Switch AI Code 4.0

CheckPlayerMoveTypeMatchups:
; Check how well the moves you've already used
; fare against the enemy's Pokemon.  Used to
; score a potential switch.
    push hl
    push de
    push bc
    ld a, BASE_AI_SWITCH_SCORE
    ld [wEnemyAISwitchScore], a
    ld hl, wPlayerUsedMoves
    ld a, [hl]
    and a
    jr z, .unknown_moves

    ld d, NUM_MOVES
    ld e, 0
.loop
    ld a, [hli]
    and a
    jr z, .exit
    push hl
    dec a
    ld hl, Moves + MOVE_POWER
    call GetMoveAttr
    and a
    jr z, .next

    inc hl
    call GetMoveByte
    ld hl, wEnemyMonType
    call CheckTypeMatchup
    ld a, [wTypeMatchup]
    cp EFFECTIVE ; 1.0 + 0.1
    jr c, .super_effective
    jr z, .neutral

; not very effective
    ld a, e
    cp 1 ; 0.1
    jr nc, .next
    ld e, 1
    jr .next

.neutral
    ld e, 2
    jr .next

.super_effective
    call .doubledown
    pop hl
    jr .done

.next
    pop hl
    dec d
    jr nz, .loop

.exit
    ld a, e
    cp 2
    jr z, .done
    call .IncreaseScore
    ld a, e
    and a
    jr nz, .done
    call .IncreaseScore

.done
    call .CheckEnemyMoveMatchups
    pop bc
    pop de
    pop hl
    ret

.unknown_moves
    ld a, [wBattleMonType1]
    ld b, a
    ld hl, wEnemyMonType1
    call CheckTypeMatchup
    ld a, [wTypeMatchup]
    cp EFFECTIVE ; 1.0 + 0.1
    jr z, .ok
    jr c, .se
    call .IncreaseScore
    jr .ok
.se
    call .DecreaseScore
.ok
    ld a, [wBattleMonType2]
    cp b
    jr z, .done
    call CheckTypeMatchup
    ld a, [wTypeMatchup]
    cp EFFECTIVE ; 1.0 + 0.1
    jr z, .done
    jr c, .se2
    call .IncreaseScore
    jr .done
.se2
    call .DecreaseScore
    jr .done

.CheckEnemyMoveMatchups:
    ld de, wEnemyMonMoves
    ld b, NUM_MOVES + 1
    ld c, 0

    ld a, [wTypeMatchup]
    push af
.loop2
    dec b
    jr z, .exit2

    ld a, [de]
    and a
    jr z, .exit2

    inc de
    dec a
    ld hl, Moves + MOVE_POWER
    call GetMoveAttr
    and a
    jr z, .loop2

    inc hl
    call GetMoveByte
    ld hl, wBattleMonType1
    call CheckTypeMatchup

    ld a, [wTypeMatchup]
     ; immune
    and a
    jr z, .loop2
     ; not very effective
    inc c
    cp EFFECTIVE
    jr c, .loop2
     ; neutral
    inc c
    inc c
    inc c
    inc c
    inc c
    cp EFFECTIVE
    jr z, .loop2
     ; super effective
    ld c, 100
    call .IncreaseScore
    jr .loop2

.exit2
    pop af
    ld [wTypeMatchup], a

    ld a, c
    and a
    jr z, .doubledown ; double down
    cp 5
    jr c, .DecreaseScore ; down
    cp 100
    ret c
    jr .IncreaseScore ; up

.doubledown
    call .DecreaseScore
.DecreaseScore:
    ld a, [wEnemyAISwitchScore]
    dec a
    ld [wEnemyAISwitchScore], a
    ret

.IncreaseScore:
    ld a, [wEnemyAISwitchScore]
    inc a
    ld [wEnemyAISwitchScore], a
    ret

CheckAbleToSwitch:
    xor a
    ld [wEnemySwitchMonParam], a
    call FindAliveEnemyMons
    ret c

    ld hl, TrainerClassAttributes + TRNATTR_AI_ITEM_SWITCH

    ld a, [wTrainerClass]
    dec a
    ld bc, NUM_TRAINER_ATTRIBUTES
    call AddNTimes

