Patched SecondaryRomanceChanceFactor for incest precept

Source/IdeologyAddon/Patches/Rimworld_Patch.cs

@@ -5,6 +5,8 @@ using RJWSexperience.Ideology.HistoryEvents;
 using RJWSexperience.Ideology.Precepts;
 using System.Collections.Generic;
 using System.Linq;
+using System.Reflection;
+using System.Reflection.Emit;
 using Verse;
 
 namespace RJWSexperience.Ideology.Patches
@@ -55,6 +57,7 @@ namespace RJWSexperience.Ideology.Patches
 		}
 	}
 
+	[HarmonyPatch(typeof(RelationsUtility), "Incestuous")]
 	public static class Rimworld_Patch_IncestuousManualRomance
 	{
 		/// <summary>
@@ -64,7 +67,6 @@ namespace RJWSexperience.Ideology.Patches
 		/// <param name="two">Target for romance</param>
 		/// <param name="__result">Result of the original method</param>
 		/// <returns>Run original method implementation</returns>
-		[HarmonyPatch(typeof(RelationsUtility), "Incestuous")]
 		public static bool Prefix(Pawn one, Pawn two, ref bool __result)
 		{
 			__result = RsiIncestuous(one, two);
@@ -91,4 +93,91 @@ namespace RJWSexperience.Ideology.Patches
 			return !allowManualRomanceOnlyFor.Contains(relationDegree);
 		}
 	}
+
+	[HarmonyPatch(typeof(Pawn_RelationsTracker), nameof(Pawn_RelationsTracker.SecondaryRomanceChanceFactor))]
+	public static class Rimworld_Patch_SecondaryRomanceChanceFactor
+	{
+		/// <summary>
+		/// <para>
+		/// Replace
+		/// float num = 1f;
+		/// foreach (PawnRelationDef pawnRelationDef in this.pawn.GetRelations(otherPawn))
+		/// {
+		/// 	num *= pawnRelationDef.romanceChanceFactor;
+		/// }
+		/// </para>
+		/// <para>with</para>
+		/// <para>
+		/// float num = 1f;
+		/// num = RomanceChanceFactorHelpers.GetRomanceChanceFactor(this.pawn, otherPawn)
+		/// </para>
+		/// </summary>
+		/// <param name="instructions">Original method body</param>
+		/// <returns>Modified method body</returns>
+		public static IEnumerable<CodeInstruction> Transpiler(IEnumerable<CodeInstruction> instructions)
+		{
+			MethodInfo getRelationsInfo = AccessTools.Method(
+				typeof(PawnRelationUtility),
+				nameof(PawnRelationUtility.GetRelations),
+				new[] { typeof(Pawn), typeof(Pawn) });
+			MethodInfo helperInfo = AccessTools.Method(
+				typeof(RomanceChanceFactorHelpers),
+				nameof(RomanceChanceFactorHelpers.GetRomanceChanceFactor),
+				new[] { typeof(Pawn), typeof(Pawn) });
+			bool skipping = false;
+			bool yieldNext = false;
+			bool finished = false;
+
+			// Original IL looks something like this:
+			// Load this.pawn
+			// Load otherPawn
+			// Call GetRelations
+			// Start loop
+			// ...
+			// Mul num and romanceChanceFactor
+			// Store result
+			// ...
+			// Endfinaly
+
+			// Idea is to substitute GetRelations call with a method with the same signature,
+			// store results in the same place original loop does and remove everything else until Endfinaly
+
+			foreach (CodeInstruction instruction in instructions)
+			{
+				if (finished)
+				{
+					yield return instruction;
+					continue;
+				}
+
+				if (skipping)
+				{
+					if (yieldNext)
+					{
+						yield return instruction;
+						yieldNext = false;
+					}
+					else if (instruction.opcode == OpCodes.Mul)
+					{
+						yieldNext = true;
+					}
+					else if (instruction.opcode == OpCodes.Endfinally)
+					{
+						finished = true;
+					}
+
+					continue;
+				}
+
+				if (instruction.Calls(getRelationsInfo))
+				{
+					yield return new CodeInstruction(OpCodes.Call, helperInfo);
+					skipping = true;
+					continue;
+				}
+
+				yield return instruction;
+			}
+		}
+	}
 }