battle 9 is decompiled

1 files changed, 951 insertions, 0 deletions

diff --git a/src/battle_ai_switch_items.c b/src/battle_ai_switch_items.c
new file mode 100644
index 000000000..661759a98
--- /dev/null
+++ b/src/battle_ai_switch_items.c
@@ -0,0 +1,951 @@
+#include "global.h"
+#include "battle.h"
+#include "battle_controllers.h"
+#include "abilities.h"
+#include "moves.h"
+#include "pokemon.h"
+#include "species.h"
+#include "rng.h"
+#include "util.h"
+#include "items.h"
+#include "pokemon_item_effects.h"
+
+extern u8 gActiveBank;
+extern u8 gAbsentBankFlags;
+extern u32 gBattleTypeFlags;
+extern u32 gStatuses3[BATTLE_BANKS_COUNT];
+extern struct BattlePokemon gBattleMons[BATTLE_BANKS_COUNT];
+extern u16 gBattlePartyID[BATTLE_BANKS_COUNT];
+extern u16 gUnknown_02024250[BATTLE_BANKS_COUNT];
+extern u8 gUnknown_02024270[BATTLE_BANKS_COUNT];
+extern u16 gDynamicBasePower;
+extern u8 gBattleMoveFlags;
+extern u8 gCritMultiplier;
+extern s32 gBattleMoveDamage;
+
+extern const struct BattleMove gBattleMoves[];
+extern const struct BaseStats gBaseStats[];
+extern const u8 gTypeEffectiveness[];
+extern const u8 * const gItemEffectTable[]; // todo: fix once struct is declared
+
+// this file's functions
+static bool8 HasSuperEffectiveMoveAgainstOpponents(bool8 noRng);
+static bool8 FindMonWithFlagsAndSuperEffective(u8 flags, u8 moduloPercent);
+static bool8 ShouldUseItem(void);
+
+static bool8 ShouldSwitchIfPerishSong(void)
+{
+    if (gStatuses3[gActiveBank] & STATUS3_PERISH_SONG
+        && gDisableStructs[gActiveBank].perishSong1 == 0)
+    {
+        *(gBattleStruct->field_294 + gActiveBank) = 6;
+        EmitCmd_x21(1, 2, 0);
+        return TRUE;
+    }
+
+    return FALSE;
+}
+
+static bool8 ShouldSwitchIfWonderGuard(void)
+{
+    u8 opposingIdentity;
+    u8 opposingBank;
+    u8 moveFlags;
+    s32 i, j;
+    s32 firstId;
+    s32 lastId; // + 1
+    struct Pokemon *party = NULL;
+    u16 move;
+
+    if (gBattleTypeFlags & BATTLE_TYPE_DOUBLE)
+        return FALSE;
+
+    opposingIdentity = GetBankIdentity(gActiveBank) ^ BIT_SIDE;
+
+    if (gBattleMons[GetBankByIdentity(opposingIdentity)].ability != ABILITY_WONDER_GUARD)
+        return FALSE;
+
+    // check if pokemon has a super effective move
+    for (opposingBank = GetBankByIdentity(opposingIdentity), i = 0; i < 4; i++)
+    {
+        move = gBattleMons[gActiveBank].moves[i];
+        if (move == MOVE_NONE)
+            continue;
+
+        moveFlags = AI_TypeCalc(move, gBattleMons[opposingBank].species, gBattleMons[opposingBank].ability);
+        if (moveFlags & MOVESTATUS_SUPEREFFECTIVE)
+            return FALSE;
+    }
+
+    // get party information
+    if (gBattleTypeFlags & (BATTLE_TYPE_TWO_OPPONENTS | BATTLE_TYPE_x800000))
+    {
+        if ((gActiveBank & BIT_MON) == 0)
+            firstId = 0, lastId = 3;
+        else
+            firstId = 3, lastId = 6;
+    }
+    else
+    {
+        firstId = 0, lastId = 6;
+    }
+
+    if (GetBankSide(gActiveBank) == SIDE_PLAYER)
+        party = gPlayerParty;
+    else
+        party = gEnemyParty;
+
+    // find a pokemon in the party that has a super effective move
+    for (i = firstId; i < lastId; i++)
+    {
+        if (GetMonData(&party[i], MON_DATA_HP) == 0)
+            continue;
+        if (GetMonData(&party[i], MON_DATA_SPECIES2) == SPECIES_NONE)
+            continue;
+        if (GetMonData(&party[i], MON_DATA_SPECIES2) == SPECIES_EGG)
+            continue;
+        if (i == gBattlePartyID[gActiveBank])
+            continue;
+
+        GetMonData(&party[i], MON_DATA_SPECIES); // unused return value
+        GetMonData(&party[i], MON_DATA_ALT_ABILITY); // unused return value
+
+        for (opposingBank = GetBankByIdentity(opposingIdentity), j = 0; j < 4; j++)
+        {
+            move = GetMonData(&party[i], MON_DATA_MOVE1 + j);
+            if (move == MOVE_NONE)
+                continue;
+
