render := @use("../../../../libraries/render/src/lib.hb");
.{math, random} := @use("../../../../libraries/stn/src/lib.hb")
Vec2 := math.Vec2

/* expected result:
   a grid of green lines scrolling from the left top corner to the right bottom one
   with a "target" randomly apperaing in one of them and a "seeker" "catching" it */

example := fn(): void {
	screen := render.init(true)

	width := screen.width
	height := screen.height
	cell_size := 0
	range := Vec2(int).(0, 0)
	if width > height {
		cell_size = width / 40
		range = .(39, height / cell_size - 1)
	} else {
		cell_size = height / 40
		range = .(width / cell_size - 1, 39)
	}
	width -= 1
	height -= 1

	scroll := 0
	target := Vec2(int).(random.range(int, 0, range.x), random.range(int, 0, range.y))

	halfcell := cell_size / 2
	octcell := cell_size / 8
	sevenoctcell := cell_size - octcell

	seeker := Vec2(int).(random.range(int, 0, range.x), random.range(int, 0, range.y))

	loop {
		render.clear(screen, render.black)

		target_pixel_coord := target * .(cell_size, cell_size) + .(scroll, scroll)
		render.put_trirect(screen, target_pixel_coord, .(cell_size, cell_size), render.red, render.light_red)

		render.put_hline(screen, target_pixel_coord.y + halfcell, target_pixel_coord.x - octcell, target_pixel_coord.x - sevenoctcell, render.light_red)
		render.put_hline(screen, target_pixel_coord.y + halfcell, target_pixel_coord.x + cell_size + octcell, target_pixel_coord.x + cell_size + sevenoctcell, render.light_red)
		render.put_vline(screen, target_pixel_coord.x + halfcell, target_pixel_coord.y - octcell, target_pixel_coord.y - sevenoctcell, render.light_red)
		render.put_vline(screen, target_pixel_coord.x + halfcell, target_pixel_coord.y + cell_size + octcell, target_pixel_coord.y + cell_size + sevenoctcell, render.light_red)

		x := scroll
		loop if x > width break else {
			render.put_vline(screen, x, 0, height, .(0, 127, 0, 127))
			x += cell_size
		}

		y := scroll
		loop if y > height break else {
			render.put_hline(screen, y, 0, width, .(0, 127, 0, 127))
			y += cell_size
		}

		render.put_hline(screen, seeker.y * cell_size + halfcell + scroll, 0, width, render.blue)
		render.put_vline(screen, seeker.x * cell_size + halfcell + scroll, 0, height, render.blue)

		render.sync(screen)

		if seeker.x < target.x {
			seeker.x += 1
		} else if seeker.x > target.x {
			seeker.x -= 1
		} else if seeker.y < target.y {
			seeker.y += 1
		} else if seeker.y > target.y {
			seeker.y -= 1
		} else {
			target = .(random.range(int, 0, range.x), random.range(int, 0, range.y))
		}

		scroll += 1
		if scroll > cell_size {
			scroll = 0
			target += .(1, 1)
			seeker += .(1, 1)
		}
	}
	return
}