#include "drivers/port.h"
#include "drivers/vga.h"

void vga_set_cursor(unsigned offset) {
    port_byte_out(VGA_CTRL_REGISTER, VGA_OFFSET_HIGH);
    port_byte_out(VGA_DATA_REGISTER, offset >> 8);
    port_byte_out(VGA_CTRL_REGISTER, VGA_OFFSET_LOW);
    port_byte_out(VGA_DATA_REGISTER, offset & ((1 << 8) - 1));
}

void vga_putc(char c) {
    unsigned offset = vga_get_cursor();
    if (c == 0xa) {
        unsigned new_offset = ((offset) / COLS + 1) * COLS;
        vga_set_cursor(new_offset);
        offset = new_offset;
    } else {
        vga_set_char(offset, c);
        ++offset;
    }
    if (offset == ROWS * COLS) {
        for (int i = 0; i < ROWS * COLS; ++i) {
            if (i >= (ROWS - 1) * COLS) {
                vga_set_char(i, ' ');
            } else {
                video_memory[2 * i] = video_memory[2 * (i + COLS)];
            }
        }
        offset -= COLS;
    }
    vga_set_cursor(offset);
}