emit proxy classes directly to simplify crossplatform compatibility (#409)

5 files changed, 149 insertions, 8 deletions

diff --git a/src/SMAPI/Framework/ModHelpers/ModRegistryHelper.cs b/src/SMAPI/Framework/ModHelpers/ModRegistryHelper.cs
index 9574a632..ea0dbb38 100644
--- a/src/SMAPI/Framework/ModHelpers/ModRegistryHelper.cs
+++ b/src/SMAPI/Framework/ModHelpers/ModRegistryHelper.cs
@@ -1,6 +1,6 @@
 using System.Collections.Generic;
 using System.Linq;
-using ImpromptuInterface;
+using StardewModdingAPI.Framework.Reflection;
 
 namespace StardewModdingAPI.Framework.ModHelpers
 {
@@ -19,6 +19,9 @@ namespace StardewModdingAPI.Framework.ModHelpers
         /// <summary>The mod IDs for APIs accessed by this instanced.</summary>
         private readonly HashSet<string> AccessedModApis = new HashSet<string>();
 
+        /// <summary>Generates proxy classes to access mod APIs through an arbitrary interface.</summary>
+        private readonly InterfaceProxyBuilder ProxyBuilder;
+
 
         /*********
         ** Public methods
@@ -26,11 +29,13 @@ namespace StardewModdingAPI.Framework.ModHelpers
         /// <summary>Construct an instance.</summary>
         /// <param name="modID">The unique ID of the relevant mod.</param>
         /// <param name="registry">The underlying mod registry.</param>
+        /// <param name="proxyBuilder">Generates proxy classes to access mod APIs through an arbitrary interface.</param>
         /// <param name="monitor">Encapsulates monitoring and logging for the mod.</param>
-        public ModRegistryHelper(string modID, ModRegistry registry, IMonitor monitor)
+        public ModRegistryHelper(string modID, ModRegistry registry, InterfaceProxyBuilder proxyBuilder, IMonitor monitor)
             : base(modID)
         {
             this.Registry = registry;
+            this.ProxyBuilder = proxyBuilder;
             this.Monitor = monitor;
         }
 
