From ae80d545c5b4f2f86baf702d4527d88c11b935b0 Mon Sep 17 00:00:00 2001
From: DizzyEggg <jajkodizzy@wp.pl>
Date: Thu, 20 Apr 2023 16:12:11 +0200
Subject: [PATCH] Support for multi battles where Trainer has only one mon
 (#2670)

---
 src/battle_controller_opponent.c | 12 +++++++-----
 src/battle_interface.c           |  5 +++++
 src/battle_main.c                |  1 +
 3 files changed, 13 insertions(+), 5 deletions(-)

diff --git a/src/battle_controller_opponent.c b/src/battle_controller_opponent.c
index cb0499ac8..4eda81b09 100644
--- a/src/battle_controller_opponent.c
+++ b/src/battle_controller_opponent.c
@@ -228,9 +228,11 @@ static void Intro_DelayAndEnd(void)
     }
 }
 
-static bool32 TwoIntroMons(u32 battlerId) // Double battle with both player pokemon active.
+static bool32 TwoIntroMons(u32 battlerId) // Double battle with both opponent pokemon active.
 {
-    return (IsDoubleBattle() && IsValidForBattle(&gEnemyParty[gBattlerPartyIndexes[BATTLE_PARTNER(battlerId)]]));
+    return (IsDoubleBattle()
+            && IsValidForBattle(&gEnemyParty[gBattlerPartyIndexes[battlerId]])
+            && IsValidForBattle(&gEnemyParty[gBattlerPartyIndexes[BATTLE_PARTNER(battlerId)]]));
 }
 
 static void Intro_WaitForShinyAnimAndHealthbox(void)
@@ -1969,7 +1971,7 @@ static void SpriteCB_FreeOpponentSprite(struct Sprite *sprite)
 
 static void Task_StartSendOutAnim(u8 taskId)
 {
-    u8 savedActiveBank = gActiveBattler;
+    u8 savedActiveBattler = gActiveBattler;
 
     gActiveBattler = gTasks[taskId].data[0];
     if ((!TwoIntroMons(gActiveBattler) || (gBattleTypeFlags & BATTLE_TYPE_MULTI)) && !BATTLE_TWO_VS_ONE_OPPONENT)
@@ -1977,7 +1979,7 @@ static void Task_StartSendOutAnim(u8 taskId)
         gBattleResources->bufferA[gActiveBattler][1] = gBattlerPartyIndexes[gActiveBattler];
         StartSendOutAnim(gActiveBattler, FALSE);
     }
-    else if ((gBattleTypeFlags & BATTLE_TYPE_TWO_OPPONENTS))
+    else if ((gBattleTypeFlags & BATTLE_TYPE_TWO_OPPONENTS) || (BATTLE_TWO_VS_ONE_OPPONENT && !TwoIntroMons(gActiveBattler)))
     {
         gBattleResources->bufferA[gActiveBattler][1] = gBattlerPartyIndexes[gActiveBattler];
         StartSendOutAnim(gActiveBattler, FALSE);
@@ -1992,7 +1994,7 @@ static void Task_StartSendOutAnim(u8 taskId)
         gActiveBattler ^= BIT_FLANK;
     }
     gBattlerControllerFuncs[gActiveBattler] = Intro_TryShinyAnimShowHealthbox;
-    gActiveBattler = savedActiveBank;
+    gActiveBattler = savedActiveBattler;
     DestroyTask(taskId);
 }
 
diff --git a/src/battle_interface.c b/src/battle_interface.c
index 7f7e1d20f..bbe61a372 100644
--- a/src/battle_interface.c
+++ b/src/battle_interface.c
@@ -690,12 +690,17 @@ static void InitLastUsedBallAssets(void)
 }
 
 // This function is here to cover a specific case - one player's mon in a 2 vs 1 double battle. In this scenario - display singles layout.
+// The same goes for a 2 vs 1 where opponent has only one pokemon.
 u32 WhichBattleCoords(u32 battlerId) // 0 - singles, 1 - doubles
 {
     if (GetBattlerPosition(battlerId) == B_POSITION_PLAYER_LEFT
         && gPlayerPartyCount == 1
         && !(gBattleTypeFlags & BATTLE_TYPE_MULTI))
         return 0;
+    else if (GetBattlerPosition(battlerId) == B_POSITION_OPPONENT_LEFT
+             && gEnemyPartyCount == 1
+             && !(gBattleTypeFlags & BATTLE_TYPE_TWO_OPPONENTS))
+        return 0;
     else
         return IsDoubleBattle();
 }
diff --git a/src/battle_main.c b/src/battle_main.c
index a5a9b5bbf..2eecda65b 100644
--- a/src/battle_main.c
+++ b/src/battle_main.c
@@ -594,6 +594,7 @@ static void CB2_InitBattleInternal(void)
         if (gBattleTypeFlags & BATTLE_TYPE_TWO_OPPONENTS && !BATTLE_TWO_VS_ONE_OPPONENT)
             CreateNPCTrainerParty(&gEnemyParty[PARTY_SIZE / 2], gTrainerBattleOpponent_B, FALSE);
         SetWildMonHeldItem();
+        CalculateEnemyPartyCount();
     }
 
     gMain.inBattle = TRUE;