Acercándonos a la Programación Funcional a través de la Arquitectura Hexagonal - ScMad+ScalaMad

1. Acercándonos a la Programación Funcional 🦄 a través de la Arquitectura Hexagonal 🎯 Habla Computing + CodelyTV

2. Madrid, 21 de Noviembre de 2018

3. Functional Programming intro based on Hexagonal Architecture Who we are @JavierCane@juanshac

4. Session goal 🤔  Rethinking time Functional Programming intro based on Hexagonal Architecture Reviewing different technics to solve the same problems with more modularity

5. 🗺Design principles %Implementation details 🦄 Functional Architectures 🎯 Hexagonal Architecture Functional Programming intro based on Hexagonal Architecture 🦄 Functional Architectures 🎯 Hexagonal Architecture 🏗 APIs ⚡ Errors 🏗 APIs ⚡ Errors

7. 🗺 Design principles > 🎯 Hexagonal Architecture 🛀 Clean Architectures

8. 🤯 Ports & adapters 🚫 🗺 Design principles > 🎯 Hexagonal Architecture

9. Layers & dependency rule Infrastructure Application Domain 🗺 Design principles > 🎯 Hexagonal Architecture

10. Layered Architecture Presentation Domain Database 🗺 Design principles > 🎯 Hexagonal Architecture

11. Layered vs Hexagonal Presentation Domain Database Infrastructure Application Domain 🗺 Design principles > 🎯 Hexagonal Architecture

13. CONTROLLER REPOS MODELS SERVICES APPLICATION SERVICE D A I Request flow IMPLEMENTATION Acceptance test Unit test Integration test 🗺 Design principles > 🎯 Hexagonal Architecture

14. Acceptance test Unit test Integration test CONTROLLER REPOS MODELS SERVICES APPLICATION SERVICE D A I Request flow IMPLEMENTATION 🗺 Design principles > 🎯 Hexagonal Architecture Port Adapter

15. VideoPostController VideoRepository VideoVideoCreator D A I DoobieMySqlVideoRepo Acceptance test Unit test Integration test Request flow example 🗺 Design principles > 🎯 Hexagonal Architecture

16. VideoPostController VideoRepository VideoVideoCreator D A I DoobieMySqlVideoRepo Acceptance test Unit test Integration test Port Adapter 🗺 Design principles > 🎯 Hexagonal Architecture Request flow example

18. Domain Events, CQRS, and Event Sourcing as an optional further step

21. What is a functional architecture? DSL1 DSL2 DSLN … 🗺 Design principles > 🦄 Functional Architectures A FUNCTIONAL LANGUAGE IS A DOMAIN- SPECIFIC LANGUAGE FOR DEFINING DOMAIN-SPECIFIC LANGUAGES

22. The DSLs of your application • Infrastructure DSLs • HTTP • Databases • Messaging • Application-speciﬁc DSLs • Use cases • Repos • … HTTP SERVICE DSL SQL REPO DSL 🗺 Design principles > 🦄 Functional Architectures

23. Are hexagonal and functional architectures like apples and oranges? HTTP SERVICE DSL SQL REPO DSL CONTROLLER SERVICE IMPL. ORM DB ADAPTER/INTERP. PORT/DSL 🗺 Design principles > 🦄 Functional Architectures

24. There are no exceptions • Everything is either a port or an adapter • Every adapter implements a given port • Adapters are implemented on top of other ports VideoPostController VideoRepositoryVideoRepoC DoobieMySqlVideoRepo VideoCreator HTTP 🗺 Design principles > 🦄 Functional Architectures

25. 🎯 🦄 VideoPostController VideoRepository VideoCreator DoobieMySqlVideoRepo VideoPostController VideoRepositoryVideoRepoC DoobieMySqlVideoRepo VideoCreator HTTP

26. 🗺 Design principles > 🦄 Functional Architectures … VideoPostController VideoRepoC VideoCreator HTTPVideoPostClient VideoCreator… …… Why to declare the Application Service API?

