client.go

package gws

import (
	"log"
	"net/http"
	"time"

	"github.com/gorilla/websocket"
	"github.com/satori/go.uuid"
)

const (
	writeWait      = 10 * time.Second
	pongWait       = 60 * time.Second
	pingPeriod     = (pongWait * 9) / 10
	maxMessageSize = 4096
)

var upgrader = websocket.Upgrader{
	ReadBufferSize:  1024,
	WriteBufferSize: 1024,
	CheckOrigin: func(r *http.Request) bool {
		// Allow cross origin
		return true
	},
}

type client struct {
	id  string
	hub *Hub

	conn *websocket.Conn

	// Buffered channel of outbound message
	send chan []byte
}

// readPump pumps messages from the websocket connection to the hub
//
// The application runs readPump in a routine for each connection.
// This ensures that there is only one reader on a connection by
// executing all reads from this goroutine.
func (c *client) readPump() {
	defer func() {
		c.hub.unregister <- c
		c.conn.Close()
	}()
	c.conn.SetReadLimit(maxMessageSize)
	c.conn.SetReadDeadline(time.Now().Add(pongWait))
	c.conn.SetPongHandler(func(string) error { c.conn.SetReadDeadline(time.Now().Add(pongWait)); return nil })
	for {
		_, rawMessage, err := c.conn.ReadMessage()
		if err != nil {
			if websocket.IsUnexpectedCloseError(err, websocket.CloseGoingAway) {
				log.Printf("err: %v", err)
			}
			break
		}

		message := newMessage(c.id, ClientMessage, rawMessage)
		c.hub.fromClient <- *message
	}
}

// writePump pumps messages from the hub to the websocket connection.
//
// a goroutine running writePump is started for each connection.
func (c *client) writePump() {
	ticker := time.NewTicker(pingPeriod)
	defer func() {
		ticker.Stop()
		c.conn.Close()
	}()
	for {
		select {
		case message, ok := <-c.send:
			c.conn.SetWriteDeadline(time.Now().Add(writeWait))
			if !ok {
				// The hub closed the channel.
				c.conn.WriteMessage(websocket.CloseMessage, []byte{})
				return
			}

			w, err := c.conn.NextWriter(websocket.TextMessage)
			if err != nil {
				return
			}

			w.Write(message)

			// Add queued messages to the current websocket message
			n := len(c.send)
			for i := 0; i < n; i++ {
				w.Write(<-c.send)
			}

			if err := w.Close(); err != nil {
				return
			}
		case <-ticker.C:
			c.conn.SetWriteDeadline(time.Now().Add(writeWait))
			if err := c.conn.WriteMessage(websocket.PingMessage, []byte{}); err != nil {
				return
			}
		}
	}
}

func serveWs(hub *Hub, w http.ResponseWriter, r *http.Request) {
	conn, err := upgrader.Upgrade(w, r, nil)
	if err != nil {
		log.Println(err)
		return
	}

	c := &client{id: uuid.NewV4().String(), hub: hub, conn: conn, send: make(chan []byte)}
	c.hub.register <- c

	go c.writePump()
	c.readPump()
}