telegram-bot/modules/CodeWatcher/Handler.cs

using System.Collections.Concurrent;
using BotFramework;
using BotFramework.Attributes;
using BotFramework.Enums;
using Kruzya.TelegramBot.Core.Extensions;
using Telegram.Bot;
using Telegram.Bot.Types;
using Telegram.Bot.Types.Enums;

namespace West.TelegramBot.CodeWatcher;

public class Handler : BotEventHandler
{
    private readonly ConcurrentBag<DeleteRequest> _requests;

    public Handler(ConcurrentBag<DeleteRequest> requests)
    {
        _requests = requests;
    }

    [Update(InChat.Public, UpdateFlag.Message | UpdateFlag.EditedMessage)]
    public async Task HandleMessage()
    {
        var message = RawUpdate.Message ?? RawUpdate.EditedMessage;

        if (message?.Entities == null)
        {
            return;
        }

        if (!await Bot.CanDeleteMessagesAsync(Chat))
        {
            return;
        }

        foreach (var entity in message.Entities)
        {
            if (entity.Type is MessageEntityType.Code or MessageEntityType.Pre)
            {
                var entityLines = message.Text!
                    .Substring(entity.Offset, entity.Length)
                    .SplitToLines()
                    .ToList();

                if (entityLines.Count < 2)
                {
                    continue;
                }

                if (entityLines.Count >= 20 || entityLines.Any(line => line.Length > 160))
                {
                    await DeleteAndNotifyAsync(message);
                    return;
                }
            }
        }
    }

    public async Task DeleteAndNotifyAsync(Message message)
    {
        await Bot.DeleteMessageAsync(Chat.Id, message.MessageId);
        var notifyMsg = await Bot.SendTextMessageAsync(Chat.Id,
            (message.From?.ToHtml() ?? "") + ", не стоит публиковать столь большой код прямо в чат. " +
            "Вместо этого загрузите его на https://pastebin.com и отправьте в виде ссылки.", 
            ParseMode.Html);

        // TODO: maybe write a wrapper-service around collection to avoid direct interactions with the collection, West, 07.07.2022, 16:53
        _requests.Add(new DeleteRequest
        {
            ChatId = notifyMsg.Chat.Id,
            MessageId = notifyMsg.MessageId,
            DeleteAt = DateTime.Now.AddSeconds(30)
        });
    }
}