add a few examples

README.md

@@ -8,3 +8,184 @@ Small lightweight event-sourcing library.
 composer require patchlevel/event-sourcing
 ```
 
+## define aggregate
+
+```php
+<?php declare(strict_types=1);
+
+namespace App\Domain\Profile;
+
+use App\Domain\Profile\Event\MessagePublished;
+use App\Domain\Profile\Event\ProfileCreated;
+use App\EventSourcing\AggregateRoot;
+
+final class Profile extends AggregateRoot
+{
+    private ProfileId $id;
+    private Email $email;
+    /** @var array<Message> */
+    private array $messages;
+
+    private function __construct()
+    {
+    }
+
+    public function email(): Email
+    {
+        return $this->email;
+    }
+
+    /**
+     * @return array<Message>
+     */
+    public function messages(): array
+    {
+        return $this->messages;
+    }
+
+    public static function createProfile(ProfileId $id, Email $email): self
+    {
+        $self = new self();
+        $self->apply(ProfileCreated::raise($id, $email));
+
+        return $self;
+    }
+
+    public function publishMessage(Message $message): void
+    {
+        $this->apply(MessagePublished::raise(
+            $this->id,
+            $message,
+        ));
+    }
+
+    protected function applyProfileCreated(ProfileCreated $event): void
+    {
+        $this->id = $event->profileId();
+        $this->email = $event->email();
+        $this->messages = [];
+    }
+
+    protected function applyMessagePublished(MessagePublished $event): void
+    {
+        $this->messages[] = $event->message();
+    }
+
+    public function aggregateRootId(): string
+    {
+        return $this->id->toString();
+    }
+}
+```
+
+## define events
+
+```php
+<?php declare(strict_types=1);
+
+namespace App\Domain\Profile\Event;
+
+use App\Domain\Profile\Email;
+use App\Domain\Profile\ProfileId;
+use App\EventSourcing\AggregateChanged;
+
+final class ProfileCreated extends AggregateChanged
+{
+    public static function raise(
+        ProfileId $id,
+        Email $email
+    ): AggregateChanged {
+        return self::occur(
+            $id->toString(),
+            [
+                'profileId' => $id->toString(),
+                'email' => $email->toString(),
+            ]
+        );
+    }
+
+    public function profileId(): ProfileId
+    {
+        return ProfileId::fromString($this->aggregateId);
+    }
+
+    public function email(): Email
+    {
+        return Email::fromString($this->payload['email']);
+    }
+}
+```
+
+# define projection
+
+```php
+<?php declare(strict_types=1);
+
+namespace App\ReadModel\Projection;
+
+use const DATE_ATOM;
+use App\Domain\Profile\Event\MessagePublished;
+use App\EventSourcing\Projection;
+use App\Infrastructure\MongoDb\MongoDbManager;
+
+final class MessageProjection extends Projection
+{
+    private MongoDbManager $db;
+
+    public function __construct(MongoDbManager $db)
+    {
+        $this->db = $db;
+    }
+
+    public static function getHandledMessages(): iterable
+    {
+        yield MessagePublished::class => 'applyMessagePublished';
+    }
+
+    public function applyMessagePublished(MessagePublished $event): void
+    {
+        $message = $event->message();
+
+        $this->db->collection('message')->insertOne([
+            '_id' => $message->id()->toString(),
+            'profile_id' => $event->profileId()->toString(),
+            'text' => $message->text(),
+            'created_at' => $message->createdAt()->format(DATE_ATOM),
+        ]);
+    }
+
+    public function drop(): void
+    {
+        $this->db->collection('message')->drop();
+    }
+}
+```
+
+## usage
+
+```php
+<?php declare(strict_types=1);
+
+namespace App\Domain\Profile\Handler;
+
+use App\Domain\Profile\Command\CreateProfile;
+use App\Domain\Profile\Profile;
+use App\Domain\Profile\ProfileRepository;
+
+final class CreateProfileHandler
+{
+    private ProfileRepository $profileRepository;
+
+    public function __construct(ProfileRepository $profileRepository)
+    {
+        $this->profileRepository = $profileRepository;
+    }
+
+    public function __invoke(CreateProfile $command): void
+    {
+        $profile = Profile::createProfile($command->profileId(), $command->email());
+
+        $this->profileRepository->store($profile);
+    }
+}
+```