/*
 *
 * (c) Copyright Ascensio System Limited 2010-2020
 *
 * This program is freeware. You can redistribute it and/or modify it under the terms of the GNU 
 * General Public License (GPL) version 3 as published by the Free Software Foundation (https://www.gnu.org/copyleft/gpl.html). 
 * In accordance with Section 7(a) of the GNU GPL 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 more details, see GNU GPL at https://www.gnu.org/copyleft/gpl.html
 *
 * You can contact Ascensio System SIA by email at sales@onlyoffice.com
 *
 * The interactive user interfaces in modified source and object code versions of ONLYOFFICE must display 
 * Appropriate Legal Notices, as required under Section 5 of the GNU GPL version 3.
 *
 * Pursuant to Section 7 § 3(b) of the GNU GPL you must retain the original ONLYOFFICE logo which contains 
 * relevant author attributions when distributing the software. If the display of the logo in its graphic 
 * form is not reasonably feasible for technical reasons, you must include the words "Powered by ONLYOFFICE" 
 * in every copy of the program you distribute. 
 * Pursuant to Section 7 § 3(e) we decline to grant you any rights under trademark law for use of our trademarks.
 *
*/

namespace ASC.Core.Common.Notify;

[Scope]
public class TelegramHelper
{
    public enum RegStatus
    {
        NotRegistered,
        Registered,
        AwaitingConfirmation
    }

    private readonly ConsumerFactory _consumerFactory;
    private readonly CachedTelegramDao _cachedTelegramDao;
    private readonly TelegramServiceClient _telegramServiceClient;
    private readonly ILog _logger;

    public TelegramHelper(
        ConsumerFactory consumerFactory,
        IOptionsSnapshot<CachedTelegramDao> cachedTelegramDao,
        TelegramServiceClient telegramServiceClient,
        ILog logger)
    {
        _consumerFactory = consumerFactory;
        _cachedTelegramDao = cachedTelegramDao.Value;
        _telegramServiceClient = telegramServiceClient;
        _logger = logger;
    }

    public string RegisterUser(Guid userId, int tenantId)
    {
        var token = GenerateToken(userId);

        _telegramServiceClient.RegisterUser(userId.ToString(), tenantId, token);

        return GetLink(token);
    }

    public void SendMessage(NotifyMessage msg)
    {
        _telegramServiceClient.SendMessage(msg);
    }

    public bool CreateClient(int tenantId, string token, int tokenLifespan, string proxy)
    {
        var client = InitClient(token, proxy);
        if (TestingClient(client))
        {
            _telegramServiceClient.CreateOrUpdateClient(tenantId, token, tokenLifespan, proxy);

            return true;
        }
        else
        {
            return false;
        }
    }

    public RegStatus UserIsConnected(Guid userId, int tenantId)
    {
        if (_cachedTelegramDao.GetUser(userId, tenantId) != null)
        {
            return RegStatus.Registered;
        }

        return IsAwaitingRegistration(userId, tenantId) ? RegStatus.AwaitingConfirmation : RegStatus.NotRegistered;
    }

    public string CurrentRegistrationLink(Guid userId, int tenantId)
    {
        var token = GetCurrentToken(userId, tenantId);
        if (token == null || token.Length == 0)
        {
            return string.Empty;
        }

        return GetLink(token);
    }

    public void DisableClient(int tenantId)
    {
        _telegramServiceClient.DisableClient(tenantId);
    }

    public void Disconnect(Guid userId, int tenantId)
    {
        _cachedTelegramDao.Delete(userId, tenantId);
    }

    private bool IsAwaitingRegistration(Guid userId, int tenantId)
    {
        return GetCurrentToken(userId, tenantId) != null;
    }

    private string GetCurrentToken(Guid userId, int tenantId)
    {
        return _telegramServiceClient.RegistrationToken(userId.ToString(), tenantId);
    }

    private string GenerateToken(Guid userId)
    {
        var id = userId.ToByteArray();
        var d = BitConverter.GetBytes(DateTime.Now.Ticks);

        var buf = id.Concat(d).ToArray();

        using var sha = SHA256.Create();

        return Convert.ToBase64String(sha.ComputeHash(buf))
            .Replace('+', '-').Replace('/', '_').Replace("=", ""); // make base64 url safe
    }

    private string GetLink(string token)
    {
        var tgProvider = (ITelegramLoginProvider)_consumerFactory.GetByKey("telegram");
        var botname = tgProvider == null ? default : tgProvider.TelegramBotName;
        if (string.IsNullOrEmpty(botname))
        {
            return null;
        }

        return $"t.me/{botname}?start={token}";
    }

    public bool TestingClient(TelegramBotClient telegramBotClient)
    {
        try
        {
            if (!telegramBotClient.TestApiAsync().GetAwaiter().GetResult())
            {
                return false;
            }
        }
        catch (Exception e)
        {
            _logger.DebugFormat("Couldn't test api connection: {0}", e);

            return false;
        }

        return true;
    }

    public TelegramBotClient InitClient(string token, string proxy)
    {
        return string.IsNullOrEmpty(proxy) ? new TelegramBotClient(token) : new TelegramBotClient(token, new WebProxy(proxy));
    }
}