// (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.
//
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// of MERCHANTABILITY or FITNESS FOR A PARTICULAR  PURPOSE. For details, see
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namespace ASC.Data.Backup.Services;

[Singletone]
internal sealed class BackupCleanerService : BackgroundService
{
    private readonly ILog _logger;
    private readonly TimeSpan _backupCleanerPeriod;
    private readonly IServiceScopeFactory _scopeFactory;

    public BackupCleanerService(
        ConfigurationExtension configuration,
        ILog logger,
        IServiceScopeFactory scopeFactory)
    {
        _scopeFactory = scopeFactory;
        _logger = logger;
        _backupCleanerPeriod = configuration.GetSetting<BackupSettings>("backup").Cleaner.Period;
    }

    protected override async Task ExecuteAsync(CancellationToken stoppingToken)
    {
        _logger.Debug("BackupCleanerService is starting.");

        stoppingToken.Register(() => _logger.Debug("#1 BackupCleanerService background task is stopping."));

        while (!stoppingToken.IsCancellationRequested)
        {
            _logger.Debug("BackupCleanerService background task is doing background work.");

            using var serviceScope = _scopeFactory.CreateScope();

            var registerInstanceService = serviceScope.ServiceProvider.GetService<IRegisterInstanceManager<BackupCleanerService>>();

            if (!await registerInstanceService.IsActive(RegisterInstanceWorkerService<BackupCleanerService>.InstanceId))
            {
                _logger.Debug($"BackupCleanerService background task with instance id {RegisterInstanceWorkerService<BackupCleanerService>.InstanceId} is't active.");

                await Task.Delay(1000, stoppingToken);

                continue;
            }

            ExecuteBackupCleaner(stoppingToken);

            await Task.Delay(_backupCleanerPeriod, stoppingToken);
        }

        _logger.Debug("BackupCleanerService background task is stopping.");
    }

    private void ExecuteBackupCleaner(CancellationToken stoppingToken)
    {
        using var serviceScope = _scopeFactory.CreateScope();

        var backupRepository = serviceScope.ServiceProvider.GetRequiredService<BackupRepository>();
        var backupStorageFactory = serviceScope.ServiceProvider.GetRequiredService<BackupStorageFactory>();

        _logger.Debug("started to clean expired backups");

        var backupsToRemove = backupRepository.GetExpiredBackupRecords();

        _logger.DebugFormat("found {0} backups which are expired", backupsToRemove.Count);

        foreach (var scheduledBackups in backupRepository.GetScheduledBackupRecords().GroupBy(r => r.TenantId))
        {
            if (stoppingToken.IsCancellationRequested) return;

            var schedule = backupRepository.GetBackupSchedule(scheduledBackups.Key);

            if (schedule != null)
            {
                var scheduledBackupsToRemove = scheduledBackups.OrderByDescending(r => r.CreatedOn).Skip(schedule.BackupsStored).ToList();
                if (scheduledBackupsToRemove.Any())
                {
                    _logger.DebugFormat("only last {0} scheduled backup records are to keep for tenant {1} so {2} records must be removed", schedule.BackupsStored, schedule.TenantId, scheduledBackupsToRemove.Count);
                    backupsToRemove.AddRange(scheduledBackupsToRemove);
                }
            }
            else
            {
                backupsToRemove.AddRange(scheduledBackups);
            }
        }

        foreach (var backupRecord in backupsToRemove)
        {
            if (stoppingToken.IsCancellationRequested) return;

            try
            {
                var backupStorage = backupStorageFactory.GetBackupStorage(backupRecord);
                if (backupStorage == null)
                {
                    continue;
                }

                backupStorage.Delete(backupRecord.StoragePath);

                backupRepository.DeleteBackupRecord(backupRecord.Id);
            }
            catch (ProviderInfoArgumentException error)
            {
                _logger.Warn("can't remove backup record " + backupRecord.Id, error);

                if (DateTime.UtcNow > backupRecord.CreatedOn.AddMonths(6))
                {
                    backupRepository.DeleteBackupRecord(backupRecord.Id);
                }
            }
            catch (Exception error)
            {
                _logger.Warn("can't remove backup record: " + backupRecord.Id, error);
            }
        }

    }
}