From 03d8ce2e5a9830ec21c5412061f03194fc68e43b Mon Sep 17 00:00:00 2001
From: Cj <161484149+CJ-SPT@users.noreply.github.com>
Date: Sun, 3 Aug 2025 02:15:16 -0400
Subject: [PATCH] Add patch cache

---
 .../Patching/AbstractPatch.cs                 | 57 ++++++++++--
 .../Patching/ModPatchCache.cs                 | 89 +++++++++++++++++++
 2 files changed, 139 insertions(+), 7 deletions(-)
 create mode 100644 Libraries/SPTarkov.Reflection/Patching/ModPatchCache.cs

diff --git a/Libraries/SPTarkov.Reflection/Patching/AbstractPatch.cs b/Libraries/SPTarkov.Reflection/Patching/AbstractPatch.cs
index c6fe34af..59e49188 100644
--- a/Libraries/SPTarkov.Reflection/Patching/AbstractPatch.cs
+++ b/Libraries/SPTarkov.Reflection/Patching/AbstractPatch.cs
@@ -3,8 +3,29 @@ using HarmonyLib;
 
 namespace SPTarkov.Reflection.Patching;
 
+/// <summary>
+///     Harmony patch wrapper class. See mod example 6.1 for usage.
+/// </summary>
 public abstract class AbstractPatch
 {
+    /// <summary>
+    ///     Method this patch targets
+    /// </summary>
+    public MethodBase? TargetMethod { get; private set; }
+
+    /// <summary>
+    ///     Is this patch active?
+    /// </summary>
+    public bool IsActive { get; private set; }
+
+    /// <summary>
+    ///     The harmony Id assigned to this patch, usually the name of the patch class.
+    /// </summary>
+    public string HarmonyId
+    {
+        get { return _harmony.Id; }
+    }
+
     private readonly Harmony _harmony;
     private readonly List<HarmonyMethod> _prefixList;
     private readonly List<HarmonyMethod> _postfixList;
@@ -69,9 +90,15 @@ public abstract class AbstractPatch
     /// </summary>
     public void Enable()
     {
-        var target = GetTargetMethod();
+        // We never want to have duplicated patches, prevent it.
+        if (IsActive)
+        {
+            return;
+        }
 
-        if (target == null)
+        TargetMethod = GetTargetMethod();
+
+        if (TargetMethod == null)
         {
             throw new InvalidOperationException($"{_harmony.Id}: TargetMethod is null");
         }
@@ -80,28 +107,31 @@ public abstract class AbstractPatch
         {
             foreach (var prefix in _prefixList)
             {
-                _harmony.Patch(target, prefix: prefix);
+                _harmony.Patch(TargetMethod, prefix: prefix);
             }
 
             foreach (var postfix in _postfixList)
             {
-                _harmony.Patch(target, postfix: postfix);
+                _harmony.Patch(TargetMethod, postfix: postfix);
             }
 
             foreach (var transpiler in _transpilerList)
             {
-                _harmony.Patch(target, transpiler: transpiler);
+                _harmony.Patch(TargetMethod, transpiler: transpiler);
             }
 
             foreach (var finalizer in _finalizerList)
             {
-                _harmony.Patch(target, finalizer: finalizer);
+                _harmony.Patch(TargetMethod, finalizer: finalizer);
             }
 
             foreach (var ilmanipulator in _ilManipulatorList)
             {
-                _harmony.Patch(target, ilmanipulator: ilmanipulator);
+                _harmony.Patch(TargetMethod, ilmanipulator: ilmanipulator);
             }
+
+            ModPatchCache.AddPatch(this);
+            IsActive = true;
         }
         catch (Exception ex)
         {
@@ -114,6 +144,12 @@ public abstract class AbstractPatch
     /// </summary>
     public void Disable()
     {
+        // Nothing to disable
+        if (!IsActive)
+        {
+            return;
+        }
+
         var target = GetTargetMethod();
 
