Encounter Code Range v1.0

LoadWildMonData:
    call _GrassWildmonLookup
    jr c, .copy
    ld hl, wMornEncounterRate
    xor a
    ld [hli], a
    ld [hli], a
    ld [hl], a
    jr .done_copy

.copy
    inc hl
    inc hl
    ld de, wMornEncounterRate
    ld bc, 3
    call CopyBytes
.done_copy
    call _WaterWildmonLookup
    ld a, 0
    jr nc, .no_copy
    inc hl
    inc hl
    ld a, [hl]
.no_copy
    ld [wWaterEncounterRate], a
    ret

FindNest:
; Parameters:
; e: 0 = Johto, 1 = Kanto
; wNamedObjectIndex: species
    hlcoord 0, 0
    ld bc, SCREEN_WIDTH * SCREEN_HEIGHT
    xor a
    call ByteFill
    ld a, e
    and a
    jr nz, .kanto
    decoord 0, 0
    ld hl, JohtoGrassWildMons
    call .FindGrass
    ld hl, JohtoWaterWildMons
    call .FindWater
    call .RoamMon1
    call .RoamMon2
    ret

.kanto
    decoord 0, 0
    ld hl, KantoGrassWildMons
    call .FindGrass
    ld hl, KantoWaterWildMons
    jp .FindWater

.FindGrass:
    ld a, [hl]
    cp -1
    ret z
    push hl
    ld a, [hli]
    ld b, a
    ld a, [hli]
    ld c, a
    inc hl
    inc hl
    inc hl
    ld a, NUM_GRASSMON * 3
    call .SearchMapForMon
    jr nc, .next_grass
    ld [de], a
    inc de

.next_grass
    pop hl
    ld bc, GRASS_WILDDATA_LENGTH
    add hl, bc
    jr .FindGrass

.FindWater:
    ld a, [hl]
    cp -1
    ret z
    push hl
    ld a, [hli]
    ld b, a
    ld a, [hli]
    ld c, a
    inc hl
    ld a, NUM_WATERMON
    call .SearchMapForMon
    jr nc, .next_water
    ld [de], a
    inc de

.next_water
    pop hl
    ld bc, WATER_WILDDATA_LENGTH
    add hl, bc
    jr .FindWater

.SearchMapForMon:
    inc hl
.ScanMapLoop:
    push af
    ld a, [wNamedObjectIndex]
    cp [hl]
    jr z, .found
    inc hl
    inc hl
    inc hl
    pop af
    dec a
    jr nz, .ScanMapLoop
    and a
    ret

.found
    pop af
    jp .AppendNest

.AppendNest:
    push de
    call GetWorldMapLocation
    ld c, a
    hlcoord 0, 0
    ld de, SCREEN_WIDTH * SCREEN_HEIGHT
.AppendNestLoop:
    ld a, [hli]
    cp c
    jr z, .found_nest
    dec de
    ld a, e
    or d
    jr nz, .AppendNestLoop
    ld a, c
    pop de
    scf
    ret

.found_nest
    pop de
    and a
    ret

.RoamMon1:
    ld a, [wRoamMon1Species]
    ld b, a
    ld a, [wNamedObjectIndex]
    cp b
    ret nz
    ld a, [wRoamMon1MapGroup]
    ld b, a
    ld a, [wRoamMon1MapNumber]
    ld c, a
    call .AppendNest
    ret nc
    ld [de], a
    inc de
    ret

.RoamMon2:
    ld a, [wRoamMon2Species]
    ld b, a
    ld a, [wNamedObjectIndex]
    cp b
    ret nz
    ld a, [wRoamMon2MapGroup]
    ld b, a
    ld a, [wRoamMon2MapNumber]
    ld c, a
    call .AppendNest
    ret nc
    ld [de], a
    inc de
    ret

TryWildEncounter::
; Try to trigger a wild encounter.
    call .EncounterRate
    jr nc, .no_battle
    call ChooseWildEncounter
    jr nz, .no_battle
    call CheckRepelEffect
    jr nc, .no_battle
    xor a
    ret

