/* Brain of Reese — the in-app token gate (phase 79, task 05).
 *
 * The owner's sentence (TODO.md L5): "The web ui should ask for a
 * token before letting a user through and should cache that token in
 * browser storage so they don't have to keep entering it."
 *
 * One reusable mount point for the two gated surfaces:
 *
 *   • the shell (index.html) — app.js's boot IIFE awaits
 *     mountGate(#main, onAuthed) BEFORE its initSharedHeader;
 *   • the document viewer (document.html) — document.js wires
 *     mountGate(#main, onAuthed) around the existing boot sequence
 *     (whoami → load content).
 *
 * Both carry the same gate markup (class .auth-gate; the ids differ —
 * #auth-gate / #doc-auth-gate — so the gate is found by CLASS: the
 * ONE .auth-gate section on the page).
 *
 * The contract (pinned at source level in
 * tests/unit/test_token_gate.py):
 *
 *   • the gate SHIPS hidden + inert (the phase-16 ship-hidden pattern):
 *     an authenticated boot never shows it for a frame.
 *   • (1) at mount, a CACHED token (localStorage["bor.token"]) is
 *     re-sent to POST /api/token-auth SILENTLY — BEFORE the whoami
 *     check. On ANY failure the key is removed (the token may have
 *     been revoked) and the mount falls through to the role check.
 *   • (2) the role check is header.js's fetchWhoami() — the SAME
 *     cached promise the page's own header boot uses (exactly one
 *     /api/whoami per page load in dev): role "user" or "admin" →
 *     onAuthed() (the gate NEVER shows); "anonymous" → the gate is
 *     revealed (hidden AND inert dropped), the lock root is locked
 *     (lockRoot.inert = true — WCAG: the locked app must not receive
 *     focus or keyboard traversal, the inert-pair contract) and the
 *     token input is focused.
 *   • form submit → POST /api/token-auth: 204 → the token is cached
 *     (localStorage, try/catch — private mode: caching is a no-op,
 *     the gate still works), the whoami cache is invalidated and
 *     re-fetched (the choice below), role "user" → the gate is hidden
 *     again (hidden + inert re-added), the lock root unlocks,
 *     onAuthed() runs, and the shared header re-boots
 *     (initSharedHeader — a mid-page login must not leave the
 *     anonymous header state: Sign in hidden, Sign out visible).
 *     401 (or any failure) → the #auth-gate-error (role=alert) line
 *     is revealed, the input cleared and re-focused — the entered
 *     token never lingers in the field.
 *   • the whoami-cache choice: CLEAR THE MODULE CACHE (header.js's
 *     resetWhoami) rather than a direct re-fetch — a direct fetch
 *     would verify the role for the gate but leave header.js's cache
 *     stale (the boot fired it pre-auth, when the page was still
 *     anonymous), so the header re-boot and every later fetchWhoami()
 *     would still read anonymous. Resetting makes the NEXT
 *     fetchWhoami() the single fresh post-auth request for the whole
 *     page (gate + header + view gates all reuse it).
 *   • ALL localStorage access is try/catch (the fail-silence storage
 *     contract — private mode or a storage error degrades to
 *     "re-enter the token each visit", never to a broken gate).
 *
 * The module has NO import-time side effects: pages call mountGate at
 * boot (the shell from app.js's boot IIFE, the viewer from
 * document.js). On the shell the call is AWAITED before app.js's
 * initSharedHeader, so a silent re-auth lands before the FIRST whoami
 * fires — the header sees the post-auth role deterministically (no
 * stale "Sign in" for a returning token user). No CDN, no framework.
 */

import { fetchWhoami, initSharedHeader, resetWhoami } from "./header.js";

/* The cached-token key (the owner's sentence: "cache that token in
   browser storage"). The server stores only the SHA-256 digest of the
   full token (app/core/tokens.py) — the plaintext lives here, in the
   browser, and is re-sent verbatim to /api/token-auth (the server
   hashes it for the unique-index lookup). */
const TOKEN_KEY = "bor.token";

/* ---------- the fail-silence storage contract ----------
 * Every localStorage access is try/catch: private mode or a storage
 * error degrades to "re-enter the token each visit" — the gate itself
 * still works either way. */

const readCachedToken = () => {
  try {
    const t = localStorage.getItem(TOKEN_KEY);
    return typeof t === "string" && t.trim() !== "" ? t : null;
  } catch {
    return null; // private mode / storage error — nothing cached
  }
};

const storeToken = (token) => {
  try {
    localStorage.setItem(TOKEN_KEY, token);
  } catch {
    /* private mode: the gate still works, caching is a no-op */
  }
};

const removeToken = () => {
  try {
    localStorage.removeItem(TOKEN_KEY);
  } catch {
    /* nothing was stored */
  }
};

/* POST /api/token-auth — every failure shape (malformed / unknown /
   revoked / empty) is ONE generic 401 "invalid token" server-side
   (the phase-16 no-enumeration contract), so the client only needs
   the status: 204 = the session cookie is (re)set. */
async function tryTokenAuth(token) {
  const r = await fetch("/api/token-auth", {
    method: "POST",
    headers: { "Content-Type": "application/json" },
    body: JSON.stringify({ token }),
  });
  return r.status === 204;
}