+            moveFlags = AI_TypeCalc(move, gBattleMons[opposingBank].species, gBattleMons[opposingBank].ability);
+            if (moveFlags & MOVESTATUS_SUPEREFFECTIVE && Random() % 3 < 2)
+            {
+                // we found a mon
+                *(gBattleStruct->field_294 + gActiveBank) = i;
+                EmitCmd_x21(1, 2, 0);
+                return TRUE;
+            }
+        }
+    }
+
+    return FALSE; // at this point there is not a single pokemon in the party that has a super effective move against a pokemon with wonder guard
+}
+
+static bool8 FindMonThatAbsorbsOpponentsMove(void)
+{
+    u8 bankIn1, bankIn2;
+    u8 absorbingTypeAbility;
+    s32 firstId;
+    s32 lastId; // + 1
+    struct Pokemon *party;
+    s32 i;
+
+    if (HasSuperEffectiveMoveAgainstOpponents(TRUE) && Random() % 3 != 0)
+        return FALSE;
+    if (gUnknown_02024250[gActiveBank] == 0)
+        return FALSE;
+    if (gUnknown_02024250[gActiveBank] == 0xFFFF)
+        return FALSE;
+    if (gBattleMoves[gUnknown_02024250[gActiveBank]].power == 0)
+        return FALSE;
+
+    if (gBattleTypeFlags & BATTLE_TYPE_DOUBLE)
+    {
+        bankIn1 = gActiveBank;
+        if (gAbsentBankFlags & gBitTable[GetBankByIdentity(GetBankIdentity(gActiveBank) ^ BIT_MON)])
+            bankIn2 = gActiveBank;
+        else
+            bankIn2 = GetBankByIdentity(GetBankIdentity(gActiveBank) ^ BIT_MON);
+    }
+    else
+    {
+        bankIn1 = gActiveBank;
+        bankIn2 = gActiveBank;
+    }
+
+    if (gBattleMoves[gUnknown_02024250[gActiveBank]].type == TYPE_FIRE)
+        absorbingTypeAbility = ABILITY_FLASH_FIRE;
+    else if (gBattleMoves[gUnknown_02024250[gActiveBank]].type == TYPE_WATER)
+        absorbingTypeAbility = ABILITY_WATER_ABSORB;
+    else if (gBattleMoves[gUnknown_02024250[gActiveBank]].type == TYPE_ELECTRIC)
+        absorbingTypeAbility = ABILITY_VOLT_ABSORB;
+    else
+        return FALSE;
+
+    if (gBattleMons[gActiveBank].ability == absorbingTypeAbility)
+        return FALSE;
+
+    if (gBattleTypeFlags & (BATTLE_TYPE_TWO_OPPONENTS | BATTLE_TYPE_x800000))
+    {
+        if ((gActiveBank & BIT_MON) == 0)
+            firstId = 0, lastId = 3;
+        else
+            firstId = 3, lastId = 6;
+    }
+    else
+    {
+        firstId = 0, lastId = 6;
+    }
+
+    if (GetBankSide(gActiveBank) == SIDE_PLAYER)
+        party = gPlayerParty;
+    else
+        party = gEnemyParty;
+
+    for (i = firstId; i < lastId; i++)
+    {
+        u16 species;
+        u8 monAbility;
+
+        if (GetMonData(&party[i], MON_DATA_HP) == 0)
+            continue;
+        if (GetMonData(&party[i], MON_DATA_SPECIES2) == SPECIES_NONE)
+            continue;
+        if (GetMonData(&party[i], MON_DATA_SPECIES2) == SPECIES_EGG)
+            continue;
+        if (i == gBattlePartyID[bankIn1])
+            continue;
+        if (i == gBattlePartyID[bankIn2])
+            continue;
+        if (i == *(gBattleStruct->field_5C + bankIn1))
+            continue;
+        if (i == *(gBattleStruct->field_5C + bankIn2))
+            continue;
+
+        species = GetMonData(&party[i], MON_DATA_SPECIES);
+        if (GetMonData(&party[i], MON_DATA_ALT_ABILITY) != 0)
+            monAbility = gBaseStats[species].ability2;
+        else
+            monAbility = gBaseStats[species].ability1;
+
+        if (absorbingTypeAbility == monAbility && Random() & 1)
+        {
+            // we found a mon
+            *(gBattleStruct->field_294 + gActiveBank) = i;
+            EmitCmd_x21(1, 2, 0);
+            return TRUE;
+        }
+    }
+
+    return FALSE;
+}
+
+static bool8 ShouldSwitchIfNaturalCure(void)
+{
+    if (!(gBattleMons[gActiveBank].status1 & STATUS_SLEEP))
+        return FALSE;
+    if (gBattleMons[gActiveBank].ability != ABILITY_NATURAL_CURE)
+        return FALSE;
+    if (gBattleMons[gActiveBank].hp < gBattleMons[gActiveBank].maxHP / 2)
