Synnefo » Pithos MS Client

using System;

using System.Collections.Generic;

using System.ComponentModel;

using System.ComponentModel.Composition;

using System.Diagnostics;

using System.Diagnostics.Contracts;

using System.IO;

using System.Linq;

using System.Net;

using System.Text;

using System.Threading;

using System.Threading.Tasks;

using Pithos.Interfaces;

using Pithos.Network;

using log4net;

namespace Pithos.Core.Agents

{

    [Export]

    public class NetworkAgent

    {

        private Agent<CloudAction> _agent;

        [Import]

        public IStatusKeeper StatusKeeper { get; set; }

        public IStatusNotification StatusNotification { get; set; }

/*

        [Import]

        public FileAgent FileAgent {get;set;}

*/

       /* public int BlockSize { get; set; }

        public string BlockHash { get; set; }*/

        private static readonly ILog Log = LogManager.GetLogger("NetworkAgent");

        private List<AccountInfo> _accounts=new List<AccountInfo>();

        public void Start(/*int blockSize, string blockHash*/)

        {

/*

            if (blockSize<0)

                throw new ArgumentOutOfRangeException("blockSize");

            if (String.IsNullOrWhiteSpace(blockHash))

                throw new ArgumentOutOfRangeException("blockHash");

            Contract.EndContractBlock();

*/

/*

            BlockSize = blockSize;

            BlockHash = blockHash;

*/

            _agent = Agent<CloudAction>.Start(inbox =>

            {

                Action loop = null;

                loop = () =>

                {

                    var message = inbox.Receive();

                    var process=message.Then(Process,inbox.CancellationToken);

                    inbox.LoopAsync(process, loop);

                };

                loop();

            });

        }

        private Task<object> Process(CloudAction action)

        {

            if (action == null)

                throw new ArgumentNullException("action");

            if (action.AccountInfo==null)

                throw new ArgumentException("The action.AccountInfo is empty","action");

            Contract.EndContractBlock();

            var accountInfo = action.AccountInfo;

            using (log4net.ThreadContext.Stacks["NETWORK"].Push("PROCESS"))

            {                

                Log.InfoFormat("[ACTION] Start Processing {0}:{1}->{2}", action.Action, action.LocalFile,

                               action.CloudFile.Name);

                var localFile = action.LocalFile;

                var cloudFile = action.CloudFile;

                var downloadPath = action.GetDownloadPath();

                try

                {

                    switch (action.Action)

                    {

                        case CloudActionType.UploadUnconditional:

                            UploadCloudFile(action);

                            break;

                        case CloudActionType.DownloadUnconditional:

                            DownloadCloudFile(accountInfo,  cloudFile,downloadPath);

                            break;

                        case CloudActionType.DeleteCloud:

                            DeleteCloudFile(accountInfo, cloudFile, cloudFile.Name);

                            break;

                        case CloudActionType.RenameCloud:

                            var moveAction = (CloudMoveAction)action;

                            RenameCloudFile(accountInfo, cloudFile, moveAction);

                            break;

                        case CloudActionType.MustSynch:

                            if (!File.Exists(downloadPath))

                            {                                

                                DownloadCloudFile(accountInfo, cloudFile, downloadPath);

                            }

                            else

                            {

                                SyncFiles(accountInfo, action);

                            }

                            break;

                    }

                    Log.InfoFormat("[ACTION] End Processing {0}:{1}->{2}", action.Action, action.LocalFile,

                                           action.CloudFile.Name);

                }

                catch (OperationCanceledException)

                {

                    throw;

                }

                catch (FileNotFoundException exc)

                {

                    Log.ErrorFormat("{0} : {1} -> {2}  failed because the file was not found.\n Rescheduling a delete",

                        action.Action, action.LocalFile, action.CloudFile, exc);

                    //Post a delete action for the missing file

                    Post(new CloudDeleteAction(action));

                }

                catch (Exception exc)

                {

                    Log.ErrorFormat("[REQUEUE] {0} : {1} -> {2} due to exception\r\n{3}",

                                     action.Action, action.LocalFile, action.CloudFile, exc);

                    _agent.Post(action);

                }

                return CompletedTask<object>.Default;

            }

        }

        private void SyncFiles(AccountInfo accountInfo,CloudAction action)

        {

            if (accountInfo == null)

                throw new ArgumentNullException("accountInfo");

            if (action==null)

                throw new ArgumentNullException("action");

            if (action.LocalFile==null)

                throw new ArgumentException("The action's local file is not specified","action");

            if (!Path.IsPathRooted(action.LocalFile.FullName))

                throw new ArgumentException("The action's local file path must be absolute","action");

            if (action.CloudFile== null)

                throw new ArgumentException("The action's cloud file is not specified", "action");

