From 15db0815bcce59a59e176a3b3dab8000498011dd Mon Sep 17 00:00:00 2001
From: Antoine Lelaisant <antoine.lelaisant@knplabs.com>
Date: Mon, 7 Nov 2022 13:55:52 +0100
Subject: [PATCH] step 10: introduce domain events

---
 config/packages/messenger.yaml                |  9 ++++
 config/services.yaml                          |  2 +
 config/services/domain_events.yaml            | 12 +++++
 config/services/messenger.yaml                |  9 ++++
 .../Controller/DinosaursController.php        | 18 +++----
 .../LogWhenDinosaurDied.php                   | 35 +++++++++++++
 .../LogWhenDinosaurIsBorn.php                 | 43 ++++++++++++++++
 src/Application/MessageBus/EventBus.php       | 10 ++++
 src/Domain/Event/DinosaurDied.php             | 27 ++++++++++
 src/Domain/Event/DinosaurIsBorn.php           | 20 ++++++++
 src/Domain/Event/EventInterface.php           | 10 ++++
 src/Domain/EventsRegisterer.php               | 31 +++++++++++
 src/Domain/HasEventsRegisterer.php            | 30 +++++++++++
 src/Domain/Model/AggregateRoot.php            | 11 ++++
 src/Domain/Model/Dinosaur.php                 |  2 +-
 src/Domain/UseCase/CreateDinosaur/Handler.php |  6 +++
 src/Domain/UseCase/RemoveDinosaur/Handler.php |  6 +++
 .../Symfony/Messenger/EventBus.php            | 33 ++++++++++++
 .../Middleware/DomainEventDispatcher.php      | 51 +++++++++++++++++++
 19 files changed, 354 insertions(+), 11 deletions(-)
 create mode 100644 config/services/domain_events.yaml
 create mode 100644 src/Application/DomainEventsHandler/LogWhenDinosaurDied.php
 create mode 100644 src/Application/DomainEventsHandler/LogWhenDinosaurIsBorn.php
 create mode 100644 src/Application/MessageBus/EventBus.php
 create mode 100644 src/Domain/Event/DinosaurDied.php
 create mode 100644 src/Domain/Event/DinosaurIsBorn.php
 create mode 100644 src/Domain/Event/EventInterface.php
 create mode 100644 src/Domain/EventsRegisterer.php
 create mode 100644 src/Domain/HasEventsRegisterer.php
 create mode 100644 src/Domain/Model/AggregateRoot.php
 create mode 100644 src/Infrastructure/Symfony/Messenger/EventBus.php
 create mode 100644 src/Infrastructure/Symfony/Messenger/Middleware/DomainEventDispatcher.php

diff --git a/config/packages/messenger.yaml b/config/packages/messenger.yaml
index 55cd4eb..5386421 100644
--- a/config/packages/messenger.yaml
+++ b/config/packages/messenger.yaml
@@ -6,7 +6,16 @@ framework:
 
     buses:
       command.bus:
+        default_middleware: true
         middleware:
+          - Infrastructure\Symfony\Messenger\Middleware\DomainEventDispatcher
+          - dispatch_after_current_bus
           - doctrine_transaction
 
       query.bus: ~
+
+      event.bus:
+        default_middleware: allow_no_handlers
+        middleware:
+          - dispatch_after_current_bus
+          - doctrine_transaction
\ No newline at end of file
diff --git a/config/services.yaml b/config/services.yaml
index d877526..941cb31 100644
--- a/config/services.yaml
+++ b/config/services.yaml
@@ -12,3 +12,5 @@ services:
 
