[Platform] Add event system for string input conversion

src/platform/composer.json

@@ -49,7 +49,8 @@
         "symfony/property-info": "^6.4 || ^7.1",
         "symfony/serializer": "^6.4 || ^7.1",
         "symfony/type-info": "^7.2.3",
-        "symfony/uid": "^6.4 || ^7.1"
+        "symfony/uid": "^6.4 || ^7.1",
+        "symfony/event-dispatcher": "^6.4 || ^7.1"
     },
     "require-dev": {
         "async-aws/bedrock-runtime": "^0.1.0",
@@ -61,7 +62,6 @@
         "symfony/ai-agent": "@dev",
         "symfony/console": "^6.4 || ^7.1",
         "symfony/dotenv": "^6.4 || ^7.1",
-        "symfony/event-dispatcher": "^6.4 || ^7.1",
         "symfony/finder": "^6.4 || ^7.1",
         "symfony/process": "^6.4 || ^7.1",
         "symfony/var-dumper": "^6.4 || ^7.1"

src/platform/src/Event/PlatformInvokationEvent.php

@@ -0,0 +1,34 @@
+<?php
+
+/*
+ * This file is part of the Symfony package.
+ *
+ * (c) Fabien Potencier <[email protected]>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace Symfony\AI\Platform\Event;
+
+use Symfony\AI\Platform\Model;
+use Symfony\Contracts\EventDispatcher\Event;
+
+/**
+ * Event dispatched before platform invocation to allow modification of input data.
+ *
+ * @author Ramy Hakam <[email protected]>
+ */
+final class PlatformInvokationEvent extends Event
+{
+    /**
+     * @param array<string, mixed>|string|object $input
+     * @param array<string, mixed>               $options
+     */
+    public function __construct(
+        public readonly Model $model,
+        public array|string|object $input,
+        public readonly array $options = [],
+    ) {
+    }
+}

src/platform/src/EventListener/StringToMessageBagListener.php

@@ -0,0 +1,41 @@
+<?php
+
+/*
+ * This file is part of the Symfony package.
+ *
+ * (c) Fabien Potencier <[email protected]>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace Symfony\AI\Platform\EventListener;
+
+use Symfony\AI\Platform\Capability;
+use Symfony\AI\Platform\Event\PlatformInvokationEvent;
+use Symfony\AI\Platform\Message\Message;
+use Symfony\AI\Platform\Message\MessageBag;
+
+/**
+ * Converts string inputs to MessageBag for models that support INPUT_MESSAGES capability.
+ *
+ * @author Ramy Hakam <[email protected]>
+ */
+final class StringToMessageBagListener
+{
+    public function __invoke(PlatformInvokationEvent $event): void
+    {
+        // Only process string inputs
+        if (!\is_string($event->input)) {
+            return;
+        }
+
+        // Only process models that support INPUT_MESSAGES capability
+        if (!$event->model->supports(Capability::INPUT_MESSAGES)) {
+            return;
+        }
+
+        // Convert string to MessageBag with a user message
+        $event->input = new MessageBag(Message::ofUser($event->input));
+    }
+}

src/platform/src/Platform.php

@@ -11,6 +11,8 @@
 
 namespace Symfony\AI\Platform;
 
+use Psr\EventDispatcher\EventDispatcherInterface;
+use Symfony\AI\Platform\Event\PlatformInvokationEvent;
 use Symfony\AI\Platform\Exception\RuntimeException;
 use Symfony\AI\Platform\Result\RawResultInterface;
 use Symfony\AI\Platform\Result\ResultPromise;
@@ -38,6 +40,7 @@ public function __construct(
         iterable $modelClients,
         iterable $resultConverters,
         private ?Contract $contract = null,
+        private ?EventDispatcherInterface $eventDispatcher = null,
     ) {
         $this->contract = $contract ?? Contract::create();
         $this->modelClients = $modelClients instanceof \Traversable ? iterator_to_array($modelClients) : $modelClients;
@@ -46,6 +49,13 @@ public function __construct(
 
     public function invoke(Model $model, array|string|object $input, array $options = []): ResultPromise
     {
+        // Dispatch event to allow input modification
+        if ($this->eventDispatcher) {
+            $event = new PlatformInvokationEvent($model, $input, $options);
+            $this->eventDispatcher->dispatch($event);
+            $input = $event->input;
+        }
+
         $payload = $this->contract->createRequestPayload($model, $input);
         $options = array_merge($model->getOptions(), $options);
 

