feat: initial ws client

backend/services/controller/internal/ws/ws.go

@@ -0,0 +1,95 @@
+package ws
+
+import (
+	"context"
+	"log"
+	"time"
+
+	"github.com/gorilla/websocket"
+)
+
+type Ws struct {
+	Addr  string
+	Port  string
+	Token string
+	Route string
+	Auth  bool
+	TLS   bool
+	Ctx   context.Context
+}
+
+const (
+	WS_CONNECTION_RETRY = 10 * time.Second
+)
+
+// Global Websocket connection used in this package
+var wsConn *websocket.Conn
+
+func (w *Ws) Connect() {
+
+	var wsUrl string
+	if w.Auth {
+		log.Println("WS token: ", w.Token)
+		// e.g. ws://localhost:8080/ws/controller?token=123456
+		wsUrl = "ws://" + w.Addr + ":" + w.Port + w.Route + "?token=" + w.Token
+	} else {
+		// e.g. ws://localhost:8080/ws/controller
+		wsUrl = "ws://" + w.Addr + ":" + w.Port + w.Route
+	}
+
+	// Keeps trying to connect to the WS endpoint until it succeeds or receives a stop signal
+	go func() {
+		for {
+			c, _, err := websocket.DefaultDialer.Dial(wsUrl, nil)
+			if err != nil {
+				log.Printf("Error to connect to %s, err: %s", wsUrl, err)
+				time.Sleep(WS_CONNECTION_RETRY)
+				continue
+			}
+			// instantiate global ws connection
+			wsConn = c
+			log.Println("Connected to WS endpoint--> ", wsUrl)
+			go w.Subscribe()
+			break
+		}
+	}()
+}
+
+func (w *Ws) Disconnect() {
+	log.Println("Disconnecting from WS endpoint...")
+
+	if wsConn != nil {
+		err := wsConn.Close()
+		if err != nil {
+			log.Println("Error while disconnecting from WS endpoint:", err.Error())
+		}
+		log.Println("Succesfully disconnected from WS endpoint")
+	} else {
+		log.Println("No WS connection to close")
+	}
+}
+
+// Websockets doesn't follow pub/sub architecture, but we use these
+// naming here to implement the Broker interface and abstract the MTP layer.
+/* -------------------------------------------------------------------------- */
+
+func (w *Ws) Subscribe() {
+	for {
+		_, message, err := wsConn.ReadMessage()
+		if err != nil {
+			log.Println("read:", err)
+			return
+		}
+		log.Printf("recv: %s", message)
+	}
+}
+
+func (w *Ws) Publish(msg []byte, topic, respTopic string, retain bool) {
+	err := wsConn.WriteMessage(websocket.TextMessage, msg)
+	if err != nil {
+		log.Println("write:", err)
+		return
+	}
+}
+
+/* -------------------------------------------------------------------------- */