Reversing an RFC 6570 URI Template

match expression

^(?<part0>/v2/)(?<part1>(?:(?:(?:(?:(?:(?:[a-zA-Z0-9._~-]|(?:%[a-fA-F0-9]{2})))*)|(?:(?:(?:[a-zA-Z0-9._~-]|(?:%[a-fA-F0-9]{2})))*)(?:,(?:(?:(?:[a-zA-Z0-9._~-]|(?:%[a-fA-F0-9]{2})))*))*?|(?:(?:(?:(?:[a-zA-Z0-9._~-]|(?:%[a-fA-F0-9]{2})))*),(?:(?:(?:[a-zA-Z0-9._~-]|(?:%[a-fA-F0-9]{2})))*))(?:,(?:(?:(?:(?:[a-zA-Z0-9._~-]|(?:%[a-fA-F0-9]{2})))*),(?:(?:(?:[a-zA-Z0-9._~-]|(?:%[a-fA-F0-9]{2})))*)))*?)))?)(?<part2>/servers)(?<part3>(?:\?(?:(?:(?:(?:changes%2Dsince)=(?:(?:(?:[a-zA-Z0-9._~-]|(?:%[a-fA-F0-9]{2})))*)|(?:changes%2Dsince)=(?:(?:(?:[a-zA-Z0-9._~-]|(?:%[a-fA-F0-9]{2})))*)(?:,(?:(?:(?:[a-zA-Z0-9._~-]|(?:%[a-fA-F0-9]{2})))*))*?|(?:changes%2Dsince)=(?:(?:(?:(?:[a-zA-Z0-9._~-]|(?:%[a-fA-F0-9]{2})))*),(?:(?:(?:[a-zA-Z0-9._~-]|(?:%[a-fA-F0-9]{2})))*))(?:,(?:(?:(?:(?:[a-zA-Z0-9._~-]|(?:%[a-fA-F0-9]{2})))*),(?:(?:(?:[a-zA-Z0-9._~-]|(?:%[a-fA-F0-9]{2})))*)))*?)|(?:(?:image)=(?:(?:(?:[a-zA-Z0-9._~-]|(?:%[a-fA-F0-9]{2})))*)|(?:image)=(?:(?:(?:[a-zA-Z0-9._~-]|(?:%[a-fA-F0-9]{2})))*)(?:,(?:(?:(?:[a-zA-Z0-9._~-]|(?:%[a-fA-F0-9]{2})))*))*?|(?:image)=(?:(?:(?:(?:[a-zA-Z0-9._~-]|(?:%[a-fA-F0-9]{2})))*),(?:(?:(?:[a-zA-Z0-9._~-]|(?:%[a-fA-F0-9]{2})))*))(?:,(?:(?:(?:(?:[a-zA-Z0-9._~-]|(?:%[a-fA-F0-9]{2})))*),(?:(?:(?:[a-zA-Z0-9._~-]|(?:%[a-fA-F0-9]{2})))*)))*?)|(?:(?:flavor)=(?:(?:(?:[a-zA-Z0-9._~-]|(?:%[a-fA-F0-9]{2})))*)|(?:flavor)=(?:(?:(?:[a-zA-Z0-9._~-]|(?:%[a-fA-F0-9]{2})))*)(?:,(?:(?:(?:[a-zA-Z0-9._~-]|(?:%[a-fA-F0-9]{2})))*))*?|(?:flavor)=(?:(?:(?:(?:[a-zA-Z0-9._~-]|(?:%[a-fA-F0-9]{2})))*),(?:(?:(?:[a-zA-Z0-9._~-]|(?:%[a-fA-F0-9]{2})))*))(?:,(?:(?:(?:(?:[a-zA-Z0-9._~-]|(?:%[a-fA-F0-9]{2})))*),(?:(?:(?:[a-zA-Z0-9._~-]|(?:%[a-fA-F0-9]{2})))*)))*?)|(?:(?:name)=(?:(?:(?:[a-zA-Z0-9._~-]|(?:%[a-fA-F0-9]{2})))*)|(?:name)=(?:(?:(?:[a-zA-Z0-9._~-]|(?:%[a-fA-F0-9]{2})))*)(?:,(?:(?:(?:[a-zA-Z0-9._~-]|(?:%[a-fA-F0-9]{2})))*))*?|(?:name)=(?:(?:(?:(?:[a-zA-Z0-9._~-]|(?:%[a-fA-F0-9]{2})))*),(?:(?:(?:[a-zA-Z0-9._~-]|(?:%[a-fA-F0-9]{2})))*))(?:,(?:(?:(?:(?:[a-zA-Z0-9._~-]|(?:%[a-fA-F0-9]{2})))*),(?:(?:(?:[a-zA-Z0-9._~-]|(?:%[a-fA-F0-9]{2})))*)))*?)