import "github.com/abrander/go-supervisord"
  
func main() {
	c, err := supervisord.NewClient("http://127.0.0.1:9001/RPC2")
	if err != nil {
		panic(err.Error())
	}
	
	err = c.ClearLog()
	if err != nil {
		panic(err.Error())
	}
	
	err = c.Restart()
	if err != nil {
		panic(err.Error())
	}
}

func (s *businessLogService) TailLog(name string, ws *ghttp.WebSocket) error {
	c, err := supervisord.NewClient("http://127.0.0.1:9001/RPC2")
	if err != nil {
		return err
	}
	defer c.Close()
	processInfo, err := c.GetProcessInfo(name)
	if err != nil {
		logger.Error(err)
		return err
	}
	filename = processInfo.StdoutLogfile
	logger.Debug(filename)
	s.serveWs(ws)
	return nil
}

/***
編譯時需要安裝以下依賴：
go get github.com/gorilla/websocket
go get github.com/hpcloud/tail
*/
const (
	// Time allowed to write the file to the client.
	//writeWait = 1 * time.Second
	writeWait = 100 * time.Millisecond

	// Time allowed to read the next pong message from the client.
	//pongWait = 24 * time.Hour
	pongWait = 60 * time.Second

	// Send pings to client with this period. Must be less than pongWait.
	pingPeriod = (pongWait * 9) / 10

	// Poll file for changes with this period.
	filePeriod = 1 * time.Second
)

var (
	filename string
)

func (s *businessLogService) readFileIfModified(lastMod time.Time) ([]byte, time.Time, error) {
	fi, err := os.Stat(filename)
	if err != nil {
		return nil, lastMod, err
	}
	if !fi.ModTime().After(lastMod) {
		return nil, lastMod, nil
	}
	p, err := ioutil.ReadFile(filename)
	if err != nil {
		return nil, fi.ModTime(), err
	}
	return p, fi.ModTime(), nil
}

func (s *businessLogService) reader(ws *ghttp.WebSocket) {
	defer ws.Close()
	ws.SetReadLimit(512)
	ws.SetReadDeadline(time.Now().Add(pongWait))
	ws.SetPongHandler(func(string) error { ws.SetReadDeadline(time.Now().Add(pongWait)); return nil })
	for {
		_, _, err := ws.ReadMessage()
		if err != nil {
			logger.Warn(err)
			break
		}
	}
}

func (s *businessLogService) tailFile() *tail.Tail {
	tailFd, err := tail.TailFile(filename, tail.Config{
		ReOpen:    true,                                 // 文件被移除或被打包，需要重新打開
		Follow:    true,                                 // 實時跟蹤
		Location:  &tail.SeekInfo{Offset: 0, Whence: 2}, // 如果程序出現異常，保存上次讀取的位置，避免重新讀取。
		MustExist: false,                                // 如果文件不存在，是否推出程序，false是不退出
		Poll:      true,
	})

	if err != nil {
		logger.Error("tail file failed, err:", err)
		return nil
	}
	return tailFd
}

func (s *businessLogService) writer(ws *ghttp.WebSocket) {
	tailFd := s.tailFile()
	pingTicker := time.NewTicker(pingPeriod)
	fileTicker := time.NewTicker(filePeriod)
	maxTimeout := time.NewTicker(time.Duration(1) * time.Minute)
	defer func() {
		pingTicker.Stop()
		fileTicker.Stop()
		ws.Close()
	}()

	for {
		select {
		case msg, ok := <-tailFd.Lines:
			if ok {
				ws.SetWriteDeadline(time.Now().Add(writeWait))
				logger.Debug("read file content： %s\n", msg)
				if err := ws.WriteMessage(websocket.TextMessage, []byte(msg.Text)); err != nil {
					return
				}
			}
		case <-pingTicker.C:
			ws.SetWriteDeadline(time.Now().Add(writeWait))
			if err := ws.WriteMessage(websocket.PingMessage, []byte{}); err != nil {
				return
			}
		case <-maxTimeout.C:
			ws.WriteMessage(websocket.TextMessage, []byte("Maximum timeout"))
			ws.Close()
		}
	}
}

func (s *businessLogService) serveWs(ws *ghttp.WebSocket) {
	go s.writer(ws)
	s.reader(ws)
}