.286
.model small

.code
    mov ax, 0006h
    int 10h

    mov ax, 0b800h
    mov es, ax

    ;call draw_horizontal_line 
    call draw_vertical_line 

    xor ax, ax
    int 16h

    mov ax, 0003h
    int 10h

    mov ax, 4c00h
    int 21h
    
    draw_horizontal_line:
        push bp
        mov bp, sp
        sub sp, 7
    
        mov word ptr [bp - 2], 05h; X start coord
        mov word ptr [bp - 4], 7Fh; Length of line
        mov byte ptr [bp - 5], 5Fh; Y start coord
        mov byte ptr [bp - 6], 00h; value of first byte
        mov byte ptr [bp - 7], 00h; value of last  byte
    
        ;Cut length

        mov ax, word ptr [bp - 4]
        mov bx, word ptr [bp - 2]

        add ax, bx
        cmp ax, 280h
        jl less_than_width

        mov ax, 280h
        sub ax, bx

        mov word ptr [bp - 4], ax

        less_than_width:
            
        ;Compute last byte

        add ax, bx
        and al, 07h

        mov cl, al
        
        mov al, 0FFh
        shr al, cl
        not al

        mov byte ptr [bp - 7], al

        ;Compute first byte

        mov cx, word ptr [bp - 2]
        and cl, 07h

        mov al, 0FFh
        shr al, cl

        mov byte ptr [bp - 6], al 

        ;Compute address

        mov al, byte ptr [bp - 5]
        shr al, 1

        mov bl, 50h
        mul bl

        mov di, ax
        
        mov al, byte ptr [bp - 5]
        and al, 01h
        jz even_line
    
        add di, 02000h
        
        even_line:

        mov al, byte ptr [bp - 2]
        shr al, 3

        xor ah, ah
        add di, ax

        ;Drawing!
    
        mov al, byte ptr [bp - 6]

        mov bl, byte ptr [bp - 4] 
        cmp bl, 01h
        je draw_one_byte
        jl drawing_end 
        jne draw_some_bytes
        
        draw_one_byte:

        mov bl, byte ptr [bp - 7]
        and al, bl

        stosb
        jmp drawing_end

        draw_some_bytes:
        
        mov bx, word ptr [bp - 4]

        drawing_loop:
            stosb

            mov al, 0FFh
            sub bx, 8 
            cmp bx, 0
            jg drawing_loop
    
        mov al, byte ptr [bp - 7]
        stosb
        
        drawing_end:
        mov sp, bp
        pop bp
        ret

    draw_vertical_line:
        push bp
        mov bp, sp
        sub sp, 5

        mov word ptr [bp - 2], 0FFh; X
        mov byte ptr [bp - 3], 00h; Y
        mov byte ptr [bp - 4], 8Fh; Len 
        mov byte ptr [bp - 5], 00h; byte value
        mov word ptr [bp - 7], 00h; base address

        ;Byte value

        mov al, 80h
        mov bx, word ptr [bp - 2]

        mov cl, bl
        and cl, 07h

        shr al, cl
        mov byte ptr [bp - 5], al

        ;Byte address, X is in bx
        
        shr bx, 3

        mov al, byte ptr [bp - 3]
        shr al, 1

        mov cl, 50h

        mul cl

        add bx, ax

        mov word ptr [bp - 7], bx

        ;Cut len

        ;mov al, byte ptr [bp - 3]
        ;mov ah, byte ptr [bp - 4]
        ;add ah, al

        xor ax,ax
        xor bx,bx 
        
        mov al, byte ptr [bp - 3]
        mov bl, byte ptr [bp - 4]
    
        add bx, ax

        cmp bx, 0C8h
        jle less_than_height
        
        xor ax, ax
        xor bx, bx

        mov al, byte ptr [bp - 3]
        mov bl, 0C8h
            
        sub bx, ax

        mov byte ptr [bp - 4], bl

        less_than_height:

        xor ax, ax
        mov al, byte ptr [bp - 5] 
        
        xor cx,cx
    
        mov ch, 02h

        draw_loop:

            mov cl, byte ptr [bp - 4]
            shr cl, 1

            mov di, word ptr [bp - 7]

            mov dl, ch
            and dl, 01h
            jz draw_half

            add di, 2000h

            draw_half:
                
                mov es:[di], al
                add di, 50h

            dec cl
            jnz draw_half

        dec ch
        jnz draw_loop
    
        mov sp, bp
        pop bp
        ret
end