     Application\:
         resource: '../src/Application/'
+        exclude:
+          - '../src/Application/DomainEventsHandler/'
diff --git a/config/services/domain_events.yaml b/config/services/domain_events.yaml
new file mode 100644
index 0000000..a3030d7
--- /dev/null
+++ b/config/services/domain_events.yaml
@@ -0,0 +1,12 @@
+---
+services:
+  _defaults:
+    autowire: true
+    public: false
+
+  Domain\EventsRegisterer: ~
+
+  Application\DomainEventsHandler\:
+    resource: '%kernel.project_dir%/src/Application/DomainEventsHandler/**.php'
+    tags:
+      - { name: messenger.message_handler, bus: event.bus }
diff --git a/config/services/messenger.yaml b/config/services/messenger.yaml
index a5bd415..d234e70 100644
--- a/config/services/messenger.yaml
+++ b/config/services/messenger.yaml
@@ -5,6 +5,9 @@ services:
     autoconfigure: true
     public: false
 
+  Infrastructure\Symfony\Messenger\Middleware\:
+    resource: '%kernel.project_dir%/src/Infrastructure/Symfony/Messenger/Middleware/**.php'
+
   Infrastructure\Symfony\Messenger\CommandBus:
     $messageBus: '@command.bus'
 
@@ -16,3 +19,9 @@ services:
 
   Application\MessageBus\QueryBus:
     alias: Infrastructure\Symfony\Messenger\QueryBus
+
+  Infrastructure\Symfony\Messenger\EventBus:
+    $messageBus: '@event.bus'
+
+  Application\MessageBus\EventBus:
+    alias: Infrastructure\Symfony\Messenger\EventBus
\ No newline at end of file
diff --git a/src/Application/Controller/DinosaursController.php b/src/Application/Controller/DinosaursController.php
index b97f232..9766be8 100644
--- a/src/Application/Controller/DinosaursController.php
+++ b/src/Application/Controller/DinosaursController.php
@@ -5,7 +5,9 @@
 use Application\Form\Type\DinosaurType;
 use Application\Form\Type\SearchType;
 use Application\MessageBus\CommandBus;
+use Application\MessageBus\EventBus;
 use Application\MessageBus\QueryBus;
+use Domain\Event\DinosaurIsBorn;
 use Domain\Exception\DinosaurNotFoundException;
 use Domain\Query\GetSingleDinosaur;
 use Domain\Query\GetAllDinosaurs;
@@ -22,7 +24,8 @@ class DinosaursController extends AbstractController
 {
     public function __construct(
         private CommandBus $commandBus,
-        private QueryBus $queryBus
+        private QueryBus $queryBus,
+        private EventBus $eventBus
     ) {}
 
     #[Route('/dinosaurs', name: 'app_list_dinosaurs')]
@@ -54,15 +57,10 @@ public function list(Request $request): Response
     )]
     public function single(string $id): Response
     {
-        $dinosaur = $this
-            ->dinosaursCollection
-            ->find($id)
-        ;
-
-        if ($dinosaur === false) {
-            throw $this->createNotFoundException(
-                'The dinosaur you are looking for does not exists.'
-            );
+        try {
+            $dinosaur = $this->queryBus->dispatch(new GetSingleDinosaur\Query($id));
+        } catch (DinosaurNotFoundException $e) {
+            throw $this->createNotFoundException();
         }
 
