#include <stdint.h>
#include <multiboot2.h>
#include <graphics.h>
#include <debug.h>

uint64_t* pixel_offset(fb_t fb, uint32_t x, uint32_t y)
{
	return (uint64_t*)((uint32_t*)fb.addr + y * fb.pitch / 4 + x);
}

void fb_draw_pixel(fb_t fb, uint32_t x, uint32_t y, uint32_t col)
{
	uint64_t* fb_offset = pixel_offset(fb, x, y);
	*fb_offset = col;
}

void fb_draw_line_low(fb_t fb, uint32_t x0, uint32_t y0, uint32_t x1, uint32_t y1, uint32_t col)
{
	uint32_t dx = x1 - x0;
	uint32_t dy = y1 - y0;
	uint32_t yi = 1;
	if (dy < 0) {
		yi = -1;
		dy = -dy;
	}
	uint32_t D = (2 * dy) - dx;
	uint32_t y = y0;

	for (uint32_t x = x0; x < x1; x++) {
		fb_draw_pixel(fb, x, y, col);
		if (D > 0) {
			y = y + yi;
			D = D + (2 * (dy - dx));
		} else {
			D = D + 2*dy;
		}
	}

}

void fb_draw_line_high(fb_t fb, int32_t x0, int32_t y0, int32_t x1, int32_t y1, int32_t col)
{
	int32_t dx = x1 - x0;
	int32_t dy = y1 - y0;
	int32_t xi = 1;
	if (dx < 0) {
		xi = -1;
		dx = -dx;
	}
	int32_t D = (2 * dx) - dy;
	int32_t x = x0;

	for (int32_t y = y0; y <= y1; y++) {
		fb_draw_pixel(fb, x, y, col);
		if (D > 0) {
			x = x + xi;
			D = D + (2 * (dx - dy));
		} else {
			D = D + 2*dx;
		}
	}
}

uint32_t abs(int64_t val)
{
	if (val < 0) return -val;
	return val;
}

void fb_draw_line(fb_t fb, int32_t x0, int32_t y0, int32_t x1, int32_t y1, int32_t col)
{
	if (abs(y1 - y0) < abs(x1 - x0)) {
		if (x0 > x1)
			fb_draw_line_low(fb, x1, y1, x0, y0, col);
		else
			fb_draw_line_low(fb, x0, y0, x1, y1, col);
	} else {
		if (y0 > y1)
			fb_draw_line_high(fb, x1, y1, x0, y0, col);
		else
			fb_draw_line_high(fb, x0, y0, x1, y1, col);
	}
}