sw.js

self.addEventListener('install', (event) => {
  console.log('SW', 'install', location.protocol, event);

  // Don't block activation
  if (self.skipWaiting) {
    self.skipWaiting();
  }
});

self.addEventListener('activate', (event) => {
  console.log('SW', 'activate', OFFLINE_VERSION, event);

  if (self.clients && 'claim' in self.clients) {
    self.clients.claim();
  }
});

self.addEventListener('controllerchange', () => {
  if (self.skipWaiting) {
    self.skipWaiting();
  }
});

// ExtendableMessageEvent
self.addEventListener('message', (event) => {
  console.log('SW', 'message', event.origin, JSON.stringify(event.data));
});

// Focus a window and send a message
function sendWindowMessage(windowMessage) {
  return self.clients.matchAll({
    type: 'window',
    includeUncontrolled: true,
  })
    .then((windowClients) => {
      if (windowClients.length) {
        if ('focus' in windowClients[0]) {
          return windowClients[0].focus();
        }
        windowClients[0].postMessage(windowMessage);
      }
    });
}

function getNotificationMessage(notif) {
  return JSON.stringify({
    type: notif.data.event_type,
    tag: notif.tag,
    timestamp: notif.timestamp || Date.now(),
  });
}

// Notification was clicked, i.e. "Open" or "Dismiss" clicked
self.addEventListener('notificationclick', (event) => {
  console.log('SW', 'notificationclick', event.action);

  // Android doesn't close the notification when you click on it
  // See: http://crbug.com/463146
  event.notification.close();

  let data = getNotificationMessage(event.notification);;
  let windowMessage = {
    action: 'serviceworker-notification',
    data: data,
  };

  // KaiOS 2.5
  if (clients && 'openApp' in clients) {
    event.waitUntil(
      Promise.all([
        sendWindowMessage(windowMessage), // Focus existing window
        clients.openApp({ msg: data }), // Open app
      ])
    );
  }
});