using System;
using System.ComponentModel.Composition;
using System.Diagnostics.Contracts;
using System.IO;
using System.Reflection;
using System.Threading;
using System.Threading.Tasks;
using Pithos.Interfaces;
using Pithos.Network;
using log4net;

namespace Pithos.Core.Agents
{
    [Export(typeof(Downloader))]
    public class Downloader
    {
        private static readonly ILog Log = LogManager.GetLogger(MethodBase.GetCurrentMethod().DeclaringType);

        [Import]
        private IStatusKeeper StatusKeeper { get; set; }

        [Import]
        private IPithosSettings Settings { get; set; }
        
        public IStatusNotification StatusNotification { get; set; }

/*
        private CancellationTokenSource _cts=new CancellationTokenSource();

        public void SignalStop()
        {
            _cts.Cancel();
        }
*/


        //Download a file.
        public async Task<TreeHash> DownloadCloudFile(AccountInfo accountInfo, ObjectInfo cloudFile, string filePath,CancellationToken cancellationToken)
        {
            if (accountInfo == null)
                throw new ArgumentNullException("accountInfo");
            if (cloudFile == null)
                throw new ArgumentNullException("cloudFile");
            if (String.IsNullOrWhiteSpace(cloudFile.Account))
                throw new ArgumentNullException("cloudFile");
            if (cloudFile.Container==null)
                throw new ArgumentNullException("cloudFile");
            if (cloudFile.Container.IsAbsoluteUri)
                throw new ArgumentNullException("cloudFile");
            if (String.IsNullOrWhiteSpace(filePath))
                throw new ArgumentNullException("filePath");
            if (!Path.IsPathRooted(filePath))
                throw new ArgumentException("The filePath must be rooted", "filePath");
            Contract.EndContractBlock();
                using (ThreadContext.Stacks["Operation"].Push("DownloadCloudFile"))
                {
                   // var cancellationToken=_cts.Token;//  .ThrowIfCancellationRequested();

                    //The file's treehash after download completes. For directories, the treehash is always the empty hash
                    var finalHash = TreeHash.Empty;

                    if (await WaitOrAbort(accountInfo,cloudFile, cancellationToken).ConfigureAwait(false))
                        return finalHash;

                    var fileName = Path.GetFileName(filePath);

                    var info = FileInfoExtensions.FromPath(filePath).WithProperCapitalization();

                    TreeHash localTreeHash;

                    using (StatusNotification.GetNotifier("Hashing for Download {0}", "Hashed for Download {0}", fileName))
                    {
                        var state = StatusKeeper.GetStateByFilePath(filePath);
                        var progress = new Progress<double>(d =>
                            StatusNotification.Notify(new StatusNotification(String.Format("Hashing for Download {0} of {1}", d, fileName))));

                        localTreeHash = StatusAgent.CalculateTreeHash(info, accountInfo, state, Settings.HashingParallelism, cancellationToken, progress);
                    }
                    
                    var localPath = info.FullName;
                    var relativeUrl = cloudFile.Name;

                    var url = relativeUrl.ToString();
                    if (url.EndsWith(".ignore", StringComparison.InvariantCultureIgnoreCase))
                        return finalHash;

                    if (!Selectives.IsSelected(accountInfo,cloudFile))
                        return finalHash;


                    //Are we already downloading or uploading the file? 
                    using (var gate = NetworkGate.Acquire(localPath, NetworkOperation.Downloading))
                    {
                        if (gate.Failed)
                            return finalHash;

                        var client = new CloudFilesClient(accountInfo);
                        var account = cloudFile.Account;
                        var container = cloudFile.Container;

                        if (cloudFile.IsDirectory)
                        {
                            if (!Directory.Exists(localPath))
                                try
                                {
                                    Directory.CreateDirectory(localPath);
                                    if (Log.IsDebugEnabled)
                                        Log.DebugFormat("Created Directory [{0}]", localPath);
                                }
                                catch (IOException)
                                {
                                    var localInfo = new FileInfo(localPath);
                                    if (localInfo.Exists && localInfo.Length == 0)
                                    {
                                        Log.WarnFormat("Malformed directory object detected for [{0}]", localPath);
                                        localInfo.Delete();
                                        Directory.CreateDirectory(localPath);
                                        if (Log.IsDebugEnabled)
                                            Log.DebugFormat("Created Directory [{0}]", localPath);
                                    }
                                }
                        }
                        else
                        {
                            var isChanged = IsObjectChanged(cloudFile, localPath,localTreeHash);
                            if (isChanged)
                            {
                                //Retrieve the hashmap from the server
                                var serverHash = await client.GetHashMap(account, container, relativeUrl).ConfigureAwait(false);
                                //If it's a small file
                                if (serverHash.Hashes.Count == 1)
                                    //Download it in one go
                                    await
                                        DownloadEntireFileAsync(accountInfo, client, cloudFile, relativeUrl, localPath,cancellationToken);
                                    //Otherwise download it block by block
                                else
                                    await
                                        DownloadWithBlocks(accountInfo, client, cloudFile, relativeUrl, localPath,localTreeHash,
                                                           serverHash,cancellationToken);

