EventCacheFunctions

gistfile1.txt

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using System.Collections.Generic;
using System.Collections.ObjectModel;
using System.Linq;
using System.Threading.Tasks;
using DCAP.Common.Classes.Fields;
using DCAP.Common.Classes.Monads.Strict.Option;
using DCAP.Common.Helpers.Cache;
using DCAP.CQRS.Classes.StrongTypes;
using DCAP.CQRS.Classes.StrongTypes.Command;
using DCAP.CQRS.Interfaces;
using DCAP.CQRS.Interfaces.Command;
using DCAP.CQRS.Repositories.Interfaces;

namespace DCAP.CQRS.Services.Caching
{
    /// <summary>
    ///     Functions which generally take a <see cref="CQRSEventCache" /> and <see cref="IEventReadRepository" /> and get events from those.
    ///     I had this as a class / service, but it seemed to be complicated with registrations etc. This way, the <see cref="CQRSEventCache" /> can be registered as singleton (or instantiated as needed) and the
    ///     <see cref="IEventReadRepository" /> can be instance per lifetime etc so as to participate in transactions. Yay Functional patterns!
    /// </summary>
    public static class EventCacheFunctions
    {
        
        public static void AddEventToCache(this IEvent<AggregateTypeId> @event, CQRSEventCache cache)
            => cache.AddItemToCache(@event, @event.EventId.Value);
        
        public static async Task<Option<IEvent<AggregateTypeId>>> GetEvent(this CQRSEventCache cache, Option<PostgresSchema> postgresSchema, EventId id, IEventReadRepository readRepository)
        {
            var value = cache.ItemFromCache<IEvent<AggregateTypeId>>(id);
            if (value.HasValue) return value;

            var persisted = await readRepository.EventById(postgresSchema, id);
            if (!persisted.HasValue) return Option<IEvent<AggregateTypeId>>.Nothing;

            cache.AddItemToCache(persisted.Value, persisted.Value.EventId);
            return persisted.Value.ToOptionStrict();
        }

        public static async Task<Collection<IEvent<AggregateTypeId>>> GetEventsAsync(this CQRSEventCache cache, Option<PostgresSchema> postgresSchema, IEnumerable<EventId> ids, IEventReadRepository readRepository)
        {
            var allIds = ids.ToList();
            var missingIds = new HashSet<EventId>();
            var result = new Collection<IEvent<AggregateTypeId>>();
            foreach (var id in allIds)
            {
                var item = cache.ItemFromCache<IEvent<AggregateTypeId>>(id);
                if (item.HasValue)
                    result.Add(item.Value);
                else
                    missingIds.Add(id);
            }

            if (!missingIds.Any())
                return result;

            var newItems = await readRepository.EventsById(postgresSchema, missingIds);
            foreach (var newItem in newItems)
            {
                cache.AddItemToCache(newItem, newItem.EventId);
                result.Add(newItem);
            }

            return result;
        }
    }
}