function loadImage(src) {
  return new Promise((resolve, reject) => {
    const img = new Image();
    img.crossOrigin = "anonymous";
    img.onload = () => resolve(img);
    img.onerror = reject;
    img.src = src;
  });
}

export async function buildGifFromFrames(frames, fps = 6) {
  if (!frames?.length) throw new Error("No frames to build GIF.");

  const delay = Math.max(40, Math.floor(1000 / Math.max(1, fps)));
  const images = await Promise.all(frames.map(loadImage));

  const gif = new GIF({
    workers: 2,
    quality: 10,
    workerScript: "https://cdn.jsdelivr.net/npm/gif.js.optimized/dist/gif.worker.js",
    width: images[0].naturalWidth,
    height: images[0].naturalHeight
  });

  for (const img of images) gif.addFrame(img, { delay });

  const blob = await new Promise((resolve) => {
    gif.on("finished", resolve);
    gif.render();
  });

  return URL.createObjectURL(blob);
}