import random
import utime


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

    def run(self, preset):
        colors = preset.c if preset.c else [(255, 255, 255), (180, 220, 255)]
        density = max(1, int(preset.n1) if int(preset.n1) > 0 else 20)
        speed = max(1, int(preset.n2) if int(preset.n2) > 0 else 1)
        flakes = []
        last = utime.ticks_ms()
        while True:
            d = max(1, int(preset.d))
            now = utime.ticks_ms()
            if utime.ticks_diff(now, last) >= d:
                bg_color = self.driver.apply_brightness(colors[-1], preset.b)
                if random.randint(0, 255) < density:
                    flakes.append([self.driver.num_leds - 1, random.randint(0, len(colors)-1)])
                for i in range(self.driver.num_leds):
                    self.driver.n[i] = bg_color
                nf = []
                for pos, ci in flakes:
                    if 0 <= pos < self.driver.num_leds:
                        self.driver.n[pos] = self.driver.apply_brightness(colors[ci], preset.b)
                    pos -= speed
                    if pos >= -1:
                        nf.append([pos, ci])
                flakes = nf
                self.driver.n.write()
                last = utime.ticks_add(last, d)
                if not preset.a:
                    yield
                    return
            yield