format binary
use32
org 0x100000

; multiboot skips us to 32bit mode
; 16bit mode required to set video mode
; multiboot might not set our video mode (looking at you, syslinux!)
; TODO: make the own bootloader and ditch multiboot
; users can(will) have inexpensive small harddrives or usbs dedicated to this shit
multiboot:
	dd 0x1BADB002 ; magic
	dd 00000000000000010000000000000000b ; aout kludge flag
	dd 0xE4514FFE ; mboot checksum
	dd 0x100000 ; header address
	dd 0x100000 ; load address
	dd 0 ; load end address, 0=assume whole file
	dd 0 ; bss end address,   0=don't zero-init
	dd 0x100030	; entry address

	; we don't ask for video mode really as it's too unreliable
	; but here's it zeroed-out anyway
	dd 0 ; videomode 0=linear 1=ega text
	dd 0 ; width  0=no pref
	dd 0 ; height 0=no pref
	dd 0 ; depth  0=no pref
start:
	; Setup stack
	mov ebp, stack_top
	mov esp, stack_top

	;push ebx ; mboot info struct addr
	;push eax ; 0x2BADB002

	mov [mbootmagic], eax
	;mov [mbootaddr], ebx

	call con_disable_cursor
	call conclear

	mov esi, msg.roskainiting
	call conwriteln


hang:
	;cli
	.loop:
		;hlt
		jmp .loop

;give character in AL
conputchar:
	mov ah, [txtbuf.col]
	mov dx, ax
	; dx has the whole character cell now
	xor eax, eax
	mov al, [txtbuf.y]
	mov bl, 80
	mul bl
	movzx bx, [txtbuf.x]
	add ax, bx
	add ax, ax
	add eax, 0xb8000
	mov [eax], dx
	cmp bl, 79
	je connewline
	inc bl
	mov [txtbuf.x], bl
	ret
conwriteln:
	lodsb
	cmp al, 0
	je connewline
	call conputchar
	jmp conwriteln
connewline:
	mov [txtbuf.x], 0
	mov al, [txtbuf.y]
	cmp al, 24
	je conscroll
	inc al
	mov [txtbuf.y], al
	ret
conscroll:
	ret

conclear:
	mov ecx, 80*25
	mov edi, 0xb8000
	mov ah, 0x07
	mov al, 0
	rep stosw
	mov [txtbuf.col], ah
	mov [txtbuf.x], 0
	mov [txtbuf.y], 0
	ret

con_disable_cursor:
	mov dx, 0x3D4
	mov al, 0xA	; low cursor shape register
	out dx, al

	inc dx
	mov al, 0x20	; bits 6-7 unused, bit 5 disables the cursor, bits 0-4 control the cursor shape
	out dx, al
	ret

mbootaddr: dd 0
mbootmagic: dd 0
txtbuf:
	.x db 0
	.y db 0
	.col db 0x07 ;gray on black

fb:
	.addr dd 0
	.pitch dd 0
	.width dd 0
	.height dd 0
	.depth db 0
	.bytespp db 0
	.rpos db 0
	;.rmasksize db 0
	.gpos db 0
	;.gmasksize db 0
	.bpos db 0
	;.bmasksize db 0

msg:
	.roskainiting db "rOSka initializing...", 0

align 4096
bss_start:
align 4096
stack_bottom:
rb 16384
stack_top:
bss_end: