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#region

/* -----------------------------------------------------------------------

 * <copyright file="CollectionExtensions.cs" company="GRNet">

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#endregion

using System.Collections.Concurrent;

using System.Diagnostics.Contracts;

using Pithos.Interfaces;

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);

        }

        public static IEnumerable<ObjectInfo> FilterBelow(this IEnumerable<ObjectInfo> infos,List<Uri> filterUris  )

        {

            if (filterUris == null)

                return infos;

            if (filterUris.Count == 0)

                return infos;

            //Allow all objects whose Uris start with any of the filters            

            var filteredUris = from info in infos

                                  where filterUris.Any(f => info.Uri.IsAtOrBelow(f)) 

                                  select info;            

            return filteredUris;

        }

        public static IEnumerable<ObjectInfo> FilterDirectlyBelow(this IEnumerable<ObjectInfo> infos,List<Uri> filterUris  )

        {

            if (filterUris == null)

                return infos;

            if (filterUris.Count == 0)

                return infos;

            //Allow all objects whose Uris start with any of the filters            

            var filteredUris = from info in infos

                                  where filterUris.Any(f => info.Uri.IsAtOrDirectlyBelow(f)) 

                                  select info;            

            return filteredUris;

        }

        public static bool IsAtOrBelow(this Uri target,Uri root)

        {

            Contract.Requires(root != null);

            Contract.Requires(target != null);

            var targetSegments = target.Segments;

            var rootSegments = root.Segments;

            return InnerAtOrBelow(targetSegments, rootSegments);

        }

        private static bool InnerAtOrBelow(string[] targetSegments, string[] rootSegments)

        {

            //If the uri is shorter than the root, no point in comparing

            if (targetSegments.Length < rootSegments.Length)

                return false;

            //If the uri is below the root, it should match the root's segments one by one

            //If there is any root segment that doesn't match its corresponding target segment,

            //the target is not below the root

            var mismatch = rootSegments

                .Where((t, i) => !String.Equals(targetSegments[i], t))

                .Any();

            return !mismatch;

        }

        public static bool IsAtOrDirectlyBelow(this Uri target,Uri root)

        {

            Contract.Requires(root!=null);

            Contract.Requires(target!=null);

            return

                //If the target is directly below the root, it will have exactly 

                //one segment more than the root            

                target.Segments.Length == root.Segments.Length + 1

                //Ensure that the candidate target is indeed below the root

                && target.IsAtOrBelow(root);

        }

        public static bool IsAtOrBelow(this string targetPath, string rootPath)

        {

            Contract.Requires(!String.IsNullOrWhiteSpace(targetPath));

            Contract.Requires(!String.IsNullOrWhiteSpace(rootPath));

            var targetSegments = targetPath.Split('\\');

            var rootSegments = rootPath.Split('\\');

            return InnerAtOrBelow(targetSegments, rootSegments);

        }

        public static bool IsAtOrDirectlyBelow(this string targetPath, string rootPath)

        {

            Contract.Requires(!String.IsNullOrWhiteSpace(targetPath));

            Contract.Requires(!String.IsNullOrWhiteSpace(rootPath));

            var targetSegments = targetPath.Split('\\');

            var rootSegments = rootPath.Split('\\');

            return

                //If the target is directly below the root, it will have exactly 

                //one segment more than the root            

                targetSegments.Length == rootSegments.Length + 1

                //Ensure that the candidate target is indeed below the root

                && InnerAtOrBelow(targetSegments, rootSegments);

        }

    }

}