island-story/src/player.s

INCLUDE "hardware.inc"
INCLUDE "input.inc"
INCLUDE "oam.inc"

Section "Player Data", WRAM0

playerWorldX: dw
playerWorldY: dw

; player data
PLAYER_X:: db
PLAYER_Y:: db
PLAYER_DIR:: db

Section "Player Code", ROM0

spriteData:
    INCBIN "png/sprite/player.2bpp"

DEF SPRITE_OAM_IDX EQU 0
DEF SPRITE_IDX EQU 32 ; tile index, rename later
DEF SPRITE_WIDTH EQU 2
DEF SPRITE_HEIGHT EQU 2

Player_Init::
    ; clear player data
    ld hl, PLAYER_X
    ld [hl], 0
    inc hl
    ld [hl], 144-32
    inc hl
    ld [hl], 0

    ld a, 8
    ld hl, _OAM + 1
    ld [hl], a

    ld bc, _VRAM8000 + SPRITE_IDX * 16
    ld hl, spriteData
    ld d, 16 * (SPRITE_WIDTH * SPRITE_HEIGHT)
    call memcpy

    OAM_set SPRITE_OAM_IDX + 0, 8, 144-8-8, SPRITE_IDX, 0
    OAM_set SPRITE_OAM_IDX + 1, 16, 144-8-8, SPRITE_IDX + 1, 0
    OAM_set SPRITE_OAM_IDX + 2, 8, 144-8, SPRITE_IDX + 2, 0
    OAM_set SPRITE_OAM_IDX + 3, 16, 144-8, SPRITE_IDX + 3, 0

    ld bc, _OAMRAM
    ld hl, _OAM
    ld d, 4 * (SPRITE_WIDTH * SPRITE_HEIGHT)
    call memcpy

    ret

Player_Update::
    ; Only update every 2 frames
    ; ld hl, frame
    ; ld a, [hl]
    ; and %1
    ; cp %1
    ; ret nz

    ld hl, keys
    ld b, [hl]

    ; check for move right
    ld a, b
    and BTN_RIGHT
    jr z, .left

    ; check for right boundary
    ld hl, PLAYER_X
    ld a, [hl]
    add 16
    cp SCRN_X
    jr nc, .left

    inc [hl]

    call player_bg_collides
    jr z, .right_rollback

    ld hl, PLAYER_DIR
    ld [hl], 0

    call update_oam
    ret

.right_rollback:
    ld hl, PLAYER_X
    dec [hl]
    ret

.left:
    ; check for left button
    ld a, b
    and BTN_LEFT
    ret z

    ; check for left boundary
    ld hl, PLAYER_X
    ld a, [hl]
    or a
    ret z

    dec [hl]

    call player_bg_collides
    jr z, .left_rollback

    ld hl, PLAYER_DIR
    ld [hl], $ff

    call update_oam
    ret

.left_rollback:
    ld hl, PLAYER_X
    dec [hl]
    ret

; Update player metasprite with positional data
update_oam:
    ld hl, PLAYER_DIR
    ld a, [hl-] ; dir (0 = right , $ff = left)
    and OAMF_XFLIP
    ld c, a

    ld a, [hl-] ; y
    add 16

    ld d, a
    ld a, [hl] ; x
    add 8
    ld b, a
    ld a, d

    ld_OAM_y hl, SPRITE_OAM_IDX

    ; top left sprite
    ld [hli], a
    ld [hl], b
    inc hl
    ld [hl], SPRITE_IDX
    inc hl
    ld [hl], c
    inc hl

    ; top right
    ld d, a
    ld a, b
    add 8
    ld b, a
    ld a, d

    ld [hli], a
    ld [hl], b
    inc hl
    ld [hl], SPRITE_IDX + 1
    inc hl
    ld [hl], c
    inc hl

    ; bottom left
    add 8
    ld d, a
    ld a, b
    sub 8
    ld b, a
    ld a, d

    ld [hli], a
    ld [hl], b
    inc hl
    ld [hl], SPRITE_IDX + 2
    inc hl
    ld [hl], c
    inc hl

    ; bottom right
    ld d, a
    ld a, b
    add 8
    ld b, a
    ld a, d

    ld [hli], a
    ld [hl], b
    inc hl
    ld [hl], SPRITE_IDX + 3
    inc hl
    ld [hl], c

    ; flip tile indices if necessary
    ld a, c
    or c
    jr z, .done

    ld_OAM_tile hl, SPRITE_OAM_IDX
    ld [hl], SPRITE_IDX + 1

    ld_OAM_tile hl, SPRITE_OAM_IDX + 1
    ld [hl], SPRITE_IDX

    ld_OAM_tile hl, SPRITE_OAM_IDX + 2
    ld [hl], SPRITE_IDX + 3

    ld_OAM_tile hl, SPRITE_OAM_IDX + 3
    ld [hl], SPRITE_IDX + 2

.done:
    ret