telegram-bot/Core/Service/MemoryAntiFloodService.cs

using System;
using System.Collections;
using System.Collections.Generic;
using System.Linq;
using Microsoft.Extensions.Configuration;
using Telegram.Bot.Types;

namespace Kruzya.TelegramBot.Core.Service;

public class MemoryAntiFloodService : IAntiFlood
{
    private IDictionary<string, IList<DateTime>> _floodUsers;
    private IDictionary<string, DateTime> _bannedUsers;
    private int _floodStartsAfter = 3;
    private TimeSpan _banningTimeSpan; 

    public MemoryAntiFloodService(IConfiguration configuration)
    {
        _floodUsers = new Dictionary<string, IList<DateTime>>();
        _bannedUsers = new Dictionary<string, DateTime>();
        _floodStartsAfter = configuration.GetValue<int>("FloodActions");
        _banningTimeSpan = TimeSpan.FromMinutes(configuration.GetValue<double>("FloodBanTime"));
    }

    public bool IsUserFlooding(Chat chat, User user)
    {
        var dictKey = DictKey(chat, user);
        if (_bannedUsers.TryGetValue(dictKey, out var expirationTime))
        {
            if (DateTime.UtcNow <= expirationTime)
            {
                expirationTime = DateTime.MinValue;
                _bannedUsers.Remove(dictKey);
            }
        }

        return (DateTime.UtcNow >= expirationTime);
    }

    public void RecordAction(Chat chat, User user)
    {
        var dictKey = DictKey(chat, user);
        if (!_floodUsers.TryGetValue(dictKey, out var actionTimeList))
        {
            actionTimeList = new List<DateTime>();
        }

        actionTimeList.Add(DateTime.UtcNow);
        actionTimeList = actionTimeList.Where(e => e.Subtract(_banningTimeSpan) <= DateTime.UtcNow).ToList();
        _floodUsers[dictKey] = actionTimeList;

        if (actionTimeList.Count > _floodStartsAfter)
        {
            actionTimeList.Clear();
            _bannedUsers[dictKey] = DateTime.UtcNow.Add(_banningTimeSpan);
        }
    }

    private string DictKey(Chat chat, User user)
    {
        return $"{chat.Id}-{user.Id}";
    }
}