From 6e441f95c59ac4b3cffd5cc40fe08d3d68bed7fd Mon Sep 17 00:00:00 2001
From: Christopher Galpin <52485+CodeOptimist@users.noreply.github.com>
Date: Sat, 4 May 2024 19:10:53 -0600
Subject: [PATCH] handle `Find.CurrentMap`

---
 Source/Client/Patches/Determinism.cs | 41 ++++++++++++++++------------
 1 file changed, 24 insertions(+), 17 deletions(-)

diff --git a/Source/Client/Patches/Determinism.cs b/Source/Client/Patches/Determinism.cs
index e6c6df24..24dacbef 100644
--- a/Source/Client/Patches/Determinism.cs
+++ b/Source/Client/Patches/Determinism.cs
@@ -123,31 +123,38 @@ static void Postfix(ref FloodUnfogResult __result)
                 __result.allOnScreen = false;
         }
     }
-    
+
     [HarmonyPatch]
-    static class UnnaturalCorpsePatch // v1.5
+    static class UnnaturalCorpsePatch
     {
         static IEnumerable<MethodBase> TargetMethods()
         {
+            // both of these actually combine "is valid" semantics with "is unseen"
             yield return AccessTools.DeclaredMethod(typeof(AnomalyUtility), nameof(AnomalyUtility.IsValidUnseenCell));
             yield return AccessTools.DeclaredMethod(typeof(UnnaturalCorpse), nameof(UnnaturalCorpse.IsOutsideView));
         }
         
-        static MethodInfo CellRectContains = AccessTools.Method(typeof(CellRect), nameof(CellRect.Contains));
-    
-        static IEnumerable<CodeInstruction> Transpiler(IEnumerable<CodeInstruction> insts)
-        {
-            foreach (var inst in insts)
-            {
-                yield return inst;
-    
-                // consider it always outside view (not contained in CurrentViewRect)
-                if (inst.operand == CellRectContains)
-                {
-                    yield return new CodeInstruction(OpCodes.Ldc_I4_0);
-                    yield return new CodeInstruction(OpCodes.And);
-                }
-            }
+        // primarily for `IsValidUnseenCell()` but works fine for `IsOutsideView()` as well (maybe others)
+        static IEnumerable<CodeInstruction> Transpiler(IEnumerable<CodeInstruction> insts, ILGenerator gen)
+        {
+            var cm = new CodeMatcher(insts, gen);
+            
+            cm.MatchStartForward(Code.Call[AccessTools.DeclaredPropertyGetter(typeof(Find), nameof(Find.CurrentMap))]);
+            cm.SearchForward(inst => inst.Branches(out _));
+            // consider it always on current map, so we can proceed (with finding a nice walkable cell etc.)
+            //  keeping `Beq` and `Bne` avoids needing `[Code.Pop, Code.Pop]`
+            if (cm.Opcode == OpCodes.Beq_S)
+                cm.Advance(1).Insert(Code.Br_S[cm.InstructionAt(-1).operand]);  // force jump as if equal
+            else if (cm.Opcode == OpCodes.Bne_Un_S)
+                cm.CreateLabelWithOffsets(1, out var label).Operand = label;    // not-equal jump goes nowhere
+            else
+                cm.ThrowIfFalse("Couldn't find equality branch opcode following `Find.CurrentMap`", _ => false);
+
+            cm.MatchStartForward(Code.Call[AccessTools.DeclaredMethod(typeof(CellRect), nameof(CellRect.Contains))]);
+            // consider it always outside view (not contained in `CurrentViewRect`) so we can proceed
+            cm.Advance(1).Insert([Code.Ldc_I4_0, Code.And]);
+            
+            return cm.Instructions();
         }
     }