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#region
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/* -----------------------------------------------------------------------
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 * <copyright file="PollAgent.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 System.ComponentModel.Composition;
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using System.Diagnostics;
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using System.Diagnostics.Contracts;
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using System.IO;
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using System.Reflection;
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using System.Threading;
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using System.Threading.Tasks;
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using Castle.ActiveRecord;
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using Pithos.Interfaces;
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using Pithos.Network;
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using log4net;
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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;
61

    
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    /// <summary>
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    /// PollAgent periodically polls the server to detect object changes. The agent retrieves a listing of all
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    /// objects and compares it with a previously cached version to detect differences. 
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    /// New files are downloaded, missing files are deleted from the local file system and common files are compared
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    /// to determine the appropriate action
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    /// </summary>
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    [Export]
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    public class PollAgent
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    {
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        private static readonly ILog Log = LogManager.GetLogger(MethodBase.GetCurrentMethod().DeclaringType);
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        [System.ComponentModel.Composition.Import]
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        public IStatusKeeper StatusKeeper { get; set; }
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        [System.ComponentModel.Composition.Import]
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        public IPithosSettings Settings { get; set; }
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        [System.ComponentModel.Composition.Import]
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        public NetworkAgent NetworkAgent { get; set; }
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        public IStatusNotification StatusNotification { get; set; }
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        private bool _firstPoll = true;
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        //The Sync Event signals a manual synchronisation
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        private readonly AsyncManualResetEvent _syncEvent = new AsyncManualResetEvent();
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        private readonly ConcurrentDictionary<string, DateTime> _lastSeen = new ConcurrentDictionary<string, DateTime>();
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        private readonly ConcurrentDictionary<string, AccountInfo> _accounts = new ConcurrentDictionary<string,AccountInfo>();
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        /// <summary>
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        /// Start a manual synchronization
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        /// </summary>
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        public void SynchNow()
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        {            
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            _syncEvent.Set();
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        }
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        /// <summary>
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        /// Remote files are polled periodically. Any changes are processed
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        /// </summary>
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        /// <param name="since"></param>
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        /// <returns></returns>
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        public async Task PollRemoteFiles(DateTime? since = null)
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        {
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            Debug.Assert(Thread.CurrentThread.IsBackground, "Polling Ended up in the main thread!");
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            UpdateStatus(PithosStatus.Syncing);
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            StatusNotification.Notify(new PollNotification());
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            using (ThreadContext.Stacks["Retrieve Remote"].Push("All accounts"))
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            {
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                //If this poll fails, we will retry with the same since value
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                var nextSince = since;
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                try
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                {
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                    //Next time we will check for all changes since the current check minus 1 second
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                    //This is done to ensure there are no discrepancies due to clock differences
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                    var current = DateTime.Now.AddSeconds(-1);
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                    var tasks = from accountInfo in _accounts.Values
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                                select ProcessAccountFiles(accountInfo, since);
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                    await TaskEx.WhenAll(tasks.ToList());
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                    _firstPoll = false;
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                    //Reschedule the poll with the current timestamp as a "since" value
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                    nextSince = current;
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                }
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                catch (Exception ex)
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                {
134
                    Log.ErrorFormat("Error while processing accounts\r\n{0}", ex);
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                    //In case of failure retry with the same "since" value
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                }
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                UpdateStatus(PithosStatus.InSynch);
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                //The multiple try blocks are required because we can't have an await call
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                //inside a finally block
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                //TODO: Find a more elegant solution for reschedulling in the event of an exception
142
                try
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                {
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                    //Wait for the polling interval to pass or the Sync event to be signalled
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                    nextSince = await WaitForScheduledOrManualPoll(nextSince);
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                }
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                finally
148
                {
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                    //Ensure polling is scheduled even in case of error
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                    TaskEx.Run(() => PollRemoteFiles(nextSince));                        
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                }
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            }
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        }
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        /// <summary>
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        /// Wait for the polling period to expire or a manual sync request
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        /// </summary>
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        /// <param name="since"></param>
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        /// <returns></returns>
160
        private async Task<DateTime?> WaitForScheduledOrManualPoll(DateTime? since)
161
        {
162
            var sync = _syncEvent.WaitAsync();
163
            var wait = TaskEx.Delay(TimeSpan.FromSeconds(Settings.PollingInterval), NetworkAgent.CancellationToken);
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            var signaledTask = await TaskEx.WhenAny(sync, wait);
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166
            //Wait for network processing to finish before polling
167
            var pauseTask=NetworkAgent.ProceedEvent.WaitAsync();
168
            await TaskEx.WhenAll(signaledTask, pauseTask);
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170
            //If polling is signalled by SynchNow, ignore the since tag
171
            if (sync.IsCompleted)
172
            {
173
                //TODO: Must convert to AutoReset
174
                _syncEvent.Reset();
175
                return null;
176
            }
177
            return since;
178
        }
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180
        public async Task ProcessAccountFiles(AccountInfo accountInfo, DateTime? since = null)
181
        {
182
            if (accountInfo == null)
183
                throw new ArgumentNullException("accountInfo");
184
            if (String.IsNullOrWhiteSpace(accountInfo.AccountPath))
185
                throw new ArgumentException("The AccountInfo.AccountPath is empty", "accountInfo");
186
            Contract.EndContractBlock();
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188