/* The in-app token gate. `lockRoot` is the element the gate locks
   while visible (#main on both pages — the locked app must not
   receive focus or keyboard traversal: the inert-pair contract);
   `onAuthed` runs ONLY once the visitor is signed in (role "user" or
   "admin") — the shell passes a no-op (the lazy views mount on first
   show exactly as today), the viewer passes its existing boot
   sequence (the shared header + the content load). */
export async function mountGate(lockRoot, onAuthed) {
  const gate = document.querySelector(".auth-gate");
  const form = gate ? gate.querySelector("form") : null;
  const input = gate ? gate.querySelector('input[name="token"]') : null;
  const error = gate ? gate.querySelector(".auth-gate-error") : null;
  const submit = form ? form.querySelector('button[type="submit"]') : null;

  const hideGate = () => {
    if (gate) {
      gate.hidden = true;
      gate.inert = true;
    }
  };

  const showError = () => {
    if (error) error.hidden = false;
    if (input) {
      input.value = ""; // the entered token never lingers in the field
      input.focus();
    }
  };

  /* (1) SILENT RE-AUTH — before the whoami check. A cached token
      is re-sent to /api/token-auth first: on success the session
      cookie is (re)set NOW, before any whoami on this page settles —
      the cache is invalidated (resetWhoami) so the role check below
      is a FRESH request (a boot-fired pre-auth whoami would still
      say anonymous). On ANY failure the key is DROPPED — the token
      may have been revoked — and the mount falls through to the role
      check (the page may already be signed in as the admin, and the
      anonymous visitor simply gets the gate). */
  const cached = readCachedToken();
  if (cached) {
    const ok = await tryTokenAuth(cached).catch(() => false);
    if (ok) {
      resetWhoami(); // the cached whoami (boot-fired, pre-auth) is stale
      const who = await fetchWhoami();
      if (who.authenticated) {
        // role "user" (the re-auth landed) or "admin" (the browser
        // also holds an admin session — admin wins, whoami's
        // contract): unlock and run onAuthed — the gate NEVER shows
        // for a cached valid token (no flash).
        if (lockRoot) lockRoot.inert = false;
        hideGate(); // defensive: it ships hidden — the boot never
        // reveals it for an authenticated role, so this is a no-op.
        onAuthed();
        return;
      }
      // token-auth said 204 but whoami still says no (the cookie did
      // not land): treat it as a dead cached token.
      removeToken();
    } else {
      removeToken(); // a failed silent re-auth drops the key
    }
  }

  /* (2) ROLE CHECK — header.js's fetchWhoami(): the SAME cached
      promise the page's own header boot awaits (app.js on the shell,
      the viewer's onAuthed on document.html) — exactly one
      /api/whoami per page load. */
  const who = await fetchWhoami();
  if (who.authenticated) {
    // role "user" or "admin" — the gate NEVER shows.
    if (lockRoot) lockRoot.inert = false;
    onAuthed();
    return;
  }

  /* Anonymous: reveal the gate (drop hidden AND inert — the inert-pair
     contract), lock the app, focus the token input. The gate is the
     only interactive surface while visible: the lock root is inert,
     so Tab never reaches the locked app (the composer on the shell,
     the content on the viewer). */
  if (gate) {
    gate.hidden = false;
    gate.inert = false;
  }
  if (lockRoot) lockRoot.inert = true;
  if (input) input.focus();
  if (!form) return; // no gate markup — nothing to bind

  /* Form submit: preventDefault → POST /api/token-auth → 204: cache
     the token, invalidate + re-fetch the whoami cache (the documented
     choice: clear the module cache — a direct re-fetch would leave
     header.js's boot-fired anonymous cache stale for the header
     re-boot), role "user" → hide the gate, unlock, onAuthed(), and
     re-boot the shared header for the new role. 401 / failure: the
     role=alert error line, the input cleared + re-focused, the
     button re-enabled (never stale, PLAN §7.4). */
  form.addEventListener("submit", (e) => {
    e.preventDefault();
    void (async () => {
      const token = (input && input.value ? input.value : "").trim();
      if (!token || (submit && submit.disabled)) return;
      if (error) error.hidden = true;
      if (submit) submit.disabled = true; // one auth at a time
      const ok = await tryTokenAuth(token).catch(() => false);
      if (!ok) {
        showError();
        if (submit) submit.disabled = false;
        return;
      }
      storeToken(token); // try/catch — private mode: caching is a no-op
      resetWhoami(); // the boot-fired whoami says anonymous — stale
      const after = await fetchWhoami(); // the single fresh post-auth request
      if (!after.authenticated) {
        // token-auth said 204 but whoami still says anonymous (the
        // session cookie did not land): drop the cache just written
        // and let the user retry. (role "admin" here — an admin
        // signed in from another tab in the meantime — is
        // authenticated: the gate's job is to let them through.)
        removeToken();
        showError();
        if (submit) submit.disabled = false;
        return;
      }
      hideGate();
      if (lockRoot) lockRoot.inert = false;
      onAuthed();
      // A mid-page login must not leave the anonymous header state
      // (Sign in visible / Sign out hidden): re-boot the shared
      // header on the fresh post-auth whoami (idempotent — it just
      // re-toggles the same controls).
      void initSharedHeader();
    })();
  });
}