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// <copyright file="CollectionExtensions.cs" company="GRNET">

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using System.Collections.Concurrent;

namespace Pithos.Core.Agents

{

    using System;

    using System.Collections.Generic;

    using System.Linq;

    using System.Text;

    /// <summary>

    /// Extension methods for collections

    /// </summary>

    public static class CollectionExtensions

    {

        /// <summary>

        /// Remove the first message in a queue that matches the predicate

        /// </summary>

        /// <param name="predicate">The condition to match</param>

        /// <remarks>Removes the first message that matches the predicate by dequeing all 

        /// messages and re-enqueing all except the first matching message</remarks>

        public static void RemoveFirst<TMessage>(this ConcurrentQueue<TMessage> queue, Func<TMessage, bool> predicate)

        {

            //Can this work? Dequeue all items 

            //and then enqueue everything except the filtered items

            //Possible problems: 

            //* A matching item may be dequeued between one TryDequeue and the next

            var temp = new Queue<TMessage>();

            TMessage message;

            var alreadyFound = false;

            while (queue.TryDequeue(out message))

            {

                if (!predicate(message) || alreadyFound)

                    temp.Enqueue(message);

                else

                {

                    alreadyFound = true;

                }

            }

            queue.AddFromEnumerable(temp);

        }

    }

}