FictionArchive/FictionArchive.Service.NovelService/Sagas/NovelImportSaga.cs

using FictionArchive.Service.Shared.Contracts.Events;
using MassTransit;
using NodaTime;

namespace FictionArchive.Service.NovelService.Sagas;

public class NovelImportSaga : MassTransitStateMachine<NovelImportSagaState>
{
    public State Importing { get; private set; } = null!;
    public State Processing { get; private set; } = null!;
    public State Completed { get; private set; } = null!;
    public State Failed { get; private set; } = null!;

    public Event<INovelImportRequested> NovelImportRequested { get; private set; } = null!;
    public Event<INovelMetadataImported> NovelMetadataImported { get; private set; } = null!;
    public Event<IChapterPullCompleted> ChapterPullCompleted { get; private set; } = null!;
    public Event<IFileUploadRequestStatusUpdate> FileUploadStatusUpdate { get; private set; } = null!;
    public Event<Fault<IChapterPullRequested>> ChapterPullFaulted { get; private set; } = null!;
    public Event<Fault<IFileUploadRequestCreated>> FileUploadFaulted { get; private set; } = null!;

    private readonly IClock _clock;

    public NovelImportSaga(IClock clock)
    {
        _clock = clock;

        InstanceState(x => x.CurrentState);

        Event(() => NovelImportRequested, x => x.CorrelateById(ctx => ctx.Message.ImportId));
        Event(() => NovelMetadataImported, x => x.CorrelateById(ctx => ctx.Message.ImportId));
        Event(() => ChapterPullCompleted, x => x.CorrelateById(ctx => ctx.Message.ImportId));
        Event(() => FileUploadStatusUpdate, x =>
        {
            x.CorrelateById(ctx => ctx.Message.ImportId ?? Guid.Empty);
            x.OnMissingInstance(m => m.Discard());
        });
        Event(() => ChapterPullFaulted, x => x.CorrelateById(ctx => ctx.Message.Message.ImportId));
        Event(() => FileUploadFaulted, x =>
        {
            x.CorrelateById(ctx => ctx.Message.Message.ImportId ?? Guid.Empty);
            x.OnMissingInstance(m => m.Discard());
        });

        Initially(
            When(NovelImportRequested)
                .Then(ctx =>
                {
                    ctx.Saga.NovelUrl = ctx.Message.NovelUrl;
                    ctx.Saga.StartedAt = _clock.GetCurrentInstant();
                })
                .TransitionTo(Importing)
        );

        During(Importing,
            When(NovelMetadataImported)
                .Then(ctx =>
                {
                    ctx.Saga.NovelId = ctx.Message.NovelId;
                    ctx.Saga.ExpectedChapters = ctx.Message.ChaptersPendingPull;
                })
                .IfElse(
                    ctx => ctx.Saga.ExpectedChapters == 0,
                    thenBinder => thenBinder
                        .Then(ctx => ctx.Saga.CompletedAt = _clock.GetCurrentInstant())
                        .TransitionTo(Completed)
                        .PublishAsync(ctx => ctx.Init<INovelImportCompleted>(new NovelImportCompleted(
                            ctx.Saga.CorrelationId,
                            ctx.Saga.NovelId,
                            true,
                            null))),
                    elseBinder => elseBinder.TransitionTo(Processing)
                )
        );

        During(Processing,
            When(ChapterPullCompleted)
                .Then(ctx =>
                {
                    ctx.Saga.CompletedChapters++;
                    ctx.Saga.ExpectedImages += ctx.Message.ImagesQueued;
                })
                .If(ctx => IsComplete(ctx.Saga), ctx => ctx
                    .Then(c => c.Saga.CompletedAt = _clock.GetCurrentInstant())
                    .TransitionTo(Completed)
                    .PublishAsync(c => c.Init<INovelImportCompleted>(new NovelImportCompleted(
                        c.Saga.CorrelationId,
                        c.Saga.NovelId,
                        true,
                        null)))),

            When(FileUploadStatusUpdate)
                .Then(ctx => ctx.Saga.CompletedImages++)
                .If(ctx => IsComplete(ctx.Saga), ctx => ctx
                    .Then(c => c.Saga.CompletedAt = _clock.GetCurrentInstant())
                    .TransitionTo(Completed)
                    .PublishAsync(c => c.Init<INovelImportCompleted>(new NovelImportCompleted(
                        c.Saga.CorrelationId,
                        c.Saga.NovelId,
                        true,
                        null)))),

            When(ChapterPullFaulted)
                .Then(ctx =>
                {
                    ctx.Saga.ErrorMessage = ctx.Message.Exceptions.FirstOrDefault()?.Message;
                    ctx.Saga.CompletedAt = _clock.GetCurrentInstant();
                })
                .TransitionTo(Failed)
                .PublishAsync(ctx => ctx.Init<INovelImportCompleted>(new NovelImportCompleted(
                    ctx.Saga.CorrelationId,
                    ctx.Saga.NovelId,
                    false,
                    ctx.Saga.ErrorMessage))),

            When(FileUploadFaulted)
                .Then(ctx =>
                {
                    ctx.Saga.ErrorMessage = ctx.Message.Exceptions.FirstOrDefault()?.Message;
                    ctx.Saga.CompletedAt = _clock.GetCurrentInstant();
                })
                .TransitionTo(Failed)
                .PublishAsync(ctx => ctx.Init<INovelImportCompleted>(new NovelImportCompleted(
                    ctx.Saga.CorrelationId,
                    ctx.Saga.NovelId,
                    false,
                    ctx.Saga.ErrorMessage)))
        );

        SetCompletedWhenFinalized();
    }

    private static bool IsComplete(NovelImportSagaState saga) =>
        saga.CompletedChapters >= saga.ExpectedChapters &&
        saga.CompletedImages >= saga.ExpectedImages;
}