owin dynamic routing idea

DynamicRouting.cs

// WARNING this gist is an example with potentially non-compilable code!

using System;
using System.Collections.Generic;
using System.Threading.Tasks;

namespace Owin.Routing
{
	using AppFunc = Func<IDictionary<string, object>, Task>;

	static class DynamicRouter
	{
		/// <summary>
		/// Selects OWIN pipeline at runtime.
		/// </summary>
		/// <param name="app">holds initial owin pipeline state</param>
		/// <param name="selector">function to build new owin pipeline</param>
		/// <param name="routesChanged">signal to rebuild pipeline</param>
		/// <returns></returns>
		public static IAppBuilder UseDynamicRouting(this IAppBuilder app,
			Func<IAppBuilder, IAppBuilder> selector,
			IObservable<bool> routesChanged)
		{
			var api = selector(app);
			var handler = (AppFunc) api.Build(typeof(AppFunc));

			routesChanged.Subscribe(_ =>
			{
				api = selector(app);
				handler = (AppFunc) api.Build(typeof(AppFunc));
			});

			return app.Use((ctx, next) => handler(ctx.Environment));
		}
	}
}

Sorry ... I am having a hard time understanding how to implement this ...