Musify/backend/Core/Musify.Infrastructure/MassTransit/Sagas/AlbumProcessingStateMachine.cs

using MassTransit;
using Musify.Application.Events;

namespace Musify.Infrastructure.MassTransit.Sagas
{
    public sealed class AlbumProcessingStateMachine : MassTransitStateMachine<AlbumProcessingState>
    {
        public State Processing { get; private set; } = null!;
        public State Failed { get; private set; } = null!;

        public Event<CreateAlbumResourcesEvent> ProcessingStarted { get; private set; } = null!;
        public Event<AlbumPictureProcessed> PictureProcessed { get; private set; } = null!;
        public Event<AlbumPictureProcessingFailed> PictureFailed { get; private set; } = null!;

        public AlbumProcessingStateMachine()
        {
            InstanceState(state => state.CurrentState);

            Event(() => ProcessingStarted, config => config.CorrelateById(context => context.Message.AlbumId));
            Event(() => PictureProcessed, config =>
            {
                config.CorrelateById(context => context.Message.AlbumId);
                config.OnMissingInstance(instance => instance.Discard());
            });
            Event(() => PictureFailed, config =>
            {
                config.CorrelateById(context => context.Message.AlbumId);
                config.OnMissingInstance(instance => instance.Discard());
            });

            Initially(
                When(ProcessingStarted)
                    .Then(context =>
                    {
                        context.Saga.CreatedAt = DateTime.UtcNow;
                        context.Saga.UpdatedAt = DateTime.UtcNow;
                        context.Saga.Bucket = context.Message.Bucket;
                        context.Saga.PictureKey = context.Message.PictureDestinationKey;
                    })
                    .TransitionTo(Processing));

            During(Processing,
                When(PictureProcessed).Finalize(),
                When(PictureFailed)
                    .Then(context => context.Saga.UpdatedAt = DateTime.UtcNow)
                    .TransitionTo(Failed)
                    .Publish(context => new AlbumProcessingFailed(
                        context.Saga.CorrelationId,
                        context.Saga.Bucket,
                        context.Saga.PictureKey)));

            During(Failed,
                Ignore(PictureProcessed),
                Ignore(PictureFailed));

            SetCompletedWhenFinalized();
        }
    }
}