27. 🤔 Rethinking time 🗺 Design principles

28. 🗺 Design principles > 🤔 Rethinking time Final goals • Decouple from infrastructure • Testing easiness (test doubles when testing out use cases) • Change tolerance • ¡Same goals!

29. 🗺 Design principles > 🤔 Rethinking time Differences: More decoupling and indirection levels • Controllers: • Consistency (APIs for all DSLs) vs. Speciﬁc needs • Conclusion: We need industry standards. PHP-FIG as example to follow • Application Services: • Consistency (APIs for all DSLs) vs. Speciﬁc needs • Reuse use case APIs in clients (e.g. user clients)

32. Remembering the Architecture layers VideoPostController VideoRepositoryVideoCreator DoctrineMySqlVideoRepo App Dom Infra

33. 🐘 PHP

34. final class VideoPostController extends ApiController { private $creator; public function __construct(VideoCreator $creator) { parent::__construct(); $this->creator = $creator; } public function __invoke(Request $request) { VideoPostController - HTTP API Controller VideoPostController VideoRepositoryVideoCreator DoctrineMySqlVideoRepo

35. final class VideoPostController extends ApiController { private $creator; public function __construct(VideoCreator $creator) { parent::__construct(); $this->creator = $creator; } public function __invoke(Request $request) { VideoPostController - HTTP API Controller VideoPostController VideoRepositoryVideoCreator DoctrineMySqlVideoRepo

36. final class VideoPostController extends ApiController { private $creator; public function __construct(VideoCreator $creator) { parent::__construct(); $this->creator = $creator; } public function __invoke(Request $request) { $id = new VideoId($request->get('id')); $type = new VideoType($request->get('type')); $title = new VideoTitle($request->get('title')); $url = new VideoUrl($request->get('url')); $courseId = new CourseId($request->get('course_id')); $this->creator->create( $id, $type, $title, $url, $courseId ); return new ApiHttpCreatedResponse(); VideoPostController - HTTP API Controller VideoPostController VideoRepositoryVideoCreator DoctrineMySqlVideoRepo

37. final class VideoPostController extends ApiController { private $creator; public function __construct(VideoCreator $creator) { parent::__construct(); $this->creator = $creator; } public function __invoke(Request $request) { $id = new VideoId($request->get('id')); $type = new VideoType($request->get('type')); $title = new VideoTitle($request->get('title')); $url = new VideoUrl($request->get('url')); $courseId = new CourseId($request->get('course_id')); $this->creator->create( $id, $type, $title, $url, $courseId ); return new ApiHttpCreatedResponse(); VideoPostController - HTTP API Controller VideoPostController VideoRepositoryVideoCreator DoctrineMySqlVideoRepo

38. final class VideoCreator { private $repository; private $publisher; public function __construct( VideoRepository $repository, DomainEventPublisher $publisher ) { $this->repository = $repository; $this->publisher = $publisher; } public function create( VideoCreator - Application Service/Use case VideoPostController VideoRepositoryVideoCreator DoobieMySqlVideoRepoDoctrineMySqlVideoRepo

39. final class VideoCreator { private $repository; private $publisher; public function __construct( VideoRepository $repository, DomainEventPublisher $publisher ) { $this->repository = $repository; $this->publisher = $publisher; } public function create( VideoCreator - Application Service/Use case VideoPostController VideoRepositoryVideoCreator DoctrineMySqlVideoRepo

40. private $repository; private $publisher; public function __construct( VideoRepository $repository, DomainEventPublisher $publisher ) { $this->repository = $repository; $this->publisher = $publisher; } public function create( VideoId $id, VideoType $type, VideoTitle $title, VideoUrl $url, CourseId $courseId ) { $video = Video::create($id, $type, $title, $url, $courseId); $this->repository->save($video); $this->publisher->publish(...$video->pullDomainEvents()); } } VideoCreator - Application Service/Use case VideoPostController VideoRepositoryVideoCreator DoctrineMySqlVideoRepo