            Contract.EndContractBlock();

            var localFile = action.LocalFile;

            var cloudFile = action.CloudFile;

            var downloadPath=action.LocalFile.FullName.ToLower();

            var cloudHash = cloudFile.Hash.ToLower();

            var localHash = action.LocalHash.Value.ToLower();

            var topHash = action.TopHash.Value.ToLower();

            //Not enough to compare only the local hashes, also have to compare the tophashes

            //If any of the hashes match, we are done

            if ((cloudHash == localHash || cloudHash == topHash))

            {

                Log.InfoFormat("Skipping {0}, hashes match",downloadPath);

                return;

            }

            //The hashes DON'T match. We need to sync

            var lastLocalTime = localFile.LastWriteTime;

            var lastUpTime = cloudFile.Last_Modified;

            //If the local file is newer upload it

            if (lastUpTime <= lastLocalTime)

            {

                //It probably means it was changed while the app was down                        

                UploadCloudFile(action);

            }

            else

            {

                //It the cloud file has a later date, it was modified by another user or computer.

                //We need to check the local file's status                

                var status = StatusKeeper.GetFileStatus(downloadPath);

                switch (status)

                {

                    case FileStatus.Unchanged:                        

                        //If the local file's status is Unchanged, we can go on and download the newer cloud file

                        DownloadCloudFile(accountInfo,cloudFile,downloadPath);

                        break;

                    case FileStatus.Modified:

                        //If the local file is Modified, we may have a conflict. In this case we should mark the file as Conflict

                        //We can't ensure that a file modified online since the last time will appear as Modified, unless we 

                        //index all files before we start listening.                       

                    case FileStatus.Created:

                        //If the local file is Created, it means that the local and cloud files aren't related,

                        // yet they have the same name.

                        //In both cases we must mark the file as in conflict

                        ReportConflict(downloadPath);

                        break;

                    default:

                        //Other cases should never occur. Mark them as Conflict as well but log a warning

                        ReportConflict(downloadPath);

                        Log.WarnFormat("Unexcepted status {0} for file {1}->{2}", status,

                                       downloadPath, action.CloudFile.Name);

                        break;

                }

            }

        }

        private void ReportConflict(string downloadPath)

        {

            if (String.IsNullOrWhiteSpace(downloadPath))

                throw new ArgumentNullException("downloadPath");

            Contract.EndContractBlock();

            StatusKeeper.SetFileOverlayStatus(downloadPath, FileOverlayStatus.Conflict);

            var message = String.Format("Conflict detected for file {0}", downloadPath);

            Log.Warn(message);

            StatusNotification.NotifyChange(message, TraceLevel.Warning);

        }

        public void Post(CloudAction cloudAction)

        {

            if (cloudAction == null)

                throw new ArgumentNullException("cloudAction");

            if (cloudAction.AccountInfo==null)

                throw new ArgumentException("The CloudAction.AccountInfo is empty","cloudAction");

            Contract.EndContractBlock();

            //If the action targets a local file, add a treehash calculation

            if (cloudAction.LocalFile != null)

            {

                var accountInfo = cloudAction.AccountInfo;

                if (cloudAction.LocalFile.Length>accountInfo.BlockSize)

                    cloudAction.TopHash = new Lazy<string>(() => Signature.CalculateTreeHashAsync(cloudAction.LocalFile,

                                    accountInfo.BlockSize, accountInfo.BlockHash).Result

                                     .TopHash.ToHashString());

                else

                {

                    cloudAction.TopHash=new Lazy<string>(()=> cloudAction.LocalHash.Value);

                }

            }

            _agent.Post(cloudAction);

        }

        class ObjectInfoByNameComparer:IEqualityComparer<ObjectInfo>

        {

            public bool Equals(ObjectInfo x, ObjectInfo y)

            {

                return x.Name.Equals(y.Name,StringComparison.InvariantCultureIgnoreCase);

            }

            public int GetHashCode(ObjectInfo obj)

            {

                return obj.Name.ToLower().GetHashCode();

            }

        }

        //Remote files are polled periodically. Any changes are processed

        public Task ProcessRemoteFiles(DateTime? since=null)

        {

            return Task<Task>.Factory.StartNewDelayed(10000, () =>

            {

                using (log4net.ThreadContext.Stacks["Retrieve Remote"].Push("All accounts"))

