feat: add multiplayer session support with ENet host/join

src/Features/Console/Application/Commands/HostCommand.cs

@@ -0,0 +1,29 @@
+using System.Collections.Generic;
+using Game.Features.Console.Contracts;
+using Game.Features.Multiplayer.Contracts;
+using Game.Features.Multiplayer.Contracts.Exceptions;
+
+namespace Game.Features.Console.Application.Commands;
+
+public sealed class HostCommand(IMultiplayerPeer multiplayer) : ICommand
+{
+    public string Name => "host";
+    public string Description => "Starts hosting a multiplayer session on the given port.";
+    public IReadOnlyList<CommandArgSpec> Args { get; } = new CommandArgsBuilder().AddIntArg("port").Build();
+
+    public CommandResult Execute(CommandArgValues args)
+    {
+        int port = args.GetInt(0);
+
+        try
+        {
+            multiplayer.Host(port);
+        }
+        catch (MultiplayerException ex)
+        {
+            return CommandResult.Fail(ex.Message);
+        }
+
+        return CommandResult.Ok($"Hosting on port {port}.");
+    }
+}

src/Features/Console/Application/Commands/HostCommand.cs.uid

@@ -0,0 +1 @@
+uid://crmnspnxcut3y

src/Features/Console/Application/Commands/JoinCommand.cs

@@ -0,0 +1,35 @@
+using System.Collections.Generic;
+using Game.Features.Console.Contracts;
+using Game.Features.Multiplayer.Contracts;
+using Game.Features.Multiplayer.Contracts.Exceptions;
+
+namespace Game.Features.Console.Application.Commands;
+
+public sealed class JoinCommand(IMultiplayerPeer multiplayer) : ICommand
+{
+    private const string AddressPattern =
+        @"^(localhost|((25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.){3}(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?))$";
+
+    public string Name => "join";
+    public string Description => "Joins a multiplayer session at the given address and port.";
+
+    public IReadOnlyList<CommandArgSpec> Args { get; } =
+        new CommandArgsBuilder().AddRegexArg("address", AddressPattern).AddIntArg("port").Build();
+
+    public CommandResult Execute(CommandArgValues args)
+    {
+        string address = args.GetString(0);
+        int port = args.GetInt(1);
+
+        try
+        {
+            multiplayer.Join(address, port);
+        }
+        catch (MultiplayerException ex)
+        {
+            return CommandResult.Fail(ex.Message);
+        }
+
+        return CommandResult.Ok($"Connecting to {address}:{port}...");
+    }
+}

src/Features/Console/Application/Commands/JoinCommand.cs.uid

@@ -0,0 +1 @@
+uid://c80rskv3u7su7

src/Features/Console/Godot/ConsoleController.cs

@@ -33,7 +33,7 @@ public partial class ConsoleController : CanvasLayer
         }
     }
 
-    private void AppendLine(string line)
+    public void AppendLine(string line)
     {
         OutputLog.AppendText(line + "\n");
     }

src/Features/Multiplayer/Contracts/Exceptions/MultiplayerAlreadyConnectedException.cs

@@ -0,0 +1,6 @@
+namespace Game.Features.Multiplayer.Contracts.Exceptions;
+
+/// <summary>
+/// Thrown when trying to host or join while already connected to a session.
+/// </summary>
+public sealed class MultiplayerAlreadyConnectedException() : MultiplayerException("Already connected to a session.");

src/Features/Multiplayer/Contracts/Exceptions/MultiplayerAlreadyConnectedException.cs.uid

@@ -0,0 +1 @@
+uid://dr6f5t6nhh60w

src/Features/Multiplayer/Contracts/Exceptions/MultiplayerAlreadyHostingException.cs

@@ -0,0 +1,6 @@
+namespace Game.Features.Multiplayer.Contracts.Exceptions;
+
+/// <summary>
+/// Thrown when trying to host or join while already hosting a session.
+/// </summary>
+public sealed class MultiplayerAlreadyHostingException() : MultiplayerException("Already hosting a session.");

src/Features/Multiplayer/Contracts/Exceptions/MultiplayerAlreadyHostingException.cs.uid

