; TODO: Check which MBR partition is bootable and it's type

    cld ; clear the direction flag so that sto* and lod* increment di

    ; Test for EDD
    mov ah, 0x41
    mov bx, 0x55AA ; boot signature word, why ?
    mov dl, 0x80 ; drive index (HDD 1)
    int 0x13
    jc exit
    cmp bx, 0xAA55
    jne exit

    ; Read sector 1
        ; fill disk address packet (read 1 sector at offset 1)
        mov ax, 0
        mov es, ax
        mov di, 0x200
        mov ax, 16      ; size of packet
        stosb
        mov ax, 0       ; always 0
        stosb
        mov ax, 1       ; number of sectors
        stosb
        mov ax, 0       ; always 0
        stosb
        mov ax, 0x200   ; offset
        stosw
        mov ax, 0x7c0   ; segment
        stosw
        mov ax, 0x1     ; lower 4 bytes of LBA
        stosd
        mov ax, 0x0     ; upper 2 bytes of LBA
        stosd
    mov ax, 0
    mov ds, ax
    mov si, 0x200
    mov ah, 0x42
    mov dl, 0x80 ; drive index (HDD 1)
    int 0x13

main_continuation:

    mov ax, 0xb800 ; protected mode video memory segment (seg / 16 + off)
    mov es, ax
    mov ax, 0x7c0
    mov ds, ax
    mov si, 0x22b
    ; mov si, msg

    call print

    cli

    jmp hang

; print using BIOS functions
; print_loop:
;     lodsb                   ; load byte from DS:SI into al
;     or al, al
;     jz hang
;     mov ah, 0x0E
;     int 0x10
;     jmp print_loop

; print without using BIOS functions
print:
    lodsb
    cmp al, 0
    jz exit_print

    mov ah, 0x0F
    mov cx, ax

    movzx bx, byte [xpos]
    shl bx, 1
    movzx ax, byte [ypos]
    mov dx, 160
    mul dx

    mov di, bx
    add di, ax

    mov ax, cx
    stosw
    add byte[xpos], 1
    jmp print

exit_print:
    add byte[ypos], 1
    mov byte[xpos], 0
    ret

hang:
    jmp hang


    ; vars
    msg     db 'Hello world', 13, 10, 0 ; Hello world CR LF \0
    xpos    db 0
    ypos    db 0


    ; fill
    times 0x1b8 -($-$$) db 0    ; fill MBR boostrap
    dd 0                        ; fill unique disk ID
    dw 0                        ; reserved
    ; write first partition table entry CHS for start and end are set to 0
    db 0x80     ; mark the partition as bootable
    db 0x0      ; partition start head
    dw 0x0      ; partition start sector and cylinder (sector = 1, cylinder = 0)
    db 0x06     ; system ID (partition type, 07 = exFAT)
    db 0x0      ; partition end head
    dw 0x0      ; partition end sector and cylinder (sector = 5, cylinder = 455)
    dd 0x1      ; partition start LBA
    dd 0x3fff   ; partition end LBA

    times 0x10 db 0             ; fill second partition table entry
    times 0x10 db 0             ; fill third partition table entry
    times 0x10 db 0             ; fill fourth partition table entry
    dw 0xAA55                   ; valid boot sector signature

    ; db 'TEST'
    ; times 0x800000 - ($-$$) db 0

exit: