package core

import (
	"bytes"
	"encoding/json"
	"github.com/gorilla/websocket"
	"github.com/pkg/sftp"
	"golang.org/x/crypto/ssh"
	"io"
	"log"
	"sync"
	"time"
)

// copy data from WebSocket to ssh server
// and copy data from ssh server to WebSocket

// write data to WebSocket
// the data comes from ssh server.
type wsBufferWriter struct {
	buffer bytes.Buffer
	mu     sync.Mutex
}

// implement Write interface to write bytes from ssh server into bytes.Buffer.
func (w *wsBufferWriter) Write(p []byte) (int, error) {
	w.mu.Lock()
	defer w.mu.Unlock()
	return w.buffer.Write(p)
}

const (
	wsMsgCmd    = "cmd"
	wsMsgResize = "resize"
)

type wsMsg struct {
	Type string `json:"type"`
	Cmd  string `json:"cmd"`
	Cols int    `json:"cols"`
	Rows int    `json:"rows"`
}

// connect to ssh server using ssh session.
type SshConn struct {
	// calling Write() to write data into ssh server
	StdinPipe io.WriteCloser
	// Write() be called to receive data from ssh server
	ComboOutput *wsBufferWriter
	Session     *ssh.Session
	SftpClient  *sftp.Client
}

//flushComboOutput flush ssh.session combine output into websocket response
func flushComboOutput(w *wsBufferWriter, wsConn *websocket.Conn) error {
	if w.buffer.Len() != 0 {
		err := wsConn.WriteMessage(websocket.BinaryMessage, w.buffer.Bytes())
		if err != nil {
			return err
		}
		w.buffer.Reset()
	}
	return nil
}

// setup ssh shell session
// set Session and StdinPipe here,
// and the Session.Stdout and Session.Sdterr are also set.
func NewSshConn(cols, rows int, sshClient *ssh.Client) (*SshConn, error) {
	sshSession, err := sshClient.NewSession()
	if err != nil {
		return nil, err
	}

	// we set stdin, then we can write data to ssh server via this stdin.
	// but, as for reading data from ssh server, we can set Session.Stdout and Session.Stderr
	// to receive data from ssh server, and write back to somewhere.
	stdinP, err := sshSession.StdinPipe()
	if err != nil {
		return nil, err
	}

	comboWriter := new(wsBufferWriter)
	//ssh.stdout and stderr will write output into comboWriter
	sshSession.Stdout = comboWriter
	sshSession.Stderr = comboWriter

	modes := ssh.TerminalModes{
		ssh.ECHO:          1,     // disable echo
		ssh.TTY_OP_ISPEED: 14400, // input speed = 14.4kbaud
		ssh.TTY_OP_OSPEED: 14400, // output speed = 14.4kbaud
	}
	// Request pseudo terminal
	if err := sshSession.RequestPty("xterm", rows, cols, modes); err != nil {
		return nil, err
	}
	// Start remote shell
	if err := sshSession.Shell(); err != nil {
		return nil, err
	}
	sftpclient, err := sftp.NewClient(sshClient)	//创建一个sftp客户端
	if err != nil {
		return nil, err
	}
	return &SshConn{StdinPipe: stdinP, ComboOutput: comboWriter, Session: sshSession, SftpClient: sftpclient}, nil
}

func (s *SshConn) Close() {
	if s.Session != nil {
		s.Session.Close()
	}
	if s.SftpClient != nil{
		s.SftpClient.Close()
	}
}

//ReceiveWsMsg  receive websocket msg do some handling then write into ssh.session.stdin
func (ssConn *SshConn) ReceiveWsMsg(wsConn *websocket.Conn, exitCh chan bool) {
	//tells other go routine quit
	defer setQuit(exitCh)
	for {
		select {
		case <-exitCh:
			return
		default:
			//read websocket msg
			_, wsData, err := wsConn.ReadMessage()
			if err != nil {
				log.Println(err.Error())
				//logrus.WithError(err).Error("reading webSocket message failed")
				return
			}
			//unmashal bytes into struct
			msgObj := wsMsg{
				Type: "cmd",
				Cmd:  "",
				Rows: 50,
				Cols: 180,
			}
			if err := json.Unmarshal(wsData, &msgObj); err != nil {
				log.Println("unmarshal websocket message failed:", string(wsData))
				continue
			}
			switch msgObj.Type {
			case wsMsgResize:
				//handle xterm.js size change
				if msgObj.Cols > 0 && msgObj.Rows > 0 {
					if err := ssConn.Session.WindowChange(msgObj.Rows, msgObj.Cols); err != nil {
						log.Println("ssh pty change windows size failed")
						continue
					}
				}
			case wsMsgCmd:
				//handle xterm.js stdin
				//decodeBytes, err := base64.StdEncoding.DecodeString(msgObj.Cmd)
				decodeBytes := []byte(msgObj.Cmd)
				if err != nil {
					log.Println("websock cmd string base64 decoding failed")
					continue
				}
				if _, err := ssConn.StdinPipe.Write(decodeBytes); err != nil {
					log.Println("ws cmd bytes write to ssh.stdin pipe failed")
					return
				}
			}
		}
	}
}
func (ssConn *SshConn) SendComboOutput(wsConn *websocket.Conn, exitCh chan bool) {
	//tells other go routine quit
	defer setQuit(exitCh)

	//every 120ms write combine output bytes into websocket response
	tick := time.NewTicker(time.Millisecond * time.Duration(120))
	//for range time.Tick(120 * time.Millisecond){}
	defer tick.Stop()
	for {
		select {
		case <-tick.C:
			//write combine output bytes into websocket response
			if err := flushComboOutput(ssConn.ComboOutput, wsConn); err != nil {
				log.Println(err.Error())
				//logrus.WithError(err).Error("ssh sending combo output to webSocket failed")
				return
			}
		case <-exitCh:
			return
		}
	}
}

func (ssConn *SshConn) SessionWait(quitChan chan bool) {
	//if err := ssConn.Session.Wait(); err != nil {
	//	log.Println("ssh session wait failed")
	//	setQuit(quitChan)
	//}
	timer := time.NewTicker(time.Second * 5)
	defer timer.Stop()
	for {
		select {
		case <-timer.C:
			{
				if _, err := ssConn.StdinPipe.Write([]byte{32, 127}); err != nil {
					log.Println("ws cmd bytes write to ssh.stdin pipe failed")
					return
				}
			}
		}
	}
}

func setQuit(ch chan bool) {
	ch <- true
}