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

    def run(self, preset):
        """
        DoubleCircle: symmetric band around a center index on the logical ring.

        - n1: center index on the logical ring (0-based, on reference strip 0)
        - n2: radius of the band (max distance from center)
        - n3: direction mode
              0 → LEDs start ALL OFF and turn ON n4 LEDs at a time outward from n1 toward n1±n2
              1 → LEDs start ALL ON within radius n2 and turn OFF n4 LEDs at a time inward toward n1
        - n4: step size in LEDs per update
        - c[0]: base color used for the band
        """
        num_leds = self.driver.num_leds
        if num_leds <= 0:
            while True:
                yield

        colors = preset.c or []
        base1 = colors[0] if len(colors) >= 1 else (255, 255, 255)
        off = (0, 0, 0)

        # Apply preset/global brightness
        color_on = self.driver.apply_brightness(base1, preset.b)
        color_off = off

        # Center index and radius from preset; clamp center to ring length
        center = int(getattr(preset, "n1", 0)) % num_leds
        radius = max(1, int(getattr(preset, "n2", 0)) or 1)
        mode = int(getattr(preset, "n3", 0) or 0)  # 0 = grow band outward, 1 = shrink band inward
        step_size = max(1, int(getattr(preset, "n4", 1)) or 1)

        num_strips = len(self.driver.strips)

        # Current "front" of the band, as a distance from center
        # mode 0: grow band outward (0 → radius)
        # mode 1: shrink band inward (radius → 0)
        if mode == 0:
            current = 0
        else:
            current = radius

        while True:
            # Draw current frame based on current radius
            for i in range(num_leds):
                # Shortest circular distance from i to center
                forward = (i - center) % num_leds
                backward = (center - i) % num_leds
                dist = forward if forward < backward else backward

                if dist > radius:
                    c = color_off
                else:
                    if mode == 0:
                        # Grow outward: lit if within current radius
                        c = color_on if dist <= current else color_off
                    else:
                        # Shrink inward: lit if within current radius (band contracts toward center)
                        c = color_on if dist <= current else color_off

                for strip_idx in range(num_strips):
                    self.driver.set(strip_idx, i, c)

            self.driver.show_all()

            # Update current radius for next frame
            if mode == 0:
                if current >= radius:
                    # Finished growing; hold final frame
                    while True:
                        yield
                current = min(radius, current + step_size)
            else:
                if current <= 0:
                    # Finished shrinking; hold final frame
                    while True:
                        yield
                current = max(0, current - step_size)

            yield