; ==================================================================
; MikeOS -- The Mike Operating System kernel
; Copyright (C) 2006 - 2021 MikeOS Developers -- see doc/LICENSE.TXT
;
; SCREEN HANDLING SYSTEM CALLS
; ==================================================================

; ------------------------------------------------------------------
; os_print_string -- Displays text
; IN: SI = message location (zero-terminated string)
; OUT: Nothing (registers preserved)

os_print_string:
	pusha

	mov ah, 0Eh			; int 10h teletype function, we're telling the BIOS we will print something

.repeat:
	lodsb				; Get char from si into al
	cmp al, 0			; Compare al to 0
	je .done			; If char is zero, end of string

	int 10h				; Otherwise, print it
	jmp .repeat			; And move on to next char

.done:
	popa
	ret

; Exact same as the above procedure, but this adds a newline 
; after priting, similar to the difference between Rust's print! and println!
os_print_string_nl:				pusha

	mov ah, 0Eh			; int 10h teletype function, we're telling the BIOS we will print something

.repeat:
	lodsb				; Get char from si into al
	cmp al, 0			; Compare al to 0
	je .done			; If char is zero, end of string

	int 10h				; Otherwise, print it
	jmp .repeat			; And move on to next char

.done:
	call os_print_newline
	popa
	ret

; --------------------------------------------

os_print_newline:
	pusha

	mov ah, 03h
	int 10h
	
	mov ah, 02h
	add dh, 1
	mov dl, 0
	int 10h
	
	popa
	ret
		

; -------------------------------------------

os_clear_screen:
        pusha

	mov ah, 00h
	mov al, 03h 		; Set video mode to textmode (80x25). 16 colors, 8 pages
	int 10h

	mov ah, 02h
	mov dh, 0
	mov dl, 0
	int 10h

        popa
        ret

; -------------------------------------------

; AX = key pressed
os_read_input:
	mov ah, 11h			; BIOS call to check for key
	int 16h				; Interrupt
	jnz .key_pressed		; Jump if input isn't 0
	
	hlt
	jmp os_read_input

.key_pressed:
	mov ah, 10h
	int 16h
	ret

; -------------------------------------------

os_display_input:	
	pusha
	mov cx, prompt_length ; Characters remaining
	
.loop:
	call .check_key_pressed

        jmp .loop

.check_key_pressed:	
        call os_read_input

	cmp al, 08h
	je .backspace

	cmp al, 0Dh
	je .enter_key

	cmp al, 1Bh
	je .esc_key

	dec cx
	call .print_current_input
	ret

.esc_key:
	call os_reboot

.enter_key:
	mov al, 0
	stosb
	mov di, user_input
	popa
	call os_read_cli

.backspace:
	cmp cx, prompt_length			; If bx < 20
	jl .move_cursor_back			; then .move_cursor_back
	call .loop				; Else .loop

.move_cursor_back:
	mov ah, 0Eh

	mov al, 08h
	int 10h
	mov al, 20h
	int 10h
	mov al, 08h
	int 10h

	dec di
	inc cx
	jmp os_display_input

.print_current_input:
	stosb
	
	mov ah, 0Eh
	int 10h


	ret