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#region

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

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

 * 

 * Copyright 2011-2012 GRNET S.A. All rights reserved.

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 * Redistribution and use in source and binary forms, with or

 * without modification, are permitted provided that the following

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 *   1. Redistributions of source code must retain the above

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 *   2. Redistributions in binary form must reproduce the above

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 *

 * THIS SOFTWARE IS PROVIDED BY GRNET S.A. ``AS IS'' AND ANY EXPRESS

 * OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED

 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR

 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL GRNET S.A OR

 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,

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 * -----------------------------------------------------------------------

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#endregion

using System.Collections.Concurrent;

using Pithos.Interfaces;

using Pithos.Network;

namespace Pithos.Core.Agents

{

    using System;

    using System.Collections.Generic;

    using System.Linq;

    using System.Text;

    /// <summary>

    /// TODO: Update summary.

    /// </summary>

    public class SnapshotDifferencer

    {

        private IEnumerable<ObjectInfo> _previous;

        private IEnumerable<ObjectInfo> _current;

        private static ObjectInfo[] _empty = new ObjectInfo[0];

        private ObjectInfoComparer _comparer = new ObjectInfoComparer();

        public SnapshotDifferencer()

        {

            _previous = new List<ObjectInfo>();

            _current= new List<ObjectInfo>();

        }

        public SnapshotDifferencer(IEnumerable<ObjectInfo> previous,IEnumerable<ObjectInfo> current  )

        {

            _previous = previous ?? new List<ObjectInfo>();

            _current= current ?? new List<ObjectInfo>();

        }

        public SnapshotDifferencer Post(IEnumerable<ObjectInfo> list)

        {

            _previous = _current;

            if (list == null)

            {

                _current = new List<ObjectInfo>();

                return this;

            }

            //The previous values that correspond to a NoModification object

            //have the same account, container and possibly the same folder

            Func<ObjectInfo, ObjectInfo, bool> correspondsTo = (info, noMod) => 

                info.Account == noMod.Account

                && info.Container == noMod.Container

                && (noMod.Name == null || info.Name.StartsWith(noMod.Name));

            //Replace any NoModification entries with previous values that have

            //the same account, container and possibly, folder

            _current=list.Replace(

                info => info is NoModificationInfo, 

                noMod => _previous.Where(info => correspondsTo(info, noMod)))

                .ToList();

            return this;

        }

        public IEnumerable<ObjectInfo> Deleted

        {

            get { return _previous.Except(_current,_comparer); }

        }

        public IEnumerable<ObjectInfo> Created

        {

            get { return _current.Except(_previous,_comparer); }

        }

        public IEnumerable<ObjectInfo> Changed

        {

            get

            {

                var changes = from newItem in _current 

                              let oldItem=_previous.FirstOrDefault(old=>_comparer.Equals(old,newItem))

                              where oldItem !=null &&

                                    newItem.Hash != oldItem.Hash

                              select newItem;

                return changes;

            }

        }

        public IEnumerable<ObjectInfo> Unchanged

        {

            get

            {

                var unChanged = from newItem in _current

                              let oldItem = _previous.FirstOrDefault(old => _comparer.Equals(old, newItem))

                              where oldItem != null &&

                                    newItem.Hash == oldItem.Hash

                              select newItem;

                return unChanged;

            }

        }

    }

    public class AccountsDifferencer

    {

        ConcurrentDictionary<string, SnapshotDifferencer> _differencers = new ConcurrentDictionary<string, SnapshotDifferencer>();

        public ConcurrentDictionary<string, SnapshotDifferencer> Differencers { get { return _differencers; } }

        public SnapshotDifferencer PostSnapshot(AccountInfo accountInfo, List<ObjectInfo> cleanRemotes)

        {

            SnapshotDifferencer differencer;

            if (!_differencers.TryGetValue(accountInfo.UserName, out differencer))

            {

                differencer = new SnapshotDifferencer();

                _differencers[accountInfo.UserName] = differencer;

            }

            differencer.Post(cleanRemotes);

            return differencer;

        }

    }

}