+        return FALSE;
+
+    if ((gUnknown_02024250[gActiveBank] == 0 || gUnknown_02024250[gActiveBank] == 0xFFFF) && Random() & 1)
+    {
+        *(gBattleStruct->field_294 + gActiveBank) = 6;
+        EmitCmd_x21(1, 2, 0);
+        return TRUE;
+    }
+    else if (gBattleMoves[gUnknown_02024250[gActiveBank]].power == 0 && Random() & 1)
+    {
+        *(gBattleStruct->field_294 + gActiveBank) = 6;
+        EmitCmd_x21(1, 2, 0);
+        return TRUE;
+    }
+
+    if (FindMonWithFlagsAndSuperEffective(MOVESTATUS_NOTAFFECTED, 1))
+        return TRUE;
+    if (FindMonWithFlagsAndSuperEffective(MOVESTATUS_NOTVERYEFFECTIVE, 1))
+        return TRUE;
+    if (Random() & 1)
+    {
+        *(gBattleStruct->field_294 + gActiveBank) = 6;
+        EmitCmd_x21(1, 2, 0);
+        return TRUE;
+    }
+
+    return FALSE;
+}
+
+static bool8 HasSuperEffectiveMoveAgainstOpponents(bool8 noRng)
+{
+    u8 opposingIdentity;
+    u8 opposingBank;
+    s32 i;
+    u8 moveFlags;
+    u16 move;
+
+    opposingIdentity = GetBankIdentity(gActiveBank) ^ BIT_SIDE;
+    opposingBank = GetBankByIdentity(opposingIdentity);
+
+    if (!(gAbsentBankFlags & gBitTable[opposingBank]))
+    {
+        for (i = 0; i < 4; i++)
+        {
+            move = gBattleMons[gActiveBank].moves[i];
+            if (move == MOVE_NONE)
+                continue;
+
+            moveFlags = AI_TypeCalc(move, gBattleMons[opposingBank].species, gBattleMons[opposingBank].ability);
+            if (moveFlags & MOVESTATUS_SUPEREFFECTIVE)
+            {
+                if (noRng)
+                    return TRUE;
+                if (Random() % 10 != 0)
+                    return TRUE;
+            }
+        }
+    }
+    if (!(gBattleTypeFlags & BATTLE_TYPE_DOUBLE))
+        return FALSE;
+
+    opposingBank = GetBankByIdentity(opposingIdentity ^ BIT_MON);
+
+    if (!(gAbsentBankFlags & gBitTable[opposingBank]))
+    {
+        for (i = 0; i < 4; i++)
+        {
+            move = gBattleMons[gActiveBank].moves[i];
+            if (move == MOVE_NONE)
+                continue;
+
+            moveFlags = AI_TypeCalc(move, gBattleMons[opposingBank].species, gBattleMons[opposingBank].ability);
+            if (moveFlags & MOVESTATUS_SUPEREFFECTIVE)
+            {
+                if (noRng)
+                    return TRUE;
+                if (Random() % 10 != 0)
+                    return TRUE;
+            }
+        }
+    }
+
+    return FALSE;
+}
+
+static bool8 AreStatsRaised(void)
+{
+    u8 buffedStatsValue = 0;
+    s32 i;
+
+    for (i = 0; i < BATTLE_STATS_NO; i++)
+    {
+        if (gBattleMons[gActiveBank].statStages[i] > 6)
+            buffedStatsValue += gBattleMons[gActiveBank].statStages[i] - 6;
+    }
+
+    return (buffedStatsValue > 3);
+}
+
+static bool8 FindMonWithFlagsAndSuperEffective(u8 flags, u8 moduloPercent)
+{
+    u8 bankIn1, bankIn2;
+    s32 firstId;
+    s32 lastId; // + 1
+    struct Pokemon *party;
+    s32 i, j;
+    u16 move;
+    u8 moveFlags;
+
+    if (gUnknown_02024250[gActiveBank] == 0)
+        return FALSE;
+    if (gUnknown_02024250[gActiveBank] == 0xFFFF)
+        return FALSE;
+    if (gUnknown_02024270[gActiveBank] == 0xFF)
+        return FALSE;
+    if (gBattleMoves[gUnknown_02024250[gActiveBank]].power == 0)
+        return FALSE;
+
+    if (gBattleTypeFlags & BATTLE_TYPE_DOUBLE)
+    {
+        bankIn1 = gActiveBank;
+        if (gAbsentBankFlags & gBitTable[GetBankByIdentity(GetBankIdentity(gActiveBank) ^ BIT_MON)])
+            bankIn2 = gActiveBank;
+        else
+            bankIn2 = GetBankByIdentity(GetBankIdentity(gActiveBank) ^ BIT_MON);
+    }
+    else
+    {
+        bankIn1 = gActiveBank;
+        bankIn2 = gActiveBank;
+    }
+
+    if (gBattleTypeFlags & (BATTLE_TYPE_TWO_OPPONENTS | BATTLE_TYPE_x800000))
+    {
+        if ((gActiveBank & BIT_MON) == 0)
+            firstId = 0, lastId = 3;
+        else
