telegram-bot/modules/RichSiteSummary/RichSiteSummaryRepositoryExtension.cs

using System;
using System.Linq;
using System.Threading.Tasks;
using Kruzya.TelegramBot.RichSiteSummary.Data;
using Microsoft.EntityFrameworkCore;
using Telegram.Bot.Types;

namespace Kruzya.TelegramBot.RichSiteSummary
{
    public static class RichSiteSummaryRepositoryExtension
    {
        #region Subscriber

        /// <summary>
        /// Searchs the <see cref="Subscriber"/>, who reads a <see cref="Feed"/>.
        /// </summary>
        /// <param name="repository"></param>
        /// <param name="feed"></param>
        /// <returns>The array with all subscribers.</returns>
        public static async Task<Subscriber[]> ByFeed(this DbSet<Subscriber> repository, Feed feed)
        {
            return await repository.Where(subscriber => subscriber.Feed == feed)
                .ToArrayAsync();
        }

        public static IQueryable<Subscriber> AllSubscriptions(this DbSet<Subscriber> repository, Chat chat)
        {
            return repository.Where(entity => entity.SubscriberId == chat.Id);
        }

        public static async Task<bool> HasSubscription(this DbSet<Subscriber> repository, Chat chat, Feed feed)
        {
            return (await repository.Where(subscriber => subscriber.Feed == feed && subscriber.SubscriberId == chat.Id)
                       .CountAsync()) != 0;
        }

        #endregion
        
        #region Feed

        /// <summary>
        /// Searchs the <see cref="Feed"/> for fetching.
        /// </summary>
        /// <param name="repository"></param>
        /// <param name="period">The period (in seconds) from last fetching.</param>
        /// <param name="count">Max results count</param>
        /// <returns></returns>
        public static async Task<Feed[]> ForFetching(this DbSet<Feed> repository, UInt16 period, UInt16 count) =>
            await repository.Where(feed => feed.UpdatedAt < (DateTime.Now - TimeSpan.FromSeconds(period)))
                .OrderBy(feed => feed.UpdatedAt)
                .Take(count)
                .ToArrayAsync();

        /// <summary>
        /// Searchs the <see cref="Feed"/> for fetching.
        /// </summary>
        /// <param name="repository"></param>
        /// <param name="period">The period (in seconds) from last fetching.</param>
        /// <returns></returns>
        public static async Task<Feed[]> ForFetching(this DbSet<Feed> repository, UInt16 period) =>
            await repository.ForFetching(period, 25);

        #endregion
        
        #region Post

        public static async Task<Post> ByFeedAndUrl(this DbSet<Post> repository, string url, Feed feed = null) =>
            await repository.FirstOrDefaultAsync(post => post.Url == url && (feed == null || post.Feed == feed));

        #endregion
    }
}