.{Color, Surface} := @use("./lib.hb");
.{log} := @use("../../stn/src/lib.hb")

BitmapFileHeader := packed struct {
	img_type: u16,
	size: u32,
	reserved_1: u16,
	reserved_2: u16,
	offset: u32,
}

BitmapInfoHeader := packed struct {
	size: u32,
	width: i32,
	height: i32,
	planes: u16,
	bits: u16,
	compression: u32,
	image_size: u32,
	x_resolution: i32,
	y_resolution: i32,
	n_colours: u32,
	important_colours: u32,
}

BitmapColorHeader := packed struct {
	red_mask: u32,
	green_mask: u32,
	blue_mask: u32,
	alpha_mask: u32,
	color_space_type: u32,
	unused: u32,
}

surface_from_bmp := fn(bmp: ^u8): Surface {
	file_header := @as(^BitmapFileHeader, @bitcast(bmp))
	if file_header.img_type != 0x4D42 {
		log.error("failed to load bmp image: not a bmp image, idiot\0")
		return @as(Surface, idk)
	}
	info_header := @as(^BitmapInfoHeader, @bitcast(bmp + @sizeof(BitmapFileHeader)))
	bmp += file_header.offset

	a := 0
	px := info_header.width * info_header.height
	ptr := @as(^Color, @bitcast(bmp))
	tmp := @as(Color, idk)
	row := 0

	loop if row == info_header.height / 2 break else {
		col := 0
		loop if col == info_header.width break else {
			top_index := row * info_header.width + col
			bottom_index := (info_header.height - 1 - row) * info_header.width + col

			tmp = *(ptr + top_index);
			*(ptr + top_index) = *(ptr + bottom_index);
			*(ptr + bottom_index) = tmp

			col += 1
		}
		row += 1
	}

	return .(@bitcast(bmp), @intcast(info_header.width), @intcast(info_header.height))
}