import { useAuthStore } from './store';

/**
 * Cross-tab auth synchronisation via the `storage` event.
 *
 * When a user logs out (or in) in tab A, other tabs need to pick up the
 * new state without the user clicking around. The storage event fires on
 * every other tab when localStorage changes — bumping a version key in
 * tab A causes tabs B, C, ... to re-run the auth probe and converge.
 *
 * Pattern is one-way: this tab writes the version key on its own auth
 * transitions; storage events trigger `initialize()` to re-read state from
 * Directus. The actual auth state lives in cookies (server-issued), not in
 * localStorage — the version key is just a "something changed, re-check"
 * signal.
 *
 * Idempotent: safe to call multiple times (HMR-friendly).
 */

const VERSION_KEY = 'trm-auth-version';
let started = false;

export function startCrossTabSync(): void {
  if (started) return;
  started = true;

  let lastStatus: string | null = null;

  useAuthStore.subscribe((state) => {
    if (state.status === lastStatus) return;
    lastStatus = state.status;
    try {
      localStorage.setItem(VERSION_KEY, String(Date.now()));
    } catch {
      // localStorage may be unavailable (private browsing, quota). Sync
      // silently no-ops; auth still works in this tab, just not cross-tab.
    }
  });

  window.addEventListener('storage', (ev) => {
    if (ev.key !== VERSION_KEY) return;
    void useAuthStore.getState().initialize();
  });
}