A pawn in estrus will prefer partners that can impregnate them, and prefer to use their vagina

1.3/source/RJW_Menstruation/RJW_Menstruation/EstrusPartKindUsageRule.cs

@@ -0,0 +1,33 @@
+using Verse;
+using rjw;
+using rjw.Modules.Interactions.Contexts;
+using rjw.Modules.Interactions.Enums;
+using rjw.Modules.Interactions.Rules.PartKindUsageRules;
+using rjw.Modules.Shared;
+using System.Collections.Generic;
+
+namespace RJW_Menstruation.Interactions
+{
+    public class EstrusPartKindUsageRule : IPartPreferenceRule
+    {
+        private bool WillingAndAble(Pawn fucker, Pawn fucked)
+        {
+            return
+                (fucked.health?.hediffSet?.HasHediff(VariousDefOf.Hediff_Estrus) ?? false)
+                &&
+                PregnancyHelper.CanImpregnate(fucker, fucked);
+        }
+
+        public IEnumerable<Weighted<LewdablePartKind>> ModifiersForDominant(InteractionContext context)
+        {
+            if (WillingAndAble(context.Internals.Submissive.Pawn, context.Internals.Dominant.Pawn))
+                yield return new Weighted<LewdablePartKind>(Multipliers.Frequent, LewdablePartKind.Vagina);
+        }
+
+        public IEnumerable<Weighted<LewdablePartKind>> ModifiersForSubmissive(InteractionContext context)
+        {
+            if (WillingAndAble(context.Internals.Dominant.Pawn, context.Internals.Submissive.Pawn))
+                yield return new Weighted<LewdablePartKind>(Multipliers.Frequent, LewdablePartKind.Vagina);
+        }
+    }
+}

1.3/source/RJW_Menstruation/RJW_Menstruation/HediffComps/HediffComp_Menstruation.cs

@@ -1022,6 +1022,14 @@ namespace RJW_Menstruation
             }
         }
 
+        public bool IsInEstrus(bool includeConcealed = false)
+        {
+            Pawn pawn = parent.pawn;
+            if (pawn.Dead) return false;
+            if (pawn.health.hediffSet.HasHediff(VariousDefOf.Hediff_Estrus)) return true;
+            else return includeConcealed && pawn.health.hediffSet.HasHediff(VariousDefOf.Hediff_Estrus_Concealed);
+        }
+
         public void SetEstrus(int days)
         {
             HediffDef estrusdef;

1.3/source/RJW_Menstruation/RJW_Menstruation/Patch/Harmony.cs

@@ -1,4 +1,9 @@
 using HarmonyLib;
+using rjw;
+using rjw.Modules.Interactions.Internals.Implementation;
+using rjw.Modules.Interactions.Rules.PartKindUsageRules;
+using rjw.Modules.Shared.Logs;
+using System.Collections.Generic;
 using System.Reflection;
 using Verse;
 
@@ -12,10 +17,15 @@ namespace RJW_Menstruation
             var har = new Harmony("RJW_Menstruation");
             har.PatchAll(Assembly.GetExecutingAssembly());
 
+            InjectIntoRjwInteractionServices();
+        }
+        private static void InjectIntoRjwInteractionServices()
+        {
+            var log = LogManager.GetLogger("StaticConstructorOnStartup");
+
+            List<IPartPreferenceRule> partKindUsageRules = Unprivater.GetProtectedValue<List<IPartPreferenceRule>>("_partKindUsageRules", typeof(PartPreferenceDetectorService));
+            partKindUsageRules.Add(new Interactions.EstrusPartKindUsageRule());
+            log.Message("Added 1 rule to PartPreferenceDetectorService._partKindUsageRules");
         }
     }
-
-
-
-
 }

1.3/source/RJW_Menstruation/RJW_Menstruation/Patch/RJW_Patch.cs

@@ -147,6 +147,25 @@ namespace RJW_Menstruation
         }
     }
 
+    [HarmonyPatch(typeof(SexAppraiser), "GetBodyFactor")]
+    public static class GetBodyFactor_Patch
+    {
+        public static void Postfix(ref float __result, Pawn fucker, Pawn fucked)
+        {
+            if (!(fucker.health?.hediffSet?.HasHediff(VariousDefOf.Hediff_Estrus) ?? false) || !PregnancyHelper.CanImpregnate(fucked, fucker))
+                return;
+            float fert = fucked.health.capacities.GetLevel(xxx.reproduction);
+            if (fucker.def.defName != fucked.def.defName)
+            {
+                if (RJWPregnancySettings.complex_interspecies)
+                    fert *= SexUtility.BodySimilarity(fucker, fucked);
+                else
+                    fert *= RJWPregnancySettings.interspecies_impregnation_modifier;
+            }
+            __result *= (1f + fert / 4);
+        }
+    }
+
     [HarmonyPatch(typeof(CompHediffBodyPart), "updatesize")]
     public static class Updatesize_Patch
     {

1.3/source/RJW_Menstruation/RJW_Menstruation/RJW_Menstruation.csproj

@@ -61,6 +61,7 @@
     <Compile Include="Configurations.cs" />
     <Compile Include="Cum.cs" />
     <Compile Include="DebugActions.cs" />
+    <Compile Include="EstrusPartKindUsageRule.cs" />
     <Compile Include="HediffComps\HediffComp_InducedOvulator.cs" />
     <Compile Include="HediffComps\MenstruationUtility.cs" />
     <Compile Include="IngestionOutcomeDoers.cs" />