@@ -0,0 +1 @@
+uid://c41cffks8ymh0

src/Features/Multiplayer/Contracts/Exceptions/MultiplayerException.cs

@@ -0,0 +1,8 @@
+using System;
+
+namespace Game.Features.Multiplayer.Contracts.Exceptions;
+
+/// <summary>
+/// Base type for multiplayer connection failures.
+/// </summary>
+public abstract class MultiplayerException(string message) : Exception(message);

src/Features/Multiplayer/Contracts/Exceptions/MultiplayerException.cs.uid

@@ -0,0 +1 @@
+uid://ct5t3i77ovfx1

src/Features/Multiplayer/Contracts/Exceptions/MultiplayerHostException.cs

@@ -0,0 +1,11 @@
+namespace Game.Features.Multiplayer.Contracts.Exceptions;
+
+/// <summary>
+/// Thrown when starting a host fails at the transport level.
+/// </summary>
+public sealed class MultiplayerHostException(int port, string reason)
+    : MultiplayerException($"Failed to start host on port {port}: {reason}.")
+{
+    public int Port { get; } = port;
+    public string Reason { get; } = reason;
+}

src/Features/Multiplayer/Contracts/Exceptions/MultiplayerHostException.cs.uid

@@ -0,0 +1 @@
+uid://scqi785gvntu

src/Features/Multiplayer/Contracts/Exceptions/MultiplayerJoinException.cs

@@ -0,0 +1,12 @@
+namespace Game.Features.Multiplayer.Contracts.Exceptions;
+
+/// <summary>
+/// Thrown when connecting to a host fails at the transport level.
+/// </summary>
+public sealed class MultiplayerJoinException(string address, int port, string reason)
+    : MultiplayerException($"Failed to connect to {address}:{port}: {reason}.")
+{
+    public string Address { get; } = address;
+    public int Port { get; } = port;
+    public string Reason { get; } = reason;
+}

src/Features/Multiplayer/Contracts/Exceptions/MultiplayerJoinException.cs.uid

@@ -0,0 +1 @@
+uid://q8oyea00yrxy

src/Features/Multiplayer/Contracts/IMultiplayerPeer.cs

@@ -0,0 +1,18 @@
+using System;
+
+namespace Game.Features.Multiplayer.Contracts;
+
+public interface IMultiplayerPeer
+{
+    event Action Connected;
+    event Action ConnectionFailed;
+    event Action Disconnected;
+    event Action<PeerId> PeerJoined;
+    event Action<PeerId> PeerLeft;
+
+    void Host(int port);
+
+    void Join(string address, int port);
+
+    void Disconnect();
+}

src/Features/Multiplayer/Contracts/IMultiplayerPeer.cs.uid

@@ -0,0 +1 @@
+uid://bs401ksgc6qdn

src/Features/Multiplayer/Contracts/PeerId.cs

@@ -0,0 +1,6 @@
+namespace Game.Features.Multiplayer.Contracts;
+
+public readonly record struct PeerId(long Value)
+{
+    public override string ToString() => Value.ToString();
+}

src/Features/Multiplayer/Contracts/PeerId.cs.uid

@@ -0,0 +1 @@
+uid://bix11ttul7aco

src/Features/Multiplayer/Domain/MultiplayerSession.cs

@@ -0,0 +1,26 @@
+using System.Collections.Generic;
+using Game.Features.Multiplayer.Contracts;
+
+namespace Game.Features.Multiplayer.Domain;
+
+public sealed class MultiplayerSession
+{
+    public const int MaxPlayers = 4;
+    public IReadOnlyCollection<PeerId> PeerIds => _peerIds;
+    public bool IsFull => _peerIds.Count >= MaxPlayers;
+    public bool IsHosting { get; set; }
+    public bool IsConnected { get; set; }
+
+    private readonly HashSet<PeerId> _peerIds = [];
+
+    public void AddPeer(PeerId peerId) => _peerIds.Add(peerId);
+
+    public void RemovePeer(PeerId peerId) => _peerIds.Remove(peerId);
+
+    public void Reset()
+    {
+        _peerIds.Clear();
+        IsHosting = false;
+        IsConnected = false;
+    }
+}

src/Features/Multiplayer/Domain/MultiplayerSession.cs.uid

@@ -0,0 +1 @@
+uid://dbpm807l4bmfk

src/Features/Multiplayer/Godot/EnetMultiplayerPeerFactory.cs

@@ -0,0 +1,21 @@
+using Game.Features.Multiplayer.Contracts.Exceptions;
+using Godot;
+
+namespace Game.Features.Multiplayer.Godot;
+
+public sealed class EnetMultiplayerPeerFactory : IMultiplayerPeerFactory
+{
+    public MultiplayerPeer CreateHost(int port, int maxPeers)
+    {
+        ENetMultiplayerPeer peer = new();
+        Error error = peer.CreateServer(port, maxPeers);
+        return error != Error.Ok ? throw new MultiplayerHostException(port, error.ToString()) : peer;
+    }
+
+    public MultiplayerPeer CreateClient(string address, int port)
+    {
+        ENetMultiplayerPeer peer = new();
+        Error error = peer.CreateClient(address, port);
+        return error != Error.Ok ? throw new MultiplayerJoinException(address, port, error.ToString()) : peer;
+    }
+}