42. public static function create( VideoId $id, VideoType $type, VideoTitle $title, VideoUrl $url, CourseId $courseId ): Video { $video = new self($id, $type, $title, $url, $courseId); $video->record( new VideoCreatedDomainEvent( $id->value(), [ 'type' => $type->value(), 'title' => $title->value(), 'url' => $url->value(), 'courseId' => $courseId->value(), ] ) ); return $video; Video#create - AggregateRoot

43. public static function create( VideoId $id, VideoType $type, VideoTitle $title, VideoUrl $url, CourseId $courseId ): Video { $video = new self($id, $type, $title, $url, $courseId); $video->record( new VideoCreatedDomainEvent( $id->value(), [ 'type' => $type->value(), 'title' => $title->value(), 'url' => $url->value(), 'courseId' => $courseId->value(), ] ) ); return $video; Video#create - AggregateRoot

45. interface VideoRepository { public function save(Video $video): void; public function search(VideoId $id): ?Video; public function searchByCriteria(Criteria $criteria): Videos; } VideoRepository - Domain contract/Port VideoPostController VideoRepositoryVideoCreator DoctrineMySqlVideoRepo

46. DoobieMySqlVideoRepository - Infrastructure implementation/Adapter VideoPostController VideoRepositoryVideoCreator final class DoctrineMySqlVideoRepository implements VideoRepository { private $entityManager; public function __construct(EntityManager $entityManager) { $this->entityManager = $entityManager; } public function save(Video $video): void { $this->entityManager()->persist($entity); DoctrineMySqlVideoRepo

47. final class DoctrineMySqlVideoRepository implements VideoRepository { private $entityManager; public function __construct(EntityManager $entityManager) { $this->entityManager = $entityManager; } public function save(Video $video): void { $this->entityManager()->persist($entity); $this->entityManager()->flush($entity); } // ... } DoobieMySqlVideoRepository - Infrastructure implementation/Adapter VideoPostController VideoRepositoryVideoCreator DoctrineMySqlVideoRepo

48. final class DoctrineMySqlVideoRepository implements VideoRepository { private $entityManager; public function __construct(EntityManager $entityManager) { $this->entityManager = $entityManager; } public function save(Video $video): void { $this->entityManager()->persist($entity); $this->entityManager()->flush($entity); } // ... } DoobieMySqlVideoRepository - Infrastructure implementation/Adapter VideoPostController VideoRepositoryVideoCreator DoctrineMySqlVideoRepo

49. 🧖 Scala

50. final class VideoPostController(creator: VideoCreator) { def post(id: String, title: String): StandardRoute = { creator.create(VideoId(id), VideoTitle(title)) complete(HttpResponse(Created)) } } VideoPostController - HTTP API Controller VideoPostController VideoRepositoryVideoCreator DoobieMySqlVideoRepo

53. object VideoQuality { val maxQuality = 50 val minQuality = 0 } final case class VideoQuality(value: Int) { require(value <= maxQuality, s"Video quality value greater than $maxQuality") require(value >= minQuality, s"Video quality value less than $minQuality") def increase(): VideoQuality = { if (value >= maxQuality) this else copy(value + 1) } } OOP: Data+Behaviour 👤 Domain models > 🎯 OOP > VideoQuality Value Object

54. object VideoQuality { val maxQuality = 50 val minQuality = 0 } final case class VideoQuality(value: Int) { require(value <= maxQuality, s"Video quality value greater than $maxQuality") require(value >= minQuality, s"Video quality value less than $minQuality") def increase(): VideoQuality = { if (value >= maxQuality) this else copy(value + 1) } } Behaviour Simpler API + domain semantics + immutability 👤 Domain models > 🎯 OOP > VideoQuality Value Object

55. case class Video( id: VideoId, title: VideoTitle, quality: VideoQuality ) { def increaseQuality(): Video = copy(quality = quality.increase()) } VideoQualityIncreaser Video increaseQuality() Behaviour Rich domain model - Tell don’t ask 👤 Domain models > 🎯 OOP > Video Entity

58. final class VideoCreator( repository: VideoRepository, publisher: MessagePublisher ) { def create(id: VideoId, title: VideoTitle): Unit = { val video = Video(id, title) repository.save(video) publisher.publish(VideoCreated(video)) } } VideoCreator - Application Service/Use case VideoPostController VideoRepositoryVideoCreator DoobieMySqlVideoRepo

