// subscribe all websocket clients to stream data
// eg subscribe;3;stdout
func wseventSubscribe(s *server, options string) error {
	args := strings.Split(options, ";")
	if len(args) != 2 {
		return errors.New("subscribe requires 2 args")
	}
	idstr := args[0]
	streamname := args[1]
	c, err := getCmd(s, idstr)
	if err != nil {
		return err
	}
	var stream liblush.OutStream
	switch streamname {
	case "stdout":
		stream = c.Stdout()
	case "stderr":
		stream = c.Stderr()
	default:
		return errors.New("unknown stream: " + streamname)
	}
	// proxy stream data
	w := newPrefixedWriter(&s.ctrlclients, []byte("stream;"+idstr+";"+streamname+";"))
	// do not close websocket stream when command exits
	wc := newNopWriteCloser(w)
	stream.Peeker().AddWriter(wc)
	return nil
}

func connectCmdsById(s *server, fromId, toId liblush.CmdId, streamname string) error {
	var stream liblush.OutStream
	var to, from liblush.Cmd
	from = s.session.GetCommand(fromId)
	if from == nil {
		return errors.New("unknown command in from")
	}
	switch streamname {
	case "stdout":
		stream = from.Stdout()
	case "stderr":
		stream = from.Stderr()
	default:
		return errors.New("unknown stream")
	}
	if toId == 0 {
		return disconnectStream(stream)
	}
	to = s.session.GetCommand(toId)
	if to == nil {
		return errors.New("unknown command in to")
	}
	if pipedcmd(stream) != nil {
		// not strictly necessary but makes for simpler API. service to the
		// user! because that is how we roll. EaaS.
		return errors.New("already connected to another command")
	}
	stream.SetListener(to.Stdin())
	return nil
}

func disconnectStream(stream liblush.OutStream) error {
	var fwd liblush.Cmd
	fwd = pipedcmd(stream)
	if fwd == nil {
		return errors.New("no connected command found")
	}
	stream.SetListener(liblush.Devnull)
	return nil
}

func handleWsStream(ctx *web.Context, idstr, streamname string) error {
	id, _ := liblush.ParseCmdId(idstr)
	s := ctx.User.(*server)
	c := s.session.GetCommand(id)
	if c == nil {
		return web.WebError{404, "no such command: " + idstr}
	}
	var stream liblush.OutStream
	switch streamname {
	case "stdout":
		stream = c.Stdout()
	case "stderr":
		stream = c.Stderr()
	default:
		return web.WebError{400, "No such stream: " + streamname}
	}
	stream.Peeker().AddWriter(ctx.WebsockConn)
	buf := make([]byte, 1)
	ctx.WebsockConn.Read(buf)
	return nil
}

// return command that this stream pipes to, if any
func pipedcmd(outs liblush.OutStream) liblush.Cmd {
	return iscmd(outs.GetListener())
}