import utime


RED = (255, 0, 0)


class ScaleTest:
    """
    Animated test for the scale() helper.

    A single red pixel moves along the reference strip (strip 0). For each other
    strip, the position is mapped using:

        n2 = scale(l1, l2, n1)

    so that all lit pixels stay aligned by proportional position along the strips.
    """

    def __init__(self, driver):
        self.driver = driver

    def run(self, preset):
        strips = self.driver.strips
        if not strips:
            return

        src_strip_idx = 0
        l1 = self.driver.strip_length(src_strip_idx)
        if l1 <= 0:
            return

        step = self.driver.step
        delay_ms = max(1, int(getattr(preset, "d", 30) or 30))
        last_update = utime.ticks_ms()
        color = self.driver.apply_brightness(RED, getattr(preset, "b", 255))

        while True:
            now = utime.ticks_ms()
            if utime.ticks_diff(now, last_update) >= delay_ms:
                n1 = step % l1

                # Clear all strips
                for strip in strips:
                    strip.fill((0, 0, 0))

                # Light mapped position on each strip using Presets.set/show
                for dst_strip_idx, _ in enumerate(strips):
                    self.driver.set(dst_strip_idx, n1, color)
                    self.driver.show(dst_strip_idx)

                step += 1
                self.driver.step = step
                last_update = now

            yield