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

using MassTransit;
using Musify.Application.Events;

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

        public Event<CreateTrackResourcesEvent> ProcessingStarted { get; private set; } = null!;
        public Event<DownloadYouTubeTrackEvent> YouTubeDownloadStarted { get; private set; } = null!;
        public Event<TrackPictureProcessed> PictureProcessed { get; private set; } = null!;
        public Event<TrackAudioProcessed> AudioProcessed { get; private set; } = null!;
        public Event<TrackPictureProcessingFailed> PictureFailed { get; private set; } = null!;
        public Event<TrackAudioProcessingFailed> AudioFailed { get; private set; } = null!;

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

            Event(() => ProcessingStarted, config => config.CorrelateById(context => context.Message.TrackId));
            Event(() => YouTubeDownloadStarted, config => config.CorrelateById(context => context.Message.TrackId));
            Event(() => PictureProcessed, config => config.CorrelateById(context => context.Message.TrackId));
            Event(() => AudioProcessed, config => config.CorrelateById(context => context.Message.TrackId));
            Event(() => PictureFailed, config => config.CorrelateById(context => context.Message.TrackId));
            Event(() => AudioFailed, config => config.CorrelateById(context => context.Message.TrackId));

            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;
                        context.Saga.AudioKey = context.Message.AudioDestinationKey;
                    } )
                    .TransitionTo(Processing),
                When(YouTubeDownloadStarted)
                    .Then(context =>
                    {
                        context.Saga.CreatedAt = DateTime.UtcNow;
                        context.Saga.UpdatedAt = DateTime.UtcNow;
                        context.Saga.Bucket = context.Message.Bucket;
                        context.Saga.PictureKey = string.Empty;
                        context.Saga.AudioKey = string.Empty;
                    } )
                    .TransitionTo(Processing));

            During(Processing,
                Ignore(YouTubeDownloadStarted),
                When(PictureProcessed)
                    .Then(context =>
                    {
                        context.Saga.PictureProcessed = true;
                        context.Saga.UpdatedAt = DateTime.UtcNow;
                    } )
                    .If(context => context.Saga.AudioProcessed, binder => binder.Finalize()),
                When(AudioProcessed)
                    .Then(context =>
                    {
                        context.Saga.AudioProcessed = true;
                        context.Saga.UpdatedAt = DateTime.UtcNow;
                    } )
                    .If(context => context.Saga.PictureProcessed, binder => binder.Finalize()),
                When(PictureFailed)
                    .Then(context => context.Saga.UpdatedAt = DateTime.UtcNow)
                    .TransitionTo(Failed)
                    .Publish(context => new TrackProcessingFailed(
                        context.Saga.CorrelationId,
                        context.Saga.Bucket,
                        context.Saga.PictureKey,
                        context.Saga.AudioKey)),
                When(AudioFailed)
                    .Then(context => context.Saga.UpdatedAt = DateTime.UtcNow)
                    .TransitionTo(Failed)
                    .Publish(context => new TrackProcessingFailed(
                        context.Saga.CorrelationId,
                        context.Saga.Bucket,
                        context.Saga.PictureKey,
                        context.Saga.AudioKey)));

            During(Failed,
                Ignore(PictureProcessed),
                Ignore(AudioProcessed),
                Ignore(PictureFailed),
                Ignore(AudioFailed),
                When(YouTubeDownloadStarted)
                    .Then(context =>
                    {
                        context.Saga.UpdatedAt = DateTime.UtcNow;
                        context.Saga.PictureProcessed = false;
                        context.Saga.AudioProcessed = false;
                        context.Saga.Bucket = context.Message.Bucket;
                        context.Saga.PictureKey = string.Empty;
                        context.Saga.AudioKey = string.Empty;
                    } )
                    .TransitionTo(Processing));

            SetCompletedWhenFinalized();
        }
    }
}