src/Features/Multiplayer/Godot/EnetMultiplayerPeerFactory.cs.uid

@@ -0,0 +1 @@
+uid://dkymguty84h4v

src/Features/Multiplayer/Godot/IMultiplayerPeerFactory.cs

@@ -0,0 +1,10 @@
+using Godot;
+
+namespace Game.Features.Multiplayer.Godot;
+
+public interface IMultiplayerPeerFactory
+{
+    MultiplayerPeer CreateHost(int port, int maxPeers);
+
+    MultiplayerPeer CreateClient(string address, int port);
+}

src/Features/Multiplayer/Godot/IMultiplayerPeerFactory.cs.uid

@@ -0,0 +1 @@
+uid://csk14887ww6q6

src/Features/Multiplayer/Godot/MultiplayerController.cs

@@ -0,0 +1,101 @@
+using System;
+using Game.Features.Multiplayer.Contracts;
+using Game.Features.Multiplayer.Contracts.Exceptions;
+using Game.Features.Multiplayer.Domain;
+using Godot;
+
+namespace Game.Features.Multiplayer.Godot;
+
+public partial class MultiplayerController : Node, IMultiplayerPeer
+{
+    private readonly MultiplayerSession _session = new();
+    private IMultiplayerPeerFactory _multiplayerPeerFactory;
+
+    public event Action Connected;
+    public event Action ConnectionFailed;
+    public event Action Disconnected;
+    public event Action<PeerId> PeerJoined;
+    public event Action<PeerId> PeerLeft;
+
+    private void OnPeerConnected(long id)
+    {
+        PeerId peerId = new(id);
+        _session.AddPeer(peerId);
+        PeerJoined?.Invoke(peerId);
+    }
+
+    private void OnPeerDisconnected(long id)
+    {
+        PeerId peerId = new(id);
+        _session.RemovePeer(peerId);
+        PeerLeft?.Invoke(peerId);
+    }
+
+    private void OnConnectedToServer()
+    {
+        Connected?.Invoke();
+    }
+
+    private void OnConnectionFailed()
+    {
+        _session.Reset();
+        ConnectionFailed?.Invoke();
+    }
+
+    private void OnServerDisconnected()
+    {
+        _session.Reset();
+        Disconnected?.Invoke();
+    }
+    
+    private void AssertNoActiveSession()
+    {
+        if (_session.IsHosting)
+        {
+            throw new MultiplayerAlreadyHostingException();
+        }
+
+        if (_session.IsConnected)
+        {
+            throw new MultiplayerAlreadyConnectedException();
+        }
+    }
+
+    public void UsePeerFactory(IMultiplayerPeerFactory multiplayerPeerFactory)
+    {
+        _multiplayerPeerFactory = multiplayerPeerFactory;
+    }
+
+    public void Host(int port)
+    {
+        AssertNoActiveSession();
+
+        Multiplayer.MultiplayerPeer = _multiplayerPeerFactory.CreateHost(port, MultiplayerSession.MaxPlayers - 1);
+        _session.AddPeer(new PeerId(Multiplayer.GetUniqueId()));
+        _session.IsHosting = true;
+    }
+
+    public void Join(string address, int port)
+    {
+        AssertNoActiveSession();
+
+        Multiplayer.MultiplayerPeer = _multiplayerPeerFactory.CreateClient(address, port);
+        _session.IsConnected = true;
+    }
+
+    public void Disconnect()
+    {
+        Multiplayer.MultiplayerPeer?.Close();
+        Multiplayer.MultiplayerPeer = null;
+        _session.Reset();
+    }
+
+    public override void _Ready()
+    {
+        Multiplayer.PeerConnected += OnPeerConnected;
+        Multiplayer.PeerDisconnected += OnPeerDisconnected;
+        Multiplayer.ConnectedToServer += OnConnectedToServer;
+        Multiplayer.ConnectionFailed += OnConnectionFailed;
+        Multiplayer.ServerDisconnected += OnServerDisconnected;
+    }
+}

src/Features/Multiplayer/Godot/MultiplayerController.cs.uid

@@ -0,0 +1 @@
+uid://drqx0wiw0sbj1

src/Godot/GameBootstrap.cs

@@ -1,6 +1,7 @@
 using Game.Features.Console.Application.Commands;
 using Game.Features.Console.Godot;
 using Game.Features.Console.Infrastructure;
+using Game.Features.Multiplayer.Godot;
 using Game.Features.Players.Godot;
 using Game.Godot.Extensions;
 using Game.Godot.Mappings;
@@ -12,6 +13,7 @@ public partial class GameBootstrap : Node
 {
     [Export] public ConsoleController Console;
     [Export] public PlayerController Player;
+    [Export] public MultiplayerController MultiplayerController;
 
     private void RegisterConsoleCommands()
     {
@@ -20,15 +22,28 @@ public partial class GameBootstrap : Node
         registry.Register(new EchoCommand());
         registry.Register(new ClearCommand());
         registry.Register(new NoclipCommand(Player));
+        registry.Register(new HostCommand(MultiplayerController));
+        registry.Register(new JoinCommand(MultiplayerController));
 
