function createProgressiveLiveSnapshot({fetchSnapshot}) {
  let value = null;
  let flight = null;

  const hasIdentity = snapshot => {
    const user = snapshot?.context?.user || {};
    return Boolean(String(user.login || '').trim());
  };
  const requireUsable = (snapshot, options) => {
    if (!options?.requireIdentity || hasIdentity(snapshot)) return snapshot;
    if (value === snapshot) value = null;
    throw new Error('Authenticated account identity is unavailable.');
  };
  const acquire = (options = {}) => {
    if (value) return Promise.resolve().then(() => requireUsable(value, options));
    if (flight) return flight.then(snapshot => requireUsable(snapshot, options));
    flight = Promise.resolve().then(() => fetchSnapshot()).then(snapshot => {
      value = snapshot;
      flight = null;
      return snapshot;
    }, error => {
      flight = null;
      throw error;
    });
    return flight.then(snapshot => requireUsable(snapshot, options));
  };

  return {
    acquire,
    snapshot:() => value,
    pending:() => flight,
    identity() {
      const user = value?.context?.user || {};
      const login = String(user.login || '').trim();
      return {login, accountKey:login && user.id ? String(user.id) + ':' + login : login};
    },
  };
}

if (typeof window !== 'undefined') {
  window.stackchainProgressiveLiveSnapshot = createProgressiveLiveSnapshot({
    fetchSnapshot:async () => {
      const response = await fetch('api/v1/live', {headers:{Accept:'application/json'}});
      if (!response.ok) throw new Error('HTTP ' + response.status);
      return response.json();
    },
  });
}
if (typeof module !== 'undefined' && module.exports) module.exports = createProgressiveLiveSnapshot;