var VERSION = 'v51 - 2019-12-26';
var toCache = [
  '/',
  'activePage.js',
  'activePage.js.map',
  'config.js',
  'config.js.map',
  'favicon.ico',
  'hesla.js',
  'hesla.js.map',
  'hesla.webapp',
  'icon-128.png',
  'icon-30.png',
  'icon-60.png',
  'index_de.html',
  'index.html',
  'require.js',
  'screen.css'
];

self.addEventListener('install', event => {
    console.log('install version = ' + VERSION);
    event.waitUntil(
      caches.open(VERSION)
      .then(
        c => c.addAll(toCache)
          .then(v => console.log('Yay!' + VERSION), e => console.log('Error'))
      )
    );
});

self.addEventListener('activate', event => {
  console.log('activate version = ' + VERSION);
  console.log('keys:\n' + caches.keys());
  event.waitUntil(caches.keys().then(
        keys => Promise.all(
          keys.filter(key => key != VERSION).
            map(key => caches.delete(key))
        )
    )
  );
});

self.addEventListener('fetch', function(event) {
  event.respondWith(caches.match(event.request).then(function(response) {
    // caches.match() always resolves
    // but in case of success response will have value
    if (response !== undefined) {
      return response;
    } else {
      return fetch(event.request).then(function (response) {
        // response may be used only once
        // we need to save clone to put one copy in cache
        // and serve second one
        let responseClone = response.clone();

        caches.open(VERSION).then(function (cache) {
          cache.put(event.request, responseClone);
        });
        return response;
      }).catch(function () {
        return caches.match('/sw-test/gallery/myLittleVader.jpg');
      });
    }
  }));
});