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#region
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/* -----------------------------------------------------------------------
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 * <copyright file="SnapshotDifferencer.cs" company="GRNet">
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 * 
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 * Copyright 2011-2012 GRNET S.A. All rights reserved.
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 *
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 * Redistribution and use in source and binary forms, with or
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 * without modification, are permitted provided that the following
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 * conditions are met:
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 *
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 *   1. Redistributions of source code must retain the above
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 *      copyright notice, this list of conditions and the following
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 *      disclaimer.
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 *
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 *   2. Redistributions in binary form must reproduce the above
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 *      copyright notice, this list of conditions and the following
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 *      disclaimer in the documentation and/or other materials
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 *      provided with the distribution.
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 *
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 *
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 * THIS SOFTWARE IS PROVIDED BY GRNET S.A. ``AS IS'' AND ANY EXPRESS
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 * OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
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 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
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 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL GRNET S.A OR
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 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
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 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
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 * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
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 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
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 * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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 * POSSIBILITY OF SUCH DAMAGE.
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 *
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 * The views and conclusions contained in the software and
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 * documentation are those of the authors and should not be
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 * interpreted as representing official policies, either expressed
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 * or implied, of GRNET S.A.
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 * </copyright>
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 * -----------------------------------------------------------------------
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 */
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#endregion
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using System.Collections.Concurrent;
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using Pithos.Interfaces;
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using Pithos.Network;
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namespace Pithos.Core.Agents
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{
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    using System;
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    using System.Collections.Generic;
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    using System.Linq;
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    using System.Text;
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    /// <summary>
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    /// TODO: Update summary.
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    /// </summary>
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    public class SnapshotDifferencer
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    {
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        private IEnumerable<ObjectInfo> _previous;
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        private IEnumerable<ObjectInfo> _current;
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        private static ObjectInfo[] _empty = new ObjectInfo[0];
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        private ObjectInfoComparer _comparer = new ObjectInfoComparer();
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        public SnapshotDifferencer()
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        {
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            _previous = new List<ObjectInfo>();
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            _current= new List<ObjectInfo>();
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        }
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        public SnapshotDifferencer(IEnumerable<ObjectInfo> previous,IEnumerable<ObjectInfo> current  )
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        {
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            _previous = previous ?? new List<ObjectInfo>();
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            _current= current ?? new List<ObjectInfo>();
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        }
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        public SnapshotDifferencer Post(IEnumerable<ObjectInfo> list)
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        {
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            _previous = _current;
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            if (list == null)
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            {
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                _current = new List<ObjectInfo>();
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                return this;
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            }
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            //Replace any NoModification entries with previous values that have
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            //the same account, container and possibly, folder
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            _current=list.Replace(
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                info => info is NoModificationInfo, 
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                noMod => from info in _previous
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                        where 
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                            info.Account==noMod.Account 
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                            && info.Container==noMod.Container 
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                            //If the NoModification specifies a folder, use it to match items below this folder
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                            && (noMod.Name==null || info.Name.StartsWith(noMod.Name))
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                        select info);
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            return this;
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        }
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        public IEnumerable<ObjectInfo> Deleted
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        {
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            get { return _previous.Except(_current,_comparer); }
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        }
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        public IEnumerable<ObjectInfo> Created
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        {
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            get { return _current.Except(_previous,_comparer); }
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        }
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        public IEnumerable<ObjectInfo> Changed
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        {
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            get
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            {
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                var changes = from newItem in _current 
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                              let oldItem=_previous.FirstOrDefault(old=>_comparer.Equals(old,newItem))
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                              where oldItem !=null &&
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                                    newItem.Hash != oldItem.Hash
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                              select newItem;
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                return changes;
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            }
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        }
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        public IEnumerable<ObjectInfo> Unchanged
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        {
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            get
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            {
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                var unChanged = from newItem in _current
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                              let oldItem = _previous.FirstOrDefault(old => _comparer.Equals(old, newItem))
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                              where oldItem != null &&
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                                    newItem.Hash == oldItem.Hash
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                              select newItem;
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                return unChanged;
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            }
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        }
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    }
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    public class AccountsDifferencer
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    {
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        ConcurrentDictionary<string, SnapshotDifferencer> _differencers = new ConcurrentDictionary<string, SnapshotDifferencer>();
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        public ConcurrentDictionary<string, SnapshotDifferencer> Differencers { get { return _differencers; } }
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        public SnapshotDifferencer PostSnapshot(AccountInfo accountInfo, List<ObjectInfo> cleanRemotes)
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        {
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            SnapshotDifferencer differencer;
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            if (!_differencers.TryGetValue(accountInfo.UserName, out differencer))
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            {
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                differencer = new SnapshotDifferencer();
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                _differencers[accountInfo.UserName] = differencer;
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            }
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            differencer.Post(cleanRemotes);
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            return differencer;
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        }
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    }
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}