                {

                    //Next time we will check for all changes since the current check minus 1 second

                    //This is done to ensure there are no discrepancies due to clock differences

                    DateTime nextSince = DateTime.Now.AddSeconds(-1);

                    var tasks=from accountInfo in _accounts

                              select ProcessAccountFiles(accountInfo, since);

                    var process=Task.Factory.Iterate(tasks);

                    return process.ContinueWith(t =>

                    {

                        if (t.IsFaulted)

                        {

                            Log.Error("Error while processing accounts");

                            t.Exception.Handle(exc=>

                                                   {

                                                       Log.Error("Details:", exc);

                                                       return true;

                                                   });                            

                        }

                        ProcessRemoteFiles(nextSince);

                    });

                }

            });            

        }

        public Task ProcessAccountFiles(AccountInfo accountInfo,DateTime? since=null)

        {   

            if (accountInfo==null)

                throw new ArgumentNullException("accountInfo");

            if (String.IsNullOrWhiteSpace(accountInfo.AccountPath))

                throw new ArgumentException("The AccountInfo.AccountPath is empty","accountInfo");

            Contract.EndContractBlock();

            using (log4net.ThreadContext.Stacks["Retrieve Remote"].Push(accountInfo.UserName))

            {

                Log.Info("Scheduled");

                var client=new CloudFilesClient(accountInfo);

                var containers = client.ListContainers(accountInfo.UserName);

                CreateContainerFolders(accountInfo, containers);

                //Get the list of server objects changed since the last check

                var listObjects = from container in containers

                                  select Task<IList<ObjectInfo>>.Factory.StartNew(_ =>

                                        client.ListObjects(accountInfo.UserName, container.Name, since),container.Name);

                var listAll = Task.Factory.WhenAll(listObjects.ToArray());

                //Get the list of deleted objects since the last check

/*

                var listTrash = Task<IList<ObjectInfo>>.Factory.StartNew(() =>

                                client.ListObjects(accountInfo.UserName, FolderConstants.TrashContainer, since));

                var listShared = Task<IList<ObjectInfo>>.Factory.StartNew(() =>

                                client.ListSharedObjects(since));

                var listAll = Task.Factory.TrackedSequence(

                    () => listObjects,

                    () => listTrash,

                    () => listShared);

*/

                var enqueueFiles = listAll.ContinueWith(task =>

                {

                    if (task.IsFaulted)

                    {

                        //ListObjects failed at this point, need to reschedule

                        Log.ErrorFormat("[FAIL] ListObjects for{0} in ProcessRemoteFiles with {0}", accountInfo.UserName,task.Exception);

                        return;

                    }

                    using (log4net.ThreadContext.Stacks["SCHEDULE"].Push("Process Results"))

                    {

                        var dict=task.Result.ToDictionary(t=> t.AsyncState);

                        //Get all non-trash objects. Remember, the container name is stored in AsyncState

                        var remoteObjects = from objectList in task.Result

                                            where (string)objectList.AsyncState != "trash"

                                            from obj in objectList.Result

                                            select obj;

                        var trashObjects = dict["trash"].Result;

                        //var sharedObjects = ((Task<IList<ObjectInfo>>) task.Result[2]).Result;

                        //Items with the same name, hash may be both in the container and the trash

                        //Don't delete items that exist in the container

                        var realTrash = from trash in trashObjects

                                        where !remoteObjects.Any(info => info.Hash == trash.Hash)

                                        select trash;

                        ProcessDeletedFiles(accountInfo,realTrash);                        

                        var remote = from info in remoteObjects//.Union(sharedObjects)

                                     let name = info.Name

                                     where !name.EndsWith(".ignore", StringComparison.InvariantCultureIgnoreCase) &&

                                           !name.StartsWith(FolderConstants.CacheFolder +"/", StringComparison.InvariantCultureIgnoreCase)

                                     select info;

                        //Create a list of actions from the remote files

                        var allActions = ObjectsToActions(accountInfo,remote);

                        //And remove those that are already being processed by the agent

                        var distinctActions = allActions

                            .Except(_agent.GetEnumerable(), new PithosMonitor.LocalFileComparer())

                            .ToList();

                        //Queue all the actions

                        foreach (var message in distinctActions)

                        {

                            Post(message);

                        }

                        //Report the number of new files

                        var remoteCount = distinctActions.Count(action=>

                            action.Action==CloudActionType.DownloadUnconditional);

/*

                        if ( remoteCount > 0)

