From 2fc22fa8a60c2f34ce7a6cd336a98a6b5165b12f Mon Sep 17 00:00:00 2001
From: Oliver Booth <me@olivr.me>
Date: Sat, 10 Dec 2022 13:40:47 +0000
Subject: [PATCH] Move instance creation to VpSharp base

Introduces internal DepdencyInjectionUtility class
---
 VpSharp.Commands/CommandsExtension.cs         | 27 ++-----
 VpSharp/src/Assembly.cs                       |  1 +
 .../Internal/DependencyInjectionUtility.cs    | 71 +++++++++++++++++++
 3 files changed, 76 insertions(+), 23 deletions(-)
 create mode 100644 VpSharp/src/Internal/DependencyInjectionUtility.cs

diff --git a/VpSharp.Commands/CommandsExtension.cs b/VpSharp.Commands/CommandsExtension.cs
index a7f2fe5..d07a5b7 100644
--- a/VpSharp.Commands/CommandsExtension.cs
+++ b/VpSharp.Commands/CommandsExtension.cs
@@ -5,6 +5,7 @@ using VpSharp.Commands.Attributes;
 using VpSharp.Commands.Attributes.ExecutionChecks;
 using VpSharp.Entities;
 using VpSharp.EventData;
+using VpSharp.Internal;
 
 namespace VpSharp.Commands;
 
@@ -146,29 +147,9 @@ public sealed class CommandsExtension : VirtualParadiseClientExtension
             throw new ArgumentException($"Module type is not a subclass of {typeof(CommandModule)}");
         }
 
-        ConstructorInfo[] constructors = moduleType.GetTypeInfo().DeclaredConstructors.Where(c => c.IsPublic).ToArray();
-        if (constructors.Length != 1)
-        {
-            throw new ArgumentException(
-                $"Constructor for {moduleType} is not public, or {moduleType} has more than one public constructor.");
-        }
-
-        ConstructorInfo constructor = constructors[0];
-        ParameterInfo[] parameters = constructor.GetParameters();
-
         IServiceProvider? serviceProvider = _configuration.Services;
-        if (parameters.Length != 0 && serviceProvider is null)
-        {
-            throw new InvalidOperationException("No ServiceProvider has been registered!");
-        }
-
-        var args = new object[parameters.Length];
-        for (var index = 0; index < args.Length; index++)
-        {
-            args[index] = serviceProvider!.GetRequiredService(parameters[index].ParameterType);
-        }
-
-        if (Activator.CreateInstance(moduleType, args) is not CommandModule module)
+        object instance = DependencyInjectionUtility.CreateInstance(moduleType, serviceProvider);
+        if (instance is not CommandModule module)
         {
             throw new TypeInitializationException(moduleType.FullName, null);
         }
@@ -180,7 +161,7 @@ public sealed class CommandsExtension : VirtualParadiseClientExtension
     }
 
     /// <inheritdoc />
-    protected override Task OnMessageReceived(MessageReceivedEventArgs args)
+    protected internal override Task OnMessageReceived(MessageReceivedEventArgs args)
     {
         ArgumentNullException.ThrowIfNull(args);
         VirtualParadiseMessage message = args.Message;
diff --git a/VpSharp/src/Assembly.cs b/VpSharp/src/Assembly.cs
index 560422b..09e3f50 100644
--- a/VpSharp/src/Assembly.cs
+++ b/VpSharp/src/Assembly.cs
@@ -1,5 +1,6 @@
 using System.Runtime.CompilerServices;
 
 [assembly: CLSCompliant(true)]
+[assembly: InternalsVisibleTo("VpSharp.Commands")]
 [assembly: InternalsVisibleTo("VpSharp.IntegrationTests")]
 [assembly: InternalsVisibleTo("VpSharp.Tests")]
diff --git a/VpSharp/src/Internal/DependencyInjectionUtility.cs b/VpSharp/src/Internal/DependencyInjectionUtility.cs
new file mode 100644
index 0000000..61b1112
--- /dev/null
+++ b/VpSharp/src/Internal/DependencyInjectionUtility.cs
@@ -0,0 +1,71 @@
+using System.Reflection;
+using Microsoft.Extensions.DependencyInjection;
+
+namespace VpSharp.Internal;
+
+internal static class DependencyInjectionUtility
+{
+    public static T CreateInstance<T>(VirtualParadiseClient client)
+    {
+        return CreateInstance<T>(client.Services);
+    }
+
+    public static T CreateInstance<T>(IServiceProvider? serviceProvider = null)
+    {
+        return (T)CreateInstance(typeof(T), serviceProvider);
+    }
+
+    public static object CreateInstance(Type type, VirtualParadiseClient client)
+    {
+        ArgumentNullException.ThrowIfNull(type);
+        ArgumentNullException.ThrowIfNull(client);
+        return CreateInstance(type, client.Services);
+    }
+
+    public static object CreateInstance(Type type, IServiceProvider? serviceProvider = null)
+    {
+        ArgumentNullException.ThrowIfNull(type);
+        object? instance;
+
+        TypeInfo typeInfo = type.GetTypeInfo();
+        ConstructorInfo[] constructors = typeInfo.DeclaredConstructors.Where(c => c.IsPublic).ToArray();
+
+        if (constructors.Length != 1)
+        {
+            throw new InvalidOperationException($"{type} has no public constructors, or has more than one public constructor.");
+        }
+
+        ConstructorInfo constructor = constructors[0];
+        ParameterInfo[] parameters = constructor.GetParameters();
+
+        if (parameters.Length > 0 && serviceProvider is null)
+        {
+            throw new InvalidOperationException("No ServiceProvider has been registered!");
+        }
+
+        if (parameters.Length == 0)
+        {
+            instance = Activator.CreateInstance(type);
+            if (instance is null)
+            {
+                throw new TypeInitializationException(type.FullName, null);
+            }
+
+            return instance;
+        }
+
+        var args = new object[parameters.Length];
+        for (var index = 0; index < parameters.Length; index++)
+        {
+            args[index] = serviceProvider!.GetRequiredService(parameters[index].ParameterType);
+        }
+
+        instance = Activator.CreateInstance(type, args);
+        if (instance is null)
+        {
+            throw new TypeInitializationException(type.FullName, null);
+        }
+
+        return instance;
+    }
+}