Add support for client extensions

This is currently preliminary, and the only event mapped so far is chat messaging

VpSharp/src/ClientExtensions/VirtualParadiseClientExtension.cs

@@ -0,0 +1,33 @@
+using VpSharp.EventData;
+
+namespace VpSharp.ClientExtensions;
+
+/// <summary>
+///     Represents the base class for extensions to the <see cref="VirtualParadiseClient" />.
+/// </summary>
+public abstract class VirtualParadiseClientExtension
+{
+    /// <summary>
+    ///     Initializes a new instance of the <see cref="VirtualParadiseClientExtension" /> class.
+    /// </summary>
+    /// <param name="client">The owning client.</param>
+    protected VirtualParadiseClientExtension(VirtualParadiseClient client)
+    {
+        Client = client;
+    }
+
+    /// <summary>
+    ///     Gets the client to which this extension is registered.
+    /// </summary>
+    /// <value>The owning client.</value>
+    public VirtualParadiseClient Client { get; }
+
+    /// <summary>
+    ///     Called when a chat message is received.
+    /// </summary>
+    /// <param name="args">An object containing event data.</param>
+    protected internal virtual Task OnMessageReceived(MessageReceivedEventArgs args)
+    {
+        return Task.CompletedTask;
+    }
+}

VpSharp/src/VirtualParadiseClient.Extensions.cs

@@ -0,0 +1,68 @@
+using System.Globalization;
+using System.Reflection;
+using VpSharp.ClientExtensions;
+
+namespace VpSharp;
+
+public sealed partial class VirtualParadiseClient
+{
+    private readonly List<VirtualParadiseClientExtension> _extensions = new();
+
+    /// <summary>
+    ///     Adds an extension to this client.
+    /// </summary>
+    /// <param name="arguments">The arguments to pass to the extension constructor.</param>
+    /// <typeparam name="T">The type of the extension to add.</typeparam>
+    /// <returns>A new instance of the specified extension.</returns>
+    /// <exception cref="ArgumentException">
+    ///     <para><typeparamref name="T" /> is <c>abstract</c>.</para>
+    /// </exception>
+    public T AddExtension<T>(params object?[]? arguments) where T : VirtualParadiseClientExtension
+    {
+        return (AddExtension(typeof(T), arguments) as T)!;
+    }
+
+    /// <summary>
+    ///     Adds an extension to this client.
+    /// </summary>
+    /// <param name="type">The type of the extension to add.</param>
+    /// <param name="arguments">The arguments to pass to the extension constructor.</param>
+    /// <returns>A new instance of the specified extension.</returns>
+    /// <exception cref="ArgumentNullException"><paramref name="type" /> is <see langword="null" />.</exception>
+    /// <exception cref="ArgumentException">
+    ///     <para><paramref name="type" /> does not inherit from <see cref="VirtualParadiseClientExtension" />.</para>
+    ///     -or-
+    ///     <para><paramref name="type" /> is <c>abstract</c>.</para>
+    /// </exception>
+    public VirtualParadiseClientExtension AddExtension(Type type, params object?[]? arguments)
+    {
+        ArgumentNullException.ThrowIfNull(type);
+
+        if (!type.IsSubclassOf(typeof(VirtualParadiseClientExtension)))
+        {
+            throw new ArgumentException($"Type must inherit from {typeof(VirtualParadiseClientExtension)}");
+        }
+
+        if (type.IsAbstract)
+        {
+            throw new ArgumentException("Extension type cannot be abstract");
+        }
+
+        object?[] argumentsActual = {this};
+        if (arguments is not null)
+        {
+            argumentsActual = argumentsActual.Concat(arguments).ToArray();
+        }
+
+        const BindingFlags bindingFlags = BindingFlags.Public | BindingFlags.NonPublic | BindingFlags.Instance;
+        object? instance = Activator.CreateInstance(type, bindingFlags, null, argumentsActual, CultureInfo.InvariantCulture);
+        if (instance is not VirtualParadiseClientExtension extension)
+        {
+            var innerException = new Exception($"Could not instantiate {type}");
+            throw new TypeInitializationException(type.FullName, innerException);
+        }
+
+        _extensions.Add(extension);
+        return extension;
+    }
+}

VpSharp/src/VirtualParadiseClient.NativeEvents.cs

@@ -2,6 +2,7 @@ using System.Collections.Concurrent;
 using System.Drawing;
 using System.Numerics;
 using System.Threading.Channels;
+using VpSharp.ClientExtensions;
 using VpSharp.Entities;
 using VpSharp.EventData;
 using VpSharp.Internal;
@@ -79,6 +80,11 @@ public sealed partial class VirtualParadiseClient
 
         var args = new MessageReceivedEventArgs(message);
         RaiseEvent(MessageReceived, args);
+        
+        foreach (VirtualParadiseClientExtension extension in _extensions)
+        {
+            extension.OnMessageReceived(args);
+        }
     }
 
     private async void OnAvatarAddNativeEvent(IntPtr sender)