         Console.UseCommandRegistry(registry);
     }
 
+    private void InitializeMultiplayer()
+    {
+        MultiplayerController.UsePeerFactory(new EnetMultiplayerPeerFactory());
+        MultiplayerController.Connected += () => Console.AppendLine("Connected successfully.");
+        MultiplayerController.ConnectionFailed += () => Console.AppendLine("Connection failed.");
+        MultiplayerController.Disconnected += () => Console.AppendLine("Server disconnected.");
+        MultiplayerController.PeerJoined += id => Console.AppendLine($"Peer {id} joined.");
+        MultiplayerController.PeerLeft += id => Console.AppendLine($"Peer {id} left.");
+    }
+
     public override void _Ready()
     {
         this.AssertRequiredExports();
 
         MouseCapture.Capture();
+        InitializeMultiplayer();
         RegisterConsoleCommands();
     }
 

src/Godot/Scenes/GameWorld.tscn

@@ -2,9 +2,10 @@
 
 [ext_resource type="Texture2D" uid="uid://b5i827vmueyei" path="res://assets/textures/skyboxes/skybox_emx_19.png" id="1_g4n7o"]
 [ext_resource type="PackedScene" uid="uid://curuqmbndymi6" path="res://src/Godot/Scenes/FloorCeilingHr42.tscn" id="2_1kpcd"]
-[ext_resource type="PackedScene" uid="uid://bka1dmgdi5btd" path="res://src/Features/Player/Godot/PlayerNode.tscn" id="2_mvtit"]
+[ext_resource type="PackedScene" uid="uid://bka1dmgdi5btd" path="res://src/Features/Players/Godot/PlayerNode.tscn" id="2_mvtit"]
 [ext_resource type="Script" uid="uid://drctu5y21ey2y" path="res://src/Godot/GameBootstrap.cs" id="3_bootstrap"]
-[ext_resource type="PackedScene" path="res://src/Features/Console/Godot/ConsoleController.tscn" id="4_console"]
+[ext_resource type="PackedScene" uid="uid://bk0771dvonxh8" path="res://src/Features/Console/Godot/ConsoleController.tscn" id="4_console"]
+[ext_resource type="Script" uid="uid://drqx0wiw0sbj1" path="res://src/Features/Multiplayer/Godot/MultiplayerController.cs" id="5_multiplayer"]
 
 [sub_resource type="PanoramaSkyMaterial" id="PanoramaSkyMaterial_epykj"]
 panorama = ExtResource("1_g4n7o")
@@ -17,10 +18,11 @@ background_mode = 2
 sky = SubResource("Sky_1kpcd")
 glow_enabled = true
 
-[node name="GameWorld" type="Node" unique_id=222644234 node_paths=PackedStringArray("Console", "Player")]
+[node name="GameWorld" type="Node" unique_id=222644234 node_paths=PackedStringArray("Console", "Player", "MultiplayerController")]
 script = ExtResource("3_bootstrap")
 Console = NodePath("Console")
 Player = NodePath("Player")
+MultiplayerController = NodePath("Multiplayer")
 
 [node name="DirectionalLight3D" type="DirectionalLight3D" parent="." unique_id=1669211403]
 transform = Transform3D(-0.8660254, -0.43301278, 0.25, 0, 0.49999997, 0.86602545, -0.50000006, 0.75, -0.43301266, 0, 0, 0)
@@ -32,7 +34,10 @@ environment = SubResource("Environment_mvtit")
 [node name="Player" parent="." unique_id=26823676 instance=ExtResource("2_mvtit")]
 transform = Transform3D(1, 0, 0, 0, 1, 0, 0, 0, 1, 0, 1, 0)
 
-[node name="Console" parent="." instance=ExtResource("4_console")]
+[node name="Console" parent="." unique_id=1947043894 instance=ExtResource("4_console")]
+
+[node name="Multiplayer" type="Node" parent="." unique_id=1209131013]
+script = ExtResource("5_multiplayer")
 
 [node name="Entities" type="Node3D" parent="." unique_id=851492709]