// (c) Copyright Ascensio System SIA 2010-2022
//
// This program is a free software product.
// You can redistribute it and/or modify it under the terms
// of the GNU Affero General Public License (AGPL) version 3 as published by the Free Software
// Foundation. In accordance with Section 7(a) of the GNU AGPL its Section 15 shall be amended
// to the effect that Ascensio System SIA expressly excludes the warranty of non-infringement of
// any third-party rights.
//
// This program is distributed WITHOUT ANY WARRANTY, without even the implied warranty
// of MERCHANTABILITY or FITNESS FOR A PARTICULAR  PURPOSE. For details, see
// the GNU AGPL at: http://www.gnu.org/licenses/agpl-3.0.html
//
// You can contact Ascensio System SIA at Lubanas st. 125a-25, Riga, Latvia, EU, LV-1021.
//
// The  interactive user interfaces in modified source and object code versions of the Program must
// display Appropriate Legal Notices, as required under Section 5 of the GNU AGPL version 3.
//
// Pursuant to Section 7(b) of the License you must retain the original Product logo when
// distributing the program. Pursuant to Section 7(e) we decline to grant you any rights under
// trademark law for use of our trademarks.
//
// All the Product's GUI elements, including illustrations and icon sets, as well as technical writing
// content are licensed under the terms of the Creative Commons Attribution-ShareAlike 4.0
// International. See the License terms at http://creativecommons.org/licenses/by-sa/4.0/legalcode

namespace ASC.Data.Backup.Services;

[Singletone]
public class BackupWorker
{
    public const string CUSTOM_DISTRIBUTED_TASK_QUEUE_NAME = "backup";

    public string TempFolder { get; set; }

    private DistributedTaskQueue _progressQueue;
    private int _limit;
    private string _upgradesPath;
    private readonly TempPath _tempPath;
    private readonly SetupInfo _setupInfo;
    private readonly IServiceProvider _serviceProvider;
    private readonly object _synchRoot = new object();

    public BackupWorker(
        IDistributedTaskQueueFactory queueFactory,
        IServiceProvider serviceProvider,
        TempPath tempPath,
        SetupInfo setupInfo)
    {
        _serviceProvider = serviceProvider;
        _progressQueue = queueFactory.CreateQueue(CUSTOM_DISTRIBUTED_TASK_QUEUE_NAME);
        _tempPath = tempPath;
        TempFolder = Path.Combine(_tempPath.GetTempPath(), "backup");
        _setupInfo = setupInfo;
    }

    public void Start(BackupSettings settings)
    {
        if (!Directory.Exists(TempFolder))
        {
            Directory.CreateDirectory(TempFolder);
        }

        _limit = settings.Limit;
        _upgradesPath = settings.UpgradesPath;
        _setupInfo.ChunkUploadSize = settings.ChunkSize;
    }

    public void Stop()
    {
        if (_progressQueue != null)
        {
            var tasks = _progressQueue.GetAllTasks(DistributedTaskQueue.INSTANCE_ID);

            foreach (var t in tasks)
            {
                _progressQueue.DequeueTask(t.Id);
            }

            _progressQueue = null;
        }
    }

    public BackupProgress StartBackup(StartBackupRequest request)
    {
        lock (_synchRoot)
        {
            var item = _progressQueue.GetAllTasks<BackupProgressItem>().FirstOrDefault(t => t.TenantId == request.TenantId && t.BackupProgressItemEnum == BackupProgressItemEnum.Backup);

            if (item != null && item.IsCompleted)
            {
                _progressQueue.DequeueTask(item.Id);
                item = null;
            }
            if (item == null)
            {

                item = _serviceProvider.GetService<BackupProgressItem>();

                item.Init(request, false, TempFolder, _limit);

                _progressQueue.EnqueueTask(item);
            }

            item.PublishChanges();

            return ToBackupProgress(item);
        }
    }

    public void StartScheduledBackup(BackupSchedule schedule)
    {
        lock (_synchRoot)
        {
            var item = _progressQueue.GetAllTasks<BackupProgressItem>().FirstOrDefault(t => t.TenantId == schedule.TenantId && t.BackupProgressItemEnum == BackupProgressItemEnum.Backup);

            if (item != null && item.IsCompleted)
            {
                _progressQueue.DequeueTask(item.Id);
                item = null;
            }
            if (item == null)
            {
                item = _serviceProvider.GetService<BackupProgressItem>();

                item.Init(schedule, true, TempFolder, _limit);