src/platform/tests/Event/PlatformInvokationEventTest.php

@@ -0,0 +1,72 @@
+<?php
+
+/*
+ * This file is part of the Symfony package.
+ *
+ * (c) Fabien Potencier <[email protected]>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace Symfony\AI\Platform\Tests\Event;
+
+use PHPUnit\Framework\Attributes\CoversClass;
+use PHPUnit\Framework\TestCase;
+use Symfony\AI\Platform\Capability;
+use Symfony\AI\Platform\Event\PlatformInvokationEvent;
+use Symfony\AI\Platform\Message\Message;
+use Symfony\AI\Platform\Message\MessageBag;
+use Symfony\AI\Platform\Model;
+
+#[CoversClass(PlatformInvokationEvent::class)]
+final class PlatformInvokationEventTest extends TestCase
+{
+    public function testGettersReturnCorrectValues()
+    {
+        $model = new class('test-model', [Capability::INPUT_MESSAGES, Capability::OUTPUT_TEXT]) extends Model {
+        };
+
+        $input = 'Hello, world!';
+        $options = ['temperature' => 0.7];
+
+        $event = new PlatformInvokationEvent($model, $input, $options);
+
+        $this->assertSame($model, $event->model);
+        $this->assertSame($input, $event->input);
+        $this->assertSame($options, $event->options);
+    }
+
+    public function testSetInputChangesInput()
+    {
+        $model = new class('test-model', [Capability::INPUT_MESSAGES, Capability::OUTPUT_TEXT]) extends Model {
+        };
+
+        $originalInput = 'Hello, world!';
+        $newInput = new MessageBag(Message::ofUser('Hello, world!'));
+
+        $event = new PlatformInvokationEvent($model, $originalInput);
+        $event->input = $newInput;
+
+        $this->assertSame($newInput, $event->input);
+    }
+
+    public function testWorksWithDifferentInputTypes()
+    {
+        $model = new class('test-model', [Capability::INPUT_MESSAGES, Capability::OUTPUT_TEXT]) extends Model {
+        };
+
+        // Test with string
+        $stringEvent = new PlatformInvokationEvent($model, 'string input');
+        $this->assertIsString($stringEvent->input);
+
+        // Test with array
+        $arrayEvent = new PlatformInvokationEvent($model, ['key' => 'value']);
+        $this->assertIsArray($arrayEvent->input);
+
+        // Test with object
+        $objectInput = new MessageBag();
+        $objectEvent = new PlatformInvokationEvent($model, $objectInput);
+        $this->assertSame($objectInput, $objectEvent->input);
+    }
+}

src/platform/tests/EventListener/StringToMessageBagListenerTest.php

@@ -0,0 +1,89 @@
+<?php
+
+/*
+ * This file is part of the Symfony package.
+ *
+ * (c) Fabien Potencier <[email protected]>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace Symfony\AI\Platform\Tests\EventListener;
+
+use PHPUnit\Framework\Attributes\CoversClass;
+use PHPUnit\Framework\TestCase;
+use Symfony\AI\Platform\Capability;
+use Symfony\AI\Platform\Event\PlatformInvokationEvent;
+use Symfony\AI\Platform\EventListener\StringToMessageBagListener;
+use Symfony\AI\Platform\Message\Content\Text;
+use Symfony\AI\Platform\Message\Message;
+use Symfony\AI\Platform\Message\MessageBag;
+use Symfony\AI\Platform\Message\UserMessage;
+use Symfony\AI\Platform\Model;
+
+#[CoversClass(StringToMessageBagListener::class)]
+final class StringToMessageBagListenerTest extends TestCase
+{
+    public function testConvertsStringInputToMessageBagForMessagesCapableModel()
+    {
+        $model = new class('test-model', [Capability::INPUT_MESSAGES, Capability::OUTPUT_TEXT]) extends Model {
+        };
+
+        $event = new PlatformInvokationEvent($model, 'Hello, world!');
+        $listener = new StringToMessageBagListener();
+
+        $listener($event);
+
+        $this->assertInstanceOf(MessageBag::class, $event->input);
+        $this->assertCount(1, $event->input->getMessages());
+        $message = $event->input->getMessages()[0];
+        $this->assertInstanceOf(UserMessage::class, $message);
+        $this->assertCount(1, $message->content);
+        $content = $message->content[0];
+        $this->assertInstanceOf(Text::class, $content);
+        $this->assertSame('Hello, world!', $content->text);
+    }
+
+    public function testDoesNotConvertStringInputForNonMessagesCapableModel()
+    {
+        $model = new class('test-model', [Capability::INPUT_TEXT, Capability::OUTPUT_TEXT]) extends Model {
+        };
+
+        $originalInput = 'Hello, world!';
+        $event = new PlatformInvokationEvent($model, $originalInput);
+        $listener = new StringToMessageBagListener();
+
+        $listener($event);
+
+        $this->assertSame($originalInput, $event->input);
+    }
+
+    public function testDoesNotConvertNonStringInput()
+    {
+        $model = new class('test-model', [Capability::INPUT_MESSAGES, Capability::OUTPUT_TEXT]) extends Model {
+        };
+
+        $originalInput = new MessageBag(Message::ofUser('Hello'));
+        $event = new PlatformInvokationEvent($model, $originalInput);
+        $listener = new StringToMessageBagListener();
+
+        $listener($event);
+
+        $this->assertSame($originalInput, $event->input);
+    }
+
+    public function testDoesNotConvertArrayInput()
+    {
+        $model = new class('test-model', [Capability::INPUT_MESSAGES, Capability::OUTPUT_TEXT]) extends Model {
+        };
+
+        $originalInput = ['key' => 'value'];
+        $event = new PlatformInvokationEvent($model, $originalInput);
+        $listener = new StringToMessageBagListener();
+
+        $listener($event);
+
+        $this->assertSame($originalInput, $event->input);
+    }
+}