gaf-mobile/support/service-worker/offline-tracking.js

GAF mobile Web site

/**
 * This script will be imported in our service worker which would add a `fetch`
 * event handler for intercepting tracking-related requests. For the tracking
 * libraries (GTM, QTS, TTREF), the handler will observe the network-first
 * strategy, falling back to the previously cached copy. For QTS tracking
 * requests, this should handle network failures such as being offline.
 * Failed requests are stored in IndexedDB. Every time the service worker
 * starts up, this would try to replay the failed requests.
 */
 // TODO: Implement some kind of garbage collection for failed requests stored
 // in IndexedDB

 /* global self */
'use strict';

var IDB = {
  NAME: 'offline-qts',
  STORE: 'requests',
  VERSION: 1
};
var CACHE_NAME = 'offline-tracking-gaf-mobile';
var QTS_HOSTNAME = 't.freelancer.com';
var QTS_LIB_HOSTNAME = 'd2werhn82xczly.cloudfront.net';
var QTS_LIB_PATHNAME = '/20140328/main.min.js';
var GTM_HOSTNAME = 'www.googletagmanager.com';
var GTM_PATHNAME = '/gtm.js';
var TTREF_PATHNAME = '/build/js/ttref.js';

var idb = (self.IDBHelper)(IDB.NAME, IDB.VERSION, function(db) {
  // upgrade callback
  return db.createObjectStore(IDB.STORE);
});

/**
 * Upserts the failed tracking requests to IndexedDB. We will do the following
 * manipulations to the QTS request:
 * 1. Push back the original event name to `real_event_name` param
 * 2. Change event name to `mobile_offline_event`
 * 3. Add a `real_timestamp` param
 */
var enqueueOfflineQts = function(url) {
  var now = Math.round(Date.now() / 1000);
  var newUrl = url;
  var search = newUrl.search;
  var searchMap = {};

  if (search.charAt(0) === '?') {
    search = search.slice(1);
  }

  // TODO: Use URLSearchParams when widely supported (Chrome 49+ and FF 29+)
  var pairs = (search || '').split('&');
  pairs.forEach(function(pair) {
    var index = pair.indexOf('=');
    if (index > -1) {
      var key = pair.slice(0, index);
      var value = decodeURIComponent(pair.slice(index + 1));
      searchMap[key] = value;
    }
  });

  searchMap.real_event_name = searchMap.en;
  searchMap.en = 'mobile_offline_event';
  searchMap.real_timestamp = now.toString();

  var newPairs = [], key, value;
  for (key in searchMap) {
    value = encodeURIComponent(searchMap[key]);
    newPairs.push(key + '=' + value);
  }

  newUrl.search = ('?' + newPairs.join('&'));

  return idb.put(IDB.STORE, newUrl.toString(), now);
};

/**
 * Resends requests stored in IndexedDB. If the request was successfully sent,
 * the entry is deleted from the store.
 */
var resendOfflineQts = function() {
  if (self.fetch) {
    return idb.getAllKeys(IDB.STORE).then(function(urls) {
      return Promise.all(urls.map(function(url) {
        return self.fetch(url, { method: 'GET', mode: 'no-cors' })
          .then(function() {
            return idb.delete(IDB.STORE, url);
          });
      }));
    });
  }
};

/**
 * Handles requests to either the tracking libraries or QTS requests.
 */
self.addEventListener('fetch', function(event) {
  if (!self.fetch || !self.caches) { // Fetch or Cache API is not supported
    return;
  }

  var request = event.request;
  var url = new URL(request.url);

  if (request.method === 'GET') {
    if (url.hostname === QTS_HOSTNAME) {
      event.respondWith(
        self.fetch(request).catch(function() {
          enqueueOfflineQts(url);
        })
      );
    } else if ((url.pathname === TTREF_PATHNAME) ||
        (url.hostname === GTM_HOSTNAME && url.pathname === GTM_PATHNAME) ||
        (url.hostname === QTS_LIB_HOSTNAME && url.pathname === QTS_LIB_PATHNAME)
      ) {
      event.respondWith(
        self.caches.open(CACHE_NAME).then(function(cache) {
          return self.fetch(request).then(function(response) {
            return cache.put(request, response.clone()).then(function() {
              return response;
            });
          }).catch(function() {
            return cache.match(request);
          });
        })
      );
    }
  }
});

// Resend locally stored offline QTS requests every time SW starts up
resendOfflineQts();