+            firstId = 3, lastId = 6;
+    }
+    else
+    {
+        firstId = 0, lastId = 6;
+    }
+
+    if (GetBankSide(gActiveBank) == SIDE_PLAYER)
+        party = gPlayerParty;
+    else
+        party = gEnemyParty;
+
+    for (i = firstId; i < lastId; i++)
+    {
+        u16 species;
+        u8 monAbility;
+
+        if (GetMonData(&party[i], MON_DATA_HP) == 0)
+            continue;
+        if (GetMonData(&party[i], MON_DATA_SPECIES2) == SPECIES_NONE)
+            continue;
+        if (GetMonData(&party[i], MON_DATA_SPECIES2) == SPECIES_EGG)
+            continue;
+        if (i == gBattlePartyID[bankIn1])
+            continue;
+        if (i == gBattlePartyID[bankIn2])
+            continue;
+        if (i == *(gBattleStruct->field_5C + bankIn1))
+            continue;
+        if (i == *(gBattleStruct->field_5C + bankIn2))
+            continue;
+
+        species = GetMonData(&party[i], MON_DATA_SPECIES);
+        if (GetMonData(&party[i], MON_DATA_ALT_ABILITY) != 0)
+            monAbility = gBaseStats[species].ability2;
+        else
+            monAbility = gBaseStats[species].ability1;
+
+        moveFlags = AI_TypeCalc(gUnknown_02024250[gActiveBank], species, monAbility);
+        if (moveFlags & flags)
+        {
+            bankIn1 = gUnknown_02024270[gActiveBank];
+
+            for (j = 0; j < 4; j++)
+            {
+                move = GetMonData(&party[i], MON_DATA_MOVE1 + j);
+                if (move == 0)
+                    continue;
+
+                moveFlags = AI_TypeCalc(move, gBattleMons[bankIn1].species, gBattleMons[bankIn1].ability);
+                if (moveFlags & MOVESTATUS_SUPEREFFECTIVE && Random() % moduloPercent == 0)
+                {
+                    *(gBattleStruct->field_294 + gActiveBank) = i;
+                    EmitCmd_x21(1, 2, 0);
+                    return TRUE;
+                }
+            }
+        }
+    }
+
+    return FALSE;
+}
+
+static bool8 ShouldSwitch(void)
+{
+    u8 bankIn1, bankIn2;
+    u8 *activeBankPtr; // needed to match
+    s32 firstId;
+    s32 lastId; // + 1
+    struct Pokemon *party;
+    s32 i;
+    s32 availableToSwitch;
+
+    if (gBattleMons[*(activeBankPtr = &gActiveBank)].status2 & (STATUS2_WRAPPED | STATUS2_ESCAPE_PREVENTION))
+        return FALSE;
+    if (gStatuses3[gActiveBank] & STATUS3_ROOTED)
+        return FALSE;
+    if (AbilityBattleEffects(ABILITYEFFECT_CHECK_OTHER_SIDE, gActiveBank, ABILITY_SHADOW_TAG, 0, 0))
+        return FALSE;
+    if (AbilityBattleEffects(ABILITYEFFECT_CHECK_OTHER_SIDE, gActiveBank, ABILITY_ARENA_TRAP, 0, 0))
+        return FALSE; // misses the flying or levitate check
+    if (AbilityBattleEffects(ABILITYEFFECT_FIELD_SPORT, 0, ABILITY_MAGNET_PULL, 0, 0))
+    {
+        if (gBattleMons[gActiveBank].type1 == TYPE_STEEL)
+            return FALSE;
+        if (gBattleMons[gActiveBank].type2 == TYPE_STEEL)
+            return FALSE;
+    }
+    if (gBattleTypeFlags & BATTLE_TYPE_ARENA)
+        return FALSE;
+
+    availableToSwitch = 0;
+    if (gBattleTypeFlags & BATTLE_TYPE_DOUBLE)
+    {
+        bankIn1 = *activeBankPtr;
+        if (gAbsentBankFlags & gBitTable[GetBankByIdentity(GetBankIdentity(*activeBankPtr) ^ BIT_MON)])
+            bankIn2 = *activeBankPtr;
+        else
+            bankIn2 = GetBankByIdentity(GetBankIdentity(*activeBankPtr) ^ BIT_MON);
+    }
+    else
+    {
+        bankIn1 = *activeBankPtr;
+        bankIn2 = *activeBankPtr;
+    }
+
+    if (gBattleTypeFlags & (BATTLE_TYPE_TWO_OPPONENTS | BATTLE_TYPE_x800000))
+    {
+        if ((gActiveBank & BIT_MON) == 0)
+            firstId = 0, lastId = 3;
+        else
+            firstId = 3, lastId = 6;
+    }
+    else
+    {
+        firstId = 0, lastId = 6;
+    }
+
+    if (GetBankSide(gActiveBank) == SIDE_PLAYER)
+        party = gPlayerParty;
+    else
+        party = gEnemyParty;
+
+    for (i = firstId; i < lastId; i++)
