// app-offer.js: the web's "Join in the app" page (native.html, Waiting).
//
// Opens the Calls app once, with the offer in the link, and then asks
// the server every two seconds whether the app has taken it up. When it
// has, the answer names the confirmation page for the app's request and
// this tab goes there — this browser, where the person is signed in, so
// the confirmation needs no sign-in. An expired offer says so. With no
// script none of this runs: the button opens the app and the page
// refreshes itself (a <noscript> refresh), arriving at the same place.
(() => {
  'use strict';
  const box = document.getElementById('app-offer');
  if (!box) return;
  const status = document.getElementById('app-offer-status');
  const app = box.dataset.app;
  const poll = box.dataset.poll;
  const key = 'calls.appOffer:' + poll;
  let opened = false;
  try { opened = sessionStorage.getItem(key) === '1'; } catch { /* private mode */ }
  if (!opened && app) {
    try { sessionStorage.setItem(key, '1'); } catch { /* this page only */ }
    // A browser that wants a click first ignores this; the button is there.
    location.href = app;
  }
  let stopped = false;
  async function ask() {
    if (stopped) return;
    try {
      const res = await fetch(poll, { headers: { Accept: 'application/json' }, credentials: 'same-origin', cache: 'no-store' });
      const body = await res.json().catch(() => ({}));
      if (body.next) {
        stopped = true;
        location.href = body.next;
        return;
      }
      if (res.status === 404 || body.expired) {
        stopped = true;
        if (status) status.textContent = 'This link to the app has expired. Go back to the meeting and choose Join in the app again.';
        return;
      }
    } catch { /* offline for a moment: ask again */ }
    setTimeout(ask, 2000);
  }
  setTimeout(ask, 1500);
})();