                            StatusNotification.NotifyChange(String.Format("Processing {0} new files", remoteCount));

*/

                        Log.Info("[LISTENER] End Processing");                        

                    }

                });

                var log = enqueueFiles.ContinueWith(t =>

                {                    

                    if (t.IsFaulted)

                    {

                        Log.Error("[LISTENER] Exception", t.Exception);

                    }

                    else

                    {

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

                    }

                });

                return log;

            }

        }

        private static void CreateContainerFolders(AccountInfo accountInfo, IList<ContainerInfo> containers)

        {

            var containerPaths = from container in containers

                                 let containerPath = Path.Combine(accountInfo.AccountPath, container.Name)

                                 where container.Name != FolderConstants.TrashContainer && !Directory.Exists(containerPath)

                                 select containerPath;

            foreach (var path in containerPaths)

            {

                Directory.CreateDirectory(path);

            }

        }

        //Creates an appropriate action for each server file

        private IEnumerable<CloudAction> ObjectsToActions(AccountInfo accountInfo,IEnumerable<ObjectInfo> remote)

        {

            if (remote==null)

                throw new ArgumentNullException();

            Contract.EndContractBlock();

            var fileAgent = GetFileAgent(accountInfo);

            //In order to avoid multiple iterations over the files, we iterate only once

            //over the remote files

            foreach (var objectInfo in remote)

            {

                var relativePath = objectInfo.RelativeUrlToFilePath(accountInfo.UserName);

                //and remove any matching objects from the list, adding them to the commonObjects list

                if (fileAgent.Exists(relativePath))

                {

                    var localFile = fileAgent.GetFileInfo(relativePath);

                    var state = FileState.FindByFilePath(localFile.FullName);

                    //Common files should be checked on a per-case basis to detect differences, which is newer

                    yield return new CloudAction(accountInfo,CloudActionType.MustSynch,

                                                   localFile, objectInfo, state, accountInfo.BlockSize,

                                                   accountInfo.BlockHash);

                }

                else

                {

                    //If there is no match we add them to the localFiles list

                    //but only if the file is not marked for deletion

                    var targetFile = Path.Combine(accountInfo.AccountPath, relativePath);

                    var fileStatus = StatusKeeper.GetFileStatus(targetFile);

                    if (fileStatus != FileStatus.Deleted)

                    {

                        //Remote files should be downloaded

                        yield return new CloudDownloadAction(accountInfo,objectInfo);

                    }

                }

            }            

        }

        private static FileAgent GetFileAgent(AccountInfo accountInfo)

        {

            return AgentLocator<FileAgent>.Get(accountInfo.AccountPath);

        }

        private void ProcessDeletedFiles(AccountInfo accountInfo,IEnumerable<ObjectInfo> trashObjects)

        {

            var fileAgent = GetFileAgent(accountInfo);

            foreach (var trashObject in trashObjects)

            {

                var relativePath = trashObject.RelativeUrlToFilePath(accountInfo.UserName);

                //and remove any matching objects from the list, adding them to the commonObjects list

                fileAgent.Delete(relativePath);                                

            }

        }

        private void RenameCloudFile(AccountInfo accountInfo,ObjectInfo cloudFile,CloudMoveAction action)

        {

            if (accountInfo==null)

                throw new ArgumentNullException("accountInfo");

            if (cloudFile==null)

                throw new ArgumentNullException("cloudFile");

            if (action==null)

                throw new ArgumentNullException("action");

            if (String.IsNullOrWhiteSpace(action.CloudFile.Container))

                throw new ArgumentException("Invalid container", "action");

            Contract.EndContractBlock();

            //The local file is already renamed

            this.StatusKeeper.SetFileOverlayStatus(action.NewPath, FileOverlayStatus.Modified);

            var account = action.CloudFile.Account ?? accountInfo.UserName;

            var container = action.CloudFile.Container;// ?? FolderConstants.PithosContainer;

            var client = new CloudFilesClient(accountInfo);

            client.MoveObject(account, container, action.OldFileName, container, action.NewFileName);

            this.StatusKeeper.SetFileStatus(action.NewPath, FileStatus.Unchanged);

            this.StatusKeeper.SetFileOverlayStatus(action.NewPath, FileOverlayStatus.Normal);

            NativeMethods.RaiseChangeNotification(action.NewPath);

        }

        private void DeleteCloudFile(AccountInfo accountInfo, ObjectInfo cloudFile,string fileName)

