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/*!
 * @preserve
 * jquery.scrolldepth.js | v0.7
 * Copyright (c) 2014 Rob Flaherty (@robflaherty)
 * Licensed under the MIT and GPL licenses.
 */

if (window.jQuery) {
	;(function ( $, window, document, undefined ) {
	
	  "use strict";
	
	  var defaults = {
	    minHeight: 0,
	    elements: [],
	    percentage: true,
	    userTiming: true,
	    pixelDepth: true,
	    nonInteraction: true
	  };
	
	  var $window = $(window),
	    cache = [],
	    lastPixelDepth = 0,
	    universalGA,
	    classicGA,
	    standardEventHandler;
	
	  /*
	   * Plugin
	   */
	
	  $.scrollDepth = function(options) {
	
	    var startTime = +new Date;
	
	    options = $.extend({}, defaults, options);
	
	    // Return early if document height is too small
	    if ( $(document).height() < options.minHeight ) {
	      return;
	    }
	
	    /*
	     * Determine which version of GA is being used
	     * "ga", "_gaq", and "dataLayer" are the possible globals
	     */
	
	    if (typeof ga === "function") {
	      universalGA = true;
	    }
	
	    if (typeof _gaq !== "undefined" && typeof _gaq.push === "function") {
	      classicGA = true;
	    }
	
	    if (typeof options.eventHandler === "function") {
	      standardEventHandler = options.eventHandler;
	    } else if (typeof dataLayer !== "undefined" && typeof dataLayer.push === "function") {
	      standardEventHandler = dataLayer.push;
	    }
	
	    if (options.percentage) {
	      // Establish baseline (0% scroll)
	      sendEvent('Percentage', 'Baseline');
	    } else if (options.elements) {
	      sendEvent('Elements', 'Baseline');
	    }
	
	    /*
	     * Functions
	     */
	
	    function sendEvent(action, label, scrollDistance, timing) {
	
	      if (standardEventHandler) {
	
	        standardEventHandler({'event': 'ScrollDistance', 'eventCategory': 'Scroll Depth', 'eventAction': action, 'eventLabel': label, 'eventValue': 1, 'eventNonInteraction': options.nonInteraction});
	
	        if (options.pixelDepth && arguments.length > 2 && scrollDistance > lastPixelDepth) {
	          lastPixelDepth = scrollDistance;
	          standardEventHandler({'event': 'ScrollDistance', 'eventCategory': 'Scroll Depth', 'eventAction': 'Pixel Depth', 'eventLabel': rounded(scrollDistance), 'eventValue': 1, 'eventNonInteraction': options.nonInteraction});
	        }
	
	        if (options.userTiming && arguments.length > 3) {
	          standardEventHandler({'event': 'ScrollTiming', 'eventCategory': 'Scroll Depth', 'eventAction': action, 'eventLabel': label, 'eventTiming': timing});
	        }
	
	      } else {
	
	        if (universalGA) {
	
	          ga('send', 'event', 'Scroll Depth', action, label, 1, {'nonInteraction': options.nonInteraction});
	
	          if (options.pixelDepth && arguments.length > 2 && scrollDistance > lastPixelDepth) {
	            lastPixelDepth = scrollDistance;
	            ga('send', 'event', 'Scroll Depth', 'Pixel Depth', rounded(scrollDistance), 1, {'nonInteraction': options.nonInteraction});
	          }
	
	          if (options.userTiming && arguments.length > 3) {
	            ga('send', 'timing', 'Scroll Depth', action, timing, label);
	          }
	
	        }
	
	        if (classicGA) {
	
	          _gaq.push(['_trackEvent', 'Scroll Depth', action, label, 1, options.nonInteraction]);
	
	          if (options.pixelDepth && arguments.length > 2 && scrollDistance > lastPixelDepth) {
	            lastPixelDepth = scrollDistance;
	            _gaq.push(['_trackEvent', 'Scroll Depth', 'Pixel Depth', rounded(scrollDistance), 1, options.nonInteraction]);
	          }
	
	          if (options.userTiming && arguments.length > 3) {
	            _gaq.push(['_trackTiming', 'Scroll Depth', action, timing, label, 100]);
	          }
	
	        }
	
	      }
	
	    }
	
	    function calculateMarks(docHeight) {
	      return {
	        '25%' : parseInt(docHeight * 0.25, 10),
	        '50%' : parseInt(docHeight * 0.50, 10),
	        '75%' : parseInt(docHeight * 0.75, 10),
	        // 1px cushion to trigger 100% event in iOS
	        '100%': docHeight - 5
	      };
	    }
	
	    function checkMarks(marks, scrollDistance, timing) {
	      // Check each active mark
	      $.each(marks, function(key, val) {
	        if ( $.inArray(key, cache) === -1 && scrollDistance >= val ) {
	          sendEvent('Percentage', key, scrollDistance, timing);
	          cache.push(key);
	        }
	      });
	    }
	
	    function checkElements(elements, scrollDistance, timing) {
	      $.each(elements, function(index, elem) {
	        if ( $.inArray(elem, cache) === -1 && $(elem).length ) {
	          if ( scrollDistance >= $(elem).offset().top ) {
	            sendEvent('Elements', elem, scrollDistance, timing);
	            cache.push(elem);
	          }
	        }
	      });
	    }
	
	    function rounded(scrollDistance) {
	      // Returns String
	      return (Math.floor(scrollDistance/250) * 250).toString();
	    }
	
	    /*
	     * Throttle function borrowed from:
	     * Underscore.js 1.5.2
	     * http://underscorejs.org
	     * (c) 2009-2013 Jeremy Ashkenas, DocumentCloud and Investigative Reporters & Editors
	     * Underscore may be freely distributed under the MIT license.
	     */
	
	    function throttle(func, wait) {
	      var context, args, result;
	      var timeout = null;
	      var previous = 0;
	      var later = function() {
	        previous = new Date;
	        timeout = null;
	        result = func.apply(context, args);
	      };
	      return function() {
	        var now = new Date;
	        if (!previous) previous = now;
	        var remaining = wait - (now - previous);
	        context = this;
	        args = arguments;
	        if (remaining <= 0) {
	          clearTimeout(timeout);
	          timeout = null;
	          previous = now;
	          result = func.apply(context, args);
	        } else if (!timeout) {
	          timeout = setTimeout(later, remaining);
	        }
	        return result;
	      };
	    }
	
	    /*
	     * Scroll Event
	     */
	
	    $window.on('scroll.scrollDepth', throttle(function() {
	      /*
	       * We calculate document and window height on each scroll event to
	       * account for dynamic DOM changes.
	       */
	
	      var docHeight = $(document).height(),
	        winHeight = window.innerHeight ? window.innerHeight : $window.height(),
	        scrollDistance = $window.scrollTop() + winHeight,
	
	        // Recalculate percentage marks
	        marks = calculateMarks(docHeight),
	
	        // Timing
	        timing = +new Date - startTime;
	
	      // If all marks already hit, unbind scroll event
	      if (cache.length >= 4 + options.elements.length) {
	        $window.off('scroll.scrollDepth');
	        return;
	      }
	
	      // Check specified DOM elements
	      if (options.elements) {
	        checkElements(options.elements, scrollDistance, timing);
	      }
	
	      // Check standard marks
	      if (options.percentage) {
	        checkMarks(marks, scrollDistance, timing);
	      }
	    }, 500));
	
	  };
	
	})( jQuery, window, document );
}