// (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.Core.Common.Hosting;

#nullable enable

[Scope]
public class RegisterInstanceManager<T> : IRegisterInstanceManager<T> where T : IHostedService
{
    private readonly IRegisterInstanceDao<T> _registerInstanceRepository;
    private readonly int _timeUntilUnregisterInSeconds;
    public RegisterInstanceManager(IRegisterInstanceDao<T> registerInstanceRepository,
                                   IConfiguration configuration)
    {
        _registerInstanceRepository = registerInstanceRepository;

        if (!int.TryParse(configuration["core:hosting:timeUntilUnregisterInSeconds"], out _timeUntilUnregisterInSeconds))
        {
            _timeUntilUnregisterInSeconds = 15;
        }
    }
    public async Task Register(string instanceId)
    {
        var instances = await _registerInstanceRepository.GetAll();
        var registeredInstance = instances.FirstOrDefault(x => x.InstanceRegistrationId == instanceId);

        var instance = registeredInstance ?? new InstanceRegistration
        {
            InstanceRegistrationId = instanceId,
            WorkerTypeName = typeof(T).GetFormattedName()
        };

        instance.LastUpdated = DateTime.UtcNow;

        if (instances.Any() && !instances.Any(x => x.IsActive))
        {
            var firstAliceInstance = GetFirstAliveInstance(instances);

            if (firstAliceInstance != null && firstAliceInstance.InstanceRegistrationId == instance.InstanceRegistrationId)
            {
                instance.IsActive = true;
            }
        }

        await _registerInstanceRepository.AddOrUpdate(instance);
    }

    public async Task UnRegister(string instanceId)
    {
        await _registerInstanceRepository.Delete(instanceId);
    }

    public async Task<bool> IsActive(string instanceId)
    {
        var instances = await _registerInstanceRepository.GetAll();
        var instance = instances.FirstOrDefault(x => x.InstanceRegistrationId == instanceId);

        return instance is not null && instance.IsActive;
    }

    public async Task<List<string>> DeleteOrphanInstances()
    {
        var instances = await _registerInstanceRepository.GetAll();
        var oldRegistrations = instances.Where(IsOrphanInstance).ToList();

        foreach (var instanceRegistration in oldRegistrations)
        {
            await _registerInstanceRepository.Delete(instanceRegistration.InstanceRegistrationId);
        }

        return oldRegistrations.Select(x => x.InstanceRegistrationId).ToList();
    }

    private InstanceRegistration? GetFirstAliveInstance(IEnumerable<InstanceRegistration> instances)
    {
        Func<InstanceRegistration, long> _getTicksCreationService = x => Convert.ToInt64(x.InstanceRegistrationId.Split('_')[1]);

        return instances.Where(x => !IsOrphanInstance(x)).MinBy(_getTicksCreationService);
    }

    private bool IsOrphanInstance(InstanceRegistration obj)
    {
        return obj.LastUpdated.HasValue && obj.LastUpdated.Value.AddSeconds(_timeUntilUnregisterInSeconds) < DateTime.UtcNow;
    }
}