import utime


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

    def run(self, preset):
        """Independent moving segments (distinct from classic two-color chase).

        n1: segment size (LEDs per segment)
        n2: step size (phase increment each frame)
        n3: per-segment phase offset
        n4: gap spacing inside segment (0 = solid segment)
        """
        colors = preset.c if preset.c else [(255, 0, 0), (0, 0, 255)]
        seg = max(1, int(preset.n1) if int(preset.n1) > 0 else 4)
        phase_step = max(1, int(preset.n2) if int(preset.n2) > 0 else 1)
        seg_offset = max(0, int(preset.n3))
        gap = max(0, int(preset.n4))
        phase = self.driver.step % 256
        last = utime.ticks_ms()
        while True:
            d = max(1, int(preset.d))
            now = utime.ticks_ms()
            if utime.ticks_diff(now, last) >= d:
                for i in range(self.driver.num_leds):
                    seg_idx = i // seg
                    in_seg = i % seg
                    local_phase = (phase + seg_idx * seg_offset) % seg
                    lit_idx = (in_seg + local_phase) % seg
                    if gap > 0 and lit_idx >= max(1, seg - gap):
                        self.driver.n[i] = (0, 0, 0)
                    else:
                        color_idx = seg_idx % len(colors)
                        self.driver.n[i] = self.driver.apply_brightness(colors[color_idx], preset.b)
                self.driver.n.write()
                phase = (phase + phase_step) % seg
                self.driver.step = phase
                last = utime.ticks_add(last, d)
                if not preset.a:
                    yield
                    return
            yield