Wrap analytics code in GOVUK interface

Wraps our analytics code in a stripped down
version of GOVUK.Analytics to allow us to plug in
the GOVUK code for consent.

app/assets/javascripts/analytics/analytics.js

@@ -0,0 +1,39 @@
+(function (window) {
+  "use strict";
+
+  window.GOVUK = window.GOVUK || {};
+
+  // Stripped-down wrapper for Google Analytics, based on:
+  // https://github.com/alphagov/static/blob/master/app/assets/javascripts/analytics_toolkit/analytics.js
+  const Analytics = function (config) {
+    window.ga('create', config.trackingId, config.cookieDomain);
+
+    window.ga('set', 'anonymizeIp', config.anonymizeIp);
+    window.ga('set', 'displayFeaturesTask', config.displayFeaturesTask);
+    window.ga('set', 'transport', config.transport);
+
+  };
+
+  Analytics.load = function () {
+    /* jshint ignore:start */
+    (function(i, s, o, g, r, a, m){ i['GoogleAnalyticsObject'] = r; i[r] = i[r] || function () {
+      (i[r].q = i[r].q || []).push(arguments) }, i[r].l = 1 * new Date(); a = s.createElement(o),
+      m = s.getElementsByTagName(o)[0]; a.async = 1; a.src = g; m.parentNode.insertBefore(a,m)
+    })(window,document,'script','//www.google-analytics.com/analytics.js','ga');
+    /* jshint ignore:end */
+
+  };
+
+  Analytics.prototype.trackPageview = function (path, title, options) {
+
+    // strip UUIDs
+    const page = (window.location.pathname + window.location.search).replace(
+      /[a-f0-9]{8}-?[a-f0-9]{4}-?4[a-f0-9]{3}-?[89ab][a-f0-9]{3}-?[a-f0-9]{12}/g, '…'
+    );
+    window.ga('send', 'pageview', page);
+
+  };
+
+  window.GOVUK.Analytics = Analytics;
+
+})(window);

app/assets/javascripts/analytics/init.js

@@ -0,0 +1,39 @@
+(function (window) {
+  "use strict";
+
+  window.GOVUK = window.GOVUK || {};
+
+  const trackingId = 'UA-26179049-1';
+
+  // Disable analytics by default
+  window[`ga-disable-${trackingId}`] = true;
+
+  const initAnalytics = function () {
+
+    // guard against being called more than once
+    if (!('analytics' in window.GOVUK)) {
+
+      window[`ga-disable-${trackingId}`] = false;
+
+      // Load Google Analytics libraries
+      window.GOVUK.Analytics.load();
+
+      // Configure profiles and make interface public
+      // for custom dimensions, virtual pageviews and events
+      window.GOVUK.analytics = new GOVUK.Analytics({
+        trackingId: trackingId,
+        cookieDomain: 'auto',
+        anonymizeIp: true,
+        displayFeaturesTask: null,
+        transport: 'beacon'
+      });
+
+      // Track initial pageview
+      window.GOVUK.analytics.trackPageview();
+
+    }
+
+  };
+
+  window.GOVUK.initAnalytics = initAnalytics;
+})(window);

app/assets/javascripts/main.js

@@ -2,6 +2,8 @@ window.GOVUK.Frontend.initAll();
 
 $(() => GOVUK.addCookieMessage());
 
+window.GOVUK.initAnalytics();
+
 $(() => $("time.timeago").timeago());
 
 $(() => GOVUK.stickAtTopWhenScrolling.init());