/**
 * Copyright 2015 Google Inc. All rights reserved.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

'use strict';

var UPDATE_MSG = 'A new version of Whiteout Mail is available. Restart the app to update?';

if ('serviceWorker' in navigator &&
    // See http://www.chromium.org/Home/chromium-security/prefer-secure-origins-for-powerful-new-features
    (window.location.protocol === 'https:' ||
        window.location.hostname === 'localhost' ||
        window.location.hostname.indexOf('127.') === 0)) {
    // prefer new service worker cache
    useServiceWorker();

} else if ('applicationCache' in window) {
    // Fall back to app cache
    useAppCache();
}

function useServiceWorker() {
    // Your service-worker.js *must* be located at the top-level directory relative to your site.
    // It won't be able to control pages unless it's located at the same level or higher than them.
    // *Don't* register service worker file in, e.g., a scripts/ sub-directory!
    // See https://github.com/slightlyoff/ServiceWorker/issues/468
    navigator.serviceWorker.register('service-worker.js', {
        scope: './'
    }).then(function(registration) {
        // Check to see if there's an updated version of service-worker.js with new files to cache:
        // https://slightlyoff.github.io/ServiceWorker/spec/service_worker/index.html#service-worker-registration-update-method
        if (typeof registration.update === 'function') {
            registration.update();
        }

        // updatefound is fired if service-worker.js changes.
        registration.onupdatefound = function() {
            // The updatefound event implies that registration.installing is set; see
            // https://slightlyoff.github.io/ServiceWorker/spec/service_worker/index.html#service-worker-container-updatefound-event
            var installingWorker = registration.installing;

            installingWorker.onstatechange = function() {
                switch (installingWorker.state) {
                case 'installed':
                    if (navigator.serviceWorker.controller) {
                        // At this point, the old content will have been purged and the fresh content will
                        // have been added to the cache.
                        // It's the perfect time to display a "New content is available; please refresh."
                        // message in the page's interface.
                        console.log('New or updated content is available.');
                        if (window.confirm(UPDATE_MSG)) {
                            window.location.reload();
                        }
                    } else {
                        // At this point, everything has been precached, but the service worker is not
                        // controlling the page. The service worker will not take control until the next
                        // reload or navigation to a page under the registered scope.
                        // It's the perfect time to display a "Content is cached for offline use." message.
                        console.log('Content is cached, and will be available for offline use the ' +
                            'next time the page is loaded.');
                    }
                    break;

                case 'redundant':
                    throw 'The installing service worker became redundant.';
                }
            };
        };
    }).catch(function(e) {
        console.error('Error during service worker registration:', e);
    });
}

function useAppCache() {
    window.onload = function() {
        // Check if a new AppCache is available on page load.
        window.applicationCache.onupdateready = function() {
            if (window.applicationCache.status === window.applicationCache.UPDATEREADY) {
                // Browser downloaded a new app cache
                if (window.confirm(UPDATE_MSG)) {
                    window.location.reload();
                }
            }
        };
    };
}