// Copyright 2011 Google Inc. All Rights Reserved.
	
	/**
	 * @fileoverview A simple script to automatically track Facebook and Twitter
	 * buttons using Google Analytics social tracking feature.
	 * @author api.nickm@google.com (Nick Mihailovski)
	 */
	
	
	/**
	 * Namespace.
	 * @type {Object}.
	 */
	var _ga = _ga || {};
	
	
	/**
	 * Ensure global _gaq Google Anlaytics queue has be initialized.
	 * @type {Array}
	 */
	var _gaq = _gaq || [];
	
	
	/**
	 * Helper method to track social features. This assumes all the social
	 * scripts / apis are loaded synchronously. If they are loaded async,
	 * you might need to add the nextwork specific tracking call to the
	 * a callback once the network's script has loaded.
	 * @param {string} opt_pageUrl An optional URL to associate the social
	 *     tracking with a particular page.
	 * @param {string} opt_trackerName An optional name for the tracker object.
	 */
	_ga.trackSocial = function(opt_pageUrl, opt_trackerName) {
	  _ga.trackFacebook(opt_pageUrl, opt_trackerName);
	  _ga.trackTwitter(opt_pageUrl, opt_trackerName);
	};
	
	
	/**
	 * Tracks Facebook likes, unlikes and sends by suscribing to the Facebook
	 * JSAPI event model. Note: This will not track facebook buttons using the
	 * iFrame method.
	 * @param {string} opt_pageUrl An optional URL to associate the social
	 *     tracking with a particular page.
	 * @param {string} opt_trackerName An optional name for the tracker object.
	 */
	_ga.trackFacebook = function(opt_pageUrl, opt_trackerName) {
	  var trackerName = _ga.buildTrackerName_(opt_trackerName);
	  try {
	    if (FB && FB.Event && FB.Event.subscribe) {
	      FB.Event.subscribe('edge.create', function(targetUrl) {
	        _gaq.push([trackerName + '_trackSocial', 'facebook', 'like',
	            targetUrl, opt_pageUrl]);
	      });
	      FB.Event.subscribe('edge.remove', function(targetUrl) {
	        _gaq.push([trackerName + '_trackSocial', 'facebook', 'unlike',
	            targetUrl, opt_pageUrl]);
	      });
	      FB.Event.subscribe('message.send', function(targetUrl) {
	        _gaq.push([trackerName + '_trackSocial', 'facebook', 'send',
	            targetUrl, opt_pageUrl]);
	      });
	    }
	  } catch (e) {}};
	
	
	/**
	 * Returns the normalized tracker name configuration parameter.
	 * @param {string} opt_trackerName An optional name for the tracker object.
	 * @return {string} If opt_trackerName is set, then the value appended with
	 *     a . Otherwise an empty string.
	 * @private
	 */
	_ga.buildTrackerName_ = function(opt_trackerName) {
	  return opt_trackerName ? opt_trackerName + '.' : '';
	};
	
	
	/**
	 * Tracks everytime a user clicks on a tweet button from Twitter.
	 * This subscribes to the Twitter JS API event mechanism to listen for
	 * clicks coming from this page. Details here:
	 * http://dev.twitter.com/pages/intents-events#click
	 * This method should be called once the twitter API has loaded.
	 * @param {string} opt_pageUrl An optional URL to associate the social
	 *     tracking with a particular page.
	 * @param {string} opt_trackerName An optional name for the tracker object.
	 */
	_ga.trackTwitter = function(opt_pageUrl, opt_trackerName) {
	  var trackerName = _ga.buildTrackerName_(opt_trackerName);
	  try {
	    if (twttr && twttr.events && twttr.events.bind) {
	      twttr.events.bind('tweet', function(event) {
	        if (event) {
	          var targetUrl; // Default value is undefined.
	          if (event.target && event.target.nodeName == 'IFRAME') {
	            targetUrl = _ga.extractParamFromUri_(event.target.src, 'url');
	          }
	          _gaq.push([trackerName + '_trackSocial', 'twitter', 'tweet',
	            targetUrl, opt_pageUrl]);
	        }
	      });
	    }
	  } catch (e) {}};
	
	
	/**
	 * Extracts a query parameter value from a URI.
	 * @param {string} uri The URI from which to extract the parameter.
	 * @param {string} paramName The name of the query paramater to extract.
	 * @return {string} The un-encoded value of the query paramater. underfined
	 *     if there is no URI parameter.
	 * @private
	 */
	_ga.extractParamFromUri_ = function(uri, paramName) {
	  if (!uri) {return;}
	  var uri = uri.split('#')[0];  // Remove anchor.
	  var parts = uri.split('?');  // Check for query params.
	  if (parts.length == 1) {return;}
	  var query = decodeURI(parts[1]);
	
	  // Find url param.
	  paramName += '=';
	  var params = query.split('&');
	  for (var i = 0, param; param = params[i]; ++i) {
	    if (param.indexOf(paramName) === 0) {
	      return unescape(param.split('=')[1]);
	    }
	  }
	  return;
	};