MauMau-Server/Room/Room.cs

using System.Net.WebSockets;
using System.Text.Json;
using System.Text.RegularExpressions;
using MauMau_Server.Room.Messages;
using MauMau_Server.Websockets;
using Microsoft.AspNet.SignalR.Messaging;

namespace MauMau_Server.Room;

public class Room
{
    private readonly IRoomManager _roomManager;
    private readonly string _roomId;
    public readonly List<ConnectionInstance> Connections = new();
    public ConnectionInstance? Host;
    public RoomType RoomType;

    public Room(IRoomManager roomManager, string roomId)
    {
        _roomManager = roomManager;
        RoomType = new Lobby(this);
        _roomId = roomId;
    }

    public async Task InstantiateConnection(WebSocket socket, string name)
    {
        var connectionId = Guid.NewGuid();

        // If the name is empty, set it to "Mau" + the first part of the connection ID, otherwise strip potential HTML from the name and use it
        var validatedName = !string.IsNullOrWhiteSpace(name)
            ? StripHTML(name)
            : "Mau" + connectionId.ToString().Split('-')[0];
        
        var connection = new ConnectionInstance(validatedName, connectionId, socket);
        if (IsEmpty()) Host = connection;
        Connections.Add(connection);

        RoomType.OnConnect(connection);
        await HandleConnection(connection);
    }

    private async Task HandleConnection(ConnectionInstance connection)
    {
        var webSocketResponse = await WebsocketManager.ReceiveAsync(connection.Socket);
        while (!webSocketResponse.Result!.CloseStatus.HasValue)
        {
            var message = JsonSerializer.Deserialize<RoomMessage<string>>(webSocketResponse.SlicedBuffer);
            switch (message.Type)
            {
                case "CHAT":
                    HandleChatMessage(connection, message.Data);
                    break;
                case "KICK":
                    await HandleKick(Guid.Parse(message.Data));
                    break;
                default:
                    RoomType.OnMessage(connection, message);
                    break;
            }

            webSocketResponse = await WebsocketManager.ReceiveAsync(connection.Socket);
        }

        WebsocketManager.CloseAsync(connection.Socket, webSocketResponse.Result);
        HandleDisconnect(connection);
    }

    private void HandleChatMessage(ConnectionInstance sender, string chatMessage)
    {
        // Remove HTML from chat message to prevent HTML injection
        var cleanedMessage = StripHTML(chatMessage);

        // If the message is empty, set it to "Mau!"
        if (string.IsNullOrWhiteSpace(cleanedMessage)) cleanedMessage = "Mau!";

        // Create a new chat message object with the sender and the message
        var envelope = new ChatMessage(sender.Name, cleanedMessage);

        // Broadcast the chat message to all connections in the room
        BroadCast(new RoomMessage<ChatMessage>("CHAT", envelope));
    }

    private async Task HandleKick(Guid connectionId)
    {
        // Search for the connection with the given ID
        var connection = Connections.FirstOrDefault(connection => connection.Id == connectionId);

        // If the connection could not be found, return
        if (connection == null) return;
        
        // Handle the disconnect of the connection
        HandleDisconnect(connection);

        // Close the connection with the reason "You have been kicked"
        await connection.Socket.CloseAsync(WebSocketCloseStatus.NormalClosure, "You have been kicked",
            CancellationToken.None);
    }

    private void HandleDisconnect(ConnectionInstance connection)
    {
        Connections.Remove(connection);
        RoomType.OnDisconnect(connection);
        if (IsEmpty())
        {
            _roomManager.RemoveRoom(_roomId);
            return;
        }

        if (connection == Host)
        {
            Host = Connections.First();
        }
    }

    public void BroadCast<T>(RoomMessage<T> message)
    {
        foreach (var connection in Connections)
        {
            connection.SendMessageAsync(JsonSerializer.Serialize(message));
        }
    }

    public bool IsEmpty()
    {
        return Connections.Count == 0;
    }

    private static string StripHTML(string input)
    {
        return Regex.Replace(input, "<.*?>", string.Empty);
    }
}