        {

            if (accountInfo == null)

                throw new ArgumentNullException("accountInfo");

            if (cloudFile==null)

                throw new ArgumentNullException("cloudFile");

            if (String.IsNullOrWhiteSpace(fileName))

                throw new ArgumentNullException("fileName");

            if (Path.IsPathRooted(fileName))

                throw new ArgumentException("The fileName should not be rooted","fileName");

            if (String.IsNullOrWhiteSpace(cloudFile.Container))

                throw new ArgumentException("Invalid container", "cloudFile");

            Contract.EndContractBlock();

            var fileAgent = GetFileAgent(accountInfo);

            using ( log4net.ThreadContext.Stacks["DeleteCloudFile"].Push("Delete"))

            {

                var info = fileAgent.GetFileInfo(fileName);

                var fullPath = info.FullName.ToLower();

                this.StatusKeeper.SetFileOverlayStatus(fullPath, FileOverlayStatus.Modified);

                var account = cloudFile.Account ?? accountInfo.UserName;

                var container = cloudFile.Container ;//?? FolderConstants.PithosContainer;

                var client = new CloudFilesClient(accountInfo);

                client.DeleteObject(account, container, fileName);

                this.StatusKeeper.ClearFileStatus(fullPath);

            }

        }

        //Download a file.

        private void DownloadCloudFile(AccountInfo accountInfo, ObjectInfo cloudFile , string localPath)

        {

            if (accountInfo == null)

                throw new ArgumentNullException("accountInfo");

            if (cloudFile == null)

                throw new ArgumentNullException("cloudFile");

            if (String.IsNullOrWhiteSpace(cloudFile.Account))

                throw new ArgumentNullException("cloudFile");

            if (String.IsNullOrWhiteSpace(cloudFile.Container))

                throw new ArgumentNullException("cloudFile");

            if (String.IsNullOrWhiteSpace(localPath))

                throw new ArgumentNullException("localPath");

            if (!Path.IsPathRooted(localPath))

                throw new ArgumentException("The localPath must be rooted", "localPath");

            Contract.EndContractBlock();

            var download=Task.Factory.Iterate(DownloadIterator(accountInfo,cloudFile, localPath));

            download.Wait();

        }

        private IEnumerable<Task> DownloadIterator(AccountInfo accountInfo,ObjectInfo cloudFile, string localPath)

        {

            if (accountInfo == null)

                throw new ArgumentNullException("accountInfo");

            if (cloudFile == null)

                throw new ArgumentNullException("cloudFile");

            if (String.IsNullOrWhiteSpace(cloudFile.Account))

                throw new ArgumentNullException("cloudFile");

            if (String.IsNullOrWhiteSpace(cloudFile.Container))

                throw new ArgumentNullException("cloudFile");

            if (String.IsNullOrWhiteSpace(localPath))

                throw new ArgumentNullException("localPath");

            if (!Path.IsPathRooted(localPath))

                throw new ArgumentException("The localPath must be rooted", "localPath");

            Contract.EndContractBlock();

            Uri relativeUrl = new Uri(cloudFile.Name, UriKind.Relative);

            var url = relativeUrl.ToString();

            if (cloudFile.Name.EndsWith(".ignore", StringComparison.InvariantCultureIgnoreCase))

                yield break;

            //Are we already downloading or uploading the file? 

            using (var gate=NetworkGate.Acquire(localPath, NetworkOperation.Downloading))

            {

                if (gate.Failed)

                    yield break;

                //The file's hashmap will be stored in the same location with the extension .hashmap

                //var hashPath = Path.Combine(FileAgent.CachePath, relativePath + ".hashmap");

                var client = new CloudFilesClient(accountInfo);

                var account = cloudFile.Account;

                var container = cloudFile.Container;

                //Retrieve the hashmap from the server

                var getHashMap = client.GetHashMap(account, container, url);

                yield return getHashMap;

                var serverHash=getHashMap.Result;

                //If it's a small file

                var downloadTask=(serverHash.Hashes.Count == 1 )

                    //Download it in one go

                    ? DownloadEntireFile(accountInfo,client, cloudFile, relativeUrl, localPath, serverHash) 

                    //Otherwise download it block by block

                    : DownloadWithBlocks(accountInfo,client, cloudFile, relativeUrl, localPath, serverHash);

                yield return downloadTask;

                if (cloudFile.AllowedTo == "read")

                {

                    var attributes=File.GetAttributes(localPath);

                    File.SetAttributes(localPath,attributes|FileAttributes.ReadOnly);

                }

                //Now we can store the object's metadata without worrying about ghost status entries

                StatusKeeper.StoreInfo(localPath, cloudFile);

