🚧 Anti-spam system based on entities

modules/UrlLimitations/Data/ChatMember.cs

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+using Telegram.Bot.Types;
+
+namespace Kruzya.TelegramBot.UrlLimitations
+{
+    public struct ChatMember
+    {
+        public long Chat;
+        public long User;
+
+        public static ChatMember From(long chatId, long userId)
+        {
+            return new ChatMember()
+            {
+                Chat = chatId,
+                User = userId
+            };
+        }
+    }
+}

modules/UrlLimitations/MessageHandler.cs

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+using System;
+using System.Linq;
+using System.Threading.Tasks;
+using BotFramework;
+using BotFramework.Attributes;
+using BotFramework.Setup;
+using Kruzya.TelegramBot.Core.Cache;
+using Kruzya.TelegramBot.Core.Extensions;
+using Microsoft.Extensions.Logging;
+using Telegram.Bot.Types;
+using Telegram.Bot.Types.Enums;
+
+namespace Kruzya.TelegramBot.UrlLimitations
+{
+    public class MessageHandler : BotEventHandler
+    {
+        protected ILogger Logger;
+        protected MemoryCache<ChatMember, UInt16> ChatMembersCache;
+
+        public MessageHandler(ILogger<MessageHandler> logger, MemoryCache<ChatMember, UInt16> chatMembersCache)
+        {
+            Logger = logger;
+            ChatMembersCache = chatMembersCache;
+        }
+
+        [TextMessage(InChat.Public)]
+        public async Task OnMessageReceived()
+        {
+            Logger.LogDebug($"Message received from {From.Id} in {Chat.Id}");
+
+            UInt16 messageCount;
+            var chatMember = ChatMember.From(Chat.Id, From.Id);
+            if (!ChatMembersCache.TryGetValue(chatMember, out messageCount))
+            {
+                return;
+            }
+
+            if (messageCount > 10)
+            {
+                ChatMembersCache.SetValue(chatMember, 0, 0);
+                return;
+            }
+
+            messageCount++;
+            ChatMembersCache.SetValue(chatMember, messageCount);
+            var message = RawUpdate.Message;
+            if (message.Entities.Count(e => e.Type == MessageEntityType.Url || e.Type == MessageEntityType.TextLink) >
+                0)
+            {
+                var targetChat = new ChatId(Chat.Id);
+                await Bot.KickChatMemberAsync(new ChatId(Chat.Id), From.Id, DateTime.Now.AddDays(1));
+                await Bot.DeleteMessageAsync(targetChat, message.MessageId);
+                await Bot.SendTextMessageAsync(targetChat,
+                    $"Member {From.ToHtml()} has been banned.\n<b>Reason</b>: <pre>Spam suspicion</pre>", ParseMode.Html);
+            }
+        }
+    }
+}

modules/UrlLimitations/UrlLimitations.cs

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+using System;
+using Kruzya.TelegramBot.Core;
+using Kruzya.TelegramBot.Core.Extensions;
+using Microsoft.Extensions.DependencyInjection;
+
+namespace Kruzya.TelegramBot.UrlLimitations
+{
+    public class UrlLimitations : Module
+    {
+        public UrlLimitations(Core.Core core) : base(core)
+        {
+        }
+
+        public override void ConfigureServices(IServiceCollection services)
+        {
+            services.AddMemoryCache<ChatMember, UInt16>();
+        }
+    }
+}

modules/UrlLimitations/UrlLimitations.csproj

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+<Project Sdk="Microsoft.NET.Sdk">
+
+    <PropertyGroup>
+        <TargetFramework>netcoreapp3.1</TargetFramework>
+        <AssemblyName>TelegramBot.UrlLimitations</AssemblyName>
+        <RootNamespace>Kruzya.TelegramBot.UrlLimitations</RootNamespace>
+    </PropertyGroup>
+
+    <ItemGroup>
+      <ProjectReference Include="..\..\Core\Core.csproj" />
+    </ItemGroup>
+
+</Project>

modules/UrlLimitations/UserJoinHandler.cs

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+using System;
+using BotFramework;
+using BotFramework.Attributes;
+using BotFramework.Setup;
+using Kruzya.TelegramBot.Core.Cache;
+using Telegram.Bot.Types.Enums;
+
+namespace Kruzya.TelegramBot.UrlLimitations
+{
+    public class UserJoinHandler : BotEventHandler
+    {
+        protected MemoryCache<ChatMember, UInt16> ChatMembersCache;
+        
+        public UserJoinHandler(MemoryCache<ChatMember, UInt16> chatMembersCache)
+        {
+            ChatMembersCache = chatMembersCache;
+        }
+        
+        [Message(MessageType.ChatMembersAdded, InChat.Public)]
+        public void OnChatMembersAdded()
+        {
+            ChatMembersCache.SetValue(ChatMember.From(Chat.Id, From.Id), 0);
+        }
+    }
+}