;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;;;;;;; Miguel's FoolOS Helper Functions ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;
;disk_load_16
;

[bits 16]

STR_ERROR:
    db "Disk Read Error",0

STR_SPACE:
    db " ",0

STR_OK:
    db "Kernel Loaded",0
STR_PROGRESS:
    db ".",0

bpbSectorsPerTrack:
    dw 18

bpbHeadsPerCylinder:
    dw 2

LBA:
    dw 10 ; current lba

disk_load_16:

   ; check if LBA is supported
    mov    ah,0x41
    mov    bx,0x55aa
    int    0x13                                                    
    jnc disk_load_lba
    jmp disk_load_chs


;#######################

disk_load_lba:

    pusha

    mov bx,0x1800	;target es:bx
    mov es,bx
    mov bx,0

    next_sectors_lba:

    jmp skip_debug_lba
    ;show es - target
    pusha
    mov bx,es

    ;mov al,bh
    ;call print_hex_byte

    ;mov al,bl
    ;call print_hex_byte

    mov bx,[LBA]

    mov al,bh
    call print_hex_byte

    mov al,bl
    call print_hex_byte

    popa
    ;--

    skip_debug_lba:

    mov [lba_addr_sector],es
    mov ax,[LBA]
    mov [lba_first_sector],ax

    mov dl,[BOOT_DRIVE]

    mov ah,0x42
    mov bx,0
    mov ds,bx
    lea si,[lba_adr]        
    int 0x13  
    jc disk_read_error

    mov bx,es
    add bx,0x0800

    mov ax,[LBA]
    add ax,64 ; 64 sectors = 0x2000*4 bytes 
    mov [LBA],ax

    cmp bx,0x9000
    je disk_load_finish

    mov es,bx ;next target es:bx
    mov bx,0

    jmp next_sectors_lba

;#######################


disk_load_chs:

    pusha

    ; get boot drive geometry
    mov ah,8
    mov dl,[BOOT_DRIVE]
    int 0x13

    add dh,1
    and cl,0x3f

    mov [bpbSectorsPerTrack],cl
    mov [bpbHeadsPerCylinder],dh
    ;

    ;show geometry
    mov al,dh
    call print_hex_byte

    mov bx, STR_SPACE
    call print_string

    mov al,cl
    call print_hex_byte

    call print_nextline
    popa 
    ;

    pusha


    mov bx,0x1800	;target es:bx
    mov es,bx
    mov bx,0

    next_sectors_chs:

    ;jmp skip_debug
    pusha

    mov bx, STR_SPACE
    call print_string

    ;show es - target
    mov bx,es

    mov al,bh
    call print_hex_byte

    mov al,bl
    call print_hex_byte

    mov bx, STR_SPACE
    call print_string

    ;show next LBA numer
    mov ax,[LBA]
    mov al,ah
    call  print_hex_byte

    mov ax,[LBA]
    call  print_hex_byte

    mov bx, STR_SPACE
    call print_string

    popa

    mov ax,[LBA]

    ;calculate chs
    call lba_to_chs

    ;show chs sector/ head / cylinder
    mov al,cl
    call  print_hex_byte

    mov al,dh
    call  print_hex_byte

    mov al,ch
    call  print_hex_byte

    call print_nextline

    skip_debug:


    mov ax,[LBA]

    ;calculate chs
    call lba_to_chs

    ; and now READ it!
    mov al,1		;number of sectors to read
    mov dl,[BOOT_DRIVE]

    mov ah,0x02		;BIOS read sector func
    int 0x13		;bios interrupt

    jc disk_read_error

    mov bx,es
    add bx,0x0020
    cmp bx,0x9000
    je disk_load_finish

    mov es,bx
    mov bx,0

    mov ax,[LBA]
    add ax,1
    mov [LBA],ax

    jmp next_sectors_chs

disk_read_error:
    mov bx, STR_ERROR
    call print_string
    call print_nextline
    ;jmp $

disk_load_finish:
    
    mov bx, STR_PROGRESS
    call print_string
;    call print_nextline

    popa
    ret



;lba to chs translation: 
; input :   ax - lba
; output:   cl - sector
;	    dh - head
;	    ch - cylinder / track

lba_to_chs:

          xor     dx, dx                              ; prepare dx:ax for operation
          div     WORD [bpbSectorsPerTrack]           ; divide by sectors per track
          inc     dl                                  ; add 1 (obsolute sector formula)
          mov     cl, dl
 
          xor     dx, dx                              ; prepare dx:ax for operation
          div     WORD [bpbHeadsPerCylinder]          ; mod by number of heads (Absolue head formula)
          mov     dh,dl			             ; everything else was already done from the first formula
 
          mov     ch, al		            ; not much else to do :)
          ret

;; here we hold the lba addr
lba_adr:

    dw 0x10	    ; size of packet ( 16 byte)
    dw 64	    ; number of sectors to read

    ; target is 0x10000

    dw 0x0000	    ; target addr. offset

lba_addr_sector:
    dw 0x1800	    ; target addr. sector

lba_first_sector:
    dw 10	    ; first sector to read
    dw 0

    dd 0 

    ;