.no_battle
    xor a ; BATTLETYPE_NORMAL
    ld [wTempWildMonSpecies], a
    ld [wBattleType], a
    ld a, 1
    and a
    ret

.EncounterRate:
    call GetMapEncounterRate
    call ApplyMusicEffectOnEncounterRate
    call ApplyCleanseTagEffectOnEncounterRate
    call Random
    cp b
    ret

GetMapEncounterRate:
    ld hl, wMornEncounterRate
    call CheckOnWater
    ld a, wWaterEncounterRate - wMornEncounterRate
    jr z, .ok
    ld a, [wTimeOfDay]
.ok
    ld c, a
    ld b, 0
    add hl, bc
    ld b, [hl]
    ret

ApplyMusicEffectOnEncounterRate::
; Pokemon March and Ruins of Alph signal double encounter rate.
; Pokemon Lullaby halves encounter rate.
    ld a, [wMapMusic]
    cp MUSIC_POKEMON_MARCH
    jr z, .double
    cp MUSIC_RUINS_OF_ALPH_RADIO
    jr z, .double
    cp MUSIC_POKEMON_LULLABY
    ret nz
    srl b
    ret

.double
    sla b
    ret

ApplyCleanseTagEffectOnEncounterRate::
; Cleanse Tag halves encounter rate.
    ld hl, wPartyMon1Item
    ld de, PARTYMON_STRUCT_LENGTH
    ld a, [wPartyCount]
    ld c, a
.loop
    ld a, [hl]
    cp CLEANSE_TAG
    jr z, .cleansetag
    add hl, de
    dec c
    jr nz, .loop
    ret

.cleansetag
    srl b
    ret

ChooseWildEncounter:
; Pick a random mon out of ContestMons.
    call LoadWildMonDataPointer
    jp nc, .nowildbattle
    call CheckEncounterRoamMon
    jp c, .startwildbattle

    inc hl
    inc hl
    inc hl
    call CheckOnWater
    ld de, WaterMonProbTable
    jr z, .watermon
    inc hl
    inc hl
    ld a, [wTimeOfDay]
    ld bc, NUM_GRASSMON * 3
    call AddNTimes
    ld de, GrassMonProbTable

.watermon
; hl contains the pointer to the wild mon data, let's save that to the stack
    push hl
.randomloop
    call Random
    cp 100
    jr nc, .randomloop
    inc a ; 1 <= a <= 100
    ld h, d
    ld l, e
; This next loop chooses which mon to load up.
.prob_bracket_loop
    ld a, [hli]
    cp b
    jr nc, .got_it
    inc hl
    jr .prob_bracket_loop

.got_it
    ld c, [hl]
    ld b, 0
    pop hl
    add hl, bc ; this selects our mon
; Min level
    ld a, [hli]
    ld b, a

; Max level
    inc hl
    ld a, [hl]

    sub b
    jr nz, .RandomLevel

; If min and max are the same.
    ld a, b
    jr .GotLevel

.RandomLevel:
; Get a random level between the min and max.
    ld c, a
    inc c
    call Random
    ldh a, [hRandomAdd]
    call SimpleDivide
    add b

.GotLevel:
    ld [wCurPartyLevel], a
    ld b, [hl]
    ; ld a, b
    call ValidateTempWildMonSpecies
    jr c, .nowildbattle

    ld a, b ; This is in the wrong place.
    cp UNOWN
    jr nz, .done

    ld a, [wUnlockedUnowns]
    and a
    jr z, .nowildbattle

.done
    jr .loadwildmon

.nowildbattle
    ld a, 1
    and a
    ret

.loadwildmon
    ld a, b
    ld [wTempWildMonSpecies], a

.startwildbattle
    xor a
    ret

TryWildEncounter_BugContest:
    ld a, [wPlayerStandingTile]
    call CheckSuperTallGrassTile
    ld b, 40 percent
    jr z, .ok
    ld b, 20 percent

.ok
    farcall ApplyMusicEffectOnEncounterRate
    farcall ApplyCleanseTagEffectOnEncounterRate
    call Random
    ldh a, [hRandomAdd]
    cp b
    ret c
    ld a, 1
    and a
    ret

INCLUDE "data/wild/probabilities.asm"

