#region
/* -----------------------------------------------------------------------
 * <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
            //DON'T FORGET that Uri segments include the slashes. Must remove them to ensure proper checks
            var mismatch = rootSegments
                .Where((t, i) => !String.Equals(targetSegments[i].TrimEnd('/'), t.TrimEnd('/')))
                .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();

            if (target.Equals(root))
                return true;
            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();

            if (targetPath==rootPath)
                return true;
            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;
        }
    }


}