From f631cbbecd428672a241060bdbcf623b2846d25c Mon Sep 17 00:00:00 2001
From: Kurt <kaphotics@gmail.com>
Date: Thu, 31 Dec 2020 15:51:06 -0800
Subject: [PATCH] Generate gen2 eggs via gen2 method, ignore gen1 versions

For searching, only return versions compatible with the save file
Don't bother filtering out BU for Japanese-only.
---
 .../Generator/EncounterEggGenerator.cs        | 13 +++++++++---
 .../Generator/EncounterMovesetGenerator.cs    | 13 ++++++++----
 PKHeX.Core/PKM/Searching/SearchSettings.cs    | 20 ++++++++++++-------
 3 files changed, 32 insertions(+), 14 deletions(-)

diff --git a/PKHeX.Core/Legality/Encounters/Generator/EncounterEggGenerator.cs b/PKHeX.Core/Legality/Encounters/Generator/EncounterEggGenerator.cs
index a77a2359c..d6c5d8ecf 100644
--- a/PKHeX.Core/Legality/Encounters/Generator/EncounterEggGenerator.cs
+++ b/PKHeX.Core/Legality/Encounters/Generator/EncounterEggGenerator.cs
@@ -7,7 +7,6 @@ namespace PKHeX.Core
 {
     public static class EncounterEggGenerator
     {
-        // EncounterEgg
         public static IEnumerable<EncounterEgg> GenerateEggs(PKM pkm, bool all = false)
         {
             var table = EvolutionTree.GetEvolutionTree(pkm, Math.Max(2, pkm.Format));
@@ -98,9 +97,17 @@ private static bool HasOtherGamePair(GameVersion ver)
     /// </summary>
     internal static class EncounterEggGenerator2
     {
-        public static IEnumerable<IEncounterable> GenerateEggs(PKM pkm, IReadOnlyList<EvoCriteria> chain)
+        public static IEnumerable<EncounterEgg> GenerateEggs(PKM pkm, bool all = false)
         {
-            var canBeEgg = GetCanBeEgg(pkm);
+            var table = EvolutionTree.GetEvolutionTree(pkm, 2);
+            int maxSpeciesOrigin = GetMaxSpeciesOrigin(2);
+            var evos = table.GetValidPreEvolutions(pkm, maxLevel: 100, maxSpeciesOrigin: maxSpeciesOrigin, skipChecks: true);
+            return GenerateEggs(pkm, evos, all);
+        }
+
+        public static IEnumerable<EncounterEgg> GenerateEggs(PKM pkm, IReadOnlyList<EvoCriteria> chain, bool all = false)
+        {
+            var canBeEgg = all || GetCanBeEgg(pkm);
             if (!canBeEgg)
                 yield break;
 
diff --git a/PKHeX.Core/Legality/Encounters/Generator/EncounterMovesetGenerator.cs b/PKHeX.Core/Legality/Encounters/Generator/EncounterMovesetGenerator.cs
index e22056556..82a349820 100644
--- a/PKHeX.Core/Legality/Encounters/Generator/EncounterMovesetGenerator.cs
+++ b/PKHeX.Core/Legality/Encounters/Generator/EncounterMovesetGenerator.cs
@@ -191,7 +191,7 @@ private static IEnumerable<IEncounterable> GetPossibleOfType(PKM pk, IReadOnlyCo
         {
             return type switch
             {
-                EncounterOrder.Egg => GetEggs(pk, needs, version),
+                EncounterOrder.Egg => GetEggs(pk, needs, chain, version),
                 EncounterOrder.Mystery => GetGifts(pk, needs, chain),
                 EncounterOrder.Static => GetStatic(pk, needs, chain),
                 EncounterOrder.Trade => GetTrades(pk, needs, chain),
@@ -205,14 +205,19 @@ private static IEnumerable<IEncounterable> GetPossibleOfType(PKM pk, IReadOnlyCo
         /// </summary>
         /// <param name="pk">Rough Pokémon data which contains the requested species, gender, and form.</param>
         /// <param name="needs">Moves which cannot be taught by the player.</param>
+        /// <param name="chain">Origin possible evolution chain</param>
         /// <param name="version">Specific version to iterate for. Necessary for retrieving possible Egg Moves.</param>
         /// <returns>A consumable <see cref="IEncounterable"/> list of possible encounters.</returns>
-        private static IEnumerable<EncounterEgg> GetEggs(PKM pk, IReadOnlyCollection<int> needs, GameVersion version)
+        private static IEnumerable<EncounterEgg> GetEggs(PKM pk, IReadOnlyCollection<int> needs, IReadOnlyList<EvoCriteria> chain, GameVersion version)
         {
             if (GameVersion.CXD.Contains(version) || GameVersion.Gen7b.Contains(version))
                 yield break; // no eggs from these games
-
-            var eggs = EncounterEggGenerator.GenerateEggs(pk, all: true);
+            int gen = version.GetGeneration();
+            if (gen < 2)
+                yield break;
+            var eggs = gen == 2
+                ? EncounterEggGenerator2.GenerateEggs(pk, chain, all: true)
+                : EncounterEggGenerator.GenerateEggs(pk, chain, all: true);
             foreach (var egg in eggs)
             {
                 if (needs.Count == 0)
diff --git a/PKHeX.Core/PKM/Searching/SearchSettings.cs b/PKHeX.Core/PKM/Searching/SearchSettings.cs
index b5c6f5b65..b784bdd85 100644
--- a/PKHeX.Core/PKM/Searching/SearchSettings.cs
+++ b/PKHeX.Core/PKM/Searching/SearchSettings.cs
@@ -141,14 +141,20 @@ public IReadOnlyList<GameVersion> GetVersions(SaveFile sav, GameVersion fallback
         {
             if (Version > 0)
                 return new[] {(GameVersion) Version};
-            if (Generation != 0)
-            {
-                return fallback.GetGeneration() == Generation
-                    ? GameUtil.GetVersionsWithinRange(sav, Generation).ToArray()
-                    : GameUtil.GameVersions;
-            }
 
-            return GameUtil.GameVersions;
+            return Generation switch
+            {
+                1 when !ParseSettings.AllowGen1Tradeback => new[] {GameVersion.RD, GameVersion.BU, GameVersion.GN, GameVersion.YW},
+                2 when sav is SAV2 {Korean: true} => new[] {GameVersion.GD, GameVersion.SV},
+                1 or 2 => new[]
+                {
+                    GameVersion.RD, GameVersion.BU, GameVersion.GN, GameVersion.YW,
+                    GameVersion.GD, GameVersion.SV, GameVersion.C
+                },
+
+                _ when fallback.GetGeneration() == Generation => GameUtil.GetVersionsWithinRange(sav, Generation).ToArray(),
+                _ => GameUtil.GameVersions,
+            };
         }
 
         private static GameVersion GetFallbackVersion(ITrainerInfo sav)