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package main
import (
"github.com/gin-gonic/gin"
"github.com/gorilla/websocket"
log "github.com/sirupsen/logrus"
"net"
"net/http"
"time"
)
const (
InsertNotification = "insert"
UpdateNotification = "update"
DeleteNotification = "delete"
writeWait = 10 * time.Second
pongWait = 60 * time.Second
pingPeriod = (pongWait * 9) / 10
maxMessageSize = 512
)
type NotificationController struct {
upgrader websocket.Upgrader
clients map[net.Addr]*client
broadcast chan interface{}
register chan *client
unregister chan *client
applicationContext *ApplicationContext
}
func NewNotificationController(applicationContext *ApplicationContext) *NotificationController {
return &NotificationController{
upgrader: websocket.Upgrader{
ReadBufferSize: 1024,
WriteBufferSize: 1024,
},
clients: make(map[net.Addr]*client),
broadcast: make(chan interface{}),
register: make(chan *client),
unregister: make(chan *client),
applicationContext: applicationContext,
}
}
type client struct {
conn *websocket.Conn
send chan interface{}
notificationController *NotificationController
}
func (wc *NotificationController) NotificationHandler(w http.ResponseWriter, r *http.Request) error {
conn, err := wc.upgrader.Upgrade(w, r, nil)
if err != nil {
log.WithError(err).Error("failed to set websocket upgrade")
return err
}
client := &client{
conn: conn,
send: make(chan interface{}),
notificationController: wc,
}
wc.register <- client
go client.readPump()
go client.writePump()
return nil
}
func (wc *NotificationController) Run() {
for {
select {
case client := <-wc.register:
wc.clients[client.conn.RemoteAddr()] = client
payload := gin.H{"event": "connected", "message": gin.H{
"version": wc.applicationContext.Version,
"is_configured": wc.applicationContext.IsConfigured,
"connected_clients": len(wc.clients),
}}
client.send <- payload
log.WithField("connected_clients", len(wc.clients)).
WithField("remote_address", client.conn.RemoteAddr()).
Info("[+] a websocket client connected")
case client := <-wc.unregister:
if _, ok := wc.clients[client.conn.RemoteAddr()]; ok {
close(client.send)
_ = client.conn.WriteMessage(websocket.CloseMessage, nil)
_ = client.conn.Close()
delete(wc.clients, client.conn.RemoteAddr())
log.WithField("connected_clients", len(wc.clients)).
WithField("remote_address", client.conn.RemoteAddr()).
Info("[-] a websocket client disconnected")
}
case payload := <-wc.broadcast:
for _, client := range wc.clients {
select {
case client.send <- payload:
default:
close(client.send)
delete(wc.clients, client.conn.RemoteAddr())
}
}
}
}
}
func (wc *NotificationController) Notify(event string, eventType string, message interface{}) {
wc.broadcast <- gin.H{"event": event, "event_type": eventType, "message": message}
}
func (c *client) readPump() {
c.conn.SetReadLimit(maxMessageSize)
if err := c.conn.SetReadDeadline(time.Now().Add(pongWait)); err != nil {
c.close()
return
}
c.conn.SetPongHandler(func(string) error { return c.conn.SetReadDeadline(time.Now().Add(pongWait)) })
for {
if _, _, err := c.conn.ReadMessage(); err != nil {
if websocket.IsUnexpectedCloseError(err, websocket.CloseGoingAway) {
log.WithError(err).WithField("remote_address", c.conn.RemoteAddr()).
Warn("unexpected websocket disconnection")
}
break
}
}
c.close()
}
func (c *client) writePump() {
ticker := time.NewTicker(pingPeriod)
defer ticker.Stop()
for {
select {
case payload, ok := <-c.send:
if !ok {
return
}
if err := c.conn.SetWriteDeadline(time.Now().Add(writeWait)); err != nil {
c.close()
return
}
if err := c.conn.WriteJSON(payload); err != nil {
c.close()
return
}
case <-ticker.C:
if err := c.conn.SetWriteDeadline(time.Now().Add(writeWait)); err != nil {
c.close()
return
}
if err := c.conn.WriteMessage(websocket.PingMessage, nil); err != nil {
c.close()
return
}
}
}
}
func (c *client) close() {
c.notificationController.unregister <- c
}
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