         return $this->render('dinosaur.html.twig', [
diff --git a/src/Application/DomainEventsHandler/LogWhenDinosaurDied.php b/src/Application/DomainEventsHandler/LogWhenDinosaurDied.php
new file mode 100644
index 0000000..944baea
--- /dev/null
+++ b/src/Application/DomainEventsHandler/LogWhenDinosaurDied.php
@@ -0,0 +1,35 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Application\DomainEventsHandler;
+
+use Domain\Event\DinosaurDied;
+use Domain\Event\EventInterface;
+use Psr\Log\LoggerInterface;
+use Symfony\Component\Messenger\Handler\MessageSubscriberInterface;
+
+class LogWhenDinosaurDied implements MessageSubscriberInterface
+{
+    public function __construct(
+        private LoggerInterface $logger
+    ) {
+    }
+
+    public function __invoke(EventInterface $event): void
+    {
+        if (!$event instanceof DinosaurDied) {
+            return;
+        }
+
+        $this->logger->info(sprintf(
+            'Dinosaur %s died',
+            $event->getDinosaurName()
+        ));
+    }
+
+    public static function getHandledMessages(): iterable
+    {
+        yield DinosaurDied::class;
+    }
+}
diff --git a/src/Application/DomainEventsHandler/LogWhenDinosaurIsBorn.php b/src/Application/DomainEventsHandler/LogWhenDinosaurIsBorn.php
new file mode 100644
index 0000000..70bde7a
--- /dev/null
+++ b/src/Application/DomainEventsHandler/LogWhenDinosaurIsBorn.php
@@ -0,0 +1,43 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Application\DomainEventsHandler;
+
+use Domain\Collection\DinosaursCollection;
+use Domain\Event\DinosaurIsBorn;
+use Domain\Event\EventInterface;
+use Domain\Exception\DinosaurNotFoundException;
+use Domain\Model\Dinosaur;
+use Psr\Log\LoggerInterface;
+use Symfony\Component\Messenger\Handler\MessageSubscriberInterface;
+
+class LogWhenDinosaurIsBorn implements MessageSubscriberInterface
+{
+    public function __construct(
+        private DinosaursCollection $dinosaursCollection,
+        private LoggerInterface $logger
+    ) {
+    }
+
+    public function __invoke(EventInterface $event): void
+    {
+        $dinosaurId = $event->getAggregateRootId();
+
+        $dinosaur = $this->dinosaursCollection->find($dinosaurId);
+
+        if (!$dinosaur instanceof Dinosaur) {
+            throw new DinosaurNotFoundException($dinosaurId);
+        }
+
+        $this->logger->info(sprintf(
+            'Dinosaur %s was born',
+            $dinosaur->getName()
+        ));
+    }
+
+    public static function getHandledMessages(): iterable
+    {
+        yield DinosaurIsBorn::class;
+    }
+}
diff --git a/src/Application/MessageBus/EventBus.php b/src/Application/MessageBus/EventBus.php
new file mode 100644
index 0000000..ddb0b07
--- /dev/null
+++ b/src/Application/MessageBus/EventBus.php
@@ -0,0 +1,10 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Application\MessageBus;
+
+interface EventBus
+{
+    public function dispatch(object $event): void;
+}
diff --git a/src/Domain/Event/DinosaurDied.php b/src/Domain/Event/DinosaurDied.php
new file mode 100644
index 0000000..cb10371
--- /dev/null
+++ b/src/Domain/Event/DinosaurDied.php
@@ -0,0 +1,27 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Domain\Event;
+
+use Domain\Model\Dinosaur;
+
+final class DinosaurDied implements EventInterface
+{
+    private string $dinosaurName;
+
