.org 0

.equ INT_VECTOR 0xff00

    call init

;
; Menu entry point
;
menu:
    ; reset the blink flag
    ld x, <blink
    ld a, >blink
    ld y, 0
    ld [a : x], y

    call clear_screen

menu_loop:
    halt

    call stars_update
    call menu_draw

    ; read controller 1
    ld b, 0xf0
    port b, b

    ; start
    bit b, 7
    bnz
    jmp menu_loop


;
; Gameplay entry point
;
play:
    call init_game

game_loop:
    halt

    call entities_erase
    call stars_update
    call entities_update
    call entities_draw

    ; read controller 1
    ld b, 0xf0
    port b, b

    ; select to exit
    bit b, 6
    bnz
    jmp game_loop

    jmp menu

;
; Setup the game after the menu
;
init_game:
    halt

    ; set player initial coordinates
    ld x, <player_coord
    ld a, >player_coord

    ld y, 56
    ld [a : x], y
    inc x
    bo
    inc a
    ld y, 104
    ld [a : x], y

    call clear_screen
    call entities_draw

    ret

;
; Helper to clear the screen
;
clear_screen:
    ; erase the screen
    ld b, 0
    ld a, 0xbf
    ld x, 0
    ld y, 0x40
fill_loop:
    ld [a : x], b
    inc x
    bno
    jmp fill_loop
    inc a
    dec y
    bnz
    jmp fill_loop
    ret

;
; Controls the blink of the "press start" text
;
blink:
    .db 0

;
; Draws the menu
;
menu_draw:
    ; settings mode
    ld y, 128
    ld b, 0xb0
    port b, y

    ; setup
    inc b

    ; addr: title sprite
    ld y, <title
    port b, y
    ld y, >title
    port b, y

    ; x
    ld y, 26
    port b, y

    ; y
    ld y, 40
    port b, y

    ld y, 76
    port b, y
    ld y, 21
    port b, y

    ; blit
    dec b
    ; write, transparent
    ld y, 3
    port b, y

    ; settings mode
    ld y, 128
    port b, y

    ; setup
    inc b

    ld x, <blink
    ld a, >blink
    ld y, [a : x]
    inc y
    and y, 31
    ld [a : x], y
    cmp y, 10
    bnc
    jmp menu_draw_start

    ; addr: black to erase sprite
    ld y, 0
    port b, y
    ld y, 0xa0
    port b, y
    jmp menu_continue_start

menu_draw_start:
    ; addr: press start sprite
    ld y, <press
    port b, y
    ld y, >press
    port b, y

menu_continue_start:
    ; x
    ld y, 36
    port b, y

    ; y
    ld y, 80
    port b, y

    ld y, 56
    port b, y
    ld y, 8
    port b, y

    ; blit
    dec b
    ; write, transparent
    ld y, 3
    port b, y

    ; settings mode
    ld y, 128
    port b, y

    ; setup
    inc b

    ; addr: usebox logo sprite
    ld y, <usebox
    port b, y
    ld y, >usebox
    port b, y

    ; x
    ld y, 44
    port b, y

    ; y
    ld y, 118
    port b, y

    ld y, 40
    port b, y
    ld y, 8
    port b, y

    ; blit
    dec b
    ; write, transparent
    ld y, 3
    port b, y
    ret

;
; Init the TR8 (setup an int handler)
;
init:
    ; setup an int handler so we
    ; can use the frame int to sync
    ld a, >INT_VECTOR
    ld x, <INT_VECTOR
    ld b, <int_handler
    ld [a : x], b
    inc x
    ld b, >int_handler
    ld [a : x], b

    ; enable interrupts
    cif
    ret

int_handler:
    iret

.include "random.asm"
.include "starfield.asm"
.include "entities.asm"
.include "player.asm"

;
; entity data
;
entities:
    ; type
    .db ET_PLAYER
    ; x, y
player_coord:
    .db 0, 0
    ; frame
    .db 0
    .dw player_sprite
    .dw player_update

    ; 16 entities
    .ds 112, 0

    ; end of list
    .db ET_END

; sprite data
player_sprite:
    .incpng "assets/player.png"

; starfield data
stars:
    ; video addr, speed, color
    .dw 0xc361
    .db 1, 15
    .dw 0xc204
    .db 1, 6
    .dw 0xcdf9
    .db 1, 15
    .dw 0xdb87
    .db 1, 3
    .dw 0xd242
    .db 1, 15
    .dw 0xdeea
    .db 1, 6
    .dw 0xe7af
    .db 1, 15
    .dw 0xed68
    .db 1, 3
    .dw 0xf812
    .db 1, 15
    .dw 0xfbca
    .db 1, 13
    .dw 0xc361
    .db 2, 8
    .dw 0xc204
    .db 2, 9
    .dw 0xcdf9
    .db 3, 7
    .dw 0xdb87
    .db 3, 4
    .dw 0xd242
    .db 2, 8
    .dw 0xdeea
    .db 3, 9
    .dw 0xe7af
    .db 3, 6
    .dw 0xed68
    .db 2, 9
    .dw 0xf812
    .db 3, 14
    .dw 0xfbca
    .db 2, 3
    ; end of list
    .dw 0xffff

; menu data
title:
    .incpng "assets/title.png"
press:
    .incpng "assets/press.png"
usebox:
    .incpng "assets/usebox.png"