1 files changed, 83 insertions, 0 deletions
diff --git a/src/StardewModdingAPI/Framework/ModLoading/Finders/EventFinder.cs b/src/StardewModdingAPI/Framework/ModLoading/Finders/EventFinder.cs
new file mode 100644
index 00000000..ce234e39
--- /dev/null
+++ b/src/StardewModdingAPI/Framework/ModLoading/Finders/EventFinder.cs
@@ -0,0 +1,83 @@
+using Mono.Cecil;
+using Mono.Cecil.Cil;
+
+namespace StardewModdingAPI.Framework.ModLoading.Finders
+{
+    /// <summary>Finds incompatible CIL instructions that reference a given event and throws an <see cref="IncompatibleInstructionException"/>.</summary>
+    internal class EventFinder : IInstructionRewriter
+    {
+        /*********
+        ** Properties
+        *********/
+        /// <summary>The full type name for which to find references.</summary>
+        private readonly string FullTypeName;
+
+        /// <summary>The event name for which to find references.</summary>
+        private readonly string EventName;
+
+
+        /*********
+        ** Accessors
+        *********/
+        /// <summary>A brief noun phrase indicating what the instruction finder matches.</summary>
+        public string NounPhrase { get; }
+
+
+        /*********
+        ** Public methods
+        *********/
+        /// <summary>Construct an instance.</summary>
+        /// <param name="fullTypeName">The full type name for which to find references.</param>
+        /// <param name="eventName">The event name for which to find references.</param>
+        /// <param name="nounPhrase">A brief noun phrase indicating what the instruction finder matches (or <c>null</c> to generate one).</param>
+        public EventFinder(string fullTypeName, string eventName, string nounPhrase = null)
+        {
+            this.FullTypeName = fullTypeName;
+            this.EventName = eventName;
+            this.NounPhrase = nounPhrase ?? $"{fullTypeName}.{eventName} event";
+        }
+
+        /// <summary>Rewrite a method definition for compatibility.</summary>
+        /// <param name="module">The module being rewritten.</param>
+        /// <param name="method">The method definition to rewrite.</param>
+        /// <param name="assemblyMap">Metadata for mapping assemblies to the current platform.</param>
+        /// <param name="platformChanged">Whether the mod was compiled on a different platform.</param>
+        /// <returns>Returns whether the instruction was rewritten.</returns>
+        /// <exception cref="IncompatibleInstructionException">The CIL instruction is not compatible, and can't be rewritten.</exception>
+        public virtual bool Rewrite(ModuleDefinition module, MethodDefinition method, PlatformAssemblyMap assemblyMap, bool platformChanged)
+        {
+            return false;
+        }
+
+        /// <summary>Rewrite a CIL instruction for compatibility.</summary>
+        /// <param name="module">The module being rewritten.</param>
+        /// <param name="cil">The CIL rewriter.</param>
+        /// <param name="instruction">The instruction to rewrite.</param>
+        /// <param name="assemblyMap">Metadata for mapping assemblies to the current platform.</param>
+        /// <param name="platformChanged">Whether the mod was compiled on a different platform.</param>
+        /// <returns>Returns whether the instruction was rewritten.</returns>
+        /// <exception cref="IncompatibleInstructionException">The CIL instruction is not compatible, and can't be rewritten.</exception>
+        public virtual bool Rewrite(ModuleDefinition module, ILProcessor cil, Instruction instruction, PlatformAssemblyMap assemblyMap, bool platformChanged)
+        {
+            if (!this.IsMatch(instruction))
+                return false;
+
+            throw new IncompatibleInstructionException(this.NounPhrase);
+        }
+
+
+        /*********
+        ** Protected methods
+        *********/
+        /// <summary>Get whether a CIL instruction matches.</summary>
+        /// <param name="instruction">The IL instruction.</param>
+        protected bool IsMatch(Instruction instruction)
+        {
+            MethodReference methodRef = RewriteHelper.AsMethodReference(instruction);
+            return
+                methodRef != null
+                && methodRef.DeclaringType.FullName == this.FullTypeName
+                && (methodRef.Name == "add_" + this.EventName || methodRef.Name == "remove_" + this.EventName);
+        }
+    }
+}