Innovenergy_trunk/csharp/App/Backend/Websockets/WebsockerManager.cs

using System.Diagnostics.CodeAnalysis;
using System.Net;
using System.Net.Sockets;
using System.Net.WebSockets;
using System.Text;
using System.Text.Json;
using RabbitMQ.Client;
using RabbitMQ.Client.Events;

namespace InnovEnergy.App.Backend.Websockets;

public static class WebsocketManager
{
    public static readonly Dictionary<int, InstallationInfo> InstallationConnections = new Dictionary<int, InstallationInfo>();
    private static ConnectionFactory _factory = null!;
    private static IConnection _connection = null!;
    private static IModel _channel = null!;

    public static void InformInstallationsToSubscribeToRabbitMq()
    {
        var installationsIds = new List<int> { 1 };
        var installationIps = new List<string> { "10.2.3.115" };
        var maxRetransmissions = 2;

        StartRabbitMqConsumer();

        UdpClient udpClient = new UdpClient();
        udpClient.Client.ReceiveTimeout = 2000;
        int port = 9000;
        //Send a message to each installation and tell it to subscribe to the queue
        for (int i = 0; i < installationsIds.Count; i++)
        {
            using (udpClient)
            {
                //Try at most MAX_RETRANSMISSIONS times to reach an installation.
                for (int j = 0; j < maxRetransmissions; j++)
                {
                    string message = "This is a message from RabbitMQ server, you can subscribe to the RabbitMQ queue";
                    byte[] data = Encoding.UTF8.GetBytes(message);
                    udpClient.Send(data, data.Length, installationIps[i], port);

                    Console.WriteLine($"Sent UDP message to {installationIps[i]}:{port}: {message}");
                    IPEndPoint remoteEndPoint = new IPEndPoint(IPAddress.Parse(installationIps[i]), port);

                    try
                    {
                        byte[] replyData = udpClient.Receive(ref remoteEndPoint);
                        string replyMessage = Encoding.UTF8.GetString(replyData);
                        Console.WriteLine("Received "+replyMessage +" from installation " + installationsIds[i]);
                        break;
                    }
                    catch (SocketException ex)
                    {
                        if (ex.SocketErrorCode == SocketError.TimedOut)
                        {
                            Console.WriteLine("Timed out waiting for a response. Retry...");
                        }
                        else
                        {
                            Console.WriteLine("Error: " + ex.Message);
                        }
                    }
                }
            }
        }
    }

    public static void StartRabbitMqConsumer()
    {
        //string vpnServerIp = "194.182.190.208";
        string vpnServerIp = "127.0.0.1";
        _factory = new ConnectionFactory { HostName = vpnServerIp};
        _connection = _factory.CreateConnection();
        _channel = _connection.CreateModel();
        Console.WriteLine("Middleware subscribed to RabbitMQ queue, ready for receiving messages");
        _channel.QueueDeclare(queue: "statusQueue", durable: false, exclusive: false, autoDelete: false, arguments: null);

        var consumer = new EventingBasicConsumer(_channel);
        consumer.Received += (_, ea) => CallbackReceiveMessageFromQueue(ea);
        _channel.BasicConsume(queue: "statusQueue", autoAck: true, consumer: consumer);
    }

    [UnconditionalSuppressMessage("Trimming", "IL2026:Members annotated with 'RequiresUnreferencedCodeAttribute' require dynamic access otherwise can break functionality when trimming application code", Justification = "<Pending>")]
    private static void CallbackReceiveMessageFromQueue(BasicDeliverEventArgs ea)
    {
        var body = ea.Body.ToArray();
        var message = Encoding.UTF8.GetString(body);
        StatusMessage? receivedStatusMessage = JsonSerializer.Deserialize<StatusMessage>(message);

        lock (InstallationConnections)
        {
            // Process the received message
            if (receivedStatusMessage != null)
            {
                Console.WriteLine("Received a message from installation: " + receivedStatusMessage.InstallationId + " and status is: " + receivedStatusMessage.Status);
                Console.WriteLine("----------------------------------------------");
                Console.WriteLine("Update installation connection table");
                var installationId = receivedStatusMessage.InstallationId;

                if (!InstallationConnections.ContainsKey(installationId))
                {
                    Console.WriteLine("Create new empty list for installation: " + installationId);
                    InstallationConnections[installationId] = new InstallationInfo
                    {
                        Status = receivedStatusMessage.Status
                    };
                }