CheckRepelEffect::
; If there is no active Repel, there's no need to be here.
    ld a, [wRepelEffect]
    and a
    jr z, .encounter
; Get the first Pokemon in your party that isn't fainted.
    ld hl, wPartyMon1HP
    ld bc, PARTYMON_STRUCT_LENGTH - 1
.loop
    ld a, [hli]
    or [hl]
    jr nz, .ok
    add hl, bc
    jr .loop

.ok
; to PartyMonLevel
rept 4
    dec hl
endr

    ld a, [wCurPartyLevel]
    cp [hl]
    jr nc, .encounter
    and a
    ret

.encounter
    scf
    ret

LoadWildMonDataPointer:
    call CheckOnWater
    jr z, _WaterWildmonLookup

_GrassWildmonLookup:
    ld hl, SwarmGrassWildMons
    ld bc, GRASS_WILDDATA_LENGTH
    call _SwarmWildmonCheck
    ret c
    ld hl, JohtoGrassWildMons
    ld de, KantoGrassWildMons
    call _JohtoWildmonCheck
    ld bc, GRASS_WILDDATA_LENGTH
    jr _NormalWildmonOK

_WaterWildmonLookup:
    ld hl, SwarmWaterWildMons
    ld bc, WATER_WILDDATA_LENGTH
    call _SwarmWildmonCheck
    ret c
    ld hl, JohtoWaterWildMons
    ld de, KantoWaterWildMons
    call _JohtoWildmonCheck
    ld bc, WATER_WILDDATA_LENGTH
    jr _NormalWildmonOK

_JohtoWildmonCheck:
    call IsInJohto
    and a
    ret z
    ld h, d
    ld l, e
    ret

_SwarmWildmonCheck:
    call CopyCurrMapDE
    push hl
    ld hl, wSwarmFlags
    bit SWARMFLAGS_DUNSPARCE_SWARM_F, [hl]
    pop hl
    jr z, .CheckYanma
    ld a, [wDunsparceMapGroup]
    cp d
    jr nz, .CheckYanma
    ld a, [wDunsparceMapNumber]
    cp e
    jr nz, .CheckYanma
    call LookUpWildmonsForMapDE
    jr nc, _NoSwarmWildmon
    scf
    ret

.CheckYanma:
    push hl
    ld hl, wSwarmFlags
    bit SWARMFLAGS_YANMA_SWARM_F, [hl]
    pop hl
    jr z, _NoSwarmWildmon
    ld a, [wYanmaMapGroup]
    cp d
    jr nz, _NoSwarmWildmon
    ld a, [wYanmaMapNumber]
    cp e
    jr nz, _NoSwarmWildmon
    call LookUpWildmonsForMapDE
    jr nc, _NoSwarmWildmon
    scf
    ret

_NoSwarmWildmon:
    and a
    ret

_NormalWildmonOK:
    call CopyCurrMapDE
    jr LookUpWildmonsForMapDE

CopyCurrMapDE:
    ld a, [wMapGroup]
    ld d, a
    ld a, [wMapNumber]
    ld e, a
    ret

LookUpWildmonsForMapDE:
.loop
    push hl
    ld a, [hl]
    inc a
    jr z, .nope
    ld a, d
    cp [hl]
    jr nz, .next
    inc hl
    ld a, e
    cp [hl]
    jr z, .yup

.next
    pop hl
    add hl, bc
    jr .loop

.nope
    pop hl
    and a
    ret

.yup
    pop hl
    scf
    ret

InitRoamMons:
; initialize wRoamMon structs

; species
    ld a, RAIKOU
    ld [wRoamMon1Species], a
    ld a, ENTEI
    ld [wRoamMon2Species], a

; level
    ld a, 40
    ld [wRoamMon1Level], a
    ld [wRoamMon2Level], a

; raikou starting map
    ld a, GROUP_ROUTE_42
    ld [wRoamMon1MapGroup], a
    ld a, MAP_ROUTE_42
    ld [wRoamMon1MapNumber], a

; entei starting map
    ld a, GROUP_ROUTE_37
    ld [wRoamMon2MapGroup], a
    ld a, MAP_ROUTE_37
    ld [wRoamMon2MapNumber], a

