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

namespace VPS5.LimitedConnectionsExample {
    public class LimitedConnectionsExample {

        private static Semaphore pool;
        private static int _padding;
        private  static IList<Thread> treads = new List<Thread>();


        public static void DownloadFilesAsync(IEnumerable<string> urls) {
            pool = new Semaphore(0, 10);
            foreach (var url in urls) {
                Thread t = new Thread(DownloadFile);
                t.Start(url);
            }
            foreach (Thread t in treads)
                t.Join();
            pool.Release(10);
        }
        public static void DownloadFile(object url) {
            Console.WriteLine("Thread {0} begins " + "and waits for the semaphore.", (string)url);
            pool.WaitOne();
            treads.Add(Thread.CurrentThread);
            int padding = Interlocked.Add(ref _padding, 100);
            Console.WriteLine("Thread {0} enters the semaphore.", (string)url);
            Thread.Sleep(1000 + padding);
            Console.WriteLine("Thread {0} releases the semaphore.", (string)url);
            pool.Release();
        }


        public static void Main() {
            IList<String> urls = new List<String>();

            for (int i = 1; i < 12; i++) {
                urls.Add(i.ToString());
            }
            DownloadFilesAsync(urls);
        }
    }
}