var docIdentifier  = '/download';

function listenToClicks() {
  var domains    = ["oli.web.cmu.edu", document.location.hostname]; 
  var fileTypes  = ["pdf",".doc",".ppt",".xls",".exe",".zip",".mp3"];
    
	if (document.getElementsByTagName) {
    var aTags = document.getElementsByTagName('a'); 
    
    ANCHOR:
    for (var i = 0; i < aTags.length; i++) { 
      if (aTags[i]=="")                                         {continue ANCHOR; }
      if (typeof aTags[i].hostname == "undefined")              {continue ANCHOR; }
      if (aTags[i].protocol.indexOf("javascript") != -1)        {continue ANCHOR; }
      
      aDOMAIN:
      for (var j = 0; j < domains.length; j++) {
        if (aTags[i].href.indexOf(domains[j]) != -1) {  //if the anchor tag we're checking matches a domain from our list
        
          FILE:
          // look for a file extension
          for (k = 0; k < fileTypes.length; k++){
            if (aTags[i].pathname.indexOf(fileTypes[k]) != -1) {
              startListening(aTags[i],"click",trackDocuments);  continue ANCHOR; } // file extension was found, go to next anchor
          }
        }
      } // if we were tracking external links, we would do it here, after looping through all of the domains in our list and not finding a match.
    }
	}
}


function startListening (obj,evnt,func) { 
  if (obj.addEventListener) { 
    obj.addEventListener(evnt,func,false);
  } else if (obj.attachEvent) { 
    obj.attachEvent("on" + evnt,func);
  }
}


function useLinker (evnt) {  
  var lnk;
  if (evnt.srcElement) {
    var elmnt = evnt.srcElement;
    while (elmnt.tagName != "a") {
      var newelmnt = elmnt.parentNode;
      elmnt = newelmnt;
    }
    lnk = "http://" + elmnt.hostname + "/" + elmnt.pathname + elmnt.search;
  } else {
    lnk = "http://" + this.hostname + this.pathname + this.search;
  }

  if (typeof(benchmarkTracker) == "object") { 
	  benchmarkTracker._link(lnk);
	  if (evnt.preventDefault) {evnt.preventDefault();}else{evnt.returnValue=false;} 
    return false; 
	}
}

// trackDocuments:  calls _trackPageview before downloading a file
function trackDocuments (evnt) { 
  var url = (evnt.srcElement) ? "/" + evnt.srcElement.pathname : this.pathname; 
  url = docIdentifier + url;
  if (typeof(benchmarkTracker) == "object") {
	  benchmarkTracker._trackPageview(url);
  }
  if (typeof(overallTracker) == "object") {
	  overallTracker._trackPageview(url);
  }
}

startListening(window, 'load', listenToClicks); // register an event listener to run the script when the load event fires.