use websockets to logout remote users

cmd/web/main.go

@@ -119,6 +119,8 @@ func main() {
 		Session:       session,
 	}
 
+	go app.ListenToWsChannel()
+
 	app.infoLog.Println("Connected to MariaDB")
 
 	err = app.serve()

cmd/web/routes.go

@@ -12,6 +12,8 @@ func (app *application) routes() http.Handler {
 
 	mux.Get("/", app.Home)
 
+	mux.Get("/ws", app.WsEndPoint)
+
 	mux.Route("/admin", func(mux chi.Router) {
 		mux.Use(app.Auth)
 		mux.Get("/virtual-terminal", app.VirtualTerminal)

cmd/web/templates/base.layout.gohtml

@@ -105,7 +105,12 @@
         <script src="https://cdn.jsdelivr.net/npm/bootstrap@5.3.3/dist/js/bootstrap.bundle.min.js"
                 integrity="sha384-YvpcrYf0tY3lHB60NNkmXc5s9fDVZLESaAA55NDzOxhy9GkcIdslK1eN7N6jIeHz"
                 crossorigin="anonymous"></script>
-        <script src="/static/js/base.js"></script>
+        <script type="module">
+            import {wsConn, socket} from "/static/js/base.js"
+            document.addEventListener("DOMContentLoaded", function() {
+                wsConn({{.IsAuthenticated}}, {{.UserID}});
+            });
+        </script>
         {{ block "js" . }}
         {{ end }}
     </body>

cmd/web/ws-handlers.go

@@ -0,0 +1,109 @@
+package main
+
+import (
+	"fmt"
+	"net/http"
+
+	"github.com/gorilla/websocket"
+)
+
+type WebSocketConnection struct {
+	*websocket.Conn
+}
+
+type WsPayload struct {
+	Action      string              `json:"action"`
+	Message     string              `json:"message"`
+	UserName    string              `json:"user_name"`
+	MessageType string              `json:"message_type"`
+	UserID      int                 `json:"user_id"`
+	Conn        WebSocketConnection `json:"-"`
+}
+
+type WsJSONResponse struct {
+	Action  string `json:"action"`
+	Message string `json:"message"`
+	UserID  int    `json:"user_id"`
+}
+
+var upgradeConnection = websocket.Upgrader{
+	ReadBufferSize:  1024,
+	WriteBufferSize: 1024,
+	// since we don't expect any communication from the client side
+	CheckOrigin: func(r *http.Request) bool { return true },
+}
+
+var clients = make(map[WebSocketConnection]string)
+
+var wsChan = make(chan WsPayload)
+
+func (app *application) WsEndPoint(w http.ResponseWriter, r *http.Request) {
+	ws, err := upgradeConnection.Upgrade(w, r, nil)
+	if err != nil {
+		app.errorLog.Println(err)
+		return
+	}
+
+	app.infoLog.Printf("Client connected from %s\n", r.RemoteAddr)
+	var response WsJSONResponse
+	response.Message = "Connected to server"
+
+	err = ws.WriteJSON(response)
+	if err != nil {
+		app.errorLog.Println(err)
+		return
+	}
+
+	conn := WebSocketConnection{Conn: ws}
+	clients[conn] = ""
+
+	go app.ListenForWS(&conn)
+}
+
+func (app *application) ListenForWS(conn *WebSocketConnection) {
+	defer func() {
+		if r := recover(); r != nil {
+			app.errorLog.Println("ERROR:", fmt.Sprintf("%v", r))
+		}
+	}()
+
+	var payload WsPayload
+
+	for {
+		err := conn.ReadJSON(&payload)
+		if err != nil {
+			// do nothing
+			app.errorLog.Println(err)
+			break
+		}
+		payload.Conn = *conn
+		wsChan <- payload
+	}
+}
+
+func (app *application) ListenToWsChannel() {
+	var response WsJSONResponse
+	for {
+		e := <-wsChan
+		switch e.Action {
+		case "deleteUser":
+			response.Action = "logout"
+			response.Message = "Your account has ben deleted"
+			response.UserID = e.UserID
+			app.broadcastToAll(response)
+		default:
+		}
+	}
+}
+
+func (app *application) broadcastToAll(response WsJSONResponse) {
+	for client := range clients {
+		// broadcast to every connected client
+		err := client.WriteJSON(response)
+		if err != nil {
+			app.errorLog.Printf("Websocket err on %s: %s", response.Action, err)
+			_ = client.Close()
+			delete(clients, client)
+		}
+	}
+}