|(?:(?:marker)=(?:(?:(?:[a-zA-Z0-9._~-]|(?:%[a-fA-F0-9]{2})))*)|(?:marker)=(?:(?:(?:[a-zA-Z0-9._~-]|(?:%[a-fA-F0-9]{2})))*)(?:,(?:(?:(?:[a-zA-Z0-9._~-]|(?:%[a-fA-F0-9]{2})))*))*?|(?:marker)=(?:(?:(?:(?:[a-zA-Z0-9._~-]|(?:%[a-fA-F0-9]{2})))*),(?:(?:(?:[a-zA-Z0-9._~-]|(?:%[a-fA-F0-9]{2})))*))(?:,(?:(?:(?:(?:[a-zA-Z0-9._~-]|(?:%[a-fA-F0-9]{2})))*),(?:(?:(?:[a-zA-Z0-9._~-]|(?:%[a-fA-F0-9]{2})))*)))*?)|(?:(?:limit)=(?:(?:(?:[a-zA-Z0-9._~-]|(?:%[a-fA-F0-9]{2})))*)|(?:limit)=(?:(?:(?:[a-zA-Z0-9._~-]|(?:%[a-fA-F0-9]{2})))*)(?:,(?:(?:(?:[a-zA-Z0-9._~-]|(?:%[a-fA-F0-9]{2})))*))*?|(?:limit)=(?:(?:(?:(?:[a-zA-Z0-9._~-]|(?:%[a-fA-F0-9]{2})))*),(?:(?:(?:[a-zA-Z0-9._~-]|(?:%[a-fA-F0-9]{2})))*))(?:,(?:(?:(?:(?:[a-zA-Z0-9._~-]|(?:%[a-fA-F0-9]{2})))*),(?:(?:(?:[a-zA-Z0-9._~-]|(?:%[a-fA-F0-9]{2})))*)))*?)|(?:(?:status)=(?:(?:(?:[a-zA-Z0-9._~-]|(?:%[a-fA-F0-9]{2})))*)|(?:status)=(?:(?:(?:[a-zA-Z0-9._~-]|(?:%[a-fA-F0-9]{2})))*)(?:,(?:(?:(?:[a-zA-Z0-9._~-]|(?:%[a-fA-F0-9]{2})))*))*?|(?:status)=(?:(?:(?:(?:[a-zA-Z0-9._~-]|(?:%[a-fA-F0-9]{2})))*),(?:(?:(?:[a-zA-Z0-9._~-]|(?:%[a-fA-F0-9]{2})))*))(?:,(?:(?:(?:(?:[a-zA-Z0-9._~-]|(?:%[a-fA-F0-9]{2})))*),(?:(?:(?:[a-zA-Z0-9._~-]|(?:%[a-fA-F0-9]{2})))*)))*?)|(?:(?:host)=(?:(?:(?:[a-zA-Z0-9._~-]|(?:%[a-fA-F0-9]{2})))*)|(?:host)=(?:(?:(?:[a-zA-Z0-9._~-]|(?:%[a-fA-F0-9]{2})))*)(?:,(?:(?:(?:[a-zA-Z0-9._~-]|(?:%[a-fA-F0-9]{2})))*))*?|(?:host)=(?:(?:(?:(?:[a-zA-Z0-9._~-]|(?:%[a-fA-F0-9]{2})))*),(?:(?:(?:[a-zA-Z0-9._~-]|(?:%[a-fA-F0-9]{2})))*))(?:,(?:(?:(?:(?:[a-zA-Z0-9._~-]|(?:%[a-fA-F0-9]{2})))*),(?:(?:(?:[a-zA-Z0-9._~-]|(?:%[a-fA-F0-9]{2})))*)))*?))(?:&(?:(?:(?:changes%2Dsince)=(?:(?:(?:[a-zA-Z0-9._~-]|(?:%[a-fA-F0-9]{2})))*)|(?:changes%2Dsince)=(?:(?:(?:[a-zA-Z0-9._~-]|(?:%[a-fA-F0-9]{2})))*)(?:,(?:(?:(?:[a-zA-Z0-9._~-]|(?:%[a-fA-F0-9]{2})))*))*?|(?:changes%2Dsince)=(?:(?:(?:(?:[a-zA-Z0-9._~-]|(?:%[a-fA-F0-9]{2})))*),(?:(?:(?:[a-zA-Z0-9._~-]|(?:%[a-fA-F0-9]{2})))*))(?:,(?:(?:(?:(?:[a-zA-Z0-9._~-]|(?:%[a-fA-F0-9]{2})))*),(?:(?:(?:[a-zA-Z0-9._~-]|(?:%[a-fA-F0-9]{2})))*)))*?)