NancyFX extension method to get remapped url

Examples.cs

return Response.AsRedirect(request.Url.Remap(scheme="https").ToString());
return Response.AsRedirect(request.Url.Remap("~/Retry/").WithQueryParameter("Message","Invalid blah").ToString());

UrlExtensions.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using Nancy;
using System.Net;
using System.Net.Sockets;

namespace Blommekes.Infrastructure
{
    public static class NancyExtensions
    {
        /// <summary>
        /// Remaps a a url
        /// Replacing a parameter with null keeps the old value intact
        /// Replacing it with an empty string "" removes it
        /// </summary>
        /// <param name="input">The original url to base your new one on
        /// </param>
        /// <param name="path">The path to base your new one on
        ///     * null => keep the original path intact
        ///     * starts with "~/"+[xxx] resolves to base path+[xxx]
        ///     * starts with "/"+[xxx] resolves to root path+[xxx]
        ///     * others map path relative to current path
        /// </param>
        /// <param name="Query">Query to use; null=keep the original one</param>
        /// <param name="fragment">Fragment to use; null=keep the original one</param>
        /// <param name="Scheme">Scheme (i.e. http or https) to use; null=keep the original one</param>
        /// <param name="Hostname">Hostname to use; null=keep the original one</param>
        /// <param name="Port">Port to use; null=keep the original one</param>
        /// <returns></returns>
        public static Url Remap(this Nancy.Url input, string path = null, string query = "", string fragment = "", string scheme = null, string hostname = null, int? port = null)
        {
            var url = new UrlFromV10(); // did this because I'm using nuget/old version
            url.Scheme = scheme ?? input.Scheme;
            url.HostName = hostname ?? input.HostName;
            url.Port = port ?? input.Port;
            if (path == null)
                url.Path = input.Path;
            else
            {
                if (path.StartsWith("~/"))
                {
                    url.Path = path.Substring(1);
                }
                else if (path.StartsWith("/"))
                {
                    url.Path = path;
                    url.BasePath = null;
                }
                else
                {
                    path = "/" + path;
                    if (input.Path == null)
                        url.Path = path;
                    else
                    {
                        if (!input.Path.EndsWith("/"))
                            input.Path += "/";
                        url.Path = input.Path + path;
                    }
                }
            }
            url.Query = query ?? input.Query;
            url.Fragment = fragment ?? input.Fragment;
            return url;


        }

        // Untested
        public static Url WithQueryParameter(this Url url, string name, string value)
        {
            var str = name + "=" + Uri.EscapeDataString(value);
            if (!string.IsNullOrEmpty(url.Query))
                url.Query += "&";
            url.Query = str;
            return url;
        }
    }

    public class UrlFromV10 : Url
    {
        public override string ToString()
        {
            return this.Scheme + "://" +
                GetHostName(this.HostName) +
                GetPort(this.Port) +
                GetCorrectPath(this.BasePath) +
                GetCorrectPath(this.Path) +
                this.Query +
                GetFragment(this.Fragment);
        }

        private static string GetFragment(string fragment)
        {
            return (string.IsNullOrEmpty(fragment)) ? string.Empty : string.Concat("#", fragment);
        }

        private static string GetCorrectPath(string path)
        {
            return (string.IsNullOrEmpty(path) || path.Equals("/")) ? string.Empty : path;
        }

        private static string GetPort(int? port)
        {
            return (!port.HasValue) ?
                string.Empty :
                string.Concat(":", port.Value);
        }

        private static string GetHostName(string hostName)
        {
            IPAddress address;

            if (IPAddress.TryParse(hostName, out address))
            {
                return (address.AddressFamily == AddressFamily.InterNetworkV6)
                           ? string.Concat("[", address.ToString(), "]")
                           : address.ToString();

            }

            return hostName;
        }
    }


}

The module is still under dev, so I know there are some copy/paste errors in there