1 files changed, 57 insertions, 0 deletions
diff --git a/src/SMAPI/Framework/Reflection/OriginalInterfaceProxyFactory.cs b/src/SMAPI/Framework/Reflection/OriginalInterfaceProxyFactory.cs
new file mode 100644
index 00000000..d6966978
--- /dev/null
+++ b/src/SMAPI/Framework/Reflection/OriginalInterfaceProxyFactory.cs
@@ -0,0 +1,57 @@
+using System;
+using System.Collections.Generic;
+using System.Reflection;
+using System.Reflection.Emit;
+
+namespace StardewModdingAPI.Framework.Reflection
+{
+    /// <inheritdoc />
+    internal class OriginalInterfaceProxyFactory : IInterfaceProxyFactory
+    {
+        /*********
+        ** Fields
+        *********/
+        /// <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, OriginalInterfaceProxyBuilder> Builders = new Dictionary<string, OriginalInterfaceProxyBuilder>();
+
+
+        /*********
+        ** Public methods
+        *********/
+        /// <summary>Construct an instance.</summary>
+        public OriginalInterfaceProxyFactory()
+        {
+            AssemblyBuilder assemblyBuilder = AssemblyBuilder.DefineDynamicAssembly(new AssemblyName($"StardewModdingAPI.Proxies, Version={this.GetType().Assembly.GetName().Version}, Culture=neutral"), AssemblyBuilderAccess.Run);
+            this.ModuleBuilder = assemblyBuilder.DefineDynamicModule("StardewModdingAPI.Proxies");
+        }
+
+        /// <inheritdoc />
+        public TInterface CreateProxy<TInterface>(object instance, string sourceModID, string targetModID)
+            where TInterface : class
+        {
+            lock (this.Builders)
+            {
+                // 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.Builders.TryGetValue(proxyTypeName, out OriginalInterfaceProxyBuilder? builder))
+                {
+                    builder = new OriginalInterfaceProxyBuilder(proxyTypeName, this.ModuleBuilder, typeof(TInterface), targetType);
+                    this.Builders[proxyTypeName] = builder;
+                }
+
+                // create instance
+                return (TInterface)builder.CreateInstance(instance);
+            }
+        }
+    }
+}