feat: dynamic packet init function creation with deserialization.

Server/Packets/Outgoing/LoginResponseReason.cs

@@ -18,7 +18,7 @@ public enum LoginResponseReason : byte
     NoMoreTries,
     XMLError12,
     XMLRPCError,
-    FileLoadFail, // Maybe more data :)
+    FileLoadFail, // arbitrary file load error (maybe we're able to load custom files)
     ThisIsNotAServiceArea,
     None
 }

Server/Server.csproj

@@ -19,6 +19,9 @@
   <ItemGroup>
     <PackageReference Include="CouchDB.NET" Version="3.4.0"/>
     <PackageReference Include="CouchDB.NET.DependencyInjection" Version="3.4.0"/>
+    <PackageReference Include="DotNext" Version="4.13.1" />
+    <PackageReference Include="DotNext.Metaprogramming" Version="4.13.1" />
+    <PackageReference Include="DotNext.Reflection" Version="4.9.0" />
     <PackageReference Include="ErrorProne.NET.CoreAnalyzers" Version="0.1.2">
       <PrivateAssets>all</PrivateAssets>
       <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>

Server/Services/PacketDistributorService.cs

@@ -1,7 +1,10 @@
 namespace Server.Services;
 
 using System.Collections.Concurrent;
+using System.Linq.Expressions;
 using System.Reflection;
+using DotNext;
+using DotNext.Metaprogramming;
 using MassTransit.Internals;
 using Microsoft.Extensions.DependencyInjection;
 using Microsoft.Extensions.Hosting;
@@ -10,13 +13,15 @@ using Microsoft.VisualBasic.CompilerServices;
 using Newtonsoft.Json;
 using PacketHandlers;
 using Packets;
+using static DotNext.Metaprogramming.CodeGenerator;
+using static DotNext.Linq.Expressions.ExpressionBuilder;
 
 public class PacketDistributorService : IHostedService
 {
     private readonly ConcurrentQueue<RawPacket> concurrentQueue;
     private readonly ILogger<PacketDistributorService> logger;
     private readonly Dictionary<OperationCode, Type> packetHandlers;
-    private readonly Dictionary<OperationCode, Type> packetsTypes;
+    private readonly Dictionary<OperationCode, Func<byte[], IPacket>> deserializationMap;
     private readonly IServiceProvider serviceProvider;
 
     public PacketDistributorService(ILogger<PacketDistributorService> logger, IServiceProvider serviceProvider)
@@ -25,11 +30,28 @@ public class PacketDistributorService : IHostedService
         this.logger = logger;
         this.serviceProvider = serviceProvider;
         this.packetHandlers = new Dictionary<OperationCode, Type>();
-        this.packetsTypes = new Dictionary<OperationCode, Type>();
+        this.deserializationMap = new Dictionary<OperationCode, Func<byte[], IPacket>>();
 
         var executingAssembly = Assembly.GetExecutingAssembly();
-        this.packetsTypes = this.GetPacketsWithId(executingAssembly);
+        var packetsTypes = this.GetPacketsWithId(executingAssembly);
         this.packetHandlers = this.GetAllPacketHandlersWithId(executingAssembly);
+
+        foreach (var packetsType in packetsTypes)
+        {
+            var lambda = Lambda<Func<byte[], IPacket>>(fun =>
+            {
+                var arg = fun[0];
+                var newPacket = packetsType.Value.New();
+
+                var packetVariable = DeclareVariable(packetsType.Value, "packet");
+                Assign(packetVariable, newPacket);
+                Call(packetVariable, packetsType.Value.GetMethod("Deserialize"), arg);
+
+                Return(packetVariable);
+            }).Compile();
+            logger.LogInformation("Packet creation function created for {Opcode}", packetsType.Key);
+            this.deserializationMap.Add(packetsType.Key, lambda);
+        }
     }
 
     public Task StartAsync(CancellationToken cancellationToken) => Task.CompletedTask;
@@ -104,9 +126,7 @@ public class PacketDistributorService : IHostedService
     {
         this.logger.LogTrace("[{TempId}] Packet with ID: {MessageOperationCode} is being dequeued",
             item.Session.Id, item.OperationCode);
-        var packetType = this.packetsTypes[item.OperationCode];
+        var packet = this.deserializationMap[item.OperationCode].Invoke(item.MessageBody);
-        var packet = (IPacket)Activator.CreateInstance(packetType)!;
-        packet.Deserialize(item.MessageBody);
         var packetHandler =
             ActivatorUtilities.GetServiceOrCreateInstance(this.serviceProvider,
                 this.packetHandlers[item.OperationCode]);