import type { NeoPixel } from "mikro/neopixel";
import { ok } from "mikro/result";
import { sleep } from "mikro/sleep";

import { hsv } from "../color.js";

/** Comet: a bright head with a fading tail orbits the ring */
export async function comet(pixels: NeoPixel, numLeds: number, brightness: number, ms: number) {
  const TAIL_LEN = 8;
  const end = Date.now() + ms;
  let pos = 0;
  while (Date.now() < end) {
    const fillResult = pixels.fill(0, 0, 0);
    if (!fillResult.ok) return fillResult;
    for (let i = 0; i < TAIL_LEN; i++) {
      const idx = (pos - i + numLeds) % numLeds;
      const fade = 1 - i / TAIL_LEN;
      const v = fade * fade * brightness;
      const [r, g, b] = hsv(200, 1, v);
      const pixelResult = pixels.setPixel(idx, r, g, b);
      if (!pixelResult.ok) return pixelResult;
    }
    const showResult = pixels.show();
    if (!showResult.ok) return showResult;
    pos = (pos + 1) % numLeds;
    await sleep(40);
  }
  return ok(undefined);
}