From 4e558af76e939eb2a7ad878f79d012a74830caec Mon Sep 17 00:00:00 2001
From: surskitty <surskitty@gmail.com>
Date: Thu, 10 Jul 2025 14:03:46 -0400
Subject: [PATCH] AI uses After You to help set up Trick Room. (#7310)

---
 src/battle_ai_main.c        | 15 +++++++++++++--
 test/battle/ai/ai_doubles.c | 23 +++++++++++++++++++++++
 2 files changed, 36 insertions(+), 2 deletions(-)

diff --git a/src/battle_ai_main.c b/src/battle_ai_main.c
index 38999fcf65..43d01dfa2e 100644
--- a/src/battle_ai_main.c
+++ b/src/battle_ai_main.c
@@ -2991,6 +2991,14 @@ static s32 AI_DoubleBattle(u32 battlerAtk, u32 battlerDef, u32 move, s32 score)
             if (IsMoveEffectWeather(move))
                 ADJUST_SCORE(-10);
             break;
+        case EFFECT_AFTER_YOU:
+            if (effect == EFFECT_TRICK_ROOM)
+                ADJUST_SCORE(DECENT_EFFECT);
+            break;
+        case EFFECT_TRICK_ROOM:
+            if (effect == EFFECT_AFTER_YOU)
+                ADJUST_SCORE(DECENT_EFFECT);
+            break;
         default:
             break;
         }
@@ -3521,12 +3529,15 @@ static s32 AI_DoubleBattle(u32 battlerAtk, u32 battlerDef, u32 move, s32 score)
                 }
                 break;
             case EFFECT_AFTER_YOU:
+                if (!(gFieldStatuses & STATUS_FIELD_TRICK_ROOM) && HasMoveWithEffect(battlerAtkPartner, EFFECT_TRICK_ROOM))
+                    ADJUST_SCORE(DECENT_EFFECT);
+
                 if (AI_IsSlower(battlerAtkPartner, FOE(battlerAtkPartner), aiData->partnerMove)  // Opponent mon 1 goes before partner
-                 || AI_IsSlower(battlerAtkPartner, BATTLE_PARTNER(FOE(battlerAtkPartner)), aiData->partnerMove)) // Opponent mon 2 goes before partner
+                 && AI_IsSlower(battlerAtkPartner, BATTLE_PARTNER(FOE(battlerAtkPartner)), aiData->partnerMove)) // Opponent mon 2 goes before partner
                 {
                     if (partnerEffect == EFFECT_COUNTER || partnerEffect == EFFECT_MIRROR_COAT)
                         break; // These moves need to go last
-                    RETURN_SCORE_PLUS(WEAK_EFFECT);
+                    ADJUST_SCORE(WEAK_EFFECT);
                 }
                 break;
             case EFFECT_HEAL_PULSE:
diff --git a/test/battle/ai/ai_doubles.c b/test/battle/ai/ai_doubles.c
index 243c6611e9..cbf7c3423b 100644
--- a/test/battle/ai/ai_doubles.c
+++ b/test/battle/ai/ai_doubles.c
@@ -410,6 +410,29 @@ AI_DOUBLE_BATTLE_TEST("AI prioritizes Skill Swapping Contrary to allied mons tha
     }
 }
 
+AI_DOUBLE_BATTLE_TEST("AI uses After You to set up Trick Room")
+{
+    u32 move;
+
+    PARAMETRIZE { move = MOVE_TRICK_ROOM; }
+    PARAMETRIZE { move = MOVE_MOONBLAST; }
+
+    GIVEN {
+        ASSUME(GetMoveEffect(MOVE_AFTER_YOU) == EFFECT_AFTER_YOU);
+        ASSUME(GetMoveEffect(MOVE_TRICK_ROOM) == EFFECT_TRICK_ROOM);
+        AI_FLAGS(AI_FLAG_CHECK_BAD_MOVE | AI_FLAG_TRY_TO_FAINT | AI_FLAG_CHECK_VIABILITY | AI_FLAG_DOUBLE_BATTLE);
+        PLAYER(SPECIES_WOBBUFFET) { Speed(4); }
+        PLAYER(SPECIES_WOBBUFFET) { Speed(4); }
+        OPPONENT(SPECIES_INDEEDEE_M) { Speed(5); Moves(MOVE_AFTER_YOU, MOVE_PSYCHIC); }
+        OPPONENT(SPECIES_CLEFAIRY) { Speed(3); Moves(move, MOVE_PSYCHIC); }
+    } WHEN {
+        if (move == MOVE_TRICK_ROOM)
+            TURN { EXPECT_MOVE(opponentLeft, MOVE_AFTER_YOU, target:opponentRight); EXPECT_MOVE(opponentRight, MOVE_TRICK_ROOM); }
+        else
+            TURN { NOT_EXPECT_MOVE(opponentLeft, MOVE_AFTER_YOU); }
+    }
+}
+
 AI_DOUBLE_BATTLE_TEST("AI uses Guard Split to improve its stats")
 {