61. trait VideoRepository { def all(): Future[Seq[Video]] def save(video: Video): Future[Unit] } VideoRepository - Domain contract/Port VideoPostController VideoRepositoryVideoCreator DoobieMySqlVideoRepo

62. DoobieMySqlVideoRepository - Infrastructure implementation/Adapter VideoPostController VideoRepositoryVideoCreator DoobieMySqlVideoRepo final class DoobieMySqlVideoRepository(db: DoobieDbConnection) (implicit ec: ExecutionContext) extends VideoRepository { override def all(): Future[Seq[Video]] = db.read(sql”SELECT…”.query[Video].to[Seq]) override def save(video: Video): Future[Unit] = sql"INSERT INTO…”.update.run .transact(db.transactor) .unsafeToFuture().map(_ => ()) }

65. object VideoQuality { val maxQuality = 50 val minQuality = 0 } final case class VideoQuality(value: Int) { require(value <= maxQuality, s"Video quality value greater than $maxQuality") require(value >= minQuality, s"Video quality value less than $minQuality") def increase(): VideoQuality = { if (value >= maxQuality) this else copy(value + 1) } } VO: Raise exceptions for invalid states ⚡Error Handling > 🎯 OOP > Raise exceptions

66. final class VideoFinder(repository: VideoRepository) (implicit ec: ExecutionContext) { def find(id: VideoId): Future[Video] = repository.search(id).map { videoOption => if (videoOption.isEmpty) throw VideoNotFound(id) else videoOption.get } } Imperativeness ⚡Error Handling > 🎯 OOP > Raise exceptions trait VideoRepository { def search(id: VideoId): Future[Option[Video]] }

67. final class VideoGetController extends ApiController { protected function exceptions(): array { return [ VideoNotFound::class => Response::HTTP_NOT_FOUND, ]; } // … } HTTP Mapping ⚡Error Handling > 🎯 OOP > Handle exceptions

70. 🗺 Design principles > 🦄 Functional Architectures VideoController VideoFinderRepo VideoFinder HTTPVideoClient VideoFinder… … DoobieRepo… VideoRepo API

71. trait VideoRepository { def all(): Future[Seq[Video]] def save(video: Video): Future[Unit] } Domain contract/PortVideoRepository ? trait VideoRepository { def all(): cats.IO[Seq[Video]] def save(video: Video): cats.IO[Unit] } trait VideoRepository { def all(): Seq[Video] def save(video: Video): Unit }

72. trait VideoRepository { def all(): Seq[Video] def save(video: Video): Unit } trait VideoRepository { def all(): Future[Seq[Video]] def save(video: Video): Future[Unit] } trait VideoRepository { def all(): cats.IO[Seq[Video]] def save(video: Video): cats.IO[Unit] } Domain contract/Port infrastructure leaks VideoRepository ?

73. trait VideoRepository[P[_]] { def all(): P[Seq[Video]] def save(video: Video): P[Unit] } TYPE (CONSTRUCTOR) CLASSES VideoRepository ? Domain contract/Port

74. 🗺 Design principles > 🦄 Functional Architectures VideoController VideoFinderRepo VideoFinder HTTPVideoClient VideoFinder… … DoobieRepo… VideoRepo INSTANCE

75. Infrastructure implementation/Adapter import scala.concurent.Future final class DoobieMySqlVideoRepoFuture( db: DoobieDbConnection[Future])(implicit ec: ExecutionContext) extends VideoRepository[Future] { override def all(): Future[Seq[Video]] = db.read(sql"SELECT ...".query[Video].to[Seq]) override def save(video: Video): Future[Unit] = sql"INSERT INTO ... ".update.run .transact(db.transactor) .map(_ => ()) } VideoRepository DoobieVideoRepoFuture INSTANTIATION

