Connected.Logistics/Connected.Logistics.Types/Serials/SerialOps.cs

using System.Collections.Immutable;
using Connected.Caching;
using Connected.Entities;
using Connected.Entities.Storage;
using Connected.Notifications.Events;
using Connected.ServiceModel;
using Connected.Services;

namespace Connected.Logistics.Types.Serials;
internal sealed class SerialOps
{
	/// <inheritdoc cref="ISerialService.Delete(PrimaryKeyArgs{long})"/>
	public sealed class Delete : ServiceAction<PrimaryKeyArgs<long>>
	{
		public Delete(IStorageProvider storage, ISerialService serials, IEventService events, ICachingService cache)
		{
			Storage = storage;
			Serials = serials;
			Events = events;
			Cache = cache;
		}

		private IStorageProvider Storage { get; }
		private ISerialService Serials { get; }
		private IEventService Events { get; }
		private ICachingService Cache { get; }

		protected override async Task OnInvoke()
		{
			if (await Serials.Select(Arguments.Id) is not ISerial serial)
				return;
			/*
			 * Setting state of the entity enable other middleware to use the entity even after it 
			 * is deleted. For example, IEventListener will receive the state of this operation.
			 */
			SetState(serial);
			/*
			 * Perform delete.
			 */
			await Storage.Open<Serial>().Update(Arguments.AsEntity<Serial>(State.Deleted));
		}

		protected override async Task OnCommitted()
		{
			/*
			 * Remove entity from the cache.
			 */
			await Cache.Remove(Serial.EntityKey, Arguments.Id);
			/*
			 * Enqueue event so event listeners can respond to the transaction.
			 */
			await Events.Enqueue(this, Events, nameof(ISerialService.Deleted), Arguments);
		}
	}

	/// <inheritdoc  cref=" ISerialService.Insert(InsertSerialArgs)"/>
	public sealed class Insert : ServiceFunction<InsertSerialArgs, long>
	{
		public Insert(IStorageProvider storage, IEventService events)
		{
			Storage = storage;
			Events = events;
		}

		private IStorageProvider Storage { get; }
		private IEventService Events { get; }

		protected override async Task<long> OnInvoke()
		{
			/*
			 * Perform insert and return the newly inserted id.
			 */
			return (await Storage.Open<Serial>().Update(Arguments.AsEntity<Serial>(State.New))).Id;
		}

		protected override async Task OnCommitted()
		{
			await Events.Enqueue(this, Events, nameof(ISerialService.Inserted), Arguments);
		}
	}

	/// <inheritdoc cref="ISerialService.Query(QueryArgs?)"/>
	public sealed class Query : ServiceFunction<QueryArgs, ImmutableList<ISerial>>
	{
		public Query(IStorageProvider storage)
		{
			Storage = storage;
		}

		private IStorageProvider Storage { get; }

		protected override async Task<ImmutableList<ISerial>> OnInvoke()
		{
			/*
			 * For non cached entities query always hits the storage.
			 */
			return await (from e in Storage.Open<Serial>()
						  select e).WithArguments(Arguments).AsEntities<ISerial>();
		}
	}
	/// <inheritdoc cref="ISerialService.Query(PrimaryKeyListArgs{long})"/>
	public sealed class Lookup : ServiceFunction<PrimaryKeyListArgs<long>, ImmutableList<ISerial>>
	{
		public Lookup(IStorageProvider storage)
		{
			Storage = storage;
		}

		private IStorageProvider Storage { get; }

		protected override async Task<ImmutableList<ISerial>> OnInvoke()
		{
			return await (from e in Storage.Open<Serial>()
						  where Arguments.IdList.Any(f => f == e.Id)
						  select e).AsEntities<ISerial>();
		}
	}
	/// <inheritdoc cref="ISerialService.Select(PrimaryKeyArgs{long})"/>
	public sealed class Select : NullableServiceFunction<PrimaryKeyArgs<long>, ISerial>
	{
		public Select(IStorageProvider storage, ICachingService cache)
		{
			Storage = storage;
			Cache = cache;
		}

		private IStorageProvider Storage { get; }
		private ICachingService Cache { get; }

		protected override async Task<ISerial?> OnInvoke()
		{
			/*
			 * First, try to receive entity from the cache. If it doesn't exist in the cache
			 * load it from storage. If storage returns non null value, store it in the cache
			 * for subsequent calls. The entity gets remove either because of inactivity or when
			 * updating or deleting it.
			 */
			return await Cache.Get<ISerial>(Serial.EntityKey, Arguments.Id, async (f) =>
			{
				/*
				 * Doesn't exist in the cache. Let's do the storage action.
				 */
				return await (from e in Storage.Open<Serial>()
							  where e.Id == Arguments.Id
							  select e).AsEntity();
			});
		}
	}
	/// <inheritdoc cref="ISerialService.Select(SelectSerialArgs)"/>
	public sealed class SelectByValue : NullableServiceFunction<SelectSerialArgs, ISerial>
	{
		public SelectByValue(IStorageProvider storage, ICachingService cache)
		{
			Storage = storage;
			Cache = cache;
		}

		private IStorageProvider Storage { get; }
		private ICachingService Cache { get; }

		protected override async Task<ISerial?> OnInvoke()
		{
			return await Cache.Get<ISerial>(Serial.EntityKey, f => string.Equals(f.Value, Arguments.Value, StringComparison.OrdinalIgnoreCase), async (f) =>
			{
				return await (from e in Storage.Open<Serial>()
							  where string.Equals(e.Value, Arguments.Value, StringComparison.OrdinalIgnoreCase)
							  select e).AsEntity();
			});
		}
	}
	/// <inheritdoc cref="ISerialService.Update(UpdateSerialArgs)"/>
	public sealed class Update : ServiceAction<UpdateSerialArgs>
	{
		public Update(IStorageProvider storage, ICachingService cache, ISerialService packingService, IEventService events)
		{
			Storage = storage;
			Cache = cache;
			Serials = packingService;
			Events = events;
		}

		private IStorageProvider Storage { get; }
		private ICachingService Cache { get; }
		private ISerialService Serials { get; }
		private IEventService Events { get; }

		protected override async Task OnInvoke()
		{
			/*
			 * Set the state of the unchanged entity. This enable other middleware to 
			 * calculate quantity delta, for example because they receive the state of
			 * this operation. Not all middleware supports this, the primary example of
			 * such state client is IEventListener.
			 */
			if (SetState(await Serials.Select(Arguments.Id)) is not Serial entity)
				return;
			/*
			 * Sinc ethis is concurrent entity we must perform retry if the concurrency fails.
			 */
			await Storage.Open<Serial>().Update(entity.Merge(Arguments, State.Default), Arguments, async () =>
			{
				/*
				 * The update failed because of concurrency. Remove the entity from the cache to ensure
				 * it gets loaded from the storage next time with fresh values and try again.
				 */
				await Cache.Remove(Serial.EntityKey, Arguments.Id);
				/*
				 * Since the entity reloaded we must overwrite its state.
				 */
				return SetState(await Serials.Select(Arguments.Id)) as Serial;
			});
		}

		protected override async Task OnCommitted()
		{
			await Cache.Remove(Serial.EntityKey, Arguments.Id);
			await Events.Enqueue(this, Serials, nameof(Serials.Updated), Arguments);
		}
	}
}