PregnancyOverwrite now has all functions

Common/Defs/GeneDefs/GeneDefs_Breeding.xml

@@ -162,6 +162,12 @@
 
     <biostatCpx>4</biostatCpx>
     <biostatMet>-2</biostatMet>
+    <modExtensions>
+        <!-- DevNote: The chance will be multiplied by both pawns' Fertility! -->
+        <li Class="RJW_Genes.ChanceExtension">
+            <chance>0.5</chance>
+        </li>
+    </modExtensions>
   </GeneDef>
 
 </Defs>

Common/Defs/GeneDefs/GeneDefs_Reproduction.xml

@@ -115,7 +115,6 @@
             </li>
         </forcedTraits>
         <exclusionTags>
-            
             <li>rjw_genes_homosexuality_trait_giver</li>
             <li>rjw_genes_sexual_orientation</li>
         </exclusionTags>
@@ -144,7 +143,7 @@
             </li>
         </forcedTraits>
         <exclusionTags>
-            <li>rjw_genes_sexual_orientation</li>        
+            <li>rjw_genes_sexual_orientation</li>
             <li>rjw_genes_bisexuality_trait_giver</li>
         </exclusionTags>
 
@@ -207,4 +206,28 @@
         </exclusionTags>
     </GeneDef>
 
+    <GeneDef>
+        <defName>rjw_genes_pregnancy_overwrite</defName>
+        <label>Sperm Displacement</label>
+        <displayCategory>Reproduction</displayCategory>
+        <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>120</displayOrderInCategory>
+
+        <biostatCpx>4</biostatCpx>
+        <biostatMet>-2</biostatMet>
+        <modExtensions>
+            <!-- DevNote: The chance will be multiplied by both pawns' Fertility! -->
+            <li Class="RJW_Genes.ChanceExtension">
+                <chance>0.5</chance>
+            </li>
+            <li MayRequire="OskarPotocki.VanillaFactionsExpanded.Core"
+                Class="VanillaGenesExpanded.GeneExtension">
+                <backgroundPathEndogenes>Genes/Icons/RJW_Genes_Endogene_Background</backgroundPathEndogenes>
+                <backgroundPathXenogenes>Genes/Icons/RJW_Genes_Xenogene_Background</backgroundPathXenogenes>
+            </li>
+        </modExtensions>
+    </GeneDef>
+    
 </Defs>

Common/Defs/HistoryEventDefs/SpecialHistoryEventDefs.xml

@@ -10,4 +10,9 @@
         <label>Youthed a pawn with youth fountain</label>
     </HistoryEventDef>
     
+    <HistoryEventDef>
+        <defName>rjw_genes_GoodwillChangedReason_OverwritePregnancy</defName>
+        <label>Replaced a pregnancy</label>
+    </HistoryEventDef>
+
 </Defs>

Source/Genes/Special/Patches/Patch_PregnancyOverwrite.cs

@@ -51,29 +51,49 @@ namespace RJW_Genes
                 TryReplacePregnancy(pawn, partner);
         }
 
+        /// <summary>
+        /// Tries to replace an existing pregnancy with a new pregnancy at the same gestation process. 
+        /// The new pregnancy will have the same mother, but a new father and a new set of genes. 
+        /// 
+        /// There is a check for pregnancy that checks for the general fertility (using Vanilla Functions) and multiplies it with a xml-configurable chance.
+        /// If anything is replaced, there will be a faction penalty applied. 
+        /// </summary>
+        /// <param name="replacer"></param>
+        /// <param name="pregnant"></param>
         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;
+            if (DiseaseHelper.IsImmuneAgainstGeneticDisease(pregnant, GeneDefOf.rjw_genes_pregnancy_overwrite))
+            {
+                ModLog.Debug($"{pregnant} is immune against rjw_genes_pregnancy_overwrite from {replacer}");
+                return;
+            }
 
-            PregnancyUtility.ForceEndPregnancy(pregnant);
+            ChanceExtension chanceExt = GeneDefOf.rjw_genes_pregnancy_overwrite.GetModExtension<ChanceExtension>();
+            float chance = chanceExt != null ? chanceExt.chance : 0.25f;
+            chance *= PregnancyUtility.PregnancyChanceForPartners(pregnant, replacer);
 
-            PregnancyHelper.StartVanillaPregnancy(pregnant, replacer);
+            if ((new Random()).Next() < chance)
-            Hediff replacementPregnancyHediff = PregnancyUtility.GetPregnancyHediff(pregnant);
+            {
-            replacementPregnancyHediff.Severity = gestationProgress;
+                float gestationProgress = pregnancyHediff.Severity;
+
+                PregnancyUtility.ForceEndPregnancy(pregnant);
+
+                PregnancyHelper.StartVanillaPregnancy(pregnant, replacer);
+                Hediff replacementPregnancyHediff = PregnancyUtility.GetPregnancyHediff(pregnant);
+                replacementPregnancyHediff.Severity = gestationProgress;
+
+                FactionUtility.HandleFactionGoodWillPenalties(replacer, pregnant, "rjw_genes_GoodwillChangedReason_OverwritePregnancy", FACTION_GOODWILL_CHANGE);
+            } else
+            {
+                ModLog.Debug($"Did not Pregnancy-Overwrite for {replacer} and {pregnant}. Failed: roll<({chanceExt.chance} x {PregnancyUtility.PregnancyChanceForPartners(pregnant,replacer)}[PregnancyChance for Pawns])");
+            }
         }
 
     }