                                if (!cloudFile.IsWritable(accountInfo.UserName))
                                {
                                    var attributes = File.GetAttributes(localPath);
                                    File.SetAttributes(localPath, attributes | FileAttributes.ReadOnly);
                                }

                                //Once download completes, the final hash will be equal to the server hash
                                finalHash = serverHash;

                            }
                        }

                        //Now we can store the object's metadata without worrying about ghost status entries
                        StatusKeeper.StoreInfo(localPath, cloudFile,finalHash);

                    }
                    return finalHash;
                }
           
        }

        //Download a file asynchronously using blocks
        public async Task DownloadWithBlocks(AccountInfo accountInfo, CloudFilesClient client, ObjectInfo cloudFile, Uri relativeUrl, string filePath, TreeHash localTreeHash,TreeHash serverHash, CancellationToken cancellationToken)
        {
            if (client == null)
                throw new ArgumentNullException("client");
            if (cloudFile == null)
                throw new ArgumentNullException("cloudFile");
            if (relativeUrl == null)
                throw new ArgumentNullException("relativeUrl");
            if (String.IsNullOrWhiteSpace(filePath))
                throw new ArgumentNullException("filePath");
            if (!Path.IsPathRooted(filePath))
                throw new ArgumentException("The filePath must be rooted", "filePath");
            if (serverHash == null)
                throw new ArgumentNullException("serverHash");
            if (cloudFile.IsDirectory)
                throw new ArgumentException("cloudFile is a directory, not a file", "cloudFile");
            Contract.EndContractBlock();

            if (await WaitOrAbort(accountInfo, cloudFile, cancellationToken).ConfigureAwait(false))
                return;

            var fileAgent = GetFileAgent(accountInfo);
            var localPath = FileInfoExtensions.GetProperFilePathCapitalization(filePath);

            //Calculate the relative file path for the new file
            var relativePath = relativeUrl.RelativeUriToFilePath();
            var blockUpdater = new BlockUpdater(fileAgent.CachePath, localPath, relativePath, serverHash);

            StatusNotification.SetPithosStatus(PithosStatus.LocalSyncing, String.Format("Calculating hashmap for {0} before download", Path.GetFileName(localPath)));
            //Calculate the file's treehash

            var fileName = Path.GetFileName(localPath);
            var progress = new Progress<double>(d =>
                StatusNotification.Notify(new StatusNotification(String.Format("Hashing for Download {0} of {1}", d, fileName))));
            
            var treeHash = localTreeHash ?? Signature.CalculateTreeHashAsync(localPath, (int)serverHash.BlockSize, serverHash.BlockHash, Settings.HashingParallelism,cancellationToken,progress);

            //And compare it with the server's hash
            var upHashes = serverHash.GetHashesAsStrings();
            var localHashes = treeHash.HashDictionary;
            ReportDownloadProgress(Path.GetFileName(localPath), 0,0, upHashes.Length, cloudFile.Bytes);


            long i = 0;
            client.DownloadProgressChanged += (sender, args) =>
                                ReportDownloadProgress(Path.GetFileName(localPath), i, args.ProgressPercentage, upHashes.Length, cloudFile.Bytes);


            for (i = 0; i < upHashes.Length; i++)
            {
                if (await WaitOrAbort(accountInfo, cloudFile, cancellationToken).ConfigureAwait(false))
                    return;

                //For every non-matching hash
                var upHash = upHashes[i];
                if (!localHashes.ContainsKey(upHash))
                {
                    StatusNotification.Notify(new CloudNotification { Data = cloudFile });
                    ReportDownloadProgress(Path.GetFileName(localPath), i, 0,upHashes.Length, cloudFile.Bytes);

                    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);
                    long 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
                    byte[] block = await client.GetBlock(cloudFile.Account, cloudFile.Container, relativeUrl, start, end, cancellationToken).ConfigureAwait(false);

