From 9ef2016d35f39733abd74292ff135d11377b9d50 Mon Sep 17 00:00:00 2001
From: Kurt <kaphotics@gmail.com>
Date: Sun, 24 Sep 2017 10:36:16 -0700
Subject: [PATCH] Encounter Learnset move duplication fix

a level 15/16 magmar has leer/smog twice in its learnset (at level 1 and
at actual levels); returning just the 4 previous learned moves at level
15/16 yields duplicates for Smog. [Smog, Leer, Fire Punch, Smog | Leer,
Ember]. By ignoring moves already added, the true movepool is acquired

also fix TradebackType getting overwritten at the end of the method (in
case of nontradeback like korean/egg)
---
 PKHeX.Core/Legality/Analysis.cs            | 18 +++++++++---------
 PKHeX.Core/Legality/Core.cs                |  2 +-
 PKHeX.Core/Legality/Structures/Learnset.cs | 22 +++++++++++++++++-----
 3 files changed, 27 insertions(+), 15 deletions(-)

diff --git a/PKHeX.Core/Legality/Analysis.cs b/PKHeX.Core/Legality/Analysis.cs
index 964c3a0b9..aa9902178 100644
--- a/PKHeX.Core/Legality/Analysis.cs
+++ b/PKHeX.Core/Legality/Analysis.cs
@@ -212,23 +212,23 @@ private void UpdateTradebackG12()
         {
             if (pkm.Format == 1)
             {
-                Legal.GetTradebackStatusRBY(pkm);
+                Legal.SetTradebackStatusRBY(pkm);
                 return;
             }
 
             if (pkm.Format == 2 || pkm.VC2)
             {
-                // check for impossible tradeback scenarios
-                // Korean gen2 games can't tradeback because there is no gen1 korean games released
-                if (pkm.Korean || pkm.IsEgg || pkm.HasOriginalMetLocation || pkm.Species > Legal.MaxSpeciesID_1 && !Legal.FutureEvolutionsGen1.Contains(pkm.Species))
-                    pkm.TradebackStatus = TradebackType.Gen2_NotTradeback;
-                else
-                    pkm.TradebackStatus = TradebackType.Any;
+                // Check for impossible tradeback scenarios
+                // Korean Gen2 games can't tradeback because there are no Gen1 Korean games released
+                bool g2only = pkm.Korean || pkm.IsEgg || pkm.HasOriginalMetLocation ||
+                              pkm.Species > Legal.MaxSpeciesID_1 && !Legal.FutureEvolutionsGen1.Contains(pkm.Species);
+                pkm.TradebackStatus = g2only ? TradebackType.Gen2_NotTradeback : TradebackType.Any;
+                return;
             }
 
             // VC2 is released, we can assume it will be TradebackType.Any.
-            // Met date cannot be used definitively as the player can change their system clock.
-            // Is impossible to difference between a VC1 pokemon trade to gen7 after or before VC2 release.
+            // Is impossible to differentiate a VC1 pokemon traded to Gen7 after VC2 is available.
+            // Met Date cannot be used definitively as the player can change their system clock.
             pkm.TradebackStatus = TradebackType.Any;
         }
         private void UpdateTypeInfo()
diff --git a/PKHeX.Core/Legality/Core.cs b/PKHeX.Core/Legality/Core.cs
index c721d11ab..88ec58f75 100644
--- a/PKHeX.Core/Legality/Core.cs
+++ b/PKHeX.Core/Legality/Core.cs
@@ -1431,7 +1431,7 @@ private static bool GetCatchRateMatchesPreEvolution(PKM pkm, int catch_rate)
             bool IsCatchRateTrade() => (pkm.Species == 098 || pkm.Species == 099) && catch_rate == 204;
             bool IsCatchRateStadium() => Stadium_GiftSpecies.Contains(pkm.Species) && Stadium_CatchRate.Contains(catch_rate);
         }
-        internal static void GetTradebackStatusRBY(PKM pkm)
+        internal static void SetTradebackStatusRBY(PKM pkm)
         {
             if (!AllowGen1Tradeback)
             {
diff --git a/PKHeX.Core/Legality/Structures/Learnset.cs b/PKHeX.Core/Legality/Structures/Learnset.cs
index 8ffedb82c..a7c9d355c 100644
--- a/PKHeX.Core/Legality/Structures/Learnset.cs
+++ b/PKHeX.Core/Legality/Structures/Learnset.cs
@@ -44,11 +44,23 @@ public int[] GetEncounterMoves(int level, int count = 4)
             int end = Array.FindLastIndex(Levels, z => z <= level);
             if (end < 0)
                 return new int[0];
-            count = Math.Min(count, 4);
-            int start = end - count + 1;
-            if (start < 0) start = 0;
-            int[] result = new int[end - start + 1];
-            Array.Copy(Moves, start, result, 0, result.Length);
+
+            // Moves can be duplicated in the learnset.
+            // When generating the encounter, loop backwards until all moves are filled or no moves are left.
+            // Insert moves in reverse so that the first move is from the earliest position in the learnset.
+            int[] result = new int[count];
+            var list = new List<int>{Moves[end]};
+            while (end-- > 0)
+            {
+                int move = Moves[end];
+                if (list.Contains(move))
+                    continue;
+
+                list.Insert(0, move);
+                if (list.Count == count)
+                    break;
+            }
+            list.CopyTo(result);
             return result;
         }
         /// <summary>Returns the index of the lowest level move if the Pokémon were encountered at the specified level.</summary>