    
189
            using (log4net.ThreadContext.Stacks["Retrieve Remote"].Push(accountInfo.UserName))
190
            {
191
                await NetworkAgent.GetDeleteAwaiter();
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193
                Log.Info("Scheduled");
194
                var client = new CloudFilesClient(accountInfo);
195

    
196
                //We don't need to check the trash container
197
                var containers = client.ListContainers(accountInfo.UserName)
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                    .Where(c=>c.Name!="trash")
199
                    .ToList();
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201

    
202
                CreateContainerFolders(accountInfo, containers);
203

    
204
                try
205
                {
206
                    //Wait for any deletions to finish
207
                    await NetworkAgent.GetDeleteAwaiter();
208
                    //Get the poll time now. We may miss some deletions but it's better to keep a file that was deleted
209
                    //than delete a file that was created while we were executing the poll                    
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211
                    //Get the list of server objects changed since the last check
212
                    //The name of the container is passed as state in order to create a dictionary of tasks in a subsequent step
213
                    var listObjects = (from container in containers
214
                                       select Task<IList<ObjectInfo>>.Factory.StartNew(_ =>
215
                                             client.ListObjects(accountInfo.UserName, container.Name, since), container.Name)).ToList();
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217
                    var listShared = Task<IList<ObjectInfo>>.Factory.StartNew(_ => 
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                        client.ListSharedObjects(since), "shared");
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                    listObjects.Add(listShared);
220
                    var listTasks = await Task.Factory.WhenAll(listObjects.ToArray());
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222
                    using (log4net.ThreadContext.Stacks["SCHEDULE"].Push("Process Results"))
223
                    {
224
                        var dict = listTasks.ToDictionary(t => t.AsyncState);
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                        //Get all non-trash objects. Remember, the container name is stored in AsyncState
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                        var remoteObjects = from objectList in listTasks
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                                            where (string)objectList.AsyncState != "trash"
229
                                            from obj in objectList.Result
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                                            select obj;
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232
                        var sharedObjects = dict["shared"].Result;
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                        //DON'T process trashed files
235
                        //If some files are deleted and added again to a folder, they will be deleted
236
                        //even though they are new.
237
                        //We would have to check file dates and hashes to ensure that a trashed file
238
                        //can be deleted safely from the local hard drive.
239
                        /*
240
                        //Items with the same name, hash may be both in the container and the trash
241
                        //Don't delete items that exist in the container
242
                        var realTrash = from trash in trashObjects
243
                                        where
244
                                            !remoteObjects.Any(
245
                                                info => info.Name == trash.Name && info.Hash == trash.Hash)
246
                                        select trash;
247
                        ProcessTrashedFiles(accountInfo, realTrash);
248
*/
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250
                        var cleanRemotes = (from info in remoteObjects.Union(sharedObjects)
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                                            let name = info.Name??""
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                                            where !name.EndsWith(".ignore", StringComparison.InvariantCultureIgnoreCase) &&
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                                                  !name.StartsWith(FolderConstants.CacheFolder + "/",
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                                                                   StringComparison.InvariantCultureIgnoreCase)
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                                            select info).ToList();
256

