using System;

using System.Collections.Generic;

using System.Net;

using System.Reactive.Linq;

using System.Threading;

using System.Threading.Tasks;

​

namespace ConsoleApplication7

{

    internal class Program

    {

        private static void Main(string[] args)

        {

            //This guy handles the WebRequests in the background

            var handler = new Handler();

            Task.Run( () => handler.Start());

​

            //This guy handles the user input and adding the URLS to handler

            while (true)

            {

                Console.WriteLine("Give me an URL!");

               var newUrl = Console.ReadLine();

                handler.AddUrl(newUrl);

            }

        }

​

        private class Handler : IObserver<string>

        {

​

            private readonly List<string> urls = new List<string>();

​

            //One way to cast a List into an Observable

            //TODO: what are other ways?

            private IEnumerable<string> UrlsAsObservable()

            {

                for (;;)

                {

                    Thread.Sleep(1000);

                    if (urls.Count <= 0) continue;

                    yield return urls[0];

                    urls.RemoveAt(0);

                }

            }

​

            public void Start()

            {

               UrlsAsObservable().ToObservable().Subscribe(this);

            }

​

            async void IObserver<string>.OnNext(string value)

            {

                try

                {

                    if (value == null)

                    {

                        return;

                    }

                    var request = WebRequest.CreateHttp(value);

                    var response = await request.GetResponseAsync();

                    //do something with response

                    Console.WriteLine("Content-Length of " + value + ": " + response.ContentLength );

                }

                catch (UriFormatException ex)

                {

                    Console.WriteLine("Ugly URI!");

                }

                catch (WebException ex)

                {

                    Console.WriteLine("WebException in webrequest, going to Retry..");

                    Retry(value);

                }

                catch (Exception ex)

                {

                    Console.WriteLine("Unknown exception caught!");

                }

            }

​

​

            void IObserver<string>.OnError(Exception ex)

            {

                Console.WriteLine("OnError Exception! " + ex);

            }

​

            void IObserver<string>.OnCompleted()

            {

                Console.WriteLine( "OnCompleted Ready!");

            }

​

​

            internal void AddUrl(string newUrl)

            {

                urls.Add( newUrl );

            }

​

            private async void Retry(string value)

            {

                //Add back to queue in 5 seconds

                await Task.Delay(5000);

                urls.Add(value);

            }

        }

    }

}

​