$(function() {
	var $window
		, $control
		, $header
		, $footer
		, headerEnd
		, footerHeight

	var hideWhileLoading = function() {
		$control = $('#pageup a');
		$control.hide();
	}
	var init = function() {
		$header = $('header');
		$footer = $('footer');

		footerHeight = $footer.height();
		headerEnd = $header.offset().top + $header.height();

		$window = $(window);
		$window.on('scroll resize', toggleControl);
		toggleControl();
	}

	var toggleControl = function() {
		var scrollTop = $window.scrollTop()
			, scrollVisible = scrollTop + $window.height()
			, footerStart = $footer.offset().top
		if (scrollTop > headerEnd && !$control.is(':visible')) {
			$control.stop(true,true).fadeIn('fast');
		} else if (scrollTop < headerEnd && $control.is(':visible')) {
			$control.stop(true,true).fadeOut('fast');
		}
		$control.parent().css('bottom', (scrollVisible > footerStart) ? (scrollVisible - footerStart) + 'px' : '0');
	}

	$(hideWhileLoading);
	$(window).on('load', init);
});