+    {
+        if (GetMonData(&party[i], MON_DATA_HP) == 0)
+            continue;
+        if (GetMonData(&party[i], MON_DATA_SPECIES2) == SPECIES_NONE)
+            continue;
+        if (GetMonData(&party[i], MON_DATA_SPECIES2) == SPECIES_EGG)
+            continue;
+        if (i == gBattlePartyID[bankIn1])
+            continue;
+        if (i == gBattlePartyID[bankIn2])
+            continue;
+        if (i == *(gBattleStruct->field_5C + bankIn1))
+            continue;
+        if (i == *(gBattleStruct->field_5C + bankIn2))
+            continue;
+
+        availableToSwitch++;
+    }
+
+    if (availableToSwitch == 0)
+        return FALSE;
+    if (ShouldSwitchIfPerishSong())
+        return TRUE;
+    if (ShouldSwitchIfWonderGuard())
+        return TRUE;
+    if (FindMonThatAbsorbsOpponentsMove())
+        return TRUE;
+    if (ShouldSwitchIfNaturalCure())
+        return TRUE;
+    if (HasSuperEffectiveMoveAgainstOpponents(FALSE))
+        return FALSE;
+    if (AreStatsRaised())
+        return FALSE;
+    if (FindMonWithFlagsAndSuperEffective(MOVESTATUS_NOTAFFECTED, 2)
+        || FindMonWithFlagsAndSuperEffective(MOVESTATUS_NOTVERYEFFECTIVE, 3))
+        return TRUE;
+
+    return FALSE;
+}
+
+void AI_TrySwitchOrUseItem(void)
+{
+    struct Pokemon *party;
+    u8 bankIn1, bankIn2;
+    s32 firstId;
+    s32 lastId; // + 1
+    u8 bankIdentity = GetBankIdentity(gActiveBank);
+
+    if (GetBankSide(gActiveBank) == SIDE_PLAYER)
+        party = gPlayerParty;
+    else
+        party = gEnemyParty;
+
+    if (gBattleTypeFlags & BATTLE_TYPE_TRAINER)
+    {
+        if (ShouldSwitch())
+        {
+            if (*(gBattleStruct->field_294 + gActiveBank) == 6)
+            {
+                s32 monToSwitchId = GetMostSuitableMonToSwitchInto();
+                if (monToSwitchId == 6)
+                {
+                    if (!(gBattleTypeFlags & BATTLE_TYPE_DOUBLE))
+                    {
+                        bankIn1 = GetBankByIdentity(bankIdentity);
+                        bankIn2 = bankIn1;
+                    }
+                    else
+                    {
+                        bankIn1 = GetBankByIdentity(bankIdentity);
+                        bankIn2 = GetBankByIdentity(bankIdentity ^ BIT_MON);
+                    }
+
+                    if (gBattleTypeFlags & (BATTLE_TYPE_TWO_OPPONENTS | BATTLE_TYPE_x800000))
+                    {
+                        if ((gActiveBank & BIT_MON) == 0)
+                            firstId = 0, lastId = 3;
+                        else
+                            firstId = 3, lastId = 6;
+                    }
+                    else
+                    {
+                        firstId = 0, lastId = 6;
+                    }
+
+                    for (monToSwitchId = firstId; monToSwitchId < lastId; monToSwitchId++)
+                    {
+                        if (GetMonData(&party[monToSwitchId], MON_DATA_HP) == 0)
+                            continue;
+                        if (monToSwitchId == gBattlePartyID[bankIn1])
+                            continue;
+                        if (monToSwitchId == gBattlePartyID[bankIn2])
+                            continue;
+                        if (monToSwitchId == *(gBattleStruct->field_5C + bankIn1))
+                            continue;
+                        if (monToSwitchId == *(gBattleStruct->field_5C + bankIn2))
+                            continue;
+
+                        break;
+                    }
+                }
+
+                *(gBattleStruct->field_294 + gActiveBank) = monToSwitchId;
+            }
+
+            *(gBattleStruct->field_5C + gActiveBank) = *(gBattleStruct->field_294 + gActiveBank);
+            return;
+        }
+        else if (ShouldUseItem())
+        {
+            return;
+        }
+    }
+
+    EmitCmd_x21(1, 0, (gActiveBank ^ BIT_SIDE) << 8);