            }

        }

        //Download a small file with a single GET operation

        private Task DownloadEntireFile(AccountInfo accountInfo, CloudFilesClient client, ObjectInfo cloudFile, Uri relativeUrl, string localPath,TreeHash serverHash)

        {

            if (client == null)

                throw new ArgumentNullException("client");

            if (cloudFile==null)

                throw new ArgumentNullException("cloudFile");

            if (relativeUrl == null)

                throw new ArgumentNullException("relativeUrl");

            if (String.IsNullOrWhiteSpace(localPath))

                throw new ArgumentNullException("localPath");

            if (!Path.IsPathRooted(localPath))

                throw new ArgumentException("The localPath must be rooted", "localPath");

            Contract.EndContractBlock();

            //If the file already exists

            if (File.Exists(localPath))

            {

                //First check with MD5 as this is a small file

                var localMD5 = Signature.CalculateMD5(localPath);

                var cloudHash=serverHash.TopHash.ToHashString();

                if (localMD5==cloudHash)

                    return CompletedTask.Default;

                //Then check with a treehash

                var localTreeHash = Signature.CalculateTreeHash(localPath, serverHash.BlockSize, serverHash.BlockHash);

                var localHash = localTreeHash.TopHash.ToHashString();

                if (localHash==cloudHash)

                    return CompletedTask.Default;

            }

            var fileAgent = GetFileAgent(accountInfo);

            //Calculate the relative file path for the new file

            var relativePath = relativeUrl.RelativeUriToFilePath();

            //The file will be stored in a temporary location while downloading with an extension .download

            var tempPath = Path.Combine(fileAgent.CachePath, relativePath + ".download");

            //Make sure the target folder exists. DownloadFileTask will not create the folder

            var tempFolder = Path.GetDirectoryName(tempPath);

            if (!Directory.Exists(tempFolder))

                Directory.CreateDirectory(tempFolder);

            //Download the object to the temporary location

            var getObject = client.GetObject(cloudFile.Account, cloudFile.Container, relativeUrl.ToString(), tempPath).ContinueWith(t =>

            {

                t.PropagateExceptions();

                //Create the local folder if it doesn't exist (necessary for shared objects)

                var localFolder = Path.GetDirectoryName(localPath);

                if (!Directory.Exists(localFolder))

                    Directory.CreateDirectory(localFolder);

                //And move it to its actual location once downloading is finished

                if (File.Exists(localPath))

                    File.Replace(tempPath,localPath,null,true);

                else

                    File.Move(tempPath,localPath);

                //Notify listeners that a local file has changed

                StatusNotification.NotifyChangedFile(localPath);

            });

            return getObject;

        }

        //Download a file asynchronously using blocks

        public Task DownloadWithBlocks(AccountInfo accountInfo, CloudFilesClient client, ObjectInfo cloudFile, Uri relativeUrl, string localPath, TreeHash serverHash)

        {

            if (client == null)

                throw new ArgumentNullException("client");

            if (cloudFile == null)

                throw new ArgumentNullException("cloudFile");

            if (relativeUrl == null)

                throw new ArgumentNullException("relativeUrl");

            if (String.IsNullOrWhiteSpace(localPath))

                throw new ArgumentNullException("localPath");

            if (!Path.IsPathRooted(localPath))

                throw new ArgumentException("The localPath must be rooted", "localPath");

            if (serverHash == null)

                throw new ArgumentNullException("serverHash");

            Contract.EndContractBlock();

            return Task.Factory.Iterate(BlockDownloadIterator(accountInfo,client,cloudFile, relativeUrl, localPath, serverHash));

        }

        private IEnumerable<Task> BlockDownloadIterator(AccountInfo accountInfo,CloudFilesClient client,  ObjectInfo cloudFile, Uri relativeUrl, string localPath, TreeHash serverHash)

        {

            if (client == null)

                throw new ArgumentNullException("client");

            if (cloudFile==null)

                throw new ArgumentNullException("cloudFile");

            if (relativeUrl == null)

                throw new ArgumentNullException("relativeUrl");

            if (String.IsNullOrWhiteSpace(localPath))

                throw new ArgumentNullException("localPath");

            if (!Path.IsPathRooted(localPath))

                throw new ArgumentException("The localPath must be rooted", "localPath");

            if(serverHash==null)

                throw new ArgumentNullException("serverHash");

            Contract.EndContractBlock();

            var fileAgent = GetFileAgent(accountInfo);