         if (target == null)
@@ -129,5 +165,12 @@ public abstract class AbstractPatch
         {
             throw new Exception($"{_harmony.Id}:", ex);
         }
+
+        if (!ModPatchCache.RemovePatch(this))
+        {
+            throw new Exception($"{_harmony.Id}: Target patch not present in cache, a mod is likely externally altering it.");
+        }
+
+        IsActive = false;
     }
 }
diff --git a/Libraries/SPTarkov.Reflection/Patching/ModPatchCache.cs b/Libraries/SPTarkov.Reflection/Patching/ModPatchCache.cs
new file mode 100644
index 00000000..c3dbda21
--- /dev/null
+++ b/Libraries/SPTarkov.Reflection/Patching/ModPatchCache.cs
@@ -0,0 +1,89 @@
+namespace SPTarkov.Reflection.Patching;
+
+/// <summary>
+///     Cache of active patches for mod developers to use for compatibility reasons
+/// </summary>
+public static class ModPatchCache
+{
+    private static readonly List<AbstractPatch> _activePatches = [];
+
+    // This class contains tighter access rules than we usually would implement in the project,
+    // the reason for this is so that the data is a true representation of what's happening with patches without any external interference.
+
+    // TODO: Mod GUID/Name associations to patches, need to think on that.
+    // Required parameter on AbstractPatch ctor maybe?
+
+    /// <summary>
+    ///     Get all active patches
+    /// </summary>
+    /// <returns>
+    /// List of active patches
+    /// </returns>
+    /// <remarks>
+    ///     This should never be called before PreSptLoad is completed, otherwise could be empty.
+    /// </remarks>
+    public static IReadOnlyList<AbstractPatch> GetActivePatches()
+    {
+        // We're not exposing _activePatches so it cant be altered outside of this class. Do NOT implement this as a property.
+        // Mod developers can still enable/disable these patches at will, this is fine, just don't allow external removal from the cache.
+        return _activePatches.AsReadOnly();
+    }
+
+    /// <summary>
+    ///     Get all actively patched target method names
+    /// </summary>
+    /// <returns>
+    /// List of fully quantified method names; including namespace, type and method name
+    /// </returns>
+    /// <remarks>
+    ///     This should never be called before PreSptLoad is completed, otherwise could be empty.
+    /// </remarks>
+    public static List<string> GetActivePatchedMethodNames()
+    {
+        var result = new List<string>();
+
+        foreach (var patch in _activePatches)
+        {
+            // Fullname includes namespace
+            var typeName = patch.TargetMethod?.DeclaringType?.FullName;
+            var methodName = patch.TargetMethod?.Name;
+
+            if (typeName != null && methodName != null)
+            {
+                result.Add($"{typeName}.{methodName}");
+                continue;
+            }
+
+            result.Add($"{patch.HarmonyId}: Type or method is null for this patch.");
+        }
+
+        return result;
+    }
+
+    /// <summary>
+    ///     Add a patch to the cache
+    /// </summary>
+    /// <param name="patch">Patch to add to cache</param>
+    /// <remarks>
+    ///     DO NOT PATCH THIS METHOD, IT IS INTERNAL FOR A REASON. YOU ARE ONLY HARMING OTHER MOD DEVELOPERS BY DOING SO.
+    /// </remarks>
+    internal static void AddPatch(AbstractPatch patch)
+    {
+        _activePatches.Add(patch);
+    }
+
+    /// <summary>
+    ///     Remove a patch from the cache
+    /// </summary>
+    /// <param name="patch">Patch to remove</param>
+    /// <returns>
+    /// True if patch was removed
+    /// </returns>
+    /// <remarks>
+    ///     DO NOT PATCH THIS METHOD, IT IS INTERNAL FOR A REASON. YOU ARE ONLY HARMING OTHER MOD DEVELOPERS BY DOING SO.
+    /// </remarks>
+    internal static bool RemovePatch(AbstractPatch patch)
+    {
+        return _activePatches.Remove(patch);
+    }
+}