Add setting to automatically use top-level domain for duid (closes snowplow#409)

Author: jbeemster

src/js/lib/helpers.js

@@ -35,6 +35,7 @@
 
 	var 
 		lodash = require('../lib_managed/lodash'),
+		cookie = require('browser-cookie-lite'),
 
 		object = typeof exports !== 'undefined' ? exports : this; // For eventual node.js environment support
 
@@ -290,4 +291,62 @@
 		}
 	};
 
+	/**
+	 * Finds the root domain
+	 */
+	object.findRootDomain = function () {
+		var cookiePrefix = '_sp_root_domain_test_';
+		var cookieName = cookiePrefix + new Date().getTime();
+		var cookieValue = '_test_value_' + new Date().getTime();
+
+		var split = window.location.hostname.split('.');
+		var position = split.length - 1;
+		while (position >= 0) {
+			var currentDomain = split.slice(position, split.length).join('.');
+			cookie.cookie(cookieName, cookieValue, 0, '/', currentDomain);
+			if (cookie.cookie(cookieName) === cookieValue) {
+
+				// Clean up created cookie(s)
+				object.deleteCookie(cookieName, currentDomain);
+				var cookieNames = object.getCookiesWithPrefix(cookiePrefix);
+				for (var i = 0; i < cookieNames.length; i++) {
+					object.deleteCookie(cookieNames[i], currentDomain);
+				}
+
+				return currentDomain;
+			}
+			position -= 1;
+		}
+
+		// Cookies cannot be read
+		return window.location.hostname;
+	};
+
+	/**
+	 * Deletes an arbitrary cookie by setting the expiration date to the past
+	 *
+	 * @param cookieName The name of the cookie to delete
+	 * @param domainName The domain the cookie is in
+	 */
+	object.deleteCookie = function (cookieName, domainName) {
+		cookie.cookie(cookieName, '', -1, '/', domainName);
+	};
+
+	/**
+	 * Fetches the name of all cookies beginning with a certain prefix
+	 *
+	 * @param cookiePrefix The prefix to check for
+	 * @return array The cookies that begin with the prefix
+	 */
+	object.getCookiesWithPrefix = function (cookiePrefix) {
+		var cookies = document.cookie.split("; ");
+		var cookieNames = [];
+		for (var i = 0; i < cookies.length; i++) {
+			if (cookies[i].startsWith(cookiePrefix)) {
+				cookieNames.push(cookies[i]);
+			}
+		}
+		return cookieNames;
+	};
+
 }());

src/js/tracker.js

@@ -82,6 +82,7 @@
 	 * 16. bufferSize, 1
 	 * 17. crossDomainLinker, false
 	 * 18. maxPostBytes, 40000
+	 * 19. discoverRootDomain, false
 	 */
 	object.Tracker = function Tracker(functionName, namespace, version, pageViewId, mutSnowplowState, argmap) {
 
@@ -258,6 +259,10 @@
 			// Context to be added to every event
 			commonContexts = [];
 
+		if (argmap.hasOwnProperty('discoverRootDomain') && argmap.discoverRootDomain) {
+			configCookieDomain = helpers.findRootDomain();
+		}
+
 		if (autoContexts.webPage) {
 			commonContexts.push(getWebPageContext());
 		}