; hp
    xor a ; generate new stats
    ld [wRoamMon1HP], a
    ld [wRoamMon2HP], a

    ret

CheckEncounterRoamMon:
    push hl
; Don't trigger an encounter if we're on water.
    call CheckOnWater
    jr z, .DontEncounterRoamMon
; Load the current map group and number to de
    call CopyCurrMapDE
; Randomly select a beast.
    call Random
    cp 100 ; 25/64 chance
    jr nc, .DontEncounterRoamMon
    and %00000011 ; Of that, a 3/4 chance.  Running total: 75/256, or around 29.3%.
    jr z, .DontEncounterRoamMon
    dec a ; 1/3 chance that it's Entei, 1/3 chance that it's Raikou
; Compare its current location with yours
    ld hl, wRoamMon1MapGroup
    ld c, a
    ld b, 0
    ld a, 7 ; length of the roam_struct
    call AddNTimes
    ld a, d
    cp [hl]
    jr nz, .DontEncounterRoamMon
    inc hl
    ld a, e
    cp [hl]
    jr nz, .DontEncounterRoamMon
; We've decided to take on a beast, so stage its information for battle.
    dec hl
    dec hl
    dec hl
    ld a, [hli]
    ld [wTempWildMonSpecies], a
    ld a, [hl]
    ld [wCurPartyLevel], a
    ld a, BATTLETYPE_ROAMING
    ld [wBattleType], a

    pop hl
    scf
    ret

.DontEncounterRoamMon:
    pop hl
    and a
    ret

UpdateRoamMons:
    ld a, [wRoamMon1MapGroup]
    cp GROUP_N_A
    jr z, .SkipRaikou
    ld b, a
    ld a, [wRoamMon1MapNumber]
    ld c, a
    call .Update
    ld a, b
    ld [wRoamMon1MapGroup], a
    ld a, c
    ld [wRoamMon1MapNumber], a

.SkipRaikou:
    ld a, [wRoamMon2MapGroup]
    cp GROUP_N_A
    jr z, .SkipEntei
    ld b, a
    ld a, [wRoamMon2MapNumber]
    ld c, a
    call .Update
    ld a, b
    ld [wRoamMon2MapGroup], a
    ld a, c
    ld [wRoamMon2MapNumber], a

.SkipEntei:
    ld a, [wRoamMon3MapGroup]
    cp GROUP_N_A
    jr z, .Finished
    ld b, a
    ld a, [wRoamMon3MapNumber]
    ld c, a
    call .Update
    ld a, b
    ld [wRoamMon3MapGroup], a
    ld a, c
    ld [wRoamMon3MapNumber], a

.Finished:
    jp _BackUpMapIndices

.Update:
    ld hl, RoamMaps
.loop
; Are we at the end of the table?
    ld a, [hl]
    cp -1
    ret z
; Is this the correct entry?
    ld a, b
    cp [hl]
    jr nz, .next
    inc hl
    ld a, c
    cp [hl]
    jr z, .yes
; We don't have the correct entry yet, so let's continue.  A 0 terminates each entry.
.next
    ld a, [hli]
    and a
    jr nz, .next
    jr .loop

; We have the correct entry now, so let's choose a random map from it.
.yes
    inc hl
    ld d, h
    ld e, l
.update_loop
    ld h, d
    ld l, e
; Choose which map to warp to.
    call Random
    and %00011111 ; 1/8n chance it moves to a completely random map, where n is the number of roaming connections from the current map.
    jr z, JumpRoamMon
    and %11
    cp [hl]
    jr nc, .update_loop ; invalid index, try again
    inc hl
    ld c, a
    ld b, 0
    add hl, bc
    add hl, bc
    ld a, [wRoamMons_LastMapGroup]
    cp [hl]
    jr nz, .done
    inc hl
    ld a, [wRoamMons_LastMapNumber]
    cp [hl]
    jr z, .update_loop
    dec hl

