainbows::EventMachine

  include Rainbows::Base
  autoload :ResponsePipe, 'rainbows/event_machine/response_pipe'
  autoload :ResponseChunkPipe, 'rainbows/event_machine/response_chunk_pipe'
  autoload :TryDefer, 'rainbows/event_machine/try_defer'

  class Client < EM::Connection # :nodoc: all
    attr_writer :body
    include Rainbows::EvCore

    def initialize(io)
      @_io = io
      @body = nil
    end

    alias write send_data

    def receive_data(data)
      # To avoid clobbering the current streaming response
      # (often a static file), we do not attempt to process another
      # request on the same connection until the first is complete
      if @body
        @buf << data
        @_io.shutdown(Socket::SHUT_RD) if @buf.size > 0x1c000
        EM.next_tick { receive_data('') }
      else
        on_read(data)
      end
    end

    def quit
      super
      close_connection_after_writing
    end

    def app_call
      set_comm_inactivity_timeout 0
      @env[RACK_INPUT] = @input
      @env[REMOTE_ADDR] = @_io.kgio_addr
      @env[ASYNC_CALLBACK] = method(:em_write_response)
      @env[ASYNC_CLOSE] = EM::DefaultDeferrable.new

      response = catch(:async) { APP.call(@env.update(RACK_DEFAULTS)) }

      # too tricky to support pipelining with :async since the
      # second (pipelined) request could be a stuck behind a
      # long-running async response
      (response.nil? || -1 == response[0]) and return @state = :close

      alive = @hp.keepalive? && G.alive && G.kato > 0
      em_write_response(response, alive)
      if alive
        @env.clear
        @hp.reset
        @state = :headers
        if @buf.empty?
          set_comm_inactivity_timeout(G.kato)
        else
          EM.next_tick { receive_data('') }
        end
      end
    end

    def em_write_response(response, alive = false)
      status, headers, body = response
      if @hp.headers?
        headers = HH.new(headers)
        headers[CONNECTION] = alive ? KEEP_ALIVE : CLOSE
      else
        headers = nil
      end

      if body.respond_to?(:errback) && body.respond_to?(:callback)
        @body = body
        body.callback { quit }
        body.errback { quit }
        # async response, this could be a trickle as is in comet-style apps
        headers[CONNECTION] = CLOSE if headers
        alive = true
      elsif body.respond_to?(:to_path)
        st = File.stat(path = body.to_path)

        if st.file?
          write(response_header(status, headers)) if headers
          @body = stream_file_data(path)
          @body.errback do
            body.close if body.respond_to?(:close)
            quit
          end
          @body.callback do
            body.close if body.respond_to?(:close)
            @body = nil
            alive ? receive_data('') : quit
          end
          return
        elsif st.socket? || st.pipe?
          @body = io = body_to_io(body)
          chunk = stream_response_headers(status, headers) if headers
          m = chunk ? ResponseChunkPipe : ResponsePipe
          return EM.watch(io, m, self, alive, body).notify_readable = true
        end
        # char or block device... WTF? fall through to body.each
      end

      write(response_header(status, headers)) if headers
      write_body_each(self, body)
      quit unless alive
    end

    def unbind
      async_close = @env[ASYNC_CLOSE] and async_close.succeed
      @body.respond_to?(:fail) and @body.fail
      begin
        @_io.close
      rescue Errno::EBADF
        # EventMachine's EventableDescriptor::Close() may close
        # the underlying file descriptor without invalidating the
        # associated IO object on errors, so @_io.closed? isn't
        # sufficient.
      end
    end
  end

  module Server # :nodoc: all
    def close
      detach
      @io.close
    end

    def notify_readable
      return if CUR.size >= MAX
      io = @io.kgio_tryaccept or return
      sig = EM.attach_fd(io.fileno, false)
      CUR[sig] = CL.new(sig, io)
    end
  end

  def init_worker_process(worker) # :nodoc:
    Rainbows::Response.setup(Rainbows::EventMachine::Client)
    super
  end

  # runs inside each forked worker, this sits around and waits
  # for connections and doesn't die until the parent dies (or is
  # given a INT, QUIT, or TERM signal)
  def worker_loop(worker) # :nodoc:
    init_worker_process(worker)
    G.server.app.respond_to?(:deferred?) and
      G.server.app = TryDefer[G.server.app]

    # enable them both, should be non-fatal if not supported
    EM.epoll
    EM.kqueue
    logger.info "#@use: epoll=#{EM.epoll?} kqueue=#{EM.kqueue?}"
    client_class = Rainbows.const_get(@use).const_get(:Client)
    Server.const_set(:MAX, worker_connections + LISTENERS.size)
    Server.const_set(:CL, client_class)
    client_class.const_set(:APP, G.server.app)
    EM.run {
      conns = EM.instance_variable_get(:@conns) or
        raise RuntimeError, "EM @conns instance variable not accessible!"
      Server.const_set(:CUR, conns)
      EM.add_periodic_timer(1) do
        unless G.tick
          conns.each_value { |c| client_class === c and c.quit }
          EM.stop if conns.empty? && EM.reactor_running?
        end
      end
      LISTENERS.map! do |s|
        EM.watch(s, Server) { |c| c.notify_readable = true }
      end
    }
  end
end