// Only a new, recent, authoritative transition can trigger an effect.
// Initial loads, duplicate acknowledgements and old replayed events stay silent.
export function roomSound(previous, next, now = Date.now()) {
  if (!previous || previous.id !== next.id) return null;
  if (next.result?.cancelled || next.events?.at(-1)?.type === 'leave')
    return null;
  if (previous.status === 'waiting' && next.status === 'playing')
    return 'start';
  const last = next.events?.at(-1);
  if (!last || last.sequence <= (previous.events?.at(-1)?.sequence ?? 0))
    return null;
  const age = now - Date.parse(last.createdAt);
  if (age < -5000 || age > 5000) return null;
  if (next.status === 'finished' && previous.status !== 'finished') {
    const outcome = next.players.find((p) => p.seat === next.seat)?.outcome;
    return outcome === 'win' ? 'win' : outcome === 'loss' ? 'loss' : 'draw';
  }
  return last.sound ?? 'move';
}