//based on blog post that I saw here: http://www.sanraul.com/2010/08/01/implementing-doubletap-on-iphones-and-ipads/
(function($){
    $.fn.doubletap = function(fn) {
        return fn ? this.bind('doubletap', fn) : this.trigger('doubletap');
    };

    $.attrFn.doubletap = true;

    $.event.special.doubletap = {
        setup: function(data, namespaces){
            $(this).bind('touchend', $.event.special.doubletap.handler);
        },

        teardown: function(namespaces){
            $(this).unbind('touchend', $.event.special.doubletap.handler);
        },

        handler: function(event){
            var action;

            clearTimeout(action);

            var now       = new Date().getTime();
            //the first time this will make delta a negative number
            var lastTouch = $(this).data('lastTouch') || now + 1;
            var delta     = now - lastTouch;
            var delay     = delay == null? 500 : delay;

            if(delta < delay && delta > 0){
                // After we detct a doubletap, start over
                $(this).data('lastTouch', null);

                // set event type to 'doubletap'
                event.type = 'doubletap';

                // let jQuery handle the triggering of "doubletap" event handlers
                $.event.handle.apply(this, arguments);
            }else{
                $(this).data('lastTouch', now);

                action = setTimeout(function(evt){
                    // set event type to 'doubletap'
                    event.type = 'tap';

                    // let jQuery handle the triggering of "doubletap" event handlers
                    $.event.handle.apply(this, arguments);

                    clearTimeout(action); // clear the timeout
                }, delay, [event]);
            }
        }
    };
})(jQuery);