+}
+
+#define TYPE_FORESIGHT  0xFE
+#define TYPE_ENDTABLE   0xFF
+
+static void ModulateByTypeEffectiveness(u8 atkType, u8 defType1, u8 defType2, u8 *var)
+{
+    s32 i = 0;
+
+    while (gTypeEffectiveness[i] != TYPE_ENDTABLE)
+    {
+        if (gTypeEffectiveness[i] == TYPE_FORESIGHT)
+        {
+            i += 3;
+            continue;
+        }
+        else if (gTypeEffectiveness[i] == atkType)
+        {
+            // check type1
+            if (gTypeEffectiveness[i + 1] == defType1)
+                *var = (*var * gTypeEffectiveness[i + 2]) / 10;
+            // check type2
+            if (gTypeEffectiveness[i + 1] == defType2 && defType1 != defType2)
+                *var = (*var * gTypeEffectiveness[i + 2]) / 10;
+        }
+        i += 3;
+    }
+}
+
+u8 GetMostSuitableMonToSwitchInto(void)
+{
+    u8 opposingBank;
+    u8 bestDmg; // note : should be changed to u32 for obvious reasons
+    u8 bestMonId;
+    u8 bankIn1, bankIn2;
+    s32 firstId;
+    s32 lastId; // + 1
+    struct Pokemon *party;
+    s32 i, j;
+    u8 invalidMons;
+    u16 move;
+
+    if (*(gBattleStruct->field_5C + gActiveBank) != 6)
+        return *(gBattleStruct->field_5C + gActiveBank);
+    if (gBattleTypeFlags & BATTLE_TYPE_ARENA)
+        return gBattlePartyID[gActiveBank] + 1;
+
+    if (gBattleTypeFlags & BATTLE_TYPE_DOUBLE)
+    {
+        bankIn1 = gActiveBank;
+        if (gAbsentBankFlags & gBitTable[GetBankByIdentity(GetBankIdentity(gActiveBank) ^ BIT_MON)])
+            bankIn2 = gActiveBank;
+        else
+            bankIn2 = GetBankByIdentity(GetBankIdentity(gActiveBank) ^ BIT_MON);
+
+        // UB: It considers the opponent only player's side even though it can battle alongside player;
+        opposingBank = Random() & BIT_MON;
+        if (gAbsentBankFlags & gBitTable[opposingBank])
+            opposingBank ^= BIT_MON;
+    }
+    else
+    {
+        opposingBank = GetBankByIdentity(GetBankIdentity(gActiveBank) ^ BIT_SIDE);
+        bankIn1 = gActiveBank;
+        bankIn2 = gActiveBank;
+    }
+
+    if (gBattleTypeFlags & (BATTLE_TYPE_TWO_OPPONENTS | BATTLE_TYPE_x800000))
+    {
+        if ((gActiveBank & BIT_MON) == 0)
+            firstId = 0, lastId = 3;
+        else
+            firstId = 3, lastId = 6;
+    }
+    else
+    {
+        firstId = 0, lastId = 6;
+    }
+
+    if (GetBankSide(gActiveBank) == SIDE_PLAYER)
+        party = gPlayerParty;
+    else
+        party = gEnemyParty;
+
+    invalidMons = 0;
+
+    while (invalidMons != 0x3F) // all mons are invalid
+    {
+        bestDmg = 0;
+        bestMonId = 6;
+        // find the mon which type is the most suitable offensively
+        for (i = firstId; i < lastId; i++)
+        {
+            u16 species = GetMonData(&party[i], MON_DATA_SPECIES);
+            if (species != SPECIES_NONE
+                && GetMonData(&party[i], MON_DATA_HP) != 0
+                && !(gBitTable[i] & invalidMons)
+                && gBattlePartyID[bankIn1] != i
+                && gBattlePartyID[bankIn2] != i
+                && i != *(gBattleStruct->field_5C + bankIn1)
+                && i != *(gBattleStruct->field_5C + bankIn2))
+            {
+                u8 type1 = gBaseStats[species].type1;
+                u8 type2 = gBaseStats[species].type2;
+                u8 typeDmg = 10;
+                ModulateByTypeEffectiveness(gBattleMons[opposingBank].type1, type1, type2, &typeDmg);
+                ModulateByTypeEffectiveness(gBattleMons[opposingBank].type2, type1, type2, &typeDmg);
+                if (bestDmg < typeDmg)
+                {
+                    bestDmg = typeDmg;
+                    bestMonId = i;
+                }
+            }
+            else
+            {
+                invalidMons |= gBitTable[i];
+            }
+        }
+
+        // ok, we know the mon has the right typing but does it have at least one super effective move?
