/* Brain of Reese — shared header module (phase 19).
 *
 * Owner report 2026-08-23: clicking "Sources" made New Chat and Sign in
 * vanish — the user expects ONE consistent bar on every page. This module
 * is the single owner of the shared header controls:
 *
 *   • the Sign in / Sign out auth pair (phase 16, exactly one visible —
 *     decided by /api/whoami at load);
 *   • the "Sources" nav link (#nav-sources) — phase 19 UX revision
 *     (owner permission 2026-08-23): hidden for anonymous on every page
 *     that has a nav (chat, sources, login), revealed for admin. The
 *     link SHIPS hidden in the HTML (anonymous-safe default — the
 *     phase-16 "absent, not hidden" spirit), so no anonymous user ever
 *     sees it for a frame;
 *   • the sign-out click binding (POST /api/logout → reload) — moved
 *     here from app.js so there is exactly one implementation;
 *   • clearChatStorage() — the phase-14 conversation key, for the
 *     New Chat buttons on the NON-CHAT pages (sources / document
 *     viewer): a new chat means going to the chat, fresh.
 *
 * Every page loads this module (type="module", before its page script)
 * and its page script calls initSharedHeader() once at boot. init…
 * toggles ONLY the controls that exist on the page — a missing element
 * is a no-op, which is how the login page reuses the module without
 * gaining chat controls (no #new-chat-btn / #sign-in-link /
 * #sign-out-btn in its markup → none appear).
 *
 * whoami is fetched at most ONCE per page load: the promise is cached in
 * the module-level `adminPromise`, so app.js's tuning gate, the sources
 * page's catalog gate, and the header toggling all share one request.
 * Anonymous-safe: any network failure resolves to false (the anonymous
 * UI), mirroring the per-page catch the pages used before phase 19.
 *
 * A10/A11 untouched: no API change, no CDN, no state beyond the cached
 * promise; the soft gate page and the A10 API split are unchanged —
 * this is UI visibility only.
 */

let adminPromise = null;

/* The SINGLE /api/whoami call site for the whole frontend. First call
   stores the promise in `adminPromise`; every later call — on this page
   — returns the same promise, i.e. exactly one request per page load.
   Anonymous-safe: non-2xx or a network failure resolves to false. */
export function fetchIsAdmin() {
  if (!adminPromise) {
    adminPromise = fetch("/api/whoami")
      .then(async (r) => (r.ok ? (await r.json()).authenticated === true : false))
      .catch(() => false);
  }
  return adminPromise;
}

/* Toggle the shared header controls, only the ones present on this page
   (querySelector, null-safe — missing → no-op). Returns the admin flag
   so callers can reuse it instead of awaiting fetchIsAdmin() again (the
   cached promise makes both awaits the same single request). */
export async function initSharedHeader() {
  const admin = await fetchIsAdmin();
  const signIn = document.querySelector("#sign-in-link");
  if (signIn) signIn.hidden = admin;
  const signOut = document.querySelector("#sign-out-btn");
  if (signOut) signOut.hidden = !admin;
  const navSources = document.querySelector("#nav-sources");
  if (navSources) navSources.hidden = !admin;
  return admin;
}

/* Remove the phase-14 conversation key — same key + fail-silence
   contract as app.js's clearStoredConversation: private mode or a
   storage error is swallowed, the navigation still happens. */
export function clearChatStorage() {
  try {
    localStorage.removeItem("bor.chat.v1");
  } catch {
    /* nothing was stored */
  }
}

/* Sign-out binding (phase 16 behavior, now module-owned): runs at module
   import, so every page that loads header.js gets it exactly once.
   Disable during the call, POST /api/logout (the result is ignored —
   the reload resets the UI either way), then reload so the header
   re-resolves to the anonymous state (Sign in back, Sources gone). */
const signOutBtn = document.querySelector("#sign-out-btn");
if (signOutBtn) {
  signOutBtn.addEventListener("click", async () => {
    signOutBtn.disabled = true;
    try {
      await fetch("/api/logout", { method: "POST" });
    } catch {
      /* the reload resets the UI either way */
    }
    window.location.reload();
  });
}