#region
/* -----------------------------------------------------------------------
 * <copyright file="DeleteAgent.cs" company="GRNet">
 * 
 * Copyright 2011-2012 GRNET S.A. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or
 * without modification, are permitted provided that the following
 * conditions are met:
 *
 *   1. Redistributions of source code must retain the above
 *      copyright notice, this list of conditions and the following
 *      disclaimer.
 *
 *   2. Redistributions in binary form must reproduce the above
 *      copyright notice, this list of conditions and the following
 *      disclaimer in the documentation and/or other materials
 *      provided with the distribution.
 *
 *
 * THIS SOFTWARE IS PROVIDED BY GRNET S.A. ``AS IS'' AND ANY EXPRESS
 * OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL GRNET S.A OR
 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
 * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
 * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 *
 * The views and conclusions contained in the software and
 * documentation are those of the authors and should not be
 * interpreted as representing official policies, either expressed
 * or implied, of GRNET S.A.
 * </copyright>
 * -----------------------------------------------------------------------
 */
#endregion
using System.Collections.Concurrent;
using System.ComponentModel.Composition;
using System.Diagnostics.Contracts;
using System.IO;
using System.Net;
using System.Reflection;
using System.Threading.Tasks.Dataflow;
using Pithos.Interfaces;
using Pithos.Network;
using System;
using log4net;

namespace Pithos.Core.Agents
{

    /// <summary>
    /// The Delete Agent is used to delete files from the Pithos server with high priority, 
    /// blocking the network agent through the ProceedEvent until all pending deletions complete
    /// </summary>    
    [Export]
    public class DeleteAgent
    {
        private static readonly ILog Log = LogManager.GetLogger(MethodBase.GetCurrentMethod().DeclaringType);

        [Import]
        public IStatusKeeper StatusKeeper { get; set; }
        
        public IStatusNotification StatusNotification { get; set; }

        //A separate agent is used to execute delete actions immediatelly;
        private readonly ActionBlock<CloudDeleteAction> _deleteAgent;

        //The Proceed event signals the the network agent to proceed with processing.
        //Essentially this event pauses the network agent to give priority to the deletion agent
        //Initially the event is signalled because we don't need to pause
        private readonly AsyncManualResetEvent _proceedEvent = new AsyncManualResetEvent(true);

        public AsyncManualResetEvent ProceedEvent
        {
            get { return _proceedEvent; }
        }

        //Deleted file names are stored in memory so we can check that a file has already been deleted.
        //and avoid sending duplicate delete commands
        readonly ConcurrentDictionary<string, DateTime> _deletedFiles = new ConcurrentDictionary<string, DateTime>();

        public DeleteAgent()
        {
            _deleteAgent = new ActionBlock<CloudDeleteAction>(message => ProcessDelete(message), new ExecutionDataflowBlockOptions { MaxDegreeOfParallelism = 4 });

        }

        /// <summary>
        /// Processes cloud delete actions
        /// </summary>
        /// <param name="action">The delete action to execute</param>
        /// <returns></returns>
        /// <remarks>
        /// When a file/folder is deleted locally, we must delete it ASAP from the server and block any download
        /// operations that may be in progress.
        /// <para>
        /// A separate agent is used to process deletes because the main agent may be busy with a long operation.
        /// </para>
        /// </remarks>
        private void ProcessDelete(CloudDeleteAction 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["Operation"].Push("ProcessDelete"))
            {
                Log.InfoFormat("[ACTION] Start Processing {0}", action);

                var cloudFile = action.CloudFile;

                try
                {
                    //Acquire a lock on the deleted file to prevent uploading/downloading operations from the normal
                    //agent
                    using (NetworkGate.Acquire(action.LocalFile.FullName, NetworkOperation.Deleting))
                    {

                        //Add the file URL to the deleted files list
                        var key = GetFileKey(action.CloudFile);
                        _deletedFiles[key] = DateTime.Now;

