OpenTween.nicoms.Shorten C# (CSharp) Method

        public static string Shorten(string url)
        {
            //整形（http(s)://を削除）
            if (url.Length > 7 && url.Length < 128 && url.StartsWith("http://", StringComparison.OrdinalIgnoreCase))
            {
                url = url.Substring(7);
            }
            else
            {
                return url;
            }

            foreach (var nv in _nicovideo)
            {
                if (url.StartsWith(nv, StringComparison.Ordinal))
                    return string.Format("{0}{1}", "http://nico.ms/", url.Substring(nv.Length));
            }

            var i = url.IndexOf("nicovideo.jp/user/", StringComparison.OrdinalIgnoreCase);
            if (i == 0 || i == 4) return string.Format("{0}{1}", "http://nico.ms/", url.Substring(13 + i));

            i = url.IndexOf("nicovideo.jp/mylist/", StringComparison.OrdinalIgnoreCase);
            if (i == 0 || i == 4) return string.Format("{0}{1}", "http://nico.ms/", url.Substring(13 + i));

            i = url.IndexOf("seiga.nicovideo.jp/watch/", StringComparison.OrdinalIgnoreCase);
            if (i == 0) return string.Format("{0}{1}", "http://nico.ms/", url.Substring(25));

            return "http://" + url;
        }
    }