76. Infrastructure implementation/Adapter import scala.concurent.Future final class DoobieMySqlVideoRepoFuture( db: DoobieDbConnection[Future])(implicit ec: ExecutionContext) extends VideoRepository[Future] { override def all(): Future[Seq[Video]] = db.read(sql"SELECT ...".query[Video].to[Seq]) override def save(video: Video): Future[Unit] = sql"INSERT INTO ... ".update.run .transact(db.transactor) .map(_ => ()) } VideoRepository DoobieVideoRepoFuture INSTANTIATION

77. Infrastructure implementation/AdapterVideoRepository DoobieVideoRepoIO import cats.effect.IO final class DoobieMySqlVideoRepoIO( db: DoobieDbConnection[IO]) extends VideoRepository[IO] { override def all(): IO[Seq[Video]] = db.read(sql"SELECT ...".query[Video].to[Seq]) override def save(video: Video): IO[Unit] = sql"INSERT INTO ... ".update.run .transact(db.transactor) .map(_ => ()) } INSTANTIATION

78. Infrastructure implementation/AdapterVideoRepository DoobieVideoRepoIO import cats.effect.IO final class DoobieMySqlVideoRepoIO( db: DoobieDbConnection[IO]) extends VideoRepository[IO] { override def all(): IO[Seq[Video]] = db.read(sql"SELECT ...".query[Video].to[Seq]) override def save(video: Video): IO[Unit] = sql"INSERT INTO ... ".update.run .transact(db.transactor) .map(_ => ()) } INSTANTIATION

79. Infrastructure implementation/AdapterVideoRepository DoobieVideoRepo (GENERIC) INSTANTIATION final case class DoobieMySqlVideoRepo[P[_]: Monad]()( db: DoobieDbConnection[P]) extends VideoRepository[P] { override def all(): P[Seq[Video]] = db.read(sql"SELECT …”.query[Video].to[Seq]) override def save(video: Video): P[Unit] = sql"INSERT …”.update.run .transact(db.transactor) .map(_ => ()) }

80. Infrastructure implementation/AdapterVideoRepository DoobieVideoRepo (GENERIC) INSTANTIATION final case class DoobieMySqlVideoRepo[P[_]: Monad]()( db: DoobieDbConnection[P]) extends VideoRepository[P] { override def all(): P[Seq[Video]] = db.read(sql"SELECT …”.query[Video].to[Seq]) override def save(video: Video): P[Unit] = sql"INSERT …”.update.run .transact(db.transactor) .map(_ => ()) }

83. 🗺 Design principles > 🦄 Functional Architectures VideoController VideoFinderRepo VideoFinder HTTPVideoClient VideoFinder… … DoobieRepo… VideoRepo API

84. ⚡Error Handling > 🦄 FP > Raise errors trait VideoFinder[P[_]]{ def find(id: VideoId)(implicit E: MonadError[P, VideoFinderError]): P[Video] } A functional signature doesn’t hide anything! trait MonadError[F[_], E] { def raiseError[A](e: E): F[A] def handleErrorWith[A](fa: F[A])(f: E => F[A]): F[A] }

85. 🗺 Design principles > 🦄 Functional Architectures VideoController VideoFinderRepo VideoFinder HTTPVideoClient VideoFinder… … DoobieRepo… VideoRepo INSTANCE / LOGIC

86. Imperativeness ⚡Error Handling > 🦄 FP > Raise errors Declarativeness + final case class VideoFinderRepo[P[_]]()( implicit repository: VideoRepository[P] ) extends VideoFinder[P] { def find(id: VideoId)(implicit E: MonadError[P, VideoFinderError]): P[Video] = repository.search(id) flatMap { maybeVideo => maybeVideo.fold(E.raiseError[Video](VideoNotFound(id))){ video => video.pure[P] } } }

87. ⚡Error Handling > 🦄 FP > Raise errors final case class VideoFinderRepo[P[_]: Monad]()( implicit repository: VideoRepository[P] ) extends VideoFinder[P] { def find(id: VideoId)(implicit E: MonadError[P, VideoFinderError]): P[Video] = repository.search(id) flatMap { maybeVideo => maybeVideo.fold(E.raiseError[Video](VideoNotFound(id))){ video => video.pure[P] } } } Imperativeness

88. ⚡Error Handling > 🦄 FP > Raise errors final case class VideoFinderRepo[P[_]: Monad]()( implicit repository: VideoRepository[P] ) extends VideoFinder[P] { def find(id: VideoId)(implicit E: MonadError[P, VideoFinderError]): P[Video] = val maybeVideo = repository.search(id) ; if (videoOption.isEmpty) throw VideoNotFound(id) else videoOption.get } Monadic programming is imperative programming with steroids!

