telegram-bot/Core/Extensions/BotExtension.cs

using System.Threading.Tasks;
using Telegram.Bot;
using Telegram.Bot.Types;

namespace Kruzya.TelegramBot.Core.Extensions;

public static class BotExtension
{
    public static async Task<bool> CanPunishMember(this ITelegramBotClient bot, Chat chat, User user, User victim = null)
    {
        var canUse = await IsUserAdminAsync(bot, chat, user);

        if (victim != null && canUse)
        {
            var victimMember = await bot.GetChatMember(chat, victim.Id);
            canUse = victimMember is not ChatMemberOwner && victimMember is not ChatMemberAdministrator && !victim.IsBot;
        }

        return canUse;
    }

    public static async Task<bool> IsUserAdminAsync(this ITelegramBotClient bot, Chat chat, User user)
    {
        var callerMember = await bot.GetChatMember(chat, user.Id);
        var isAdmin = callerMember is ChatMemberOwner;

        if (callerMember is ChatMemberAdministrator callerAdmin)
        {
            isAdmin = callerAdmin.CanRestrictMembers;
        }

        return isAdmin;
    }

    public static async Task<bool> CanDeleteMessagesAsync(this ITelegramBotClient bot, Chat chat)
    {
        return await CanDeleteMessagesAsync(bot, chat, await bot.GetMe());
    }

    public static async Task<bool> CanDeleteMessagesAsync(this ITelegramBotClient bot, Chat chat, User user)
    {
        return await bot.GetChatMember(chat.Id, user.Id) is ChatMemberOwner 
            or ChatMemberAdministrator {CanRestrictMembers: true};
    }
}