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

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#endregion

using System.Collections.Concurrent;

using System.Diagnostics.Contracts;

using Pithos.Interfaces;

using System;

using System.Collections.Generic;

using System.Linq;

namespace Pithos.Core.Agents

{

    /// <summary>

    /// Extension methods for collections

    /// </summary>

    public static class CollectionExtensions

    {

        public static IEnumerable<T> Replace<T>(this IEnumerable<T> list,Func<T,bool> match, Func<T,IEnumerable<T>> generate)

        {

            foreach (var item in list)

            {

                if (match(item))

                    foreach (var newItem in generate(item))

                    {

                        yield return newItem;

                    }

                else

                    yield return item;

            }

        }

        /// <summary>

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

        /// </summary>

        /// <param name="queue">The queue</param>

        /// <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);

        }

        /// <summary>

        /// Return only the info objects that are below one of the filter Uris

        /// </summary>

        /// <param name="infos">ObjectInfo items to filter</param>

        /// <param name="filterUris">List of filter Uris</param>

        /// <returns>An enumerable of ObjectInfo items. If the list of filter Uris is empty or null, the original list is returned</returns>

        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;

        }

        /// <summary>

        /// Return only the info objects that are directly below one of the filter Uris

        /// </summary>

        /// <param name="infos">ObjectInfo items to filter</param>

        /// <param name="filterUris">List of filter Uris</param>

        /// <returns>An enumerable of ObjectInfo items. If the list of filter Uris is empty or null, the original list is returned</returns>

        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;

        }

        /// <summary>

        /// Checkes whether a Uri is below a root Uri

        /// </summary>

        /// <param name="target"></param>

        /// <param name="root"></param>

        /// <returns></returns>

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

        {

            if(root == null)

                throw new ArgumentNullException("root");

            if(target == null)

                throw new ArgumentNullException("target");

            Contract.EndContractBlock();

            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;

        }

        /// <summary>

        /// Checks whether a Uri is directly below a root Uri

        /// </summary>

        /// <param name="target"></param>

        /// <param name="root"></param>

        /// <returns></returns>

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

        {

            if (root==null)

                throw new ArgumentNullException("root");

            if (target==null)

                throw new ArgumentNullException("target");

            Contract.EndContractBlock();

            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);

        }

        /// <summary>

        /// Checkes whether a file path is below a root path

        /// </summary>

        /// <param name="targetPath"></param>

        /// <param name="rootPath"></param>

        /// <returns></returns>

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

        {

            if(String.IsNullOrWhiteSpace(targetPath))

                throw new ArgumentNullException("targetPath");

            if(String.IsNullOrWhiteSpace(rootPath))

                throw new ArgumentNullException("rootPath");

            Contract.EndContractBlock();

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

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

            return InnerAtOrBelow(targetSegments, rootSegments);

        }

        /// <summary>

        /// Checks whether a file path is directly below a root path

        /// </summary>

        /// <param name="targetPath"></param>

        /// <param name="rootPath"></param>

        /// <returns></returns>

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

        {

            if (String.IsNullOrWhiteSpace(targetPath))

                throw new ArgumentNullException("targetPath");

            if (String.IsNullOrWhiteSpace(rootPath))

                throw new ArgumentNullException("rootPath");

            Contract.EndContractBlock();

            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);

        }

        /// <summary>

        /// Returns the part of the target string that comes after the prefix string.

        /// The target is not modified if it doesn't start with the prefix string

        /// </summary>

        /// <param name="target"></param>

        /// <param name="prefix"></param>

        /// <returns></returns>

        public static string After(this string target,string prefix)

        {            

            //If the prefix or the target are empty, return the target

            if (String.IsNullOrWhiteSpace(prefix) || String.IsNullOrWhiteSpace(target))

                return target;

            if (target.StartsWith(prefix))

                return target.Remove(0,prefix.Length);

            return target;

        }

    }

}