lib/utils/shuffle.ts

// Fisher–Yates shuffle. Returns a new array; doesn't mutate the input.
export function shuffle<T>(input: readonly T[]): T[] {
  const out = [...input];
  for (let i = out.length - 1; i > 0; i--) {
    const j = Math.floor(Math.random() * (i + 1));
    [out[i], out[j]] = [out[j], out[i]];
  }
  return out;
}