                Console.WriteLine("----------------------------------------------");

                foreach (var installationConnection in InstallationConnections)
                {
                    if (installationConnection.Key == installationId && installationConnection.Value.Connections.Count > 0)
                    {
                        Console.WriteLine("Update all the connected websockets for installation " + installationId);
                        installationConnection.Value.Status = receivedStatusMessage.Status;

                        var jsonObject = new
                        {
                            id = installationId,
                            status = receivedStatusMessage.Status
                        };

                        string jsonString = JsonSerializer.Serialize(jsonObject);
                        byte[] dataToSend = Encoding.UTF8.GetBytes(jsonString);

                        foreach (var connection in installationConnection.Value.Connections)
                        {
                            connection.SendAsync(
                                new ArraySegment<byte>(dataToSend, 0, dataToSend.Length),
                                WebSocketMessageType.Text,
                                true, // Indicates that this is the end of the message
                                CancellationToken.None
                            );
                        }
                    }
                }
            }
        }
    }

    [UnconditionalSuppressMessage("Trimming", "IL2026:Members annotated with 'RequiresUnreferencedCodeAttribute' require dynamic access otherwise can break functionality when trimming application code", Justification = "<Pending>")]
    public static async Task HandleWebSocketConnection(WebSocket currentWebSocket)
    {
        var buffer = new byte[4096];
        try
        {
            while (currentWebSocket.State == WebSocketState.Open)
            {
                //Listen for incoming messages on this WebSocket
                var result = await currentWebSocket.ReceiveAsync(buffer, CancellationToken.None);
                Console.WriteLine("Received a new message from websocket");
                if (result.MessageType != WebSocketMessageType.Text)
                    continue;
                
                var message = Encoding.UTF8.GetString(buffer, 0, result.Count);
                var installationIds = JsonSerializer.Deserialize<int[]>(message);

                lock (InstallationConnections)
                {
                    //Each front-end will send the list of the installations it wants to access
                    //If this is a new key (installation id), initialize the list for this key and then add the websocket object for this client
                    //Then, report the status of each requested installation to the front-end that created the websocket connection
                    if (installationIds != null)
                        foreach (var installationId in installationIds)
                        {
                            if (!InstallationConnections.ContainsKey(installationId))
                            {
                                Console.WriteLine("Create new empty list for installation id " + installationId);
                                InstallationConnections[installationId] = new InstallationInfo
                                {
                                    Status = -2
                                };
                            }

                            InstallationConnections[installationId].Connections.Add(currentWebSocket);

                            var jsonObject = new
                            {
                                id = installationId,
                                status = InstallationConnections[installationId].Status
                            };

                            var jsonString = JsonSerializer.Serialize(jsonObject);
                            var dataToSend = Encoding.UTF8.GetBytes(jsonString);


                            currentWebSocket.SendAsync(dataToSend,
                                WebSocketMessageType.Text,
                                true, // Indicates that this is the end of the message
                                CancellationToken.None
                            );
                        }

                    Console.WriteLine("Printing installation connection list");
                    Console.WriteLine("----------------------------------------------");
                    foreach (var installationConnection in InstallationConnections)
                    {
                        Console.WriteLine("Installation ID: " + installationConnection.Key + " Number of Connections: " + installationConnection.Value.Connections.Count);
                    }
                    Console.WriteLine("----------------------------------------------");
                }
            }

            lock (InstallationConnections)
            {
                //When the front-end terminates the connection, the following code will be executed
                Console.WriteLine("The connection has been terminated");
                foreach (var installationConnection in InstallationConnections)
                {
                    if (installationConnection.Value.Connections.Contains(currentWebSocket))
                    {
                        installationConnection.Value.Connections.Remove(currentWebSocket);
                    }
                }
            }

            await currentWebSocket.CloseAsync(WebSocketCloseStatus.NormalClosure, "Connection closed by server", CancellationToken.None);
            lock (InstallationConnections)
            {
                //Print the installationConnections dictionary after deleting a websocket
                Console.WriteLine("Print the installation connections list after deleting a websocket");
                Console.WriteLine("----------------------------------------------");
                foreach (var installationConnection in InstallationConnections)
                {
                    Console.WriteLine("Installation ID: " + installationConnection.Key + " Number of Connections: " + installationConnection.Value.Connections.Count);
                }

                Console.WriteLine("----------------------------------------------");
            }
        }
        catch (Exception ex)
        {
            Console.WriteLine("WebSocket error: " + ex.Message);
        }
    }
    
}