pong-game/PongGame/Hubs/PongHub.cs

using Microsoft.AspNetCore.SignalR;

namespace PongGame.Hubs;

public class PongHub : Hub<IPongClient> {
    private const string PLAYER_KEY = "PLAYER";
    private readonly PongLobby Lobby;
    private readonly ILogger<PongHub> Logger;

    public PongHub(PongLobby lobby, ILogger<PongHub> logger) : base() {
        Lobby = lobby;
        Logger = logger;
    }

    private PongPlayer Player {
        get => (Context.Items.TryGetValue(PLAYER_KEY, out var player) ? player as PongPlayer : null)
            ?? throw new InvalidProgramException("Player was not assigned at connection start!");
        set => Context.Items[PLAYER_KEY] = value;
    }

    public override Task OnConnectedAsync() {
        Player = Lobby.CreatePlayer();
        Player.Client = Clients.Client(Context.ConnectionId);
        return Task.CompletedTask;
    }

    private void AssertNotInRoom() {
        if (Player.ConnectedRoom is PongRoom currentRoom)
            throw new HubException($"User is already connected to room [{currentRoom}]");
    }

    private PongRoom AssertInRoom() {
        if (Player.ConnectedRoom is not PongRoom currentRoom)
            throw new HubException($"User is not in any room!");
        return currentRoom;
    }

    public Task<string> CreateRoom() {
        AssertNotInRoom();
        var room = Lobby.CreateRoom(Player);
        return Task.FromResult(room.ID);
    }

    public async Task<string> JoinRoom(string roomId) {
        AssertNotInRoom();
        var room = await Lobby.JoinRoom(Player, roomId);
        return room.ID;
    }

    public Task MovePaddle(int dir) {
        var room = AssertInRoom();
        var direction = (PongPaddleDirection)dir;
        if (!Enum.IsDefined(direction))
            throw new HubException($"Invalid direction: {dir}!");
        return room.MovePaddle(Player, direction);
    }

    public Task LeaveRoom()
        => Lobby.LeaveRoom(Player);

    public Task RequestUsernameChange(string username)
        => Lobby.ChangeUsername(Player, username);

    public override Task OnDisconnectedAsync(Exception? exception) {
        Lobby.RemovePlayer(Player);
        return Task.CompletedTask;
    }
}