Add consent tracking to cookie functions

Taken from GOVUK components:

https://github.com/alphagov/govuk_publishing_components/blob/master/app/assets/javascripts/govuk_publishing_components/lib/cookie-functions.js

Also includes:
- make new cookie functions handle notify domains
- addition of hasConsentFor function to allow easy
  checking of consent for categories of cookie

app/assets/javascripts/consent.js

@@ -0,0 +1,15 @@
+(function (window) {
+  "use strict";
+
+  function hasConsentFor (cookieCategory) {
+    const consentCookie = window.GOVUK.getConsentCookie();
+
+    if (consentCookie === null) { return false; }
+
+    if (!(cookieCategory in consentCookie)) { return false; }
+
+    return consentCookie[cookieCategory];
+  }
+
+  window.GOVUK.hasConsentFor = hasConsentFor;
+})(window);

app/assets/javascripts/govuk/cookie-functions.js

@@ -1,8 +1,17 @@
-(function () {
-  "use strict";
+// used by the cookie banner component
 
-  var root = this;
-  if(typeof root.GOVUK === 'undefined') { root.GOVUK = {}; }
+(function (root) {
+  'use strict';
+  window.GOVUK = window.GOVUK || {};
+
+  var DEFAULT_COOKIE_CONSENT = {
+    'analytics': false
+  };
+
+  var COOKIE_CATEGORIES = {
+    '_ga': 'analytics',
+    '_gid': 'analytics'
+  };
 
   /*
     Cookie methods
@@ -19,38 +28,129 @@
       Deleting a cookie:
       GOVUK.cookie('hobnob', null);
   */
-  GOVUK.cookie = function (name, value, options) {
-    if(typeof value !== 'undefined'){
-      if(value === false || value === null) {
-        return GOVUK.setCookie(name, '', { days: -1 });
+  window.GOVUK.cookie = function (name, value, options) {
+    if (typeof value !== 'undefined') {
+      if (value === false || value === null) {
+        return window.GOVUK.setCookie(name, '', { days: -1 });
       } else {
-        return GOVUK.setCookie(name, value, options);
+        // Default expiry date of 30 days
+        if (typeof options === 'undefined') {
+          options = { days: 30 };
+        }
+        return window.GOVUK.setCookie(name, value, options);
       }
     } else {
-      return GOVUK.getCookie(name);
+      return window.GOVUK.getCookie(name);
     }
   };
-  GOVUK.setCookie = function (name, value, options) {
-    if(typeof options === 'undefined') {
-      options = {};
+
+  window.GOVUK.getConsentCookie = function () {
+    var consentCookie = window.GOVUK.cookie('cookies_policy');
+    var consentCookieObj;
+
+    if (consentCookie) {
+      try {
+        consentCookieObj = JSON.parse(consentCookie);
+      } catch (err) {
+        return null;
+      }
+
+      if (typeof consentCookieObj !== 'object' && consentCookieObj !== null) {
+        consentCookieObj = JSON.parse(consentCookieObj);
+      }
+    } else {
+      return null;
     }
-    var cookieString = name + "=" + value + "; path=/";
-    if (options.days) {
-      var date = new Date();
-      date.setTime(date.getTime() + (options.days * 24 * 60 * 60 * 1000));
-      cookieString = cookieString + "; expires=" + date.toGMTString();
-    }
-    if (document.location.protocol == 'https:'){
-      cookieString = cookieString + "; Secure";
-    }
-    document.cookie = cookieString;
+
+    return consentCookieObj;
   };
-  GOVUK.getCookie = function (name) {
-    var nameEQ = name + "=";
+
+  window.GOVUK.setConsentCookie = function (options) {
+    var cookieConsent = window.GOVUK.getConsentCookie();
+
+    if (!cookieConsent) {
+      cookieConsent = JSON.parse(JSON.stringify(DEFAULT_COOKIE_CONSENT));
+    }
+
+    for (var cookieType in options) {
+      cookieConsent[cookieType] = options[cookieType];
+
+      // Delete cookies of that type if consent being set to false
+      if (!options[cookieType]) {
+        for (var cookie in COOKIE_CATEGORIES) {
+          if (COOKIE_CATEGORIES[cookie] === cookieType) {
+            window.GOVUK.cookie(cookie, null);
+
+            if (window.GOVUK.cookie(cookie)) {
+              document.cookie = cookie + '=;expires=' + new Date() + ';domain=' + window.location.hostname.replace(/^www\./, '.') + ';path=/';
+            }
+          }
+        }
+      }
+    }
+
+    window.GOVUK.setCookie('cookies_policy', JSON.stringify(cookieConsent), { days: 365 });
+  };
+
+  window.GOVUK.checkConsentCookieCategory = function (cookieName, cookieCategory) {
+    var currentConsentCookie = window.GOVUK.getConsentCookie();
+
+    // If the consent cookie doesn't exist, but the cookie is in our known list, return true
+    if (!currentConsentCookie && COOKIE_CATEGORIES[cookieName]) {
+      return true;
+    }
+
+    currentConsentCookie = window.GOVUK.getConsentCookie();
+
+    // Sometimes currentConsentCookie is malformed in some of the tests, so we need to handle these
+    try {
+      return currentConsentCookie[cookieCategory];
+    } catch (e) {
+      console.error(e);
+      return false;
+    }
+  };
+
+  window.GOVUK.checkConsentCookie = function (cookieName, cookieValue) {
+    // If we're setting the consent cookie OR deleting a cookie, allow by default
+    if (cookieName === 'cookies_policy' || (cookieValue === null || cookieValue === false)) {
+      return true;
+    }
+
+    if (COOKIE_CATEGORIES[cookieName]) {
+      var cookieCategory = COOKIE_CATEGORIES[cookieName];
+
+      return window.GOVUK.checkConsentCookieCategory(cookieName, cookieCategory);
+    } else {
+      // Deny the cookie if it is not known to us
+      return false;
+    }
+  };
+
+  window.GOVUK.setCookie = function (name, value, options) {
+    if (window.GOVUK.checkConsentCookie(name, value)) {
+      if (typeof options === 'undefined') {
+        options = {};
+      }
+      var cookieString = name + '=' + value + '; path=/';
+      if (options.days) {
+        var date = new Date();
+        date.setTime(date.getTime() + (options.days * 24 * 60 * 60 * 1000));
+        cookieString = cookieString + '; expires=' + date.toGMTString();
+      }
+      if (document.location.protocol === 'https:') {
+        cookieString = cookieString + '; Secure';
+      }
+      document.cookie = cookieString;
+    }
+  };
+
+  window.GOVUK.getCookie = function (name) {
+    var nameEQ = name + '=';
     var cookies = document.cookie.split(';');
-    for(var i = 0, len = cookies.length; i < len; i++) {
+    for (var i = 0, len = cookies.length; i < len; i++) {
       var cookie = cookies[i];
-      while (cookie.charAt(0) == ' ') {
+      while (cookie.charAt(0) === ' ') {
         cookie = cookie.substring(1, cookie.length);
       }
       if (cookie.indexOf(nameEQ) === 0) {
@@ -59,4 +159,5 @@
     }
     return null;
   };
-}).call(this);
+}(window));
+