    
257
                        var differencer = _differencer.PostSnapshot(accountInfo, cleanRemotes);
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259
                        ProcessDeletedFiles(accountInfo, differencer.Deleted.FilterDirectlyBelow(SelectiveUris));
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                        // @@@ NEED To add previous state here as well, To compare with previous hash
262

    
263
                        
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                        //Create a list of actions from the remote files
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                        var allActions = MovesToActions(accountInfo,differencer.Moved.FilterDirectlyBelow(SelectiveUris))
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                                        .Union(
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                                        ChangesToActions(accountInfo, differencer.Changed.FilterDirectlyBelow(SelectiveUris)))
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                                        .Union(
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                                        CreatesToActions(accountInfo, differencer.Created.FilterDirectlyBelow(SelectiveUris)));
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272
                        //And remove those that are already being processed by the agent
273
                        var distinctActions = allActions
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                            .Except(NetworkAgent.GetEnumerable(), new PithosMonitor.LocalFileComparer())
275
                            .ToList();
276

    
277
                        //Queue all the actions
278
                        foreach (var message in distinctActions)
279
                        {
280
                            NetworkAgent.Post(message);
281
                        }
282

    
283
                        Log.Info("[LISTENER] End Processing");
284
                    }
285
                }
286
                catch (Exception ex)
287
                {
288
                    Log.ErrorFormat("[FAIL] ListObjects for{0} in ProcessRemoteFiles with {1}", accountInfo.UserName, ex);
289
                    return;
290
                }
291

    
292
                Log.Info("[LISTENER] Finished");
293

    
294
            }
295
        }
296

    
297
        readonly AccountsDifferencer _differencer = new AccountsDifferencer();
298
        private List<Uri> _selectiveUris=new List<Uri>();
299

    
300
        /// <summary>
301
        /// Deletes local files that are not found in the list of cloud files
302
        /// </summary>
303
        /// <param name="accountInfo"></param>
304
        /// <param name="cloudFiles"></param>
305
        private void ProcessDeletedFiles(AccountInfo accountInfo, IEnumerable<ObjectInfo> cloudFiles)
306
        {
307
            if (accountInfo == null)
308
                throw new ArgumentNullException("accountInfo");
309
            if (String.IsNullOrWhiteSpace(accountInfo.AccountPath))
310
                throw new ArgumentException("The AccountInfo.AccountPath is empty", "accountInfo");
311
            if (cloudFiles == null)
312
                throw new ArgumentNullException("cloudFiles");
313
            Contract.EndContractBlock();
314

    
315
            //On the first run
316
            if (_firstPoll)
317
            {
318
                //Only consider files that are not being modified, ie they are in the Unchanged state            
319
                var deleteCandidates = FileState.Queryable.Where(state =>
320
                    state.FilePath.StartsWith(accountInfo.AccountPath)
321
                    && state.FileStatus == FileStatus.Unchanged).ToList();
322

    
323

    
324
                //TODO: filesToDelete must take into account the Others container            
325
                var filesToDelete = (from deleteCandidate in deleteCandidates
326
                                     let localFile = FileInfoExtensions.FromPath(deleteCandidate.FilePath)
327
                                     let relativeFilePath = localFile.AsRelativeTo(accountInfo.AccountPath)
328
                                     where
329
                                         !cloudFiles.Any(r => r.RelativeUrlToFilePath(accountInfo.UserName) == relativeFilePath)
330
                                     select localFile).ToList();
331

    
332

    
333

    
334
                //Set the status of missing files to Conflict
335
                foreach (var item in filesToDelete)
336
                {
337
                    //Try to acquire a gate on the file, to take into account files that have been dequeued
338
                    //and are being processed
339
                    using (var gate = NetworkGate.Acquire(item.FullName, NetworkOperation.Deleting))
340
                    {
341
                        if (gate.Failed)
342
                            continue;
343
                        StatusKeeper.SetFileState(item.FullName, FileStatus.Conflict, FileOverlayStatus.Deleted);
344
                    }
345
                }
346
                UpdateStatus(PithosStatus.HasConflicts);
347
                StatusNotification.NotifyConflicts(filesToDelete, String.Format("{0} local files are missing from Pithos, possibly because they were deleted", filesToDelete.Count));
348
                StatusNotification.NotifyForFiles(filesToDelete, String.Format("{0} files were deleted", filesToDelete.Count), TraceLevel.Info);
349
            }
350
            else
351
            {
352
                var deletedFiles = new List<FileSystemInfo>();
353
                foreach (var objectInfo in cloudFiles)
354
                {
355
                    var relativePath = objectInfo.RelativeUrlToFilePath(accountInfo.UserName);
356
                    var item = FileAgent.GetFileAgent(accountInfo).GetFileSystemInfo(relativePath);
357
                    if (item.Exists)
358
                    {
359
                        if ((item.Attributes & FileAttributes.ReadOnly) == FileAttributes.ReadOnly)
360
                        {
361
                            item.Attributes = item.Attributes & ~FileAttributes.ReadOnly;
362

