messengerapi/code/MessengerApi.Db/Repositories/MessageRepository.cs

using MessengerApi.Db.Contracts.Repositories;
using MessengerApi.Db.Entities;
using Microsoft.EntityFrameworkCore;

namespace MessengerApi.Db.Repositories
{
    public class MessageRepository : Repository<Message>, IMessageRepository
    {
        public MessageRepository(DbSet<Message> db) : base(db)
        {
        }

        public IEnumerable<Message> GetPendingMessages(User user)
        {
            var timestamp = DateTime.UtcNow;

            return this.db
                .Where(x => x.ToId == user.Id && x.IsDelivered == false)
                .Where(x => x.PayloadLifespanInSeconds == null || x.CreatedUtc.AddSeconds(x.PayloadLifespanInSeconds.Value) >= timestamp)
                .OrderBy(x => x.CreatedUtc);
        }
    }
}