feat: basic support for Google Gemini models

.env

@@ -39,3 +39,6 @@ PINECONE_HOST=
 
 # Some examples are expensive to run, so we disable them by default
 RUN_EXPENSIVE_EXAMPLES=false
+
+# For using Gemini
+GOOGLE_API_KEY=

examples/chat-gemini-google.php

@@ -0,0 +1,28 @@
+<?php
+
+use PhpLlm\LlmChain\Bridge\Google\GoogleModel;
+use PhpLlm\LlmChain\Bridge\Google\PlatformFactory;
+use PhpLlm\LlmChain\Chain;
+use PhpLlm\LlmChain\Model\Message\Message;
+use PhpLlm\LlmChain\Model\Message\MessageBag;
+use Symfony\Component\Dotenv\Dotenv;
+
+require_once dirname(__DIR__).'/vendor/autoload.php';
+(new Dotenv())->loadEnv(dirname(__DIR__).'/.env');
+
+if (empty($_ENV['GOOGLE_API_KEY'])) {
+    echo 'Please set the GOOGLE_API_KEY environment variable.'.PHP_EOL;
+    exit(1);
+}
+
+$platform = PlatformFactory::create($_ENV['GOOGLE_API_KEY']);
+$llm = new GoogleModel(GoogleModel::GEMINI_2_FLASH);
+
+$chain = new Chain($platform, $llm);
+$messages = new MessageBag(
+    Message::forSystem('You are a pirate and you write funny.'),
+    Message::ofUser('What is the Symfony framework?'),
+);
+$response = $chain->call($messages);
+
+echo $response->getContent().PHP_EOL;

src/Bridge/Google/GoogleModel.php

@@ -0,0 +1,60 @@
+<?php
+
+declare(strict_types=1);
+
+namespace PhpLlm\LlmChain\Bridge\Google;
+
+use PhpLlm\LlmChain\Model\LanguageModel;
+
+final readonly class GoogleModel implements LanguageModel
+{
+    public const GEMINI_2_FLASH = 'gemini-2.0-flash';
+    public const GEMINI_2_PRO = 'gemini-2.0-pro-exp-02-05';
+    public const GEMINI_2_FLASH_LITE = 'gemini-2.0-flash-lite-preview-02-05';
+    public const GEMINI_2_FLASH_THINKING = 'gemini-2.0-flash-thinking-exp-01-21';
+    public const GEMINI_1_5_FLASH = 'gemini-1.5-flash';
+
+    /**
+     * @param array<string, mixed> $options The default options for the model usage
+     */
+    public function __construct(
+        private string $version = self::GEMINI_2_PRO,
+        private array $options = ['temperature' => 1.0],
+    ) {
+    }
+
+    public function getVersion(): string
+    {
+        return $this->version;
+    }
+
+    public function getOptions(): array
+    {
+        return $this->options;
+    }
+
+    public function supportsAudioInput(): bool
+    {
+        return false; // it does, but implementation here is still open; in_array($this->version, [self::GEMINI_2_FLASH, self::GEMINI_2_PRO, self::GEMINI_1_5_FLASH], true);
+    }
+
+    public function supportsImageInput(): bool
+    {
+        return false; // it does, but implementation here is still open;in_array($this->version, [self::GEMINI_2_FLASH, self::GEMINI_2_PRO, self::GEMINI_2_FLASH_LITE, self::GEMINI_2_FLASH_THINKING, self::GEMINI_1_5_FLASH], true);
+    }
+
+    public function supportsStreaming(): bool
+    {
+        return true;
+    }
+
+    public function supportsStructuredOutput(): bool
+    {
+        return false;
+    }
+
+    public function supportsToolCalling(): bool
+    {
+        return false;
+    }
+}

src/Bridge/Google/GoogleRequestBodyProducer.php

@@ -0,0 +1,97 @@
+<?php
+
+namespace PhpLlm\LlmChain\Bridge\Google;
+
+use PhpLlm\LlmChain\Model\Message\AssistantMessage;
+use PhpLlm\LlmChain\Model\Message\Content\Audio;
+use PhpLlm\LlmChain\Model\Message\Content\ContentVisitor;
+use PhpLlm\LlmChain\Model\Message\Content\Image;
+use PhpLlm\LlmChain\Model\Message\Content\Text;
+use PhpLlm\LlmChain\Model\Message\MessageBagInterface;
+use PhpLlm\LlmChain\Model\Message\MessageVisitor;
+use PhpLlm\LlmChain\Model\Message\SystemMessage;
+use PhpLlm\LlmChain\Model\Message\ToolCallMessage;
+use PhpLlm\LlmChain\Model\Message\UserMessage;
+use PhpLlm\LlmChain\Platform\RequestBodyProducer;
+
+final class GoogleRequestBodyProducer implements RequestBodyProducer, MessageVisitor, ContentVisitor, \JsonSerializable
+{
+    protected MessageBagInterface $bag;
+
+    public function __construct(MessageBagInterface $bag)
+    {
+        $this->bag = $bag;
+    }
+
+    public function createBody(): array
+    {
+        $contents = [];
+        foreach ($this->bag->withoutSystemMessage()->getMessages() as $message) {
+            $contents[] = [
+                'role' => $message->getRole(),
+                'parts' => $message->accept($this),
+            ];
+        }
+
+        $body = [
+            'contents' => $contents,
+        ];
+
+        $systemMessage = $this->bag->getSystemMessage();
+        if (null !== $systemMessage) {
+            $body['systemInstruction'] = [
+                'parts' => $systemMessage->accept($this),
+            ];
+        }
+
+        return $body;
+    }
+
+    public function visitUserMessage(UserMessage $message): array
+    {
+        $parts = [];
+        foreach ($message->content as $content) {
+            $parts[] = [...$content->accept($this)];
+        }
+
+        return $parts;
+    }
+
+    public function visitAssistantMessage(AssistantMessage $message): array
+    {
+        return [['text' => $message->content]];
+    }
+
+    public function visitSystemMessage(SystemMessage $message): array
+    {
+        return [['text' => $message->content]];
+    }
+
+    public function visitText(Text $content): array
+    {
+        return ['text' => $content->text];
+    }
+
+    public function visitImage(Image $content): array
+    {
+        // TODO: support image
+        return [];
+    }
+
+    public function visitAudio(Audio $content): array
+    {
+        // TODO: support audio
+        return [];
+    }
+
+    public function visitToolCallMessage(ToolCallMessage $message): array
+    {
+        // TODO: support tool call message
+        return [];
+    }
+
+    public function jsonSerialize(): array
+    {
+        return $this->createBody();
+    }
+}

src/Bridge/Google/ModelHandler.php

@@ -0,0 +1,103 @@
+<?php
+
+declare(strict_types=1);
+
+namespace PhpLlm\LlmChain\Bridge\Google;
+
+use PhpLlm\LlmChain\Exception\RuntimeException;
+use PhpLlm\LlmChain\Model\Message\MessageBagInterface;
+use PhpLlm\LlmChain\Model\Model;
+use PhpLlm\LlmChain\Model\Response\ResponseInterface as LlmResponse;
+use PhpLlm\LlmChain\Model\Response\StreamResponse;
+use PhpLlm\LlmChain\Model\Response\TextResponse;
+use PhpLlm\LlmChain\Platform\