    
363
                        }
364
                        item.Delete();
365
                        DateTime lastDate;
366
                        _lastSeen.TryRemove(item.FullName, out lastDate);
367
                        deletedFiles.Add(item);
368
                    }
369
                    StatusKeeper.SetFileState(item.FullName, FileStatus.Deleted, FileOverlayStatus.Deleted);
370
                }
371
                StatusNotification.NotifyForFiles(deletedFiles, String.Format("{0} files were deleted", deletedFiles.Count), TraceLevel.Info);
372
            }
373

    
374
        }
375

    
376
        /// <summary>
377
        /// Creates a Sync action for each changed server file
378
        /// </summary>
379
        /// <param name="accountInfo"></param>
380
        /// <param name="changes"></param>
381
        /// <returns></returns>
382
        private IEnumerable<CloudAction> ChangesToActions(AccountInfo accountInfo, IEnumerable<ObjectInfo> changes)
383
        {
384
            if (changes == null)
385
                throw new ArgumentNullException();
386
            Contract.EndContractBlock();
387
            var fileAgent = FileAgent.GetFileAgent(accountInfo);
388

    
389
            //In order to avoid multiple iterations over the files, we iterate only once
390
            //over the remote files
391
            foreach (var objectInfo in changes)
392
            {
393
                var relativePath = objectInfo.RelativeUrlToFilePath(accountInfo.UserName);
394
                //If a directory object already exists, we may need to sync it
395
                if (fileAgent.Exists(relativePath))
396
                {
397
                    var localFile = fileAgent.GetFileSystemInfo(relativePath);
398
                    //We don't need to sync directories
399
                    if (objectInfo.Content_Type == @"application/directory" && localFile is DirectoryInfo)
400
                        continue;
401
                    using (new SessionScope(FlushAction.Never))
402
                    {
403
                        var state = StatusKeeper.GetStateByFilePath(localFile.FullName);
404
                        _lastSeen[localFile.FullName] = DateTime.Now;
405
                        //Common files should be checked on a per-case basis to detect differences, which is newer
406

    
407
                        yield return new CloudAction(accountInfo, CloudActionType.MustSynch,
408
                                                     localFile, objectInfo, state, accountInfo.BlockSize,
409
                                                     accountInfo.BlockHash);
410
                    }
411
                }
412
                else
413
                {
414
                    //Remote files should be downloaded
415
                    yield return new CloudDownloadAction(accountInfo, objectInfo);
416
                }
417
            }
418
        }
419

    
420
        /// <summary>
421
        /// Creates a Local Move action for each moved server file
422
        /// </summary>
423
        /// <param name="accountInfo"></param>
424
        /// <param name="moves"></param>
425
        /// <returns></returns>
426
        private IEnumerable<CloudAction> MovesToActions(AccountInfo accountInfo, IEnumerable<ObjectInfo> moves)
427
        {
428
            if (moves == null)
429
                throw new ArgumentNullException();
430
            Contract.EndContractBlock();
431
            var fileAgent = FileAgent.GetFileAgent(accountInfo);
432

    
433
            //In order to avoid multiple iterations over the files, we iterate only once
434
            //over the remote files
435
            foreach (var objectInfo in moves)
436
            {
437
                var previousRelativepath = objectInfo.Previous.RelativeUrlToFilePath(accountInfo.UserName);
438
                //If the previous file already exists, we can execute a Move operation
439
                if (fileAgent.Exists(previousRelativepath))
440
                {
441
                    var previousFile = fileAgent.GetFileSystemInfo(previousRelativepath);
442
                    using (new SessionScope(FlushAction.Never))
443
                    {
444
                        var state = StatusKeeper.GetStateByFilePath(previousFile.FullName);
445
                        _lastSeen[previousFile.FullName] = DateTime.Now;
446

