telegram-bot/modules/RichSiteSummary/Service/Unsubscriber.cs

using System;
using System.Collections.Concurrent;
using System.Linq;
using System.Threading.Tasks;
using BotFramework;
using Kruzya.TelegramBot.Core.Service;
using Kruzya.TelegramBot.RichSiteSummary.Data;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Logging;
using Telegram.Bot.Types;

namespace Kruzya.TelegramBot.RichSiteSummary.Service
{
    public class Unsubscriber : AbstractTimedHostedService
    {
        protected readonly ConcurrentQueue<UserUnsubscribe> _queue;
        protected readonly IServiceScopeFactory _scopeFactory;

        protected override TimeSpan TimerPeriod => TimeSpan.FromSeconds(1);

        public Unsubscriber(ILogger<Unsubscriber> logger, ITelegramBot bot, ConcurrentQueue<UserUnsubscribe> queue, IServiceScopeFactory scopeFactory) : base(logger, bot)
        {
            _scopeFactory = scopeFactory;
            _queue = queue;
        }

        protected override async Task OnRun()
        {
            if (_queue.Count == 0)
            {
                return;
            }

            UserUnsubscribe user;
            if (!_queue.TryDequeue(out user))
            {
                return;
            }

            await UnsubscribeUser(user.ChatId);
        }

        private async Task UnsubscribeUser(ChatId chatId)
        {
            using var scope = _scopeFactory.CreateScope();
            var dbContext = scope.ServiceProvider.GetRequiredService<RichSiteSummaryContext>();
            
            dbContext.Subscriptions.RemoveRange(dbContext.Subscriptions.Where(s => s.SubscriberId == chatId.Identifier));
            await dbContext.SaveChangesAsync();
        }
    }
}