Tooltip stay in viewport

I have this piece of awesome tooltip jQuery - Open Source

Code:

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(function($){

  $.fn.BAToolTip = function(options) { 
 
        //set up default options
        var defaults = {
                tipClass: 'tip', //the class name for your tip
                tipFadeEasing: 'easeOutQuint', //easing method
                tipFadeDuration: 200, //fade duration
                tipOpacity: 1, //opacity of tip when mouseover
                tipOffset: 10 //offset the tip relative to mouse cursor in pixels
        };
         
        var opts = $.extend({}, defaults, options);       

    return this.each(function() { 
          var $this = $(this);
         
          $this.mousemove(function(e){
                  var parentElementOffset = $this.parent().offset();
                  var xPos = e.pageX - parentElementOffset.left;
                  var yPos = e.pageY - parentElementOffset.top;
                  $(this).parent().find('.'+opts.tipClass).css({'top': yPos+opts.tipOffset, 'left' : xPos+opts.tipOffset});
                  $(this).parent().find('.'+opts.tipClass).css('display', 'block').stop().animate({opacity:opts.tipOpacity},{duration:opts.tipFadeDuration, easing: opts.tipFadeEasing});
          })
         
          $this.mouseout(function(){
                  $('.'+opts.tipClass).stop().animate({opacity:0},{duration:opts.tipFadeDuration, easing: opts.tipFadeEasing, complete: function(){ $(this).css('display', 'none') } });
          })
       
    });
  };
})(jQuery);

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- this tooltip suits for what I need , and its also the only tooltip that can grab content from multiple div's with the same class , also it's fully themeable via css

There is only 1 flaw within , and that is it won't stay in viewport , it stays in one place , and if the page is small you can't see anything of it.

Is there any ways to implement a functionality to always stay in viewport no matter what like other tooltips?