            //Calculate the relative file path for the new file

            var relativePath = relativeUrl.RelativeUriToFilePath();

            var blockUpdater = new BlockUpdater(fileAgent.CachePath, localPath, relativePath, serverHash);

            //Calculate the file's treehash

            var calcHash = Signature.CalculateTreeHashAsync(localPath, serverHash.BlockSize,serverHash.BlockHash);

            yield return calcHash;                        

            var treeHash = calcHash.Result;

            //And compare it with the server's hash

            var upHashes = serverHash.GetHashesAsStrings();

            var localHashes = treeHash.HashDictionary;

            for (int i = 0; i < upHashes.Length; i++)

            {

                //For every non-matching hash

                var upHash = upHashes[i];

                if (!localHashes.ContainsKey(upHash))

                {

                    if (blockUpdater.UseOrphan(i, upHash))

                    {

                        Log.InfoFormat("[BLOCK GET] ORPHAN FOUND for {0} of {1} for {2}", i, upHashes.Length, localPath);

                        continue;

                    }

                    Log.InfoFormat("[BLOCK GET] START {0} of {1} for {2}", i, upHashes.Length, localPath);

                    var start = i*serverHash.BlockSize;

                    //To download the last block just pass a null for the end of the range

                    long? end = null;

                    if (i < upHashes.Length - 1 )

                        end= ((i + 1)*serverHash.BlockSize) ;

                    //Download the missing block

                    var getBlock = client.GetBlock(cloudFile.Account, cloudFile.Container, relativeUrl, start, end);

                    yield return getBlock;

                    var block = getBlock.Result;

                    //and store it

                    yield return blockUpdater.StoreBlock(i, block);

                    Log.InfoFormat("[BLOCK GET] FINISH {0} of {1} for {2}", i, upHashes.Length, localPath);

                }

            }

            //Want to avoid notifications if no changes were made

            var hasChanges = blockUpdater.HasBlocks;

            blockUpdater.Commit();

            if (hasChanges)

                //Notify listeners that a local file has changed

                StatusNotification.NotifyChangedFile(localPath);

            Log.InfoFormat("[BLOCK GET] COMPLETE {0}", localPath);            

        }

        private void UploadCloudFile(CloudAction action)

        {

            if (action == null)

                throw new ArgumentNullException("action");           

            Contract.EndContractBlock();

            try

            {

                var upload = Task.Factory.Iterate(UploadIterator(action));

                upload.Wait();

            }                

            catch (AggregateException ex)

            {                

                var exc = ex.InnerException as WebException;

                if (exc==null)

                    throw ex.InnerException;

                var response = exc.Response as HttpWebResponse;

                if (response==null)

                    throw exc;

                if (response.StatusCode == HttpStatusCode.Unauthorized)

                {

                    Log.Error("Not allowed to upload file", exc);

                    var message = String.Format("Not allowed to uplad file {0}",action.LocalFile.FullName);

                    StatusKeeper.SetFileState(action.LocalFile.FullName,FileStatus.Unchanged,FileOverlayStatus.Normal);

                    StatusNotification.NotifyChange(message,TraceLevel.Warning);

                    return;

                }

                throw;

            }

        }

        private IEnumerable<Task> UploadIterator(CloudAction action)

        {

            if (action == null)

                throw new ArgumentNullException("action");            

            Contract.EndContractBlock();

            var accountInfo=action.AccountInfo;

            var fileInfo=action.LocalFile;                        

            if (fileInfo.Extension.Equals("ignore", StringComparison.InvariantCultureIgnoreCase))

                yield break;

            var relativePath = fileInfo.AsRelativeTo(accountInfo.AccountPath);

            if (relativePath.StartsWith(FolderConstants.OthersFolder))

            {

                var parts=relativePath.Split('\\');

                var accountName = parts[1];

                var oldName = accountInfo.UserName;

                var absoluteUri = accountInfo.StorageUri.AbsoluteUri;

                var nameIndex=absoluteUri.IndexOf(oldName);

                var root=absoluteUri.Substring(0, nameIndex);

                accountInfo = new AccountInfo

                {

                    UserName = accountName,

                    AccountPath = Path.Combine(accountInfo.AccountPath, parts[0], parts[1]),

                    StorageUri = new Uri(root + accountName),

                    BlockHash=accountInfo.BlockHash,

                    BlockSize=accountInfo.BlockSize,

                    Token=accountInfo.Token

                };

            }

            var fullFileName = fileInfo.FullName;

            using(var gate=NetworkGate.Acquire(fullFileName,NetworkOperation.Uploading))

