func (wp *wsPty) Start() {
	var err error
	args := flag.Args()
	wp.Cmd = exec.Command(cmdFlag, args...)
	env := os.Environ()
	env = append(env, "TERM=xterm")
	wp.Cmd.Env = env
	wp.Pty, err = pty.Start(wp.Cmd)
	if err != nil {
		log.Fatalf("Failed to start command: %s\n", err)
	}
	//Set the size of the pty
	pty.Setsize(wp.Pty, 60, 200)
}
func ptyHandler(w http.ResponseWriter, r *http.Request) {
	conn, err := upgrader.Upgrade(w, r, nil)
	if err != nil {
		log.Fatalf("Websocket upgrade failed: %s\n", err)
	}
	defer conn.Close()

	wp := wsPty{}
	// TODO: check for errors, return 500 on fail
	wp.Start()

	// copy everything from the pty master to the websocket
	// using base64 encoding for now due to limitations in term.js
	go func() {
		buf := make([]byte, 8192)
		reader := bufio.NewReader(wp.Pty)
		var buffer bytes.Buffer
		// TODO: more graceful exit on socket close / process exit
		for {
			n, err := reader.Read(buf)

			if err != nil {
				log.Printf("Failed to read from pty master: %s", err)
				return
			}
			//read byte array as Unicode code points (rune in go)

			bufferBytes := buffer.Bytes()
			runeReader := bufio.NewReader(bytes.NewReader(append(bufferBytes[:], buf[:n]...)))
			buffer.Reset()
			i := 0
			for i < n {
				char, charLen, e := runeReader.ReadRune()
				if e != nil {
					log.Printf("Failed to read from pty master: %s", err)
					return
				}

				if char == utf8.RuneError {
					runeReader.UnreadRune()
					break
				}
				i += charLen
				buffer.WriteRune(char)
			}
			err = conn.WriteMessage(websocket.TextMessage, buffer.Bytes())
			if err != nil {
				log.Printf("Failed to send UTF8 char: %s", err)
				return
			}
			buffer.Reset()
			if i < n {
				buffer.Write(buf[i:n])
			}

		}
	}()

	type Message struct {
		Type string          `json:"type"`
		Data json.RawMessage `json:"data"`
	}

	// read from the web socket, copying to the pty master
	// messages are expected to be text and base64 encoded
	for {
		mt, payload, err := conn.ReadMessage()
		if err != nil {
			if err != io.EOF {
				log.Printf("conn.ReadMessage failed: %s\n", err)
				return
			}
		}
		var msg Message
		switch mt {
		case websocket.BinaryMessage:
			log.Printf("Ignoring binary message: %q\n", payload)
		case websocket.TextMessage:
			err := json.Unmarshal(payload, &msg)
			if err != nil {
				log.Printf("Invalid message %s\n", err)
				continue
			}
			switch msg.Type {
			case "resize":
				var size []float64
				err := json.Unmarshal(msg.Data, &size)
				if err != nil {
					log.Printf("Invalid resize message: %s\n", err)
				} else {
					pty.Setsize(wp.Pty, uint16(size[1]), uint16(size[0]))
				}

			case "data":
				var dat string
				err := json.Unmarshal(msg.Data, &dat)
				if err != nil {
					log.Printf("Invalid data message %s\n", err)
				} else {
					wp.Pty.Write([]byte(dat))
				}

			default:
				log.Printf("Invalid message type %d\n", mt)
				return
			}

		default:
			log.Printf("Invalid message type %d\n", mt)
			return
		}
	}

	wp.Stop()
}