Explanation of the code

This Go code defines a WebSocket server that can handle multiple channels, broadcast data to all clients in a given channel, and be started and stopped. It uses the gorilla/websocket package to manage WebSocket connections.

IWebSocketServer interface

This interface defines the methods that any implementation of the WebSocket server must implement. It includes methods for starting and stopping the server, broadcasting data to clients in a channel, and adding a channel to the server.

DefaultWebSocketServer struct

This struct is the default implementation of the IWebSocketServer interface. It has the following fields:

• upgrader: a websocket.Upgrader instance that is used to upgrade HTTP connections to WebSocket connections.
• clients: a map of WebSocket connections to a boolean value indicating whether they are still active.
• channels: a map of channel names to maps of WebSocket connections to a boolean value indicating whether they are subscribed to the channel. The struct also includes the following methods:
• Start(): starts the WebSocket server by creating an HTTP server and listening on the specified host and port. It also sets up a route for handling HTTP requests and upgrading them to WebSocket connections.
• Stop(): stops the WebSocket server by closing all WebSocket connections and deleting them from the clients and channels maps.
• handleHTTPRequest(): handles incoming HTTP requests and upgrades them to WebSocket connections if the requested URL matches an existing channel. If the URL does not match an existing channel, it returns a 404 Not Found error.
• upgradeWebSocket(): upgrades an HTTP connection to a WebSocket connection and adds the connection to the clients and channels maps.
• Broadcast(): sends a message to all WebSocket connections in a given channel.
• AddChannel(): adds a new channel to the server.

Utility functions

getEnvOrDefault(): retrieves the value of an environment variable or returns a default value if the variable is not set.

Usage

Backend setup

    // SETUP THE WEBSOCKET SERVER
	websocketServer := websockets.NewDefaultWebSocketServer()
    // ADD CHANNELS YOU WANT TO USE
	websocketServer.AddChannel("/ws/test1")
	websocketServer.AddChannel("/ws/test2")

	go func() {
		websocketServer.Start()
	}()

	// SEND DATA TO THE WEBSOCKET SERVER IN A LOOP OR WHENEVER YOU WANT AND WHATEVER YOU WANT
	for {
		time.Sleep(5 * time.Second)
		websocketServer.Broadcast("/ws/test1", "test message one")
		websocketServer.Broadcast("/ws/test2", "test message two")
	}

    // YOU CAN ALSO SEND STRUCTS
    type TestStruct struct {
        Name string
        Age int
    }
    websocketServer.Broadcast("/ws/test1", TestStruct{Name: "Naruto", Age: 30})
    websocketServer.Broadcast("/ws/test2", TestStruct{Name: "Yagami", Age: 25})

Frontend setup

    // I RECOMMEND USING THIS HELPER FUNCTION TO ESTABLISH A CONNECTION WITH THE WEBSOCKET SERVER
    // IN A CALLBACK FUNCTION YOU CAN DO WHATEVER YOU WANT WITH THE DATA YOU RECEIVE FROM THE WEBSOCKET SERVER
    function connectToWebSocketServer(p_url, p_channelName, p_functionInvokedOnMessageFromServer) {

        const socket = new WebSocket(p_url);
        socket.onopen = (event) => {
            console.log("Connected to WebSocket server: " + p_url + " on channel: " + p_channelName);
            socket.send(p_channelName);
        };

        socket.onmessage = (event) => {
            const parsedData = JSON.parse(event.data);
            p_functionInvokedOnMessageFromServer(parsedData);
        };

        socket.onclose = (event) => {
            console.log("Disconnected from WebSocket server");
        };
    }

    // THIS IS THE CALLBACK FUNCTION THAT WILL BE INVOKED WHEN THE WEBSOCKETSERVER SENDS DATA, 
    // YOU CAN DO WHATEVER YOU WANT WITH THE DATA
    function outputData(p_data) {
        console.log("Received message:", data);
        // DO YOUR STUFF HERE
    }

    // INVOKING THE HELPER FUNCTION
    connectToWebSocketServer("ws://localhost:8080", "/ws/test1", outputData);
    connectToWebSocketServer("ws://localhost:8080", "/ws/test2", outputData);


    // OR YOU CAN USE IT EXPLICITLY LIKE THIS
    // SOCKET1
    const socket = new WebSocket('ws://localhost:8080/ws/test1');
    socket.onopen = (event) => {
    console.log("Connected to WebSocket server");
    };
    socket.onmessage = (event) => {
        const data = JSON.parse(event.data);
        console.log("Received message:", data);
        // DO YOUR STUFF HERE
    };
    socket.onclose = (event) => {
    console.log("Disconnected from WebSocket server");
    };

    // SOCKET2
    const socket2 = new WebSocket('ws://localhost:8080/ws/test2');
    socket2.onopen = (event) => {
    console.log("Connected to WebSocket server");
    };
    socket2.onmessage = (event) => {
        const data = JSON.parse(vent.data);
        console.log("Received message:", data);
        // DO YOUR STUFF HERE
    };
    socket2.onclose = (event) => {
    console.log("Disconnected from WebSocket server");
    };