|(?:(?:image)=(?:(?:(?:[a-zA-Z0-9._~-]|(?:%[a-fA-F0-9]{2})))*)|(?:image)=(?:(?:(?:[a-zA-Z0-9._~-]|(?:%[a-fA-F0-9]{2})))*)(?:,(?:(?:(?:[a-zA-Z0-9._~-]|(?:%[a-fA-F0-9]{2})))*))*?|(?:image)=(?:(?:(?:(?:[a-zA-Z0-9._~-]|(?:%[a-fA-F0-9]{2})))*),(?:(?:(?:[a-zA-Z0-9._~-]|(?:%[a-fA-F0-9]{2})))*))(?:,(?:(?:(?:(?:[a-zA-Z0-9._~-]|(?:%[a-fA-F0-9]{2})))*),(?:(?:(?:[a-zA-Z0-9._~-]|(?:%[a-fA-F0-9]{2})))*)))*?)|(?:(?:flavor)=(?:(?:(?:[a-zA-Z0-9._~-]|(?:%[a-fA-F0-9]{2})))*)|(?:flavor)=(?:(?:(?:[a-zA-Z0-9._~-]|(?:%[a-fA-F0-9]{2})))*)(?:,(?:(?:(?:[a-zA-Z0-9._~-]|(?:%[a-fA-F0-9]{2})))*))*?|(?:flavor)=(?:(?:(?:(?:[a-zA-Z0-9._~-]|(?:%[a-fA-F0-9]{2})))*),(?:(?:(?:[a-zA-Z0-9._~-]|(?:%[a-fA-F0-9]{2})))*))(?:,(?:(?:(?:(?:[a-zA-Z0-9._~-]|(?:%[a-fA-F0-9]{2})))*),(?:(?:(?:[a-zA-Z0-9._~-]|(?:%[a-fA-F0-9]{2})))*)))*?)|(?:(?:name)=(?:(?:(?:[a-zA-Z0-9._~-]|(?:%[a-fA-F0-9]{2})))*)|(?:name)=(?:(?:(?:[a-zA-Z0-9._~-]|(?:%[a-fA-F0-9]{2})))*)(?:,(?:(?:(?:[a-zA-Z0-9._~-]|(?:%[a-fA-F0-9]{2})))*))*?|(?:name)=(?:(?:(?:(?:[a-zA-Z0-9._~-]|(?:%[a-fA-F0-9]{2})))*),(?:(?:(?:[a-zA-Z0-9._~-]|(?:%[a-fA-F0-9]{2})))*))(?:,(?:(?:(?:(?:[a-zA-Z0-9._~-]|(?:%[a-fA-F0-9]{2})))*),(?:(?:(?:[a-zA-Z0-9._~-]|(?:%[a-fA-F0-9]{2})))*)))*?)|(?:(?:marker)=(?:(?:(?:[a-zA-Z0-9._~-]|(?:%[a-fA-F0-9]{2})))*)|(?:marker)=(?:(?:(?:[a-zA-Z0-9._~-]|(?:%[a-fA-F0-9]{2})))*)(?:,(?:(?:(?:[a-zA-Z0-9._~-]|(?:%[a-fA-F0-9]{2})))*))*?|(?:marker)=(?:(?:(?:(?:[a-zA-Z0-9._~-]|(?:%[a-fA-F0-9]{2})))*),(?:(?:(?:[a-zA-Z0-9._~-]|(?:%[a-fA-F0-9]{2})))*))(?:,(?:(?:(?:(?:[a-zA-Z0-9._~-]|(?:%[a-fA-F0-9]{2})))*),(?:(?:(?:[a-zA-Z0-9._~-]|(?:%[a-fA-F0-9]{2})))*)))*?)|(?:(?:limit)=(?:(?:(?:[a-zA-Z0-9._~-]|(?:%[a-fA-F0-9]{2})))*)|(?:limit)=(?:(?:(?:[a-zA-Z0-9._~-]|(?:%[a-fA-F0-9]{2})))*)(?:,(?:(?:(?:[a-zA-Z0-9._~-]|(?:%[a-fA-F0-9]{2})))*))*?|(?:limit)=(?:(?:(?:(?:[a-zA-Z0-9._~-]|(?:%[a-fA-F0-9]{2})))*),(?:(?:(?:[a-zA-Z0-9._~-]|(?:%[a-fA-F0-9]{2})))*))(?:,(?:(?:(?:(?:[a-zA-Z0-9._~-]|(?:%[a-fA-F0-9]{2})))*),(?:(?:(?:[a-zA-Z0-9._~-]|(?:%[a-fA-F0-9]{2})))*)))*?)