    ld a, BANK(TrainerClassAttributes)
    call GetFarByte
    bit SWITCH_OFTEN_F, a
    jr nz, .checkstat
    bit SWITCH_SOMETIMES_F, a
    jr nz, .checkstat
    jr .checkperish
.checkstat
     ; Checks if Evasion is greater than 0
    ld a, [wEnemyEvaLevel]
    cp BASE_STAT_LEVEL + 1
    ret nc
     ; Checks if Accuracy is below -1
    ld a, [wEnemyAccLevel]
    cp BASE_STAT_LEVEL - 1
    jr c, .rollswitch
    ld hl, wPlayerStatLevels
    ld c, NUM_LEVEL_STATS - 1
    ld b, 0
    ld e, 0
.checkplayerbuff  ; Check player's stat buffs
    dec c
    jr z, .checkpt2
    ld a, [hli]
    cp BASE_STAT_LEVEL
    jr nc, .checkplayerbuff2
    jr .checkplayerbuff
.checkplayerbuff2
    sub a, BASE_STAT_LEVEL
    add b    ; b holds the stat buffs
    ld b, a
    jr .checkplayerbuff

.checkpt2
    ld hl, wEnemyStatLevels
    ld c, 7
.checkenemybuff  ; Check AI's stat buffs
    dec c
    jr z, .cont_check
    ld a, [hli]
    cp BASE_STAT_LEVEL
    jr nc, .checkenemybuff2
    jr .checkenemybuff
.checkenemybuff2
    sub a, BASE_STAT_LEVEL
    add e    ; e holds the stat buffs
    ld e, a
    jr .checkenemybuff
.cont_check
     ; Checks if AI has no boosts
    ld a, e
    cp 0
    jr c, .cont_check_2
    jr z, .cont_check_2
     ; Check if player is has 2 stat buffs
    ld a, b
    cp 2
    ret nc
     ; Otherwise, roll to check other clauses or not
    call Random
    cp 20 percent
    ret c
    jr .checkperish
.cont_check_2 ; Checks if non-spd stat (because of Curse) is below -2
    ld a, [wEnemyAtkLevel]
    cp BASE_STAT_LEVEL - 2
    jr c, .rollswitch
    ld a, [wEnemyDefLevel]
    cp BASE_STAT_LEVEL - 2
    jr c, .rollswitch
    ld a, [wEnemySAtkLevel]
    cp BASE_STAT_LEVEL - 2
    jr c, .rollswitch
    ld a, [wEnemySDefLevel]
    cp BASE_STAT_LEVEL - 2
    jr c, .rollswitch
    jr .checkperish
.rollswitch
    call Random
    cp 65 percent
    jr c, .switch
    jr .checkperish

.checkperish
    ld a, [wEnemySubStatus1]
    bit SUBSTATUS_PERISH, a
    jr z, .no_perish

    ld a, [wEnemyPerishCount]
    cp 1
    jr nz, .no_perish

.switch ; Try to switch
    call FindAliveEnemyMons
    call FindEnemyMonsWithAtLeastQuarterMaxHP
    call FindEnemyMonsThatResistPlayer
    call FindAliveEnemyMonsWithASuperEffectiveMove
    ld a, e
    cp 2
    jr nz, .not_2

    ld a, [wEnemyAISwitchScore]
    add $30 ; maximum chance
    ld [wEnemySwitchMonParam], a
    ret

.not_2
    call FindAliveEnemyMons
    sla c
    sla c
    ld b, $ff

.loop1
    inc b
    sla c
    jr nc, .loop1
    ld a, b
    add $30 ; maximum chance
    ld [wEnemySwitchMonParam], a
    ret

.no_perish
    call CheckPlayerMoveTypeMatchups
    ld a, [wEnemyAISwitchScore]
    cp 11
    ret nc

    ld a, [wLastPlayerCounterMove]
    and a
    jr z, .no_last_counter_move

    call FindEnemyMonsImmuneToLastCounterMove
    ld a, [wEnemyAISwitchScore]
    and a
    jr z, .no_last_counter_move

    ld c, a
    call FindEnemyMonsWithASuperEffectiveMove
    ld a, [wEnemyAISwitchScore]
    cp $ff
    ret z

    ld b, a
    ld a, e
    cp 2
    jr z, .not_2_again

    call CheckPlayerMoveTypeMatchups
    ld a, [wEnemyAISwitchScore]
    cp 11
    ret nc

    ld a, b
    add $20
    ld [wEnemySwitchMonParam], a
    ret

.not_2_again
    ld c, $10
    call CheckPlayerMoveTypeMatchups
    ld a, [wEnemyAISwitchScore]
    cp 10
    jr nc, .okay
    ld c, $20

