[bits    32]
    
%define     VIDMEM          0xB8000 ; Video memory mapped
%define     COLUMNS         80      ; Height of screen
%define     ROWS            25      ; Width of screen
%define     CHAR_ATTRIB     0x02    ; Character attribute
    
; Prints a character
; Input:
;   BL - The character to print
print_char_32:
    pusha
    mov     edi, VIDMEM                             ; Let EDI point to the start of video memory
    xor     eax, eax                                ; Clear EAX
    
    mov     ecx, COLUMNS
    mov     al, byte [boot_parameters.cursor_pos_y] ; Get the y position
    mul     ecx                                     ; Multiply by the number of columns (EAX = y * COLUMNS)
    
    xor     ecx, ecx
    mov     cl, byte [boot_parameters.cursor_pos_x] ; Get the x position
    add     eax, ecx                                ; Add the x position to (y * COLUMS)
    shl     eax, 1                                  ; Multiply by 2 as 2 bytes per character
    
    add     edi, eax                                ; Add the offset to the video memory address
    
    cmp     bl, 0x0A                                ; Is it a new line
    je      short .new_line
    
    mov     dl, bl                                  ; Get the character to print
    mov     dh, CHAR_ATTRIB                         ; Add the character attribute
    mov     word [edi], dx                          ; Write to the video memory
    
    inc     byte [boot_parameters.cursor_pos_x]     ; Increment the x position
    jmp     short .print_done
    
.new_line:
    mov     byte [boot_parameters.cursor_pos_x], 0  ; Set cursor to beginning of line
    inc     byte [boot_parameters.cursor_pos_y]     ; Increment new line
    
.print_done:
    popa
    ret

; Print a null terminated string to the screen
; Input:
;   ESI - Pointer to the string to print
print_string_32:
    pusha

.print_loop:
    mov     bl, byte [esi]                          ; Get the character to print
    cmp     bl, 0                                   ; Is it null
    je      short .print_end                        ; Then finish
    
    call    print_char_32                           ; Print the character
    
    inc     esi                                     ; Increment to next character
    jmp     short .print_loop
    
.print_end:
    mov     bh, byte [boot_parameters.cursor_pos_y]
    mov     bl, byte [boot_parameters.cursor_pos_x]
    call    update_cursor                           ; Update the cursor
    
    popa
    ret

; Update the cursors new position
; Input:
;   BH - y position
;   BL - x position
update_cursor:
    pusha
    
    xor     eax, eax
    mov     ecx, COLUMNS
    mov     al, bh
    mul     ecx
    add     al, bl
    mov     ebx, eax
    
    mov     al, 0x0f
    mov     dx, 0x03D4
    out     dx, al

    mov     al, bl
    mov     dx, 0x03D5
    out     dx, al
    
    xor     eax, eax

    mov     al, 0x0e
    mov     dx, 0x03D4
    out     dx, al

    mov     al, bh
    mov     dx, 0x03D5
    out     dx, al

    popa
    ret