|(?:(?:status)=(?:(?:(?:[a-zA-Z0-9._~-]|(?:%[a-fA-F0-9]{2})))*)|(?:status)=(?:(?:(?:[a-zA-Z0-9._~-]|(?:%[a-fA-F0-9]{2})))*)(?:,(?:(?:(?:[a-zA-Z0-9._~-]|(?:%[a-fA-F0-9]{2})))*))*?|(?:status)=(?:(?:(?:(?:[a-zA-Z0-9._~-]|(?:%[a-fA-F0-9]{2})))*),(?:(?:(?:[a-zA-Z0-9._~-]|(?:%[a-fA-F0-9]{2})))*))(?:,(?:(?:(?:(?:[a-zA-Z0-9._~-]|(?:%[a-fA-F0-9]{2})))*),(?:(?:(?:[a-zA-Z0-9._~-]|(?:%[a-fA-F0-9]{2})))*)))*?)|(?:(?:host)=(?:(?:(?:[a-zA-Z0-9._~-]|(?:%[a-fA-F0-9]{2})))*)|(?:host)=(?:(?:(?:[a-zA-Z0-9._~-]|(?:%[a-fA-F0-9]{2})))*)(?:,(?:(?:(?:[a-zA-Z0-9._~-]|(?:%[a-fA-F0-9]{2})))*))*?|(?:host)=(?:(?:(?:(?:[a-zA-Z0-9._~-]|(?:%[a-fA-F0-9]{2})))*),(?:(?:(?:[a-zA-Z0-9._~-]|(?:%[a-fA-F0-9]{2})))*))(?:,(?:(?:(?:(?:[a-zA-Z0-9._~-]|(?:%[a-fA-F0-9]{2})))*),(?:(?:(?:[a-zA-Z0-9._~-]|(?:%[a-fA-F0-9]{2})))*)))*?)))*))?)$

Test.cs

namespace Testing.Rfc6570
{
    using System;
    using Microsoft.VisualStudio.TestTools.UnitTesting;
    using Rackspace.Net;

    [TestClass]
    public class SampleTest
    {
        [TestMethod]
        public void TestComplicatedExpressions()
        {
            string template = "/v2/{tenant_id}/servers{?changes%2Dsince,image,flavor,name,marker,limit,status,host}";
            UriTemplate uriTemplate = new UriTemplate(template);
            Uri uri = new Uri("/v2/855564/servers?image=3&name=Foo&flavor=1", UriKind.Relative);

            UriTemplateMatch match = uriTemplate.Match(uri);
            Assert.IsNotNull(match);
            Assert.AreEqual("3", match.Bindings["image"].Value);
            Assert.AreEqual("Foo", match.Bindings["name"].Value);
            Assert.AreEqual("1", match.Bindings["flavor"].Value);
        }
    }
}

This test passes with the latest code in my working branch. The interesting part is how complicated the regular expression is which is generated internally to support matching a candidate URI to the URI Template (click the View Raw button to see the full text).