.done
    ld a, [hli]
    ld b, a
    ld c, [hl]
    ret

JumpRoamMons:
    ld a, [wRoamMon1MapGroup]
    cp GROUP_N_A
    jr z, .SkipRaikou
    call JumpRoamMon
    ld a, b
    ld [wRoamMon1MapGroup], a
    ld a, c
    ld [wRoamMon1MapNumber], a

.SkipRaikou:
    ld a, [wRoamMon2MapGroup]
    cp GROUP_N_A
    jr z, .SkipEntei
    call JumpRoamMon
    ld a, b
    ld [wRoamMon2MapGroup], a
    ld a, c
    ld [wRoamMon2MapNumber], a

.SkipEntei:
    ld a, [wRoamMon3MapGroup]
    cp GROUP_N_A
    jr z, .Finished
    call JumpRoamMon
    ld a, b
    ld [wRoamMon3MapGroup], a
    ld a, c
    ld [wRoamMon3MapNumber], a

.Finished:
    jp _BackUpMapIndices

JumpRoamMon:
.loop
    ld hl, RoamMaps
.innerloop1
    ; 0-15 are all valid indexes into RoamMaps,
    ; so this retry loop is unnecessary
    ; since NUM_ROAMMON_MAPS happens to be 16
    call Random
    maskbits NUM_ROAMMON_MAPS
    cp NUM_ROAMMON_MAPS
    jr nc, .innerloop1
    inc a
    ld b, a
.innerloop2 ; Loop to get hl to the address of the chosen roam map.
    dec b
    jr z, .ok
.innerloop3 ; Loop to skip the current roam map, which is terminated by a 0.
    ld a, [hli]
    and a
    jr nz, .innerloop3
    jr .innerloop2
; Check to see if the selected map is the one the player is currently in.  If so, try again.
.ok
    ld a, [wMapGroup]
    cp [hl]
    jr nz, .done
    inc hl
    ld a, [wMapNumber]
    cp [hl]
    jr z, .loop
    dec hl
; Return the map group and number in bc.
.done
    ld a, [hli]
    ld b, a
    ld c, [hl]
    ret

_BackUpMapIndices:
    ld a, [wRoamMons_CurMapNumber]
    ld [wRoamMons_LastMapNumber], a
    ld a, [wRoamMons_CurMapGroup]
    ld [wRoamMons_LastMapGroup], a
    ld a, [wMapNumber]
    ld [wRoamMons_CurMapNumber], a
    ld a, [wMapGroup]
    ld [wRoamMons_CurMapGroup], a
    ret

INCLUDE "data/wild/roammon_maps.asm"

ValidateTempWildMonSpecies:
; Due to a development oversight, this function is called with the wild Pokemon's level, not its species, in a.
    and a
    jr z, .nowildmon ; = 0
    cp NUM_POKEMON + 1 ; 252
    jr nc, .nowildmon ; >= 252
    and a ; 1 <= Species <= 251
    ret

.nowildmon
    scf
    ret

; Finds a rare wild Pokemon in the route of the trainer calling, then checks if it's been Seen already.
; The trainer will then tell you about the Pokemon if you haven't seen it.
RandomUnseenWildMon:
    farcall GetCallerLocation
    ld d, b
    ld e, c
    ld hl, JohtoGrassWildMons
    ld bc, GRASS_WILDDATA_LENGTH
    call LookUpWildmonsForMapDE
    jr c, .GetGrassmon
    ld hl, KantoGrassWildMons
    call LookUpWildmonsForMapDE
    jr nc, .done

.GetGrassmon:
    push hl
    ld bc, 5 + 4 * 3 ; Location of the level of the 5th wild Pokemon in that map
    add hl, bc
    ld a, [wTimeOfDay]
    ld bc, NUM_GRASSMON * 3
    call AddNTimes
.randloop1
    call Random
    and %11
    jr z, .randloop1
    dec a
    ld c, a
    ld b, 0
    add hl, bc
    add hl, bc
; We now have the pointer to one of the last (rarest) three wild Pokemon found in that area.
    inc hl
    ld c, [hl] ; Contains the species index of this rare Pokemon
    pop hl
    ld de, 5 + 0 * 3
    add hl, de
    inc hl ; Species index of the most common Pokemon on that route
    ld b, 4
.loop2
    ld a, [hli]
    cp c ; Compare this most common Pokemon with the rare one stored in c.
    jr z, .done
    inc hl
    inc hl
    dec b
    jr nz, .loop2
; This Pokemon truly is rare.
    push bc
    dec c
    ld a, c
    call CheckSeenMon
    pop bc
    jr nz, .done
; Since we haven't seen it, have the caller tell us about it.
    ld de, wStringBuffer1
    call CopyName1
    ld a, c
    ld [wNamedObjectIndex], a
    call GetPokemonName
    ld hl, .JustSawSomeRareMonText
    call PrintText
    xor a
    ld [wScriptVar], a
    ret

