From 0d0100d8f81121b88b1b26e4df63f26b7eb75cc0 Mon Sep 17 00:00:00 2001
From: Alex <93446519+AlexOn1ine@users.noreply.github.com>
Date: Mon, 15 Jul 2024 17:18:03 +0200
Subject: [PATCH] Reduces AI_WhoStrikesFirst to the most essential parts
 (#4978)

* Reduces AI_WhoStrikesFirst to the most essential parts

* abgcc

* add stall check + minor clean up

* add comment
---
 src/battle_ai_util.c | 52 ++++++++++++++++++++++++++++++++++----------
 1 file changed, 40 insertions(+), 12 deletions(-)

diff --git a/src/battle_ai_util.c b/src/battle_ai_util.c
index 54172f9193..de993f5647 100644
--- a/src/battle_ai_util.c
+++ b/src/battle_ai_util.c
@@ -1036,27 +1036,55 @@ static u32 AI_GetEffectiveness(uq4_12_t multiplier)
 }
 
 /* Checks to see if AI will move ahead of another battler
+ * The function uses a stripped down version of the checks from GetWhichBattlerFasterArgs
  * Output:
     * AI_IS_FASTER: is user(ai) faster
     * AI_IS_SLOWER: is target faster
 */
-s32 AI_WhoStrikesFirst(u32 battlerAI, u32 battler2, u32 moveConsidered)
+s32 AI_WhoStrikesFirst(u32 battlerAI, u32 battler, u32 moveConsidered)
 {
-    s8 prioAI = 0;
-    s8 prioBattler2 = 0;
-    prioAI = GetMovePriority(battlerAI, moveConsidered);
+    u32 speedBattlerAI, speedBattler;
+    u32 holdEffectAI = AI_DATA->holdEffects[battlerAI];
+    u32 holdEffectPlayer = AI_DATA->holdEffects[battler];
+    u32 abilityAI = AI_DATA->abilities[battlerAI];
+    u32 abilityPlayer = AI_DATA->abilities[battler];
 
-    if (prioAI > prioBattler2)
+    if (GetMovePriority(battlerAI, moveConsidered) > 0)
         return AI_IS_FASTER;
 
-    if (GetWhichBattlerFasterArgs(battlerAI, battler2, TRUE,
-                                  AI_DATA->abilities[battlerAI], AI_DATA->abilities[battler2],
-                                  AI_DATA->holdEffects[battlerAI], AI_DATA->holdEffects[battler2],
-                                  AI_DATA->speedStats[battlerAI], AI_DATA->speedStats[battler2],
-                                  prioAI, prioBattler2) == 1)
-        return AI_IS_FASTER;
-    else
+    speedBattlerAI = GetBattlerTotalSpeedStatArgs(battlerAI, abilityAI, holdEffectAI);
+    speedBattler   = GetBattlerTotalSpeedStatArgs(battler, abilityPlayer, holdEffectPlayer);
+
+    if (holdEffectAI == HOLD_EFFECT_LAGGING_TAIL && holdEffectPlayer != HOLD_EFFECT_LAGGING_TAIL)
         return AI_IS_SLOWER;
+    else if (holdEffectAI != HOLD_EFFECT_LAGGING_TAIL && holdEffectPlayer == HOLD_EFFECT_LAGGING_TAIL)
+        return AI_IS_FASTER;
+
+    if (abilityAI == ABILITY_STALL && abilityPlayer != ABILITY_STALL)
+        return AI_IS_SLOWER;
+    else if (abilityAI != ABILITY_STALL && abilityPlayer == ABILITY_STALL)
+        return AI_IS_FASTER;
+
+    if (speedBattlerAI > speedBattler)
+    {
+        if (gFieldStatuses & STATUS_FIELD_TRICK_ROOM)
+            return AI_IS_SLOWER;
+        else
+            return AI_IS_FASTER;
+    }
+    else if (speedBattlerAI == speedBattler)
+    {
+        return AI_IS_FASTER;
+    }
+    else
+    {
+        if (gFieldStatuses & STATUS_FIELD_TRICK_ROOM)
+            return AI_IS_FASTER;
+        else
+            return AI_IS_SLOWER;
+    }
+
+    return AI_IS_SLOWER;
 }
 
 // Check if target has means to faint ai mon.