Draft for Pregnancy Overwrite

Common/Defs/GeneDefs/GeneDefs_Breeding.xml

@@ -152,4 +152,16 @@
     <biostatCpx>1</biostatCpx>
     <biostatMet>0</biostatMet>
   </GeneDef>
+
+  <GeneDef ParentName="BreedingBase">
+    <defName>rjw_genes_pregnancy_overwrite</defName>
+    <label>Sperm Displacement</label>
+    <description>Carriers of this gene can 'overwrite' an existing pregnancy, keeping the progress but effectively replacing the father.</description>
+    <iconPath>Genes/Icons/RJW_Genes_PheromoneSpit</iconPath>
+    <displayOrderInCategory>75</displayOrderInCategory>
+
+    <biostatCpx>4</biostatCpx>
+    <biostatMet>-2</biostatMet>
+  </GeneDef>
+
 </Defs>

Source/GeneDefOf.cs

@@ -107,6 +107,7 @@ namespace RJW_Genes
         public static readonly GeneDef rjw_genes_sex_tamer;
 		public static readonly GeneDef rjw_genes_sexual_genetic_swap;
 		public static readonly GeneDef rjw_genes_sexual_genetic_thief;
+		public static readonly GeneDef rjw_genes_pregnancy_overwrite;
 
         // Cosmetic
         public static readonly GeneDef rjw_genes_succubus_tail;

Source/Genes/Special/Patches/Patch_PregnancyOverwrite.cs

@@ -0,0 +1,80 @@
+using HarmonyLib;
+using RimWorld;
+using rjw;
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+using Verse;
+using static HarmonyLib.Code;
+
+namespace RJW_Genes
+{
+    [HarmonyPatch(typeof(SexUtility), "Aftersex")]
+    public class Patch_PregnancyOverwrite
+    {
+        public const int FACTION_GOODWILL_CHANGE = -5;
+
+        public static void Postfix(SexProps props)
+        {
+            if (props == null || props.pawn == null || props.partner == null || props.partner.IsAnimal())
+            {
+                return;
+            }
+
+            Pawn pawn = props.pawn;
+            Pawn partner = props.partner;
+
+            if (pawn.genes == null || partner.genes == null) return;
+
+            // If both have the swap gene, nothing happens
+            if (GeneUtility.HasGeneNullCheck(pawn, GeneDefOf.rjw_genes_pregnancy_overwrite)
+                && GeneUtility.HasGeneNullCheck(partner, GeneDefOf.rjw_genes_pregnancy_overwrite))
+                return;
+
+            // If both are pregnant, we have some weird interaction. Exit Early 
+            if (pawn.IsPregnant() && partner.IsPregnant())
+                return;
+            // If neither are pregnant, nothing can happen.
+            if (!pawn.IsPregnant() && !partner.IsPregnant())
+                return;
+
+            ModLog.Debug("Firing Pregnancy Overwrite Patch - Passed Simple NullChecks");
+
+            if (pawn.IsPregnant() 
+                && GeneUtility.HasGeneNullCheck(partner, GeneDefOf.rjw_genes_pregnancy_overwrite))
+                    TryReplacePregnancy(partner, pawn);
+
+            if (partner.IsPregnant() 
+                && GeneUtility.HasGeneNullCheck(pawn, GeneDefOf.rjw_genes_pregnancy_overwrite))
+                TryReplacePregnancy(pawn, partner);
+        }
+
+        public static void TryReplacePregnancy(Pawn replacer, Pawn pregnant)
+        {
+            // TODO: This mostly works, but needs some more checks.
+            // - Check if there is a pregnancy occurring
+            // - Check for Disease Immunity
+            // - Add Faction Penalties
+
+            ModLog.Debug($"Firing Pregnancy Overwrite for {replacer} and {pregnant}");
+
+            // The "CanImpregnate" does not work as I want, as the pawn is already pregnant, so it wont allow to be pregnated. 
+            //PregnancyHelper.CanImpregnate(pawn, partner, props.sexType)
+
+            Hediff pregnancyHediff = PregnancyUtility.GetPregnancyHediff(pregnant);
+            if (pregnancyHediff == null)
+                return;
+
+            float gestationProgress = pregnancyHediff.Severity;
+
+            PregnancyUtility.ForceEndPregnancy(pregnant);
+
+            PregnancyHelper.StartVanillaPregnancy(pregnant, replacer);
+            Hediff replacementPregnancyHediff = PregnancyUtility.GetPregnancyHediff(pregnant);
+            replacementPregnancyHediff.Severity = gestationProgress;
+        }
+
+    }
+}

Source/Rjw-Genes.csproj

@@ -61,6 +61,7 @@
     <Compile Include="Common\Defs\ModExtensionHelper.cs" />
     <Compile Include="Common\Defs\TickBasedChanceExtension.cs" />
     <Compile Include="Common\Either.cs" />
+    <Compile Include="Common\Helpers\FactionUtility.cs" />
     <Compile Include="Common\Helpers\LaborState.cs" />
     <Compile Include="Common\Helpers\MapUtility.cs" />
     <Compile Include="Common\ModLog.cs" />
@@ -193,6 +194,7 @@
     <Compile Include="Genes\Special\Patches\Patch_GeneticSexThief.cs" />
     <Compile Include="Genes\Special\Patches\Patch_HormonalSaliva.cs" />
     <Compile Include="Genes\Special\Patches\Patch_OrgasmMytosis.cs" />
+    <Compile Include="Genes\Special\Patches\Patch_PregnancyOverwrite.cs" />
     <Compile Include="Genes\Special\Patches\Patch_SexualTamer.cs" />
     <Compile Include="Genes\Special\Thoughts\ThoughtWorker_Aphrodisiac_Pheromones_Social.cs" />
     <Compile Include="LetterDefOf.cs" />