                _progressQueue.EnqueueTask(item);
            }
        }
    }

    public BackupProgress GetBackupProgress(int tenantId)
    {
        lock (_synchRoot)
        {
            return ToBackupProgress(_progressQueue.GetAllTasks<BackupProgressItem>().FirstOrDefault(t => t.TenantId == tenantId && t.BackupProgressItemEnum == BackupProgressItemEnum.Backup));
        }
    }

    public BackupProgress GetTransferProgress(int tenantId)
    {
        lock (_synchRoot)
        {
            return ToBackupProgress(_progressQueue.GetAllTasks<TransferProgressItem>().FirstOrDefault(t => t.TenantId == tenantId && t.BackupProgressItemEnum == BackupProgressItemEnum.Transfer));
        }
    }

    public BackupProgress GetRestoreProgress(int tenantId)
    {
        lock (_synchRoot)
        {
            return ToBackupProgress(_progressQueue.GetAllTasks<RestoreProgressItem>().FirstOrDefault(t => t.TenantId == tenantId && t.BackupProgressItemEnum == BackupProgressItemEnum.Restore));
        }
    }

    public void ResetBackupError(int tenantId)
    {
        lock (_synchRoot)
        {
            var progress = _progressQueue.GetAllTasks<BackupProgressItem>().FirstOrDefault(t => t.TenantId == tenantId);
            if (progress != null)
            {
                progress.Exception = null;
            }
        }
    }

    public void ResetRestoreError(int tenantId)
    {
        lock (_synchRoot)
        {
            var progress = _progressQueue.GetAllTasks<RestoreProgressItem>().FirstOrDefault(t => t.TenantId == tenantId);
            if (progress != null)
            {
                progress.Exception = null;
            }
        }
    }

    public BackupProgress StartRestore(StartRestoreRequest request)
    {
        lock (_synchRoot)
        {
            var item = _progressQueue.GetAllTasks<RestoreProgressItem>().FirstOrDefault(t => t.TenantId == request.TenantId);
            if (item != null && item.IsCompleted)
            {
                _progressQueue.DequeueTask(item.Id);
                item = null;
            }
            if (item == null)
            {
                item = _serviceProvider.GetService<RestoreProgressItem>();
                item.Init(request, TempFolder, _upgradesPath);

                _progressQueue.EnqueueTask(item);
            }
            return ToBackupProgress(item);
        }
    }

    public BackupProgress StartTransfer(int tenantId, string targetRegion, bool notify)
    {
        lock (_synchRoot)
        {
            var item = _progressQueue.GetAllTasks<TransferProgressItem>().FirstOrDefault(t => t.TenantId == tenantId);
            if (item != null && item.IsCompleted)
            {
                _progressQueue.DequeueTask(item.Id);
                item = null;
            }

            if (item == null)
            {
                item = _serviceProvider.GetService<TransferProgressItem>();
                item.Init(targetRegion, tenantId, TempFolder, _limit, notify);

                _progressQueue.EnqueueTask(item);
            }

            return ToBackupProgress(item);
        }
    }

    internal static string GetBackupHashSHA(string path)
    {
        using (var sha256 = SHA256.Create())
        using (var fileStream = File.OpenRead(path))
        {
            fileStream.Position = 0;
            var hash = sha256.ComputeHash(fileStream);
            return BitConverter.ToString(hash).Replace("-", string.Empty);
        }
    }

    internal static string GetBackupHashMD5(string path, long chunkSize)
    {
        using (var md5 = MD5.Create())
        using (var fileStream = File.OpenRead(path))
        {var multipartSplitCount = 0;
                var splitCount = fileStream.Length / chunkSize;
                var mod = (int)(fileStream.Length - chunkSize * splitCount);
                IEnumerable<byte> concatHash = new byte[] { };

                for (var i = 0; i < splitCount; i++)
                {
                    var offset = i == 0 ? 0 : chunkSize * i;
                    var chunk = GetChunk(fileStream, offset, (int)chunkSize);
                    var hash = md5.ComputeHash(chunk);
                    concatHash = concatHash.Concat(hash);
                    multipartSplitCount++;
                }
                if (mod != 0)
                {
                    var chunk = GetChunk(fileStream, chunkSize * splitCount, mod);
                    var hash = md5.ComputeHash(chunk);
                    concatHash = concatHash.Concat(hash);
                    multipartSplitCount++;
                }
                var multipartHash = BitConverter.ToString(md5.ComputeHash(concatHash.ToArray())).Replace("-", string.Empty);
                return multipartHash + "-" + multipartSplitCount;
        }
    }

    private static byte[] GetChunk(Stream sourceStream, long offset, int count)
    {
        var buffer = new byte[count];
        sourceStream.Position = offset;
        sourceStream.Read(buffer, 0, count);
        return buffer;
    }

    private BackupProgress ToBackupProgress(BaseBackupProgressItem progressItem)
    {
        if (progressItem == null)
        {
            return null;
        }
        var progress = new BackupProgress
        {
            IsCompleted = progressItem.IsCompleted,
            Progress = (int)progressItem.Percentage,
            Error = progressItem.Exception != null ? progressItem.Exception.Message : "",
            TenantId = progressItem.TenantId,
            BackupProgressEnum = progressItem.BackupProgressItemEnum.Convert()
        };

        if ((progressItem.BackupProgressItemEnum == BackupProgressItemEnum.Backup || progressItem.BackupProgressItemEnum == BackupProgressItemEnum.Transfer) && progressItem.Link != null)
        {
            progress.Link = progressItem.Link;
        }

        return progress;
    }

    public bool IsInstanceTooBusy()
    {
        var instanceTasks = _progressQueue.GetAllTasks(DistributedTaskQueue.INSTANCE_ID);

        if (_progressQueue.MaxThreadsCount >= instanceTasks.Count())
        {
            return false;
        }

        return true;
    }
}