(function (root, factory) {
  if (typeof module !== 'undefined' && module.exports) module.exports = factory;
  else {
    const base = new URL('./', root.location.href).pathname;
    const originalFetch = root.fetch.bind(root);
    const boundary = factory({
      cookie: () => root.document.cookie,
      origin: root.location.origin,
      base,
      fetchImpl: originalFetch,
      localStorage: root.localStorage,
      sessionStorage: root.sessionStorage,
      indexedDB: root.indexedDB,
      caches: root.caches,
      location: root.location,
      onExpired: () => root.dispatchEvent(new CustomEvent('stackchain:session-expired')),
    });
    root.fetch = boundary.fetch;
    const attach = () => {
      const button = root.document.getElementById('sign-out');
      if (button) button.addEventListener('click', () => boundary.signOut());
    };
    if (root.document.readyState === 'loading') root.document.addEventListener('DOMContentLoaded', attach);
    else attach();
    root.stackchainSession = boundary;
  }
})(typeof window !== 'undefined' ? window : this, function createSessionBoundary({
  cookie, origin, base, fetchImpl, localStorage, sessionStorage, indexedDB, caches, location,
  onExpired = () => {},
}) {
  const SAFE_METHODS = new Set(['GET', 'HEAD', 'OPTIONS']);

  function csrfToken() {
    const entry = String(cookie?.() || '').split(';')
      .map(value => value.trim())
      .find(value => value.startsWith('stackchain_csrf='));
    return entry ? decodeURIComponent(entry.slice('stackchain_csrf='.length)) : '';
  }

  function isSameOrigin(input) {
    try { return new URL(String(input?.url || input), origin).origin === origin; }
    catch (_error) { return false; }
  }

  async function sessionFetch(input, options = {}) {
    const method = String(options.method || input?.method || 'GET').toUpperCase();
    const requestOptions = { ...options };
    if (!SAFE_METHODS.has(method) && isSameOrigin(input)) {
      const headers = new Headers(options.headers || input?.headers || {});
      const csrf = csrfToken();
      if (csrf) headers.set('X-CSRF-Token', csrf);
      requestOptions.headers = headers;
    }
    const response = await fetchImpl(input, requestOptions);
    if (response.status === 401) onExpired();
    return response;
  }

  function removeDashboardStorage(storage) {
    if (!storage) return;
    const keys = [];
    try {
      for (let index = 0; index < storage.length; index += 1) {
        const key = storage.key(index);
        if (key?.startsWith('stackchain.')) keys.push(key);
      }
      keys.forEach(key => storage.removeItem(key));
    } catch (_error) { /* Cookie invalidation still protects server data. */ }
  }

  async function clearPrivateDeviceData() {
    removeDashboardStorage(localStorage);
    if (sessionStorage !== localStorage) removeDashboardStorage(sessionStorage);
    try { indexedDB?.deleteDatabase('stackchain-background-outbox-v1'); }
    catch (_error) { /* Continue clearing other dashboard state. */ }
    try {
      const keys = await caches?.keys?.() || [];
      await Promise.all(keys.filter(key => key.startsWith('stackchain-dashboard-')).map(key => caches.delete(key)));
    } catch (_error) { /* A later service-worker activation can clear stale caches. */ }
  }

  async function signOut() {
    try {
      await sessionFetch(base + 'api/v1/session', { method: 'DELETE' });
    } finally {
      await clearPrivateDeviceData();
      location.assign(base + 'login');
    }
  }

  return { fetch: sessionFetch, signOut, clearPrivateDeviceData };
});