+        if (bestMonId != 6)
+        {
+            for (i = 0; i < 4; i++)
+            {
+                move = GetMonData(&party[bestMonId], MON_DATA_MOVE1 + i);
+                if (move != MOVE_NONE && TypeCalc(move, gActiveBank, opposingBank) & MOVESTATUS_SUPEREFFECTIVE)
+                    break;
+            }
+
+            if (i != 4)
+                return bestMonId; // has both the typing and at least one super effective move
+
+            invalidMons |= gBitTable[bestMonId]; // sorry buddy, we want something better
+        }
+        else
+        {
+            invalidMons = 0x3F; // no viable mon to switch
+        }
+    }
+
+    gDynamicBasePower = 0;
+    gBattleStruct->dynamicMoveType = 0;
+    gBattleScripting.dmgMultiplier = 1;
+    gBattleMoveFlags = 0;
+    gCritMultiplier = 1;
+    bestDmg = 0;
+    bestMonId = 6;
+
+    // if we couldn't find the best mon in terms of typing, find the one that deals most damage
+    for (i = firstId; i < lastId; i++)
+    {
+        if ((u16)(GetMonData(&party[i], MON_DATA_SPECIES)) == SPECIES_NONE)
+            continue;
+        if (GetMonData(&party[i], MON_DATA_HP) == 0)
+            continue;
+        if (gBattlePartyID[bankIn1] == i)
+            continue;
+        if (gBattlePartyID[bankIn2] == i)
+            continue;
+        if (i == *(gBattleStruct->field_5C + bankIn1))
+            continue;
+        if (i == *(gBattleStruct->field_5C + bankIn2))
+            continue;
+
+        for (j = 0; j < 4; j++)
+        {
+            move = GetMonData(&party[i], MON_DATA_MOVE1 + j);
+            gBattleMoveDamage = 0;
+            if (move != MOVE_NONE && gBattleMoves[move].power != 1)
+            {
+                AI_CalcDmg(gActiveBank, opposingBank);
+                TypeCalc(move, gActiveBank, opposingBank);
+            }
+            if (bestDmg < gBattleMoveDamage)
+            {
+                bestDmg = gBattleMoveDamage;
+                bestMonId = i;
+            }
+        }
+    }
+
+    return bestMonId;
+}
+
+// TODO: use PokemonItemEffect struct instead of u8 once it's documented
+static u8 GetAI_ItemType(u8 itemId, const u8 *itemEffect) // NOTE: should take u16 as item Id argument
+{
+    if (itemId == ITEM_FULL_RESTORE)
+        return AI_ITEM_FULL_RESTORE;
+    if (itemEffect[4] & 4)
+        return AI_ITEM_HEAL_HP;
+    if (itemEffect[3] & 0x3F)
+        return AI_ITEM_CURE_CONDITION;
+    if (itemEffect[0] & 0x3F || itemEffect[1] != 0 || itemEffect[2] != 0)
+        return AI_ITEM_X_STAT;
+    if (itemEffect[3] & 0x80)
+        return AI_ITEM_GUARD_SPECS;
+
+    return AI_ITEM_NOT_RECOGNIZABLE;
+}
+
+static bool8 ShouldUseItem(void)
+{
+    struct Pokemon *party;
+    s32 i;
+    u8 validMons = 0;
+    bool8 shouldUse = FALSE;
+
+    if (gBattleTypeFlags & BATTLE_TYPE_INGAME_PARTNER && GetBankIdentity(gActiveBank) == IDENTITY_PLAYER_MON2)
+        return FALSE;
+
+    if (GetBankSide(gActiveBank) == SIDE_PLAYER)
+        party = gPlayerParty;
+    else
+        party = gEnemyParty;
+
+    for (i = 0; i < 6; i++)
+    {
+        if (GetMonData(&party[i], MON_DATA_HP) != 0
+            && GetMonData(&party[i], MON_DATA_SPECIES2) != SPECIES_NONE
+            && GetMonData(&party[i], MON_DATA_SPECIES2) != SPECIES_EGG)
+        {
+            validMons++;
+        }
+    }
+
+    for (i = 0; i < 4; i++)
+    {
+        u16 item;
+        const u8 *itemEffects;
+        u8 paramOffset;
+        u8 bankSide;
+
+        if (i != 0 && validMons > (gBattleResources->battleHistory->itemsNo - i) + 1)
+            continue;
+        item = gBattleResources->battleHistory->trainerItems[i];
+        if (item == ITEM_NONE)
+            continue;
+        if (gItemEffectTable[item - 13] == NULL)
+            continue;
+
+        if (item == ITEM_ENIGMA_BERRY)
+            itemEffects = gSaveBlock1Ptr->enigmaBerry.itemEffect;
+        else
+            itemEffects = gItemEffectTable[item - 13];
+