                    //and store it
                    blockUpdater.StoreBlock(i, block);


                    Log.InfoFormat("[BLOCK GET] FINISH {0} of {1} for {2}", i, upHashes.Length, localPath);
                }
                ReportDownloadProgress(Path.GetFileName(localPath), i, 100,upHashes.Length, cloudFile.Bytes);
            }

            //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);
            
        }

        //Download a small file with a single GET operation
        private async Task DownloadEntireFileAsync(AccountInfo accountInfo, CloudFilesClient client, ObjectInfo cloudFile, Uri relativeUrl, string filePath, CancellationToken cancellationToken)
        {
            if (client == null)
                throw new ArgumentNullException("client");
            if (cloudFile == null)
                throw new ArgumentNullException("cloudFile");
            if (relativeUrl == null)
                throw new ArgumentNullException("relativeUrl");
            if (String.IsNullOrWhiteSpace(filePath))
                throw new ArgumentNullException("filePath");
            if (!Path.IsPathRooted(filePath))
                throw new ArgumentException("The localPath must be rooted", "filePath");
            if (cloudFile.IsDirectory)
                throw new ArgumentException("cloudFile is a directory, not a file", "cloudFile");
            Contract.EndContractBlock();

            if (await WaitOrAbort(accountInfo, cloudFile, cancellationToken).ConfigureAwait(false))
                return;

            var localPath = FileInfoExtensions.GetProperFilePathCapitalization(filePath);
            StatusNotification.SetPithosStatus(PithosStatus.LocalSyncing, String.Format("Downloading {0}", Path.GetFileName(localPath)));
            StatusNotification.Notify(new CloudNotification { Data = cloudFile });
            ReportDownloadProgress(Path.GetFileName(localPath), 1, 0,1, cloudFile.Bytes);

            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
            await client.GetObject(cloudFile.Account, cloudFile.Container, relativeUrl, tempPath, cancellationToken).ConfigureAwait(false);

            //Create the local folder if it doesn't exist (necessary for shared objects)
            var localFolder = Path.GetDirectoryName(localPath);
            if (!Directory.Exists(localFolder))
                try
                {
                    Directory.CreateDirectory(localFolder);
                }
                catch (IOException)
                {
                    //A file may already exist that has the same name as the new folder.
                    //This may be an artifact of the way Pithos handles directories
                    var fileInfo = new FileInfo(localFolder);
                    if (fileInfo.Exists && fileInfo.Length == 0)
                    {
                        Log.WarnFormat("Malformed directory object detected for [{0}]", localFolder);
                        fileInfo.Delete();
                        Directory.CreateDirectory(localFolder);
                    }
                    else
                        throw;
                }
            //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);


        }


        private void ReportDownloadProgress(string fileName, long block, int blockPercentage,int totalBlocks, long fileSize)
        {
            StatusNotification.Notify(totalBlocks == 0
                                          ? new ProgressNotification(fileName, "Downloading", 1, blockPercentage,1, fileSize)
                                          : new ProgressNotification(fileName, "Downloading", block, blockPercentage, totalBlocks, fileSize));
        }

        private bool IsObjectChanged(ObjectInfo cloudFile, string localPath,TreeHash localTreeHash)
        {
            //If the target is a directory, there are no changes to download
            if (Directory.Exists(localPath))
                return false;
            //If the file doesn't exist, we have a chagne
            if (!File.Exists(localPath))
                return true;
            //If there is no stored state, we have a change
            var localState = StatusKeeper.GetStateByFilePath(localPath);
            if (localState == null)
                return true;

            var localHash= localTreeHash.TopHash.ToHashString();
            //If the file is different from the stored state, we have a change
            if (localState.Checksum != localHash)
                return true;
            //If the top hashes differ, we have a change
            return (localState.Checksum != cloudFile.X_Object_Hash);
        }

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

        private async Task<bool> WaitOrAbort(AccountInfo account,ObjectInfo cloudFile, CancellationToken token)
        {
            token.ThrowIfCancellationRequested();
            await UnpauseEvent.WaitAsync().ConfigureAwait(false);
            var shouldAbort = !Selectives.IsSelected(account,cloudFile);
            if (shouldAbort)
                Log.InfoFormat("Aborting [{0}]", cloudFile.Uri);
            return shouldAbort;
        }

        [Import]
        public Selectives Selectives { get; set; }

        public AsyncManualResetEvent UnpauseEvent { get; set; }
    }
}