using System;
using System.Threading;
using System.Collections.Generic;
namespace ln.http.threads
{
    public delegate void JobDelegate();

    public class Pool
    {
        public int Timeout { get; set; } = 15000;

        ISet<Thread> threads = new HashSet<Thread>();
        Queue<JobDelegate> queuedJobs = new Queue<JobDelegate>();
        HashSet<Thread> idleThreads = new HashSet<Thread>();

        public Pool()
        {
        }

        private void AllocateThread()
        {
            Thread thread = new Thread(pool_thread);
            thread.Start();
        }

        public void Enqueue(JobDelegate job)
        {
            lock (this)
            {
                queuedJobs.Enqueue(job);

                if (idleThreads.Count == 0)
                {
                    AllocateThread();
                }
                else
                {
                    Monitor.Pulse(this);
                }
            }
        }


        private void pool_thread()
        {
            Thread me = Thread.CurrentThread;

            try
            {
                JobDelegate job = null;
                do
                {
                    lock (this)
                    {
                        if (queuedJobs.Count == 0)
                        {
                            idleThreads.Add(me);
                            bool s = Monitor.Wait(this, Timeout);
                            idleThreads.Remove(me);
                            if (!s)
                                break;
                        }
                        job = queuedJobs.Dequeue();
                    }

                    job();

                } while (true);

            }
            catch (Exception e)
            {
                Console.WriteLine("Exception in worker thread: {0}", e);
            }

            lock (this)
            {
                threads.Remove(me);
            }
        }
    }
}