                        _proceedEvent.Reset();
                        // and then delete the file from the server
                        DeleteCloudFile(accountInfo, cloudFile);

                        Log.InfoFormat("[ACTION] End Delete {0}:{1}->{2}", action.Action, action.LocalFile,
                                       action.CloudFile.Name);
                    }
                }
                catch (WebException exc)
                {
                    Log.ErrorFormat("[WEB ERROR] {0} : {1} -> {2} due to exception\r\n{3}", action.Action, action.LocalFile, action.CloudFile, exc);
                }
                catch (OperationCanceledException)
                {
                    throw;
                }
                catch (DirectoryNotFoundException)
                {
                    Log.ErrorFormat("{0} : {1} -> {2}  failed because the directory was not found.\n Rescheduling a delete",
                        action.Action, action.LocalFile, action.CloudFile);
                    //Repost a delete action for the missing file
                    _deleteAgent.Post(action);
                }
                catch (FileNotFoundException)
                {
                    Log.ErrorFormat("{0} : {1} -> {2}  failed because the file was not found.\n Rescheduling a delete",
                        action.Action, action.LocalFile, action.CloudFile);
                    //Post a delete action for the missing file
                    _deleteAgent.Post(action);
                }
                catch (Exception exc)
                {
                    Log.ErrorFormat("[REQUEUE] {0} : {1} -> {2} due to exception\r\n{3}",
                                     action.Action, action.LocalFile, action.CloudFile, exc);

                    _deleteAgent.Post(action);
                }
                finally
                {
                    //Set the event when all delete actions are processed
                    if (_deleteAgent.InputCount == 0)
                        _proceedEvent.Set();

                }
            }
        }

        //Returns true if an action concerns a file that was deleted
        public bool IsDeletedFile(CloudAction action)
        {
            //Doesn't work for actions targeting shared files
            if (action.IsShared)
                return false;
            var key = GetFileKey(action.CloudFile);
            DateTime entryDate;
            if (_deletedFiles.TryGetValue(key, out entryDate))
            {
                //If the delete entry was created after this action, abort the action
                if (entryDate > action.Created)
                    return true;
                //Otherwise, remove the stale entry 
                _deletedFiles.TryRemove(key, out entryDate);
            }
            return false;
        }

        public void Post(CloudDeleteAction action)
        {
            _deleteAgent.Post(action);
        }

        public void DeleteCloudFile(AccountInfo accountInfo, ObjectInfo cloudFile)
        {
            if (accountInfo == null)
                throw new ArgumentNullException("accountInfo");
            if (cloudFile == null)
                throw new ArgumentNullException("cloudFile");

            if (String.IsNullOrWhiteSpace(cloudFile.Container))
                throw new ArgumentException("Invalid container", "cloudFile");
            Contract.EndContractBlock();

            var fileAgent = GetFileAgent(accountInfo);

            using (ThreadContext.Stacks["Operation"].Push("DeleteCloudFile"))
            {
                var fileName = cloudFile.RelativeUrlToFilePath(accountInfo.UserName);
                var info = fileAgent.GetFileSystemInfo(fileName);
                var fullPath = info.FullName.ToLower();

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

                var account = cloudFile.Account ?? accountInfo.UserName;
                var container = cloudFile.Container;//?? FolderConstants.PithosContainer;

                var client = new CloudFilesClient(accountInfo);
                client.DeleteObject(account, container, cloudFile.Name);

                StatusKeeper.ClearFileStatus(fullPath);
                StatusNotification.Notify(new CloudNotification{Data=cloudFile});
            }
        }


        private static string GetFileKey(ObjectInfo info)
        {
            var key = String.Format("{0}/{1}/{2}", info.Account, info.Container, info.Name);
            return key;
        }

        private static FileAgent GetFileAgent(AccountInfo accountInfo)
        {
            return AgentLocator<FileAgent>.Get(accountInfo.AccountPath);
        }

    }
}