89. 🗺 Design principles > 🦄 Functional Architectures VideoController VideoFinderRepo VideoFinder HTTPVideoClient VideoFinder… … DoobieRepo… VideoRepo LOGIC

90. object FutureBasedController{ case class VideoController( videoFinder: VideoFinder[Future] )(implicit ec: ExecutionContext) extends Http4sDsl[Future] { val service = HttpService[Future] { case GET -> Root / "videos" / id => videoFinder.find(VideoId(id)) flatMap { case video => Ok(video.asJson) } recoverWith { case error: VideoNotFound => NotFound(error.asJson) } } } } ⚡Error Handling > 🦄 FP > Raise errors Future-based HTTP Mapping LOGIC

91. case class VideoController[P[_]: Effect]( videoFinder: VideoFinder[P] ) extends Http4sDsl[P] { val service = HttpService[P] { case GET -> Root / "videos" / id => videoFinder.find(VideoId(id)) flatMap { case video => Ok(video.asJson) } handleErrorWith { case error: VideoNotFound => NotFound(error.asJson) } } } ⚡Error Handling > 🦄 FP > Raise errors Generic HTTP Mapping MonadError API LOGIC

92. 🗺 Design principles > 🦄 Functional Architectures VideoController VideoFinderRepo VideoFinder HTTPVideoClient VideoFinder… … DoobieRepo… VideoRepo INSTANCE

93. class HttpVideoFinder extends VideoFinder[Future] { def find(id: VideoId)(implicit E: MonadError[Future, VideoFinderError]): Future[Video] = Http().singleRequest(HttpRequest( method = HttpMethods.GET, uri = httpConfig.addPath("videos"))).flatMap { case HttpResponse(StatusCodes.OK, _, entity, _) => entity.dataBytes .runFold(ByteString(""))(_ ++ _) .map(_.utf8String.parseJson.convertTo[Video]) case HttpResponse(StatusCodes.NotFound, _, _, _) => E.raiseError(VideoFinderError(id)) } } ⚡Error Handling > 🦄 FP > Raise errors

94. 🤔 Rethinking time % Implementation details

95. Differences on APIs/layers implementation • Same goal: Decouple from infrastructure • 🦄 FP: • One step forward to avoid infrastructure leaks • Again, through type classes: a better API • More complexity: monads, applicatives, etc. % Implementation > 🤔 Rethinking time > 🏗 APIs

96. Differences on error handling • 🦄 FP: • FP tell no lies (or, rather, doesn’t hide anything): more robust contracts using type system • Declarative: more abstract about how the error will be raised (exceptions, Option, Either, etc) % Implementation > 🤔 Rethinking time > ⚡Error Handling

97. 🍕Takeaways

98. 🎯 🦄 VideoPostController VideoRepository VideoCreator DoobieMySqlVideoRepo VideoPostController VideoRepositoryVideoRepoC DoobieMySqlVideoRepo VideoCreator HTTP

99. 🍕Takeaways ⚡ Exceptions 🏗 Monolithic interfaces 👤 Rich domain models

100. 🍕Takeaways ⚡ Exceptions 🏗 Monolithic interfaces 👤 Rich domain models 🦄 TypeClasses ⚛ APIs with steroids 🧐 FP as a subsuming paradigm

101. ℹ More info

102. References ℹ More info

103. 👉Formación FP presencial 👈 hablapps.com

104. 👉Cursos en vídeo online 👈 Descuento asistentes charla: Primer mes 19€: bit.ly/codelytv19e

105. 4 Questions?

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