(function(){
  "use strict";
  /* global ga */
  
  var demo = true;
  
  var trackingLinks = document.getElementsByClassName('js-analytics-track'), i;

  function trackOnClick(event) {
    var config = {
          category: this.dataset.cat || 'PDF',
          action: this.dataset.action || 'Download',
          file: this.getAttribute('href')
        };
    
    // Just delete this block in production environment
    if(demo === true) {
      event.preventDefault();
      
      var result = document.getElementById('m-result');
      
      result.innerHTML = [
        'Google Analytics will track an event in the category',
        config.category,
        'action',
        config.action,
        'for the file',
        config.file,
        '.'
      ].join(' ');
    }
    
    if(typeof ga !== 'undefined') {
      ga('send', 'event', category, action, file);
    }
  }

  for(i = 0; i < trackingLinks.length; i++) {
    trackingLinks[i].addEventListener('click', trackOnClick);
  }
})();