@@ -94,7 +99,7 @@ namespace StardewModdingAPI.Framework.ModHelpers
             // get API of type
             if (api is TInterface castApi)
                 return castApi;
-            return api.ActLike<TInterface>();
+            return this.ProxyBuilder.CreateProxy<TInterface>(api, this.ModID, uniqueID);
         }
     }
 }
diff --git a/src/SMAPI/Framework/Reflection/InterfaceProxyBuilder.cs b/src/SMAPI/Framework/Reflection/InterfaceProxyBuilder.cs
new file mode 100644
index 00000000..5abebc18
--- /dev/null
+++ b/src/SMAPI/Framework/Reflection/InterfaceProxyBuilder.cs
@@ -0,0 +1,138 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Reflection;
+using System.Reflection.Emit;
+
+namespace StardewModdingAPI.Framework.Reflection
+{
+    /// <summary>Generates proxy classes to access mod APIs through an arbitrary interface.</summary>
+    internal class InterfaceProxyBuilder
+    {
+        /*********
+        ** Properties
+        *********/
+        /// <summary>The CLR module in which to create proxy classes.</summary>
+        private readonly ModuleBuilder ModuleBuilder;
+
+        /// <summary>The generated proxy types.</summary>
+        private readonly IDictionary<string, Type> GeneratedTypes = new Dictionary<string, Type>();
+
+
+        /*********
+        ** Public methods
+        *********/
+        /// <summary>Construct an instance.</summary>
+        public InterfaceProxyBuilder()
+        {
+            AssemblyBuilder assemblyBuilder = AppDomain.CurrentDomain.DefineDynamicAssembly(new AssemblyName($"StardewModdingAPI.Proxies, Version={this.GetType().Assembly.GetName().Version}, Culture=neutral"), AssemblyBuilderAccess.Run);
+            this.ModuleBuilder = assemblyBuilder.DefineDynamicModule("StardewModdingAPI.Proxies");
+        }
+
+        /// <summary>Create an API proxy.</summary>
+        /// <typeparam name="TInterface">The interface through which to access the API.</typeparam>
+        /// <param name="instance">The API instance to access.</param>
+        /// <param name="sourceModID">The unique ID of the mod consuming the API.</param>
+        /// <param name="targetModID">The unique ID of the mod providing the API.</param>
+        public TInterface CreateProxy<TInterface>(object instance, string sourceModID, string targetModID)
+            where TInterface : class
+        {
+            // validate
+            if (instance == null)
+                throw new InvalidOperationException("Can't proxy access to a null API.");
+            if (!typeof(TInterface).IsInterface)
+                throw new InvalidOperationException("The proxy type must be an interface, not a class.");
+
+            // get proxy type
+            Type targetType = instance.GetType();
+            string proxyTypeName = $"StardewModdingAPI.Proxies.From<{sourceModID}_{typeof(TInterface).FullName}>_To<{targetModID}_{targetType.FullName}>";
+            if (!this.GeneratedTypes.TryGetValue(proxyTypeName, out Type type))
+            {
+                type = this.CreateProxyType(proxyTypeName, typeof(TInterface), targetType);
+                this.GeneratedTypes[proxyTypeName] = type;
+            }
+
+            // create instance
+            ConstructorInfo constructor = type.GetConstructor(new[] { targetType });
+            if (constructor == null)
+                throw new InvalidOperationException($"Couldn't find the constructor for generated proxy type '{proxyTypeName}'."); // should never happen
+            return (TInterface)constructor.Invoke(new[] { instance });
+        }
+
+
+        /*********
+        ** Private methods
+        *********/
+        /// <summary>Define a class which proxies access to a target type through an interface.</summary>
+        /// <param name="proxyTypeName">The name of the proxy type to generate.</param>
+        /// <param name="interfaceType">The interface type through which to access the target.</param>
+        /// <param name="targetType">The target type to access.</param>
+        private Type CreateProxyType(string proxyTypeName, Type interfaceType, Type targetType)
+        {
+            // define proxy type
+            TypeBuilder proxyBuilder = this.ModuleBuilder.DefineType(proxyTypeName, TypeAttributes.Public | TypeAttributes.Class);
+            proxyBuilder.AddInterfaceImplementation(interfaceType);
+
+            // create field to store target instance
+            FieldBuilder field = proxyBuilder.DefineField("__Target", targetType, FieldAttributes.Private);
+
+            // create constructor which accepts target instance
+            {
+                ConstructorBuilder constructor = proxyBuilder.DefineConstructor(MethodAttributes.Public, CallingConventions.Standard | CallingConventions.HasThis, new[] { targetType });
+                ILGenerator il = constructor.GetILGenerator();
+
+                il.Emit(OpCodes.Ldarg_0); // this
+                // ReSharper disable once AssignNullToNotNullAttribute -- never null
+                il.Emit(OpCodes.Call, typeof(object).GetConstructor(new Type[0])); // call base constructor
+                il.Emit(OpCodes.Ldarg_0);      // this
+                il.Emit(OpCodes.Ldarg_1);      // load argument
+                il.Emit(OpCodes.Stfld, field); // set field to loaded argument
+                il.Emit(OpCodes.Ret);
+            }
+
+            // proxy methods
+            foreach (MethodInfo proxyMethod in interfaceType.GetMethods())
+            {
+                var targetMethod = targetType.GetMethod(proxyMethod.Name, proxyMethod.GetParameters().Select(a => a.ParameterType).ToArray());
+                if (targetMethod == null)
+                    throw new InvalidOperationException($"The {interfaceType.FullName} interface defines method {proxyMethod.Name} which doesn't exist in the API.");
+
+                this.ProxyMethod(proxyBuilder, targetMethod, field);
+            }
+
+            // create type
+            return proxyBuilder.CreateType();
+        }
+
+        /// <summary>Define a method which proxies access to a method on the target.</summary>
+        /// <param name="proxyBuilder">The proxy type being generated.</param>
+        /// <param name="target">The target method.</param>
+        /// <param name="instanceField">The proxy field containing the API instance.</param>
+        private void ProxyMethod(TypeBuilder proxyBuilder, MethodInfo target, FieldBuilder instanceField)
+        {
+            Type[] argTypes = target.GetParameters().Select(a => a.ParameterType).ToArray();
+
+            // create method
+            MethodBuilder methodBuilder = proxyBuilder.DefineMethod(target.Name, MethodAttributes.Public | MethodAttributes.Final | MethodAttributes.Virtual);
+            methodBuilder.SetParameters(argTypes);
+            methodBuilder.SetReturnType(target.ReturnType);
+
+            // create method body
+            {
+                ILGenerator il = methodBuilder.GetILGenerator();
+
+                // load target instance
+                il.Emit(OpCodes.Ldarg_0);
+                il.Emit(OpCodes.Ldfld, instanceField);
+
+                // invoke target method on instance
+                for (int i = 0; i < argTypes.Length; i++)
+                    il.Emit(OpCodes.Ldarg, i + 1);
+                il.Emit(OpCodes.Call, target);
+
+                // return result
+                il.Emit(OpCodes.Ret);
+            }
+        }
+    }
+}
diff --git a/src/SMAPI/Program.cs b/src/SMAPI/Program.cs
index 786549fe..7eda9c66 100644
--- a/src/SMAPI/Program.cs
+++ b/src/SMAPI/Program.cs
@@ -655,6 +655,7 @@ namespace StardewModdingAPI
 