.okay
    ld a, b
    add c
    ld [wEnemySwitchMonParam], a
    ret
 ; Smart switching
.smartswitch
    ld a, [wEnemyAISwitchScore]
    ld b, a
    call CheckPlayerMoveTypeMatchups
    ld a, [wEnemyAISwitchScore]
    cp b
    ret c

    ld a, e
    cp 2
    jr nz, .not_2
    ld a, b
    add $20
    ld [wEnemySwitchMonParam], a
    ret

.no_last_counter_move
    call CheckPlayerMoveTypeMatchups
    ld a, [wEnemyAISwitchScore]
    cp 10
    ret nc

    ld hl, TrainerClassAttributes + TRNATTR_AI_ITEM_SWITCH
    ld a, [wTrainerClass]
    dec a
    ld bc, NUM_TRAINER_ATTRIBUTES
    call AddNTimes
    ld a, BANK(TrainerClassAttributes)
    call GetFarByte
    bit SWITCH_OFTEN_F, a
    jr nz, .smartcheck
    ret
 ; Randomize switch check only for SWITCH_OFTEN AI
.smartcheck:
    call Random
    cp 55 percent
    ret c
    call Random
    cp 35 percent
    jr c, .algorithm2
     ; Algorithm 1
    call FindAliveEnemyMons
    call FindEnemyMonsWithAtLeastQuarterMaxHP
    call FindEnemyMonsThatResistPlayer
    call FindAliveEnemyMonsWithASuperEffectiveMove
    jp .smartswitch
.algorithm2
    call FindAliveEnemyMons
    call FindEnemyMonsWithAtLeastQuarterMaxHP
    call FindEnemyMonsThatResistPlayer
    jp .smartswitch

FindAliveEnemyMons:
    ld a, [wOTPartyCount]
    cp 2
    jr c, .only_one

    ld d, a
    ld e, 0
    ld b, 1 << (PARTY_LENGTH - 1)
    ld c, 0
    ld hl, wOTPartyMon1HP

.loop
    ld a, [wCurOTMon]
    cp e
    jr z, .next

    push bc
    ld b, [hl]
    inc hl
    ld a, [hld]
    or b
    pop bc
    jr z, .next

    ld a, c
    or b
    ld c, a

.next
    srl b
    push bc
    ld bc, PARTYMON_STRUCT_LENGTH
    add hl, bc
    pop bc
    inc e
    dec d
    jr nz, .loop

    ld a, c
    and a
    jr nz, .more_than_one

.only_one
    scf
    ret

.more_than_one
    and a
    ret

FindEnemyMonsImmuneToLastCounterMove:
    ld hl, wOTPartyMon1
    ld a, [wOTPartyCount]
    ld b, a
    ld c, 1 << (PARTY_LENGTH - 1)
    ld d, 0
    xor a
    ld [wEnemyAISwitchScore], a

.loop
    ld a, [wCurOTMon]
    cp d
    push hl
    jr z, .next

    push hl
    push bc
    ; If the Pokemon has at least 1 HP...
    ld bc, MON_HP
    add hl, bc
    pop bc
    ld a, [hli]
    or [hl]
    pop hl
    jr z, .next

    ld a, [hl]
    ld [wCurSpecies], a
    call GetBaseData
    ; the player's last move is damaging...
    ld a, [wLastPlayerCounterMove]
    dec a
    ld hl, Moves + MOVE_POWER
    call GetMoveAttr
    and a
    jr z, .next
    ; and the Pokemon is immune to it...
    inc hl
    call GetMoveByte
    ld hl, wBaseType
    call CheckTypeMatchup
    ld a, [wTypeMatchup]
    and a
    jr nz, .next
    ; ... encourage that Pokemon.
    ld a, [wEnemyAISwitchScore]
    or c
    ld [wEnemyAISwitchScore], a
.next
    pop hl
    dec b
    ret z

    push bc
    ld bc, PARTYMON_STRUCT_LENGTH
    add hl, bc
    pop bc

    inc d
    srl c
    jr .loop

FindAliveEnemyMonsWithASuperEffectiveMove:
    push bc
    ld a, [wOTPartyCount]
    ld e, a
    ld hl, wOTPartyMon1HP
    ld b, 1 << (PARTY_LENGTH - 1)
    ld c, 0
.loop
    ld a, [hli]
    or [hl]
    jr z, .next

    ld a, b
    or c
    ld c, a

.next
    srl b
    push bc
    ld bc, wPartyMon2HP - (wPartyMon1HP + 1)
    add hl, bc
    pop bc
    dec e
    jr nz, .loop

    ld a, c
    pop bc

    and c
    ld c, a
    ; fallthrough
FindEnemyMonsWithASuperEffectiveMove:
    ld a, -1
    ld [wEnemyAISwitchScore], a
    ld hl, wOTPartyMon1Moves
    ld b, 1 << (PARTY_LENGTH - 1)
    ld d, 0
    ld e, 0
.loop
    ld a, b
    and c
    jr z, .next

    push hl
    push bc
    ; for move on mon:
    ld b, NUM_MOVES
    ld c, 0
.loop3
    ; if move is None: break
    ld a, [hli]
    and a
    push hl
    jr z, .break3