+        *(gBattleStruct->AI_itemType + gActiveBank / 2) = GetAI_ItemType(item, itemEffects);
+
+        switch (*(gBattleStruct->AI_itemType + gActiveBank / 2))
+        {
+        case AI_ITEM_FULL_RESTORE:
+            if (gBattleMons[gActiveBank].hp >= gBattleMons[gActiveBank].maxHP / 4)
+                break;
+            if (gBattleMons[gActiveBank].hp == 0)
+                break;
+            shouldUse = TRUE;
+            break;
+        case AI_ITEM_HEAL_HP:
+            paramOffset = GetItemEffectParamOffset(item, 4, 4);
+            if (paramOffset == 0)
+                break;
+            if (gBattleMons[gActiveBank].hp == 0)
+                break;
+            if (gBattleMons[gActiveBank].hp < gBattleMons[gActiveBank].maxHP / 4 || gBattleMons[gActiveBank].maxHP - gBattleMons[gActiveBank].hp > itemEffects[paramOffset])
+                shouldUse = TRUE;
+            break;
+        case AI_ITEM_CURE_CONDITION:
+            *(gBattleStruct->AI_itemFlags + gActiveBank / 2) = 0;
+            if (itemEffects[3] & 0x20 && gBattleMons[gActiveBank].status1 & STATUS_SLEEP)
+            {
+                *(gBattleStruct->AI_itemFlags + gActiveBank / 2) |= 0x20;
+                shouldUse = TRUE;
+            }
+            if (itemEffects[3] & 0x10 && (gBattleMons[gActiveBank].status1 & STATUS_POISON || gBattleMons[gActiveBank].status1 & STATUS_TOXIC_POISON))
+            {
+                *(gBattleStruct->AI_itemFlags + gActiveBank / 2) |= 0x10;
+                shouldUse = TRUE;
+            }
+            if (itemEffects[3] & 0x8 && gBattleMons[gActiveBank].status1 & STATUS_BURN)
+            {
+                *(gBattleStruct->AI_itemFlags + gActiveBank / 2) |= 0x8;
+                shouldUse = TRUE;
+            }
+            if (itemEffects[3] & 0x4 && gBattleMons[gActiveBank].status1 & STATUS_FREEZE)
+            {
+                *(gBattleStruct->AI_itemFlags + gActiveBank / 2) |= 0x4;
+                shouldUse = TRUE;
+            }
+            if (itemEffects[3] & 0x2 && gBattleMons[gActiveBank].status1 & STATUS_PARALYSIS)
+            {
+                *(gBattleStruct->AI_itemFlags + gActiveBank / 2) |= 0x2;
+                shouldUse = TRUE;
+            }
+            if (itemEffects[3] & 0x1 && gBattleMons[gActiveBank].status2 & STATUS2_CONFUSION)
+            {
+                *(gBattleStruct->AI_itemFlags + gActiveBank / 2) |= 0x1;
+                shouldUse = TRUE;
+            }
+            break;
+        case AI_ITEM_X_STAT:
+            *(gBattleStruct->AI_itemFlags + gActiveBank / 2) = 0;
+            if (gDisableStructs[gActiveBank].isFirstTurn == 0)
+                break;
+            if (itemEffects[0] & 0xF)
+                *(gBattleStruct->AI_itemFlags + gActiveBank / 2) |= 0x1;
+            if (itemEffects[1] & 0xF0)
+                *(gBattleStruct->AI_itemFlags + gActiveBank / 2) |= 0x2;
+            if (itemEffects[1] & 0xF)
+                *(gBattleStruct->AI_itemFlags + gActiveBank / 2) |= 0x4;
+            if (itemEffects[2] & 0xF)
+                *(gBattleStruct->AI_itemFlags + gActiveBank / 2) |= 0x8;
+            if (itemEffects[2] & 0xF0)
+                *(gBattleStruct->AI_itemFlags + gActiveBank / 2) |= 0x20;
+            if (itemEffects[0] & 0x30)
+                *(gBattleStruct->AI_itemFlags + gActiveBank / 2) |= 0x80;
+            shouldUse = TRUE;
+            break;
+        case AI_ITEM_GUARD_SPECS:
+            bankSide = GetBankSide(gActiveBank);
+            if (gDisableStructs[gActiveBank].isFirstTurn != 0 && gSideTimers[bankSide].mistTimer == 0)
+                shouldUse = TRUE;
+            break;
+        case AI_ITEM_NOT_RECOGNIZABLE:
+            return FALSE;
+        }
+
+        if (shouldUse)
+        {
+            EmitCmd_x21(1, 1, 0);
+            *(gBattleStruct->field_C0 + (gActiveBank / 2) * 2) = item;
+            gBattleResources->battleHistory->trainerItems[i] = 0;
+            return shouldUse;
+        }
+    }
+
+    return FALSE;
+}