// Keep the original document boundary as well as its ticket across fallbacks.
export function captureSharingOwner() {
  var boundary = window.AccountBoundary;
  var owner = boundary && typeof boundary.capture === 'function' && typeof boundary.signal === 'function'
    ? { boundary: boundary, ticket: boundary.capture(), signal: boundary.signal() } : null;
  assertSharingOwner(owner);
  return owner;
}

export function validSharingOwner(owner) {
  return !!(owner && owner.ticket && owner.boundary === window.AccountBoundary &&
    owner.signal && !owner.signal.aborted && typeof owner.boundary.valid === 'function' && owner.boundary.valid(owner.ticket));
}

export function assertSharingOwner(owner) {
  if (!validSharingOwner(owner)) {
    throw owner && typeof owner.boundary.error === 'function' ? owner.boundary.error() : new DOMException('Account unavailable', 'AbortError');
  }
}

export function sharingFilename(prefix, extension) {
  // An already-admitted OS write can finish after freeze; never reuse B's path.
  return prefix + '-' + window.crypto.randomUUID() + '.' + extension;
}