    ; if move has no power: continue
    dec a
    ld hl, Moves + MOVE_POWER
    call GetMoveAttr
    and a
    jr z, .nope

    ; check type matchups
    inc hl
    call GetMoveByte
    ld hl, wBattleMonType1
    call CheckTypeMatchup

    ; if immune or not very effective: continue
    ld a, [wTypeMatchup]
    cp 10
    jr c, .nope

    ; if neutral: load 1 and continue
    ld e, 1
    cp EFFECTIVE + 1
    jr c, .nope

    ; if super-effective: load 2 and break
    ld e, 2
    jr .break3

.nope
    pop hl
    dec b
    jr nz, .loop3

    jr .done

.break3
    pop hl
.done
    ld a, e
    pop bc
    pop hl
    cp 2
    jr z, .done2 ; at least one move is super-effective
    cp 1
    jr nz, .next ; no move does more than half damage

    ; encourage this pokemon
    ld a, d
    or b
    ld d, a
    jr .next ; such a long jump

.next
    ; next pokemon?
    push bc
    ld bc, PARTYMON_STRUCT_LENGTH
    add hl, bc
    pop bc
    srl b
    jr nc, .loop

    ; if no pokemon has a super-effective move: return
    ld a, d
    ld b, a
    and a
    ret z

.done2
    ; convert the bit flag to an int and return
    push bc
    sla b
    sla b
    ld c, $ff
.loop2
    inc c
    sla b
    jr nc, .loop2

    ld a, c
    ld [wEnemyAISwitchScore], a
    pop bc
    ret

FindEnemyMonsThatResistPlayer:
    push bc
    ld hl, wOTPartySpecies
    ld b, 1 << (PARTY_LENGTH - 1)
    ld c, 0

.loop
    ld a, [hli]
    cp $ff
    jr z, .done

    push hl
    ld [wCurSpecies], a
    call GetBaseData
    ld a, [wLastPlayerCounterMove]
    and a
    jr z, .skip_move

    dec a
    ld hl, Moves + MOVE_POWER
    call GetMoveAttr
    and a
    jr z, .skip_move

    inc hl
    call GetMoveByte
    jr .check_type

.skip_move
    ld a, [wBattleMonType1]
    ld hl, wBaseType
    call CheckTypeMatchup
    ld a, [wTypeMatchup]
    cp 10 + 1
    jr nc, .dont_choose_mon
    ld a, [wBattleMonType2]

.check_type
    ld hl, wBaseType
    call CheckTypeMatchup
    ld a, [wTypeMatchup]
    cp EFFECTIVE + 1
    jr nc, .dont_choose_mon

    ld a, b
    or c
    ld c, a

.dont_choose_mon
    srl b
    pop hl
    jr .loop

.done
    ld a, c
    pop bc
    and c
    ld c, a
    ret

FindEnemyMonsWithAtLeastQuarterMaxHP:
    push bc
    ld de, wOTPartySpecies
    ld b, 1 << (PARTY_LENGTH - 1)
    ld c, 0
    ld hl, wOTPartyMon1HP

.loop
    ld a, [de]
    inc de
    cp $ff
    jr z, .done

    push hl
    push bc
    ld b, [hl]
    inc hl
    ld c, [hl]
    inc hl
    inc hl
; hl = MaxHP + 1
; bc = [CurHP] * 4
    srl c
    rl b
    srl c
    rl b
; if bc >= [hl], encourage
    ld a, [hld]
    cp c
    ld a, [hl]
    sbc b
    pop bc
    jr nc, .next

    ld a, b
    or c
    ld c, a

.next
    srl b
    pop hl
    push bc
    ld bc, PARTYMON_STRUCT_LENGTH
    add hl, bc
    pop bc
    jr .loop

.done
    ld a, c
    pop bc
    and c
    ld c, a
    ret