    
447
                        //For each moved object we need to move both the local file and update                                                
448
                        yield return new CloudAction(accountInfo, CloudActionType.RenameLocal,
449
                                                     previousFile, objectInfo, state, accountInfo.BlockSize,
450
                                                     accountInfo.BlockHash);
451
                        //For modified files, we need to download the changes as well
452
                        if (objectInfo.Hash!=objectInfo.PreviousHash)
453
                            yield return new CloudDownloadAction(accountInfo,objectInfo);
454
                    }
455
                }
456
                //If the previous file does not exist, we need to download it in the new location
457
                else
458
                {
459
                    //Remote files should be downloaded
460
                    yield return new CloudDownloadAction(accountInfo, objectInfo);
461
                }
462
            }
463
        }
464

    
465

    
466
        /// <summary>
467
        /// Creates a download action for each new server file
468
        /// </summary>
469
        /// <param name="accountInfo"></param>
470
        /// <param name="creates"></param>
471
        /// <returns></returns>
472
        private IEnumerable<CloudAction> CreatesToActions(AccountInfo accountInfo, IEnumerable<ObjectInfo> creates)
473
        {
474
            if (creates == null)
475
                throw new ArgumentNullException();
476
            Contract.EndContractBlock();
477
            var fileAgent = FileAgent.GetFileAgent(accountInfo);
478

    
479
            //In order to avoid multiple iterations over the files, we iterate only once
480
            //over the remote files
481
            foreach (var objectInfo in creates)
482
            {
483
                var relativePath = objectInfo.RelativeUrlToFilePath(accountInfo.UserName);
484
                //If the object already exists, we probably have a conflict
485
                if (fileAgent.Exists(relativePath))
486
                {
487
                    //If a directory object already exists, we don't need to perform any other action                    
488
                    var localFile = fileAgent.GetFileSystemInfo(relativePath);
489
                    StatusKeeper.SetFileState(localFile.FullName, FileStatus.Conflict, FileOverlayStatus.Conflict);
490
                }
491
                else
492
                {
493
                    //Remote files should be downloaded
494
                    yield return new CloudDownloadAction(accountInfo, objectInfo);
495
                }
496
            }
497
        }
498

    
499
        /// <summary>
500
        /// Notify the UI to update the visual status
501
        /// </summary>
502
        /// <param name="status"></param>
503
        private void UpdateStatus(PithosStatus status)
504
        {
505
            try
506
            {
507
                StatusKeeper.SetPithosStatus(status);
508
                StatusNotification.Notify(new Notification());
509
            }
510
            catch (Exception exc)
511
            {
512
                //Failure is not critical, just log it
513
                Log.Warn("Error while updating status", exc);
514
            }
515
        }
516

    
517
        private static void CreateContainerFolders(AccountInfo accountInfo, IEnumerable<ContainerInfo> containers)
518
        {
519
            var containerPaths = from container in containers
520
                                 let containerPath = Path.Combine(accountInfo.AccountPath, container.Name)
521
                                 where container.Name != FolderConstants.TrashContainer && !Directory.Exists(containerPath)
522
                                 select containerPath;
523

    
524
            foreach (var path in containerPaths)
525
            {
526
                Directory.CreateDirectory(path);
527
            }
528
        }
529

    
530
        public void SetSyncUris(Uri[] uris)
531
        {            
532
            SelectiveUris=uris.ToList();
533
        }
534

    
535
        protected List<Uri> SelectiveUris
536
        {
537
            get { return _selectiveUris;}
538
            set { _selectiveUris = value; }
539
        }
540

    
541
        public void AddAccount(AccountInfo accountInfo)
542
        {
543
            //Avoid adding a duplicate accountInfo
544
            _accounts.TryAdd(accountInfo.UserName, accountInfo);
545
        }
546

    
547
        public void RemoveAccount(AccountInfo accountInfo)
548
        {
549
            AccountInfo account;
550
            _accounts.TryRemove(accountInfo.UserName,out account);
551
        }
552
    }
553
}