Fixes switch in AI bug (#4338)

* Fixes switch in AI bug

* fixes fix

* test

src/battle_ai_switch_items.c

@@ -1530,7 +1530,7 @@ static u32 GetSwitchinHitsToKO(s32 damageTaken, u32 battler)
     s32 currentHP = startingHP;
 
     // No damage being dealt
-    if (damageTaken + statusDamage + recurringDamage == 0)
+    if (damageTaken + statusDamage + recurringDamage < recurringHealing)
         return startingHP;
 
     // Mon fainted to hazards
@@ -1589,7 +1589,7 @@ static u32 GetSwitchinHitsToKO(s32 damageTaken, u32 battler)
         }
 
         // Healing from items occurs before status so we can do the rest in one line
-        if (currentHP != 0)
+        if (currentHP >= 0)
             currentHP = currentHP + recurringHealing - recurringDamage - statusDamage;
 
         // Recalculate toxic damage if needed

test/battle/ai.c

@@ -526,6 +526,25 @@ AI_SINGLE_BATTLE_TEST("AI will choose either Rock Tomb or Bulldoze if Stat drop
     }
 }
 
+AI_SINGLE_BATTLE_TEST("AI_FLAG_SMART_MON_CHOICES: Number of hits to KO calculation checks whether incoming damage is less than recurring healing to avoid an infinite loop")
+{
+    GIVEN {
+        AI_FLAGS(AI_FLAG_CHECK_BAD_MOVE | AI_FLAG_TRY_TO_FAINT | AI_FLAG_CHECK_VIABILITY | AI_FLAG_SMART_SWITCHING | AI_FLAG_SMART_MON_CHOICES);
+        PLAYER(SPECIES_VENUSAUR) { Level(30); Moves(MOVE_TACKLE); }
+        // Opponent party courtesy of Skolgrahd, who triggered the bug in the first place
+        OPPONENT(SPECIES_PIKACHU) { Level(100); Moves(MOVE_ZIPPY_ZAP, MOVE_EXTREME_SPEED, MOVE_IRON_TAIL, MOVE_KNOCK_OFF); }
+        OPPONENT(SPECIES_NINETALES_ALOLAN) { Level(100); Moves(MOVE_AURORA_VEIL, MOVE_BLIZZARD, MOVE_MOONBLAST, MOVE_DISABLE); }
+        OPPONENT(SPECIES_WEAVILE) { Level(100); Moves(MOVE_NIGHT_SLASH, MOVE_TRIPLE_AXEL, MOVE_ICE_SHARD, MOVE_FAKE_OUT); }
+        OPPONENT(SPECIES_DITTO) { Level(100); Moves(MOVE_TRANSFORM); }
+        OPPONENT(SPECIES_TYPHLOSION) { Level(100); Moves(MOVE_ERUPTION, MOVE_HEAT_WAVE, MOVE_FOCUS_BLAST, MOVE_EXTRASENSORY); }
+        OPPONENT(SPECIES_UMBREON) { Level(100); Item(ITEM_LEFTOVERS); Moves(MOVE_FOUL_PLAY, MOVE_SNARL, MOVE_HELPING_HAND, MOVE_THUNDER_WAVE); }
+    } WHEN {
+            TURN { MOVE(player, MOVE_TACKLE); EXPECT_MOVES(opponent, MOVE_ZIPPY_ZAP, MOVE_EXTREME_SPEED, MOVE_IRON_TAIL, MOVE_KNOCK_OFF); }
+    } SCENE {
+        MESSAGE("Venusaur fainted!");
+    }
+}
+
 AI_SINGLE_BATTLE_TEST("AI_FLAG_SMART_MON_CHOICES: AI will not switch in a Pokemon which is slower and gets 1HKOed after fainting")
 {
     bool32 alakazamFirst;