+    public function __construct(private Dinosaur $dinosaur)
+    {
+        $this->dinosaurName = $dinosaur->getName();
+    }
+
+    public function getAggregateRootId(): string
+    {
+        return (string) $this->dinosaur->getId();
+    }
+
+    public function getDinosaurName(): string
+    {
+        return $this->dinosaurName;
+    }
+}
diff --git a/src/Domain/Event/DinosaurIsBorn.php b/src/Domain/Event/DinosaurIsBorn.php
new file mode 100644
index 0000000..1dd3af3
--- /dev/null
+++ b/src/Domain/Event/DinosaurIsBorn.php
@@ -0,0 +1,20 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Domain\Event;
+
+use Domain\Model\Dinosaur;
+
+class DinosaurIsBorn implements EventInterface
+{
+    public function __construct(
+        private Dinosaur $dinosaur
+    ) {
+    }
+
+    public function getAggregateRootId(): string
+    {
+        return (string) $this->dinosaur->getId();
+    }
+}
\ No newline at end of file
diff --git a/src/Domain/Event/EventInterface.php b/src/Domain/Event/EventInterface.php
new file mode 100644
index 0000000..318d62e
--- /dev/null
+++ b/src/Domain/Event/EventInterface.php
@@ -0,0 +1,10 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Domain\Event;
+
+interface EventInterface
+{
+    public function getAggregateRootId(): string;
+}
diff --git a/src/Domain/EventsRegisterer.php b/src/Domain/EventsRegisterer.php
new file mode 100644
index 0000000..cfc75ba
--- /dev/null
+++ b/src/Domain/EventsRegisterer.php
@@ -0,0 +1,31 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Domain;
+
+use Domain\Event\EventInterface;
+
+class EventsRegisterer
+{
+    /** @var array<EventInterface> */
+    private array $events = [];
+
+    public function register(EventInterface ...$events): void
+    {
+        array_push($this->events, ...$events);
+    }
+
+    /**
+     * @return array<EventInterface>
+     */
+    public function getEvents(): array
+    {
+        return $this->events;
+    }
+
+    public function flush(): void
+    {
+        $this->events = [];
+    }
+}
diff --git a/src/Domain/HasEventsRegisterer.php b/src/Domain/HasEventsRegisterer.php
new file mode 100644
index 0000000..8737095
--- /dev/null
+++ b/src/Domain/HasEventsRegisterer.php
@@ -0,0 +1,30 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Domain;
+
+use Domain\Event\EventInterface;
+
+trait HasEventsRegisterer
+{
+    private EventsRegisterer $eventsRegisterer;
+
+    /**
+     * @required
+     */
+    public function setEventsRegisterer(EventsRegisterer $eventsRegisterer): void
+    {
+        $this->eventsRegisterer = $eventsRegisterer;
+    }
+
+    public function getEventsRegisterer(): EventsRegisterer
+    {
+        return $this->eventsRegisterer;
+    }
+
+    public function registerEvents(EventInterface ...$events): void
+    {
+        $this->eventsRegisterer->register(...$events);
+    }
+}
diff --git a/src/Domain/Model/AggregateRoot.php b/src/Domain/Model/AggregateRoot.php
new file mode 100644
index 0000000..dc5be02
--- /dev/null
+++ b/src/Domain/Model/AggregateRoot.php
@@ -0,0 +1,11 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Domain\Model;
+
+interface AggregateRoot
+{
+    public function getId(): int;
+}
+
diff --git a/src/Domain/Model/Dinosaur.php b/src/Domain/Model/Dinosaur.php
index 849d4db..a34909c 100644
--- a/src/Domain/Model/Dinosaur.php
+++ b/src/Domain/Model/Dinosaur.php
@@ -2,7 +2,7 @@
 
