using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading;

namespace ConsoleApplication1
{
    class Program
    {
        static void Main(string[] args)
        {
            new Thread(FastClient1_OnId1).Start();
            new Thread(FastClient2_OnId1).Start();
            new Thread(SlowClient1_OnId2).Start();

            Console.ReadKey();
        }

        /// <summary>
        /// Long running from the beginning
        /// </summary>
        static void SlowClient1_OnId2()
        {
            Thread.Sleep(500); // allow a fast thread to start ...

            ConcurrencyEmergencyManager.RequestAndWaitForEmergencyGrant(2);
            Console.WriteLine("{0} Slow client works on id 2", DateTime.Now);
            Thread.Sleep(15000);
            Console.WriteLine("{0} Slow client finsihed on id 2", DateTime.Now);
            ConcurrencyEmergencyManager.ReleaseGrantForEmergency(2);
        }

        static void FastClient1_OnId1()
        {
            for (int i = 0; i < 4; i++)
            {
                ConcurrencyEmergencyManager.RequestAndWaitForEmergencyGrant(1);
                Console.WriteLine("{0} Client 1 works on id 1", DateTime.Now);
                Thread.Sleep(2000);
                ConcurrencyEmergencyManager.ReleaseGrantForEmergency(1);
            }
        }

        static void FastClient2_OnId1()
        {
            for (int i = 0; i < 4; i++)
            {
                ConcurrencyEmergencyManager.RequestAndWaitForEmergencyGrant(1);
                Console.WriteLine("{0} Client 2 works on id 1", DateTime.Now);
                Thread.Sleep(2500);
                ConcurrencyEmergencyManager.ReleaseGrantForEmergency(1);
            }
        }
    }

    public static class ConcurrencyEmergencyManager
    {
        private static object _syncRootGrant = new object();
        private static List<int> _emergenciesCurrentInUseList = new List<int>();

        public static void RequestAndWaitForEmergencyGrant(int emergencyId)
        {
            lock (_syncRootGrant)
            {
                while (_emergenciesCurrentInUseList.Where(i => i == emergencyId).Count() != 0)
                {
                    Monitor.Wait(_syncRootGrant);
                }

                _emergenciesCurrentInUseList.Add(emergencyId);
            }
        }

        public static void ReleaseGrantForEmergency(int emergencyId)
        {
            lock (_syncRootGrant)
            {
                _emergenciesCurrentInUseList.Remove(emergencyId);

                Monitor.PulseAll(_syncRootGrant);
            }
        }
    }
}