(function($, undefined) {

var states = { auto: 1, scroll: 1 },
	defOptions = { position: 'top', always: true, margin: 0 };

$.fn.scrollup = function(options) {
	if (!this[0]) {
		return;
	}
	options = $.extend({}, defOptions, options);
	var el = $(this[0]),
		eltop = el.offset().top,
		elheight = el.outerHeight(),
		position = options.position,
		p = options.parent,
		ptop, pheight,
		diff,
		origDisplay = el.css('display');
	if (!eltop && origDisplay === 'inline') {
		origDisplay = function() {
			el.css('display', 'inline');
		};
		el.css('display', 'inline-block');
		eltop = el.offset().top;
	}
	else {
		origDisplay = $.noop;
	}
	if (!p || !p.length) {
		p = el.parents().filter(function() {
			return !!states[$(this).css('overflow-y')];
		}).first();
	}
	if (p.length) {
		ptop = p.offset().top;
	}
	else {
		p = el[0].ownerDocument;
		p = $(p.parentWindow || p.defaultView);
		ptop = 0;
	}
	pheight = p.height();
	diff = eltop - ptop;
	if (elheight >= pheight && position.charAt(position.length - 1) !== '!') {
		options.always = true;
	}
	else {
		var margin = Math.min(options.margin, Math.max(0, pheight - elheight));
		switch(position.split('!')[0]) {
			case 'top':
				diff -= margin;
				break;
			case 'bottom':
				diff += elheight - pheight + margin;
				break;
			case 'center':
				diff += (elheight - pheight) / 2;
				break;
			case 'auto':
				if (eltop > ptop && elheight < pheight) {
					diff += elheight - pheight;
					if (diff <= 0) {
						diff = false;
					}
				}
				break;
		}
	}
	if (diff && (options.always || !(eltop > ptop && (eltop + elheight) < (ptop + pheight)))) {
		if (options.animation) {
			p.animate({ scrollTop: p.scrollTop() + diff }, options.animation);
		}
		else {
			p.scrollTop(p.scrollTop() + diff);
		}
	}
	origDisplay();
	return this;
};

})(jQuery);