var periodicSyncNewMsgReminderText;

const OFFLINE_CACHE = `offline`;
const offlineCacheFiles = ['offline.html','config.json'];

// on install we download the routes we want to cache for offline
self.addEventListener('install', evt => evt.waitUntil(caches.open(OFFLINE_CACHE).then(cache => {
  console.log("SW Caching offline files");
  self.skipWaiting();
  return cache.addAll(offlineCacheFiles);
})));

self.addEventListener("activate", event => {
  event.waitUntil(clients.claim());
});

// Notification click event listener
self.addEventListener("notificationclick", (e) => {
  e.notification.close();
  e.waitUntil(
    clients.matchAll({ type: "window" }).then((clientsArr) => {
      // If a Window tab matching the targeted URL already exists, focus that;
      const hadWindowToFocus = clientsArr.some((windowClient) =>
        windowClient.url === e.notification.data.url
          ? (windowClient.focus(), true)
          : false,
      );

      // Otherwise, open a new tab to the applicable URL and focus it.
      if (!hadWindowToFocus)
        clients
          .openWindow(e.notification.data.url)
          .then((windowClient) => (windowClient ? windowClient.focus() : null));
    }),
  );
});

self.addEventListener("message", (event) => {
  periodicSyncNewMsgReminderText = event.data;
});

async function checkNewMessages() {
  const cachedCredentials = await caches.open('cachedCredentials');
  // Todo...
}

// Install PWA in mobile or web to test if periodicSync notification works
// see browser compatibility: https://developer.mozilla.org/en-US/docs/Web/API/Web_Periodic_Background_Synchronization_API#browser_compatibility
self.addEventListener('periodicsync', (event) => {
  if (event.tag === 'check-new-messages') {
    let notificationTitle = periodicSyncNewMsgReminderText || "You may have new messages";
    self.registration.showNotification(notificationTitle);

    event.waitUntil(checkNewMessages());
  }
});

self.addEventListener("fetch", (event) => {
  if (event.request.mode === 'navigate') {
    return event.respondWith(
      fetch(event.request).catch((e) => {
        console.log("OFFLINE, serve offline page", e);
        return serveOfflinePage();
    }));
  } else if (event.request.url.endsWith("config.json")) {
    return fetch(event.request)
        .then((response) => {
          console.log("Caching a new version of config.json");
          let responseClone = response.clone();
          caches
            .open(OFFLINE_CACHE)
            .then((cache) => cache.put(event.request, responseClone));
          return response;
        })
  }
});

async function serveOfflinePage() {
  let mirrorUrl = null;
  const rConfig = await caches.match("config.json", { cacheName: OFFLINE_CACHE});
  if (rConfig) {
    const json = await rConfig.json();
    const mirrors = json.mirrors;
    if (mirrors && Array.isArray(mirrors) && mirrors.length > 0) {
      mirrorUrl = json.mirrors[Math.floor(Math.random() * mirrors.length)];
    }
  }
  const offlinePage = await caches.match("offline.html", { cacheName: OFFLINE_CACHE});
  if (mirrorUrl && offlinePage) {
    let text = await offlinePage.text();
    text = text.replaceAll("<!--MIRROR_URL-->", mirrorUrl);

    let title = undefined;
    let message = undefined;
    let redirect = undefined;

    await new Promise((resolve, reject) => {
      var open = indexedDB.open("ServiceWorker", 1);
      open.onerror = function() {
        resolve(false);
      }
      open.onsuccess = function() {
        // Start a new transaction
        var db = open.result;
        var tx = db.transaction("offline_strings", "readonly");
        var store = tx.objectStore("offline_strings");

        var get1 = store.get("offline_title");
        var get2 = store.get("offline_message");
        var get3 = store.get("offline_redirect");

        get1.onsuccess = function() {
          title = get1.result.translation;
        };
        get2.onsuccess = function() {
          message = get2.result.translation;
        };
        get3.onsuccess = function() {
          redirect = get3.result.translation;
        };
        
        // Close the db when the transaction is done
        tx.oncomplete = function() {
          db.close();
          resolve(true);
        };
      }
    });
    
    if (title) {
      text = text.replaceAll(/<!--OFFLINE_TITLE_START-->(.*?)<!--OFFLINE_TITLE_END-->/g, title);
    }
    if (message) {
      text = text.replaceAll(/<!--OFFLINE_MESSAGE_START-->(.*?)<!--OFFLINE_MESSAGE_END-->/g, message);
    }
    if (redirect) {
      text = text.replaceAll(/<!--OFFLINE_REDIRECT_START-->(.*?)<!--OFFLINE_REDIRECT_END-->/g, redirect);
    }
    return new Response(text, { headers: {"content-type": "text/html"}});
  }
  throw new Error("Offline");
}