; .setcpu "65C02"
    .include "./macro.inc"

; okay so rn i wanna set up a very basic system init, and write a few subroutines to draw characters at x,y coordinates
n = $01 ; temporary storage for data stack operations

key_row = $200 ; used for character lookup when key pressed
key_col = $201
cursor = $202

char_buffer = $300 ; 256 byte character buffer

kb_row = $4400 ; keyboard hardware register
kb_row_cache = $203 ; cache 

    .org $8000

reset:
    sei
    ldx #0; initialize data stack pointer

; initdisplay:
;     lda #0
;     ldy #0

; cleardisplay:
;     sta $6000,y
;     sta $6100,y
;     sta $6200,y
;     sta $6300,y
;     sta $6400,y
;     sta $6500,y
;     sta $6600,y
;     sta $6700,y ; this goes slightly over but it's fine
;     iny
;     bne cleardisplay
;     cli

main:
    jsr draw
    jmp main

draw:
char = $200
x = $201
y = $202
    .y_loop:
        .x_loop:
            inc char
            lda x
            push 
            sta 0, x
            stz 1, x
            lda y
            push 
            sta 0, x
            sta 1, x
            lda char
            push 
            sta 0, x
            sta 1, x
            jsr draw_char
            inc x
            lda #64
            cmp x
            bne .x_loop
        inc y 
        lda #30
        cmp y
        bne .y_loop
    .end:
    rts

draw_char: ; draw a character c at (x, y) (n1: x n2: y n3: c -- )
    lda 0, x ; load a with character to draw
    pop ; and pop it off the stack
    jsr get_char_address ; calculate where to put the character in memory
    sta (0, x) ; store a at the address pointed to on the stack
    rts

get_char_address:   ; gets vram address for a character at (x, y),
                    ; (n1: x n2: y -- n: $6000 + x + (64 * y))
    ;jsr push_lit ; push 64 onto stack, low byte first
    ;.byte 64
    ;.byte 0
    pha
    lda #64
    push ; doing this instead until `push_lit` is fixed
    sta 0, x
    stz 1, x
    jsr mult ; multiply 64 with y (n2)
    jsr plus ; add result with x (n1)

    ;jsr push_lit ; push vram address onto the stack
    ;.byte $00
    ;.byte $60
    lda #$60
    push
    sta 1, x
    stz 0, x
    jsr plus ; add vram start address to result

    pla
    rts

fill: ; fills an area from (x1, y1) to (x2, y2) will character c, (n1: c n2: x1 n3: y1 n4: x2 n5: y2 -- )
    jsr get_char_address

isr: ; interrupt service routine
    pha
    phx
    phy
    ; jsr keyboard
    ply
    plx
    pla
    rti

    .include "math.inc"

    .org $fffc
    .word reset
    .word isr