add upcasting possibilty

src/Serializer/DefaultEventSerializer.php

@@ -11,18 +11,23 @@
 use Patchlevel\EventSourcing\Serializer\Encoder\JsonEncoder;
 use Patchlevel\EventSourcing\Serializer\Hydrator\EventHydrator;
 use Patchlevel\EventSourcing\Serializer\Hydrator\MetadataEventHydrator;
+use Patchlevel\EventSourcing\Serializer\Upcast\Upcast;
+use Patchlevel\EventSourcing\Serializer\Upcast\Upcaster;
+use Patchlevel\EventSourcing\Serializer\Upcast\UpcasterChain;
 
 final class DefaultEventSerializer implements EventSerializer
 {
     private EventRegistry $eventRegistry;
     private EventHydrator $hydrator;
     private Encoder $encoder;
+    private Upcaster $upcaster;
 
-    public function __construct(EventRegistry $eventRegistry, EventHydrator $hydrator, Encoder $encoder)
+    public function __construct(EventRegistry $eventRegistry, EventHydrator $hydrator, Encoder $encoder, Upcaster $upcaster)
     {
         $this->eventRegistry = $eventRegistry;
         $this->hydrator = $hydrator;
         $this->encoder = $encoder;
+        $this->upcaster = $upcaster;
     }
 
     public function serialize(object $event, array $options = []): SerializedEvent
@@ -38,10 +43,12 @@ public function serialize(object $event, array $options = []): SerializedEvent
 
     public function deserialize(SerializedEvent $data, array $options = []): object
     {
-        $class = $this->eventRegistry->eventClass($data->name);
         $payload = $this->encoder->decode($data->payload, $options);
+        $upcast = ($this->upcaster)(new Upcast($data->name, $payload));
 
-        return $this->hydrator->hydrate($class, $payload);
+        $class = $this->eventRegistry->eventClass($upcast->eventName);
+
+        return $this->hydrator->hydrate($class, $upcast->payload);
     }
 
     /**
@@ -52,7 +59,8 @@ public static function createFromPaths(array $paths): static
         return new self(
             (new AttributeEventRegistryFactory())->create($paths),
             new MetadataEventHydrator(new AttributeEventMetadataFactory()),
-            new JsonEncoder()
+            new JsonEncoder(),
+            new UpcasterChain([])
         );
     }
 }

src/Serializer/Upcast/Upcast.php

@@ -0,0 +1,18 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Patchlevel\EventSourcing\Serializer\Upcast;
+
+/**
+ * @psalm-immutable
+ */
+final class Upcast
+{
+    /**
+     * @param array<string, mixed> $payload
+     */
+    public function __construct(public string $eventName, public array $payload)
+    {
+    }
+}

src/Serializer/Upcast/Upcaster.php

@@ -0,0 +1,10 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Patchlevel\EventSourcing\Serializer\Upcast;
+
+interface Upcaster
+{
+    public function __invoke(Upcast $upcast): Upcast;
+}

src/Serializer/Upcast/UpcasterChain.php

@@ -0,0 +1,24 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Patchlevel\EventSourcing\Serializer\Upcast;
+
+class UpcasterChain implements Upcaster
+{
+    /**
+     * @param array<Upcaster> $upcaster
+     */
+    public function __construct(private array $upcaster)
+    {
+    }
+
+    public function __invoke(Upcast $upcast): Upcast
+    {
+        foreach ($this->upcaster as $upcaster) {
+            $upcast = $upcaster($upcast);
+        }
+
+        return $upcast;
+    }
+}

tests/Unit/Serializer/DefaultEventSerializerTest.php

@@ -4,8 +4,15 @@
 
 namespace Patchlevel\EventSourcing\Tests\Unit\Serializer;
 
