.segment "HEADER"
    .byte 'N', 'E', 'S', $1A

    ;; We split the PRG-ROM into two 16KB sections, the first fixed (the game
    ;; itself), and then the second one, which holds the library.
    .byte $02

    ;; We keep the CHR-ROM simple: the most basic one (8KB) and no windows.
    .byte $01

    ;; - bit 1: contains battery-backed PRG RAM ($6000-7FFF)
    ;; - bit 7-4: the lower nibble of the mapper (#%0001 for MMC1)
    .byte $12

    ;; Blanked out stuff.
    .res $09, $00

;; asan:fixed-segments FIXED, LIBTREE
.segment "FIXED"
.asciiz "@mssola"

.include "../include/apu.s"
.include "../include/oam.s"
.include "../include/ppu.s"
.include "../include/mmc1.s"
.include "../include/asm.s"

.include "lib.s"
.include "interrupts.s"

.proc reset
    ;; Disable interrupts and decimal mode.
    sei
    cld

    ;; Disable APU frame counter.
    ldx #$40
    stx APU::m_frame_counter

    ;; Setup the stack.
    ldx #$FF
    txs                         ; asan:stack $80-$FF

    ;; Disable NMIs and the APU's DMC.
    inx
    stx PPU::m_control
    stx PPU::m_mask
    stx APU::m_dmc

    ;; Reset MMC1 chip.
reset_mmc1:
    inc reset_mmc1

    ;; First PPU wait.
    bit PPU::m_status
@vblankwait1:
    bit PPU::m_status
    bpl @vblankwait1

    ;; Reset all sprites by simply moving the Y coordinate out of screen.
    lda #$EF
    ldx #0
@sprite_reset_loop:
    sta OAM::m_sprites, x
    inx
    inx
    inx
    inx
    bne @sprite_reset_loop

    ;; DMA setup for sprite reset.
    lda #$00
    sta OAM::m_address
    lda #$02
    sta OAM::m_dma

    ;; Second PPU wait. After that the PPU is stable.
@vblankwait2:
    bit PPU::m_status
    bpl @vblankwait2

    ;;;
    ;; Configure the MMC1 chip.

    ;; The control register:
    ;;
    ;;  - bits 0-1: nametable arrangement: horizontal mirroring.
    ;;  - bits 2-3: PRG-ROM fixed at $8000 (game), swappable at $C000 (library).
    ;;  - bit 4:    CHR-ROM: 8KB at a time.
    lda #%00001011
    sta MMC1::m_control
    lsr
    sta MMC1::m_control
    lsr
    sta MMC1::m_control
    lsr
    sta MMC1::m_control
    lsr
    sta MMC1::m_control

    ;; CHR bank: 0.
    lda #0
    sta MMC1::m_chr_bank
    sta MMC1::m_chr_bank
    sta MMC1::m_chr_bank
    sta MMC1::m_chr_bank
    sta MMC1::m_chr_bank

    ;; The swappable bank is 1, which contains the library. Also set PRG-RAM to
    ;; be enabled.
    lda #1
    sta MMC1::m_prg_bank
    sta MMC1::m_prg_bank
    sta MMC1::m_prg_bank
    sta MMC1::m_prg_bank
    sta MMC1::m_prg_bank

    __fallthrough__ main
.endproc

.proc main
    jsr Btree::todo

@tbd:
    jmp @tbd
.endproc

.segment "VECTORS"
.addr nmi, reset, irq

.segment "CHARS"
.incbin "../assets/btree.chr"