using System;
using System.Collections.Generic;
using System.Linq;

public class DelayQueue<T>
{
    private List<DelayQueueItem<T>> items = new List<DelayQueueItem<T>>();

    public void Enqueue(T item)
    {
        Enqueue(item, TimeSpan.Zero);
    }

    public void Enqueue(T item, TimeSpan delay)
    {
        items.Add(new DelayQueueItem<T>()
        {
            Value = item,
            ReadyTime = DateTime.Now.Add(delay)
        });
    }

    public T Dequeue()
    {
        return Dequeue(TimeSpan.Zero);
    }

    public T Dequeue(TimeSpan timeout)
    {
        DateTime startTime = DateTime.Now;
        do
        {
            DateTime now = DateTime.Now;

            var item = items.FirstOrDefault(i => i.ReadyTime <= now);
            if (item == null)
                continue;

            items.Remove(item);
            return item.Value;
        }
        while (DateTime.Now - startTime < timeout);

        return default(T);
    }

    public int Count
    { 
        get
        {
            return items.Count;
        } 
    }

    private class DelayQueueItem<T>
    {
        public T Value { get; set; }
        public DateTime ReadyTime { get; set; }
    }
}