+use Patchlevel\EventSourcing\Metadata\Event\AttributeEventMetadataFactory;
+use Patchlevel\EventSourcing\Metadata\Event\AttributeEventRegistryFactory;
 use Patchlevel\EventSourcing\Serializer\DefaultEventSerializer;
+use Patchlevel\EventSourcing\Serializer\Encoder\JsonEncoder;
+use Patchlevel\EventSourcing\Serializer\Hydrator\MetadataEventHydrator;
 use Patchlevel\EventSourcing\Serializer\SerializedEvent;
+use Patchlevel\EventSourcing\Serializer\Upcast\Upcast;
+use Patchlevel\EventSourcing\Serializer\Upcast\Upcaster;
+use Patchlevel\EventSourcing\Serializer\Upcast\UpcasterChain;
 use Patchlevel\EventSourcing\Tests\Unit\Fixture\Email;
 use Patchlevel\EventSourcing\Tests\Unit\Fixture\ProfileCreated;
 use Patchlevel\EventSourcing\Tests\Unit\Fixture\ProfileId;
@@ -49,4 +56,39 @@ public function testDeserialize(): void
 
         self::assertEquals($expected, $event);
     }
+
+    public function testSerializeWithUpcasting(): void
+    {
+        $upcaster = new class implements Upcaster {
+            public function __invoke(Upcast $upcast): Upcast
+            {
+                if ($upcast->eventName !== 'profile_created_old') {
+                    return $upcast;
+                }
+
+                return new Upcast('profile_created', $upcast->payload + ['email' => 'info@patchlevel.de']);
+            }
+        };
+
+        $serializer = new DefaultEventSerializer(
+            (new AttributeEventRegistryFactory())->create([__DIR__ . '/../Fixture']),
+            new MetadataEventHydrator(new AttributeEventMetadataFactory()),
+            new JsonEncoder(),
+            new UpcasterChain([$upcaster])
+        );
+
+        $expected = new ProfileCreated(
+            ProfileId::fromString('1'),
+            Email::fromString('info@patchlevel.de')
+        );
+
+        $event = $serializer->deserialize(
+            new SerializedEvent(
+                'profile_created_old',
+                '{"profileId":"1"}'
+            )
+        );
+
+        self::assertEquals($expected, $event);
+    }
 }

tests/Unit/Serializer/Upcaster/UpcasterChainTest.php

@@ -0,0 +1,55 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Patchlevel\EventSourcing\Tests\Unit\Serializer\Upcaster;
+
+use Patchlevel\EventSourcing\Serializer\Upcast\Upcast;
+use Patchlevel\EventSourcing\Serializer\Upcast\Upcaster;
+use Patchlevel\EventSourcing\Serializer\Upcast\UpcasterChain;
+use PHPUnit\Framework\TestCase;
+
+final class UpcasterChainTest extends TestCase
+{
+    public function testChainSuccessful(): void
+    {
+        $upcasterOne = new class implements Upcaster {
+            public int $counter = 0;
+
+            public function __invoke(Upcast $upcast): Upcast
+            {
+                $this->counter++;
+
+                return new Upcast('profile_1', $upcast->payload);
+            }
+        };
+
+        $upcasterTwo = new class implements Upcaster {
+            public int $counter = 0;
+
+            public function __invoke(Upcast $upcast): Upcast
+            {
+                $this->counter++;
+
+                return new Upcast('profile_2', $upcast->payload + ['foo' => 'bar']);
+            }
+        };
+
+        $inputPayload = ['bar' => 'baz'];
+        $inputEventName = 'profile';
+
+        $chain = new UpcasterChain([$upcasterOne, $upcasterTwo]);
+        $upcast = ($chain)(new Upcast($inputEventName, $inputPayload));
+
+        self::assertSame(1, $upcasterOne->counter);
+        self::assertSame(1, $upcasterTwo->counter);
+        self::assertSame('profile_2', $upcast->eventName);
+        self::assertSame(
+            [
+                'bar' => 'baz',
+                'foo' => 'bar',
+            ],
+            $upcast->payload
+        );
+    }
+}