                 AssemblyLoader modAssemblyLoader = new AssemblyLoader(Constants.TargetPlatform, this.Monitor, this.Settings.DeveloperMode);
                 AppDomain.CurrentDomain.AssemblyResolve += (sender, e) => modAssemblyLoader.ResolveAssembly(e.Name);
+                InterfaceProxyBuilder proxyBuilder = new InterfaceProxyBuilder();
                 foreach (IModMetadata metadata in mods)
                 {
                     // get basic info
@@ -706,7 +707,7 @@ namespace StardewModdingAPI
                             ICommandHelper commandHelper = new CommandHelper(manifest.UniqueID, metadata.DisplayName, this.CommandManager);
                             IContentHelper contentHelper = new ContentHelper(contentManager, metadata.DirectoryPath, manifest.UniqueID, metadata.DisplayName, monitor);
                             IReflectionHelper reflectionHelper = new ReflectionHelper(manifest.UniqueID, metadata.DisplayName, this.Reflection, this.DeprecationManager);
-                            IModRegistry modRegistryHelper = new ModRegistryHelper(manifest.UniqueID, this.ModRegistry, monitor);
+                            IModRegistry modRegistryHelper = new ModRegistryHelper(manifest.UniqueID, this.ModRegistry, proxyBuilder, monitor);
                             ITranslationHelper translationHelper = new TranslationHelper(manifest.UniqueID, manifest.Name, contentManager.GetLocale(), contentManager.GetCurrentLanguage());
                             modHelper = new ModHelper(manifest.UniqueID, metadata.DirectoryPath, jsonHelper, contentHelper, commandHelper, modRegistryHelper, reflectionHelper, translationHelper);
                         }
diff --git a/src/SMAPI/StardewModdingAPI.csproj b/src/SMAPI/StardewModdingAPI.csproj
index 026ac106..0e8ccaa3 100644
--- a/src/SMAPI/StardewModdingAPI.csproj
+++ b/src/SMAPI/StardewModdingAPI.csproj
@@ -53,9 +53,6 @@
     <ApplicationIcon>icon.ico</ApplicationIcon>
   </PropertyGroup>
   <ItemGroup>
-    <Reference Include="ImpromptuInterface, Version=6.2.2.0, Culture=neutral, PublicKeyToken=0b1781c923b2975b, processorArchitecture=MSIL">
-      <HintPath>..\packages\ImpromptuInterface.6.2.2\lib\net40\ImpromptuInterface.dll</HintPath>
-    </Reference>
     <Reference Include="Mono.Cecil, Version=0.9.6.0, Culture=neutral, PublicKeyToken=0738eb9f132ed756, processorArchitecture=MSIL">
       <HintPath>..\packages\Mono.Cecil.0.9.6.4\lib\net45\Mono.Cecil.dll</HintPath>
       <Private>True</Private>
@@ -116,6 +113,7 @@
     <Compile Include="Framework\ContentManagerShim.cs" />
     <Compile Include="Framework\Exceptions\SAssemblyLoadFailedException.cs" />
     <Compile Include="Framework\ModLoading\AssemblyLoadStatus.cs" />
+    <Compile Include="Framework\Reflection\InterfaceProxyBuilder.cs" />
     <Compile Include="Framework\Utilities\ContextHash.cs" />
     <Compile Include="IReflectedField.cs" />
     <Compile Include="IReflectedMethod.cs" />
diff --git a/src/SMAPI/packages.config b/src/SMAPI/packages.config
index 60be6881..98d742c7 100644
--- a/src/SMAPI/packages.config
+++ b/src/SMAPI/packages.config
@@ -1,6 +1,5 @@
 <?xml version="1.0" encoding="utf-8"?>
 <packages>
-  <package id="ImpromptuInterface" version="6.2.2" targetFramework="net45" />
   <package id="Mono.Cecil" version="0.9.6.4" targetFramework="net45" />
   <package id="Newtonsoft.Json" version="10.0.3" targetFramework="net45" />
 </packages>
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