var PULL = function() {
  var content,
      pullToRefresh,
      refreshing,
      contentStartY,
      success, 
      start, 
      cancel,
      startY,
      track = false,
      refresh = false;

  var removeTransition = function() {
    content.style['-webkit-transition-duration'] = 0;
  };

  return {
    init: function(o) {
      content = document.getElementById('content');
      pullToRefresh = document.getElementById('pull_to_refresh');
      refreshing = document.getElementById('refreshing');
      success = o.success;
       start = o.start;
      cancel = o.cancel;

      document.body.addEventListener('touchstart', function(e) {
        e.preventDefault();
        contentStartY = parseInt(content.style.top);
        startY = e.touches[0].screenY;
      });

      document.body.addEventListener('touchend', function(e) {
        if(refresh) {
          content.style['-webkit-transition-duration'] = '.5s';
          content.style.top = '50px';
          
          pullToRefresh.style.display = 'none';
          refreshing.style.display = '';

          success(function() { // pass down done callback
            pullToRefresh.style.display = '';
            refreshing.style.display = 'none';
            content.style.top = '0';
            content.addEventListener('transitionEnd', removeTransition);
          });

          refresh = false;
        } else if(track) {
          content.style['-webkit-transition-duration'] = '.25s';
          content.style.top = '0';
          content.addEventListener('transitionEnd', removeTransition);

          cancel();
        }

        track = false;
      });

      document.body.addEventListener('touchmove', function(e) {
        var move_to = contentStartY - (startY - e.changedTouches[0].screenY);
        if(move_to > 0) track = true; // start tracking if near the top 
        content.style.top = move_to + 'px';

        if(move_to > 50) {
          refresh = true;
        } else {
          content.style['-webkit-transition'] = '';
          refresh = false;
        }
      });
    }
  };
}();