 namespace Domain\Model;
 
-class Dinosaur
+class Dinosaur implements AggregateRoot
 {
     private int $id;
     private string $name;
diff --git a/src/Domain/UseCase/CreateDinosaur/Handler.php b/src/Domain/UseCase/CreateDinosaur/Handler.php
index 6347f97..ad82ada 100644
--- a/src/Domain/UseCase/CreateDinosaur/Handler.php
+++ b/src/Domain/UseCase/CreateDinosaur/Handler.php
@@ -6,12 +6,16 @@
 
 use Domain\Collection\DinosaursCollection;
 use Domain\Collection\SpeciesCollection;
+use Domain\Event\DinosaurIsBorn;
 use Domain\Exception\DinosaurAlreadyExistsException;
 use Domain\Exception\SpeciesNotFoundException;
+use Domain\HasEventsRegisterer;
 use Domain\Model\Dinosaur;
 
 class Handler
 {
+    use HasEventsRegisterer;
+
     public function __construct(
         private DinosaursCollection $dinosaursCollection,
         private SpeciesCollection $speciesCollection
@@ -48,6 +52,8 @@ public function __invoke(Input $input): Output
 
         $this->dinosaursCollection->add($dinosaur);
 
+        $this->registerEvents(new DinosaurIsBorn($dinosaur));
+
         return new Output($dinosaur);
     }
 }
diff --git a/src/Domain/UseCase/RemoveDinosaur/Handler.php b/src/Domain/UseCase/RemoveDinosaur/Handler.php
index 70fabe8..f4b493d 100644
--- a/src/Domain/UseCase/RemoveDinosaur/Handler.php
+++ b/src/Domain/UseCase/RemoveDinosaur/Handler.php
@@ -5,10 +5,14 @@
 namespace Domain\UseCase\RemoveDinosaur;
 
 use Domain\Collection\DinosaursCollection;
+use Domain\Event\DinosaurDied;
 use Domain\Exception\DinosaurNotFoundException;
+use Domain\HasEventsRegisterer;
 
 class Handler
 {
+    use HasEventsRegisterer;
+
     public function __construct(
         private DinosaursCollection $dinosaursCollection
     ) {
@@ -27,6 +31,8 @@ public function __invoke(Input $input): Output
 
         $this->dinosaursCollection->remove($dinosaur);
 
+        $this->registerEvents(new DinosaurDied($dinosaur));
+
         return new Output();
     }
 }
diff --git a/src/Infrastructure/Symfony/Messenger/EventBus.php b/src/Infrastructure/Symfony/Messenger/EventBus.php
new file mode 100644
index 0000000..21be1ff
--- /dev/null
+++ b/src/Infrastructure/Symfony/Messenger/EventBus.php
@@ -0,0 +1,33 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Infrastructure\Symfony\Messenger;
+
+use Application\MessageBus\EventBus as EventBusInterface;
+use Symfony\Component\Messenger\Exception\HandlerFailedException;
+use Symfony\Component\Messenger\HandleTrait;
+use Symfony\Component\Messenger\MessageBusInterface;
+
+class EventBus implements EventBusInterface
+{
+    use HandleTrait;
+
+    public function __construct(private MessageBusInterface $messageBus) {
+    }
+
+    public function dispatch(object $event): void
+    {
+        try {
+            $this->handle($event);
+        } catch (HandlerFailedException $handlerFailedException) {
+            $nestedExceptions = $handlerFailedException->getNestedExceptions();
+
+            if (false === $nested = current($nestedExceptions)) {
+                throw $handlerFailedException;
+            }
+
+            throw $nested;
+        }
+    }
+}
diff --git a/src/Infrastructure/Symfony/Messenger/Middleware/DomainEventDispatcher.php b/src/Infrastructure/Symfony/Messenger/Middleware/DomainEventDispatcher.php
new file mode 100644
index 0000000..9c90087
--- /dev/null
+++ b/src/Infrastructure/Symfony/Messenger/Middleware/DomainEventDispatcher.php
@@ -0,0 +1,51 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Infrastructure\Symfony\Messenger\Middleware;
+
+use Application\MessageBus\EventBus;
+use Doctrine\ORM\EntityManagerInterface;
+use Domain\EventsRegisterer;
+use Symfony\Component\Messenger\Envelope;
+use Symfony\Component\Messenger\Middleware\MiddlewareInterface;
+use Symfony\Component\Messenger\Middleware\StackInterface;
+use Symfony\Component\Messenger\Stamp\HandledStamp;
+
+class DomainEventDispatcher implements MiddlewareInterface
+{
+    public function __construct(
+        private EventBus $eventBus,
+        private EventsRegisterer $eventsRegisterer,
+        private EntityManagerInterface $em
+    ) {
+    }
+
+    public function handle(Envelope $envelope, StackInterface $stack): Envelope
+    {
+        $envelope = $stack->next()->handle($envelope, $stack);
+
+        $stamp = $envelope->last(HandledStamp::class);
+
+        if (!$stamp instanceof HandledStamp) {
+            return $envelope;
+        }
+
+        /*
+         * This entity manager clear operation is mandatory since we need to have
+         * the freshest object as possible as we always read entities after several
+         * changes that might not have been updated by doctrine.
+         */
+        $this->em->clear();
+
+        $events = $this->eventsRegisterer->getEvents();
+
+        foreach ($events as $event) {
+            $this->eventBus->dispatch($event);
+        }
+
+        $this->eventsRegisterer->flush();
+
+        return $envelope;
+    }
+}