.done
    ld a, $1
    ld [wScriptVar], a
    ret

.JustSawSomeRareMonText:
    text_far _JustSawSomeRareMonText
    text_end

RandomPhoneWildMon:
    farcall GetCallerLocation
    ld d, b
    ld e, c
    ld hl, JohtoGrassWildMons
    ld bc, GRASS_WILDDATA_LENGTH
    call LookUpWildmonsForMapDE
    jr c, .ok
    ld hl, KantoGrassWildMons
    call LookUpWildmonsForMapDE

.ok
    ld bc, 5 + 0 * 3
    add hl, bc
    ld a, [wTimeOfDay]
    inc a
    ld bc, NUM_GRASSMON * 3
.loop
    dec a
    jr z, .done
    add hl, bc
    jr .loop

.done
    call Random
    and %11
    ld c, a
    ld b, 0
    add hl, bc
    add hl, bc
    inc hl
    ld a, [hl]
    ld [wNamedObjectIndex], a
    call GetPokemonName
    ld hl, wStringBuffer1
    ld de, wStringBuffer4
    ld bc, MON_NAME_LENGTH
    jp CopyBytes

RandomPhoneMon:
; Get a random monster owned by the trainer who's calling.
    farcall GetCallerLocation
    ld hl, TrainerGroups
    ld a, d
    dec a
    ld c, a
    ld b, 0
    add hl, bc
    add hl, bc
    ld a, BANK(TrainerGroups)
    call GetFarWord

.skip_trainer
    dec e
    jr z, .skipped
.skip
    ld a, BANK(Trainers)
    call GetFarByte
    inc hl
    cp -1
    jr nz, .skip
    jr .skip_trainer
.skipped

.skip_name
    ld a, BANK(Trainers)
    call GetFarByte
    inc hl
    cp "@"
    jr nz, .skip_name

    ld a, BANK(Trainers)
    call GetFarByte
    inc hl
    ld bc, 2 ; level, species
    cp TRAINERTYPE_NORMAL
    jr z, .got_mon_length
    ld bc, 2 + NUM_MOVES ; level, species, moves
    cp TRAINERTYPE_MOVES
    jr z, .got_mon_length
    ld bc, 2 + 1 ; level, species, item
    cp TRAINERTYPE_ITEM
    jr z, .got_mon_length
    ; TRAINERTYPE_ITEM_MOVES
    ld bc, 2 + 1 + NUM_MOVES ; level, species, item, moves
.got_mon_length

    ld e, 0
    push hl
.count_mon
    inc e
    add hl, bc
    ld a, BANK(Trainers)
    call GetFarByte
    cp -1
    jr nz, .count_mon
    pop hl

.rand
    call Random
    maskbits PARTY_LENGTH
    cp e
    jr nc, .rand

    inc a
.get_mon
    dec a
    jr z, .got_mon
    add hl, bc
    jr .get_mon
.got_mon

    inc hl ; species
    ld a, BANK(Trainers)
    call GetFarByte
    ld [wNamedObjectIndex], a
    call GetPokemonName
    ld hl, wStringBuffer1
    ld de, wStringBuffer4
    ld bc, MON_NAME_LENGTH
    jp CopyBytes

INCLUDE "data/wild/johto_grass.asm"
INCLUDE "data/wild/johto_water.asm"
INCLUDE "data/wild/kanto_grass.asm"
INCLUDE "data/wild/kanto_water.asm"
INCLUDE "data/wild/swarm_grass.asm"
INCLUDE "data/wild/swarm_water.asm"