(function($) {
    var currentRadius, multiplier;

    function parseOptions(options) {
        return {
            RADIUS: (options.radius || 20),
            DURATION: (options.duration || 500),
            TEXT_COLOR: (options.textColor || '#fff'),
            HALO_COLOR: (options.haloColor || '#777')
        }
    }

    function currentRadius(elem) {
        if (prop = elem.style['text-shadow']) {
            return parseInt(prop.match(/0 0 (\d+)px/));
        } else {
            return 0;
        }
    }

    function stepTextShadow(fx) {
        if (fx.state == 0) {
            fx.start = currentRadius(fx.elem);
        }

        updatedRadius = fx.end.begin ?
      Math.max(Math.min(parseInt(fx.end.radius * fx.pos))) :
      Math.max(Math.min(parseInt(fx.end.radius - (fx.end.radius * fx.pos))))

        if (fx.end.begin || (fx.state < 1)) {
            fx.elem.style['text-shadow'] = fx.end.color + ' 0 0 ' + updatedRadius + 'px';
        } else {
            fx.elem.style['text-shadow'] = 'none';
        }
    }

    function addGlow(opts) {
        var opts = parseOptions(opts || {});

        function startGlow() {
            $(this).animate({
                color: opts.TEXT_COLOR,
                textShadow: {
                    begin: true,
                    color: opts.HALO_COLOR,
                    radius: opts.RADIUS
                }
            }, opts.DURATION);
        }

        function startFade() {
            $(this).animate({
                color: $(this).data('glow.originColor'),
                textShadow: {
                    begin: false,
                    color: opts.HALO_COLOR,
                    radius: opts.RADIUS
                }
            }, opts.DURATION);
        }

        with ($(this)) {
            bind('mouseenter', startGlow);
            bind('mouseleave', startFade);
            data('glow.originColor', css('color'));
        }

        return this;
    }

    $.fx.step['textShadow'] = stepTextShadow;
    $.fn.addGlow = addGlow;
})(jQuery);