            {

                //Abort if the file is already being uploaded or downloaded

                if (gate.Failed)

                    yield break;

                var cloudFile = action.CloudFile;

                var account = cloudFile.Account ?? accountInfo.UserName;

                var client = new CloudFilesClient(accountInfo);

                //Even if GetObjectInfo times out, we can proceed with the upload            

                var info = client.GetObjectInfo(account, cloudFile.Container, cloudFile.Name);                

                var cloudHash = info.Hash.ToLower();

                var hash = action.LocalHash.Value;

                var topHash = action.TopHash.Value;

                //If the file hashes match, abort the upload

                if (hash == cloudHash  || topHash ==cloudHash)

                {

                    //but store any metadata changes 

                    this.StatusKeeper.StoreInfo(fullFileName, info);

                    Log.InfoFormat("Skip upload of {0}, hashes match", fullFileName);

                    yield break;

                }

                if (info.AllowedTo=="read")

                    yield break;

                //Mark the file as modified while we upload it

                StatusKeeper.SetFileOverlayStatus(fullFileName, FileOverlayStatus.Modified);

                //And then upload it

                //Upload even small files using the Hashmap. The server may already containt

                //the relevant folder

                //First, calculate the tree hash

                var treeHash = Signature.CalculateTreeHashAsync(fileInfo.FullName, accountInfo.BlockSize,

                    accountInfo.BlockHash);

                yield return treeHash;

                yield return Task.Factory.Iterate(UploadWithHashMap(accountInfo,cloudFile,fileInfo,cloudFile.Name,treeHash));

                //If everything succeeds, change the file and overlay status to normal

                this.StatusKeeper.SetFileState(fullFileName, FileStatus.Unchanged, FileOverlayStatus.Normal);

            }

            //Notify the Shell to update the overlays

            NativeMethods.RaiseChangeNotification(fullFileName);

            StatusNotification.NotifyChangedFile(fullFileName);

        }

        public IEnumerable<Task> UploadWithHashMap(AccountInfo accountInfo,ObjectInfo cloudFile,FileInfo fileInfo,string url,Task<TreeHash> treeHash)

        {

            if (accountInfo == null)

                throw new ArgumentNullException("accountInfo");

            if (cloudFile==null)

                throw new ArgumentNullException("cloudFile");

            if (fileInfo == null)

                throw new ArgumentNullException("fileInfo");

            if (String.IsNullOrWhiteSpace(url))

                throw new ArgumentNullException(url);

            if (treeHash==null)

                throw new ArgumentNullException("treeHash");

            if (String.IsNullOrWhiteSpace(cloudFile.Container) )

                throw new ArgumentException("Invalid container","cloudFile");

            Contract.EndContractBlock();

            var fullFileName = fileInfo.FullName;

            var account = cloudFile.Account ?? accountInfo.UserName;

            var container = cloudFile.Container ;//?? FolderConstants.PithosContainer;

            var client = new CloudFilesClient(accountInfo);

            //Send the hashmap to the server            

            var hashPut = client.PutHashMap(account, container, url, treeHash.Result);

            yield return hashPut;

            var missingHashes = hashPut.Result;

            //If the server returns no missing hashes, we are done

            while (missingHashes.Count > 0)

            {

                var buffer = new byte[accountInfo.BlockSize];

                foreach (var missingHash in missingHashes)

                {

                    //Find the proper block

                    var blockIndex = treeHash.Result.HashDictionary[missingHash];

                    var offset = blockIndex*accountInfo.BlockSize;

                    var read = fileInfo.Read(buffer, offset, accountInfo.BlockSize);

                    //And upload the block                

                    var postBlock = client.PostBlock(account, container, buffer, 0, read);

                    //We have to handle possible exceptions in a continuation because

                    //*yield return* can't appear inside a try block

                    yield return postBlock.ContinueWith(t => 

                        t.ReportExceptions(

                            exc => Log.ErrorFormat("[ERROR] uploading block {0} of {1}\n{2}", blockIndex, fullFileName, exc),

                            ()=>Log.InfoFormat("[BLOCK] Block {0} of {1} uploaded", blockIndex,fullFileName)));

                }

                //Repeat until there are no more missing hashes

                hashPut = client.PutHashMap(account, container, url, treeHash.Result);

                yield return hashPut;

                missingHashes = hashPut.Result;

            }

        }

        public void AddAccount(AccountInfo accountInfo)

        {            

            if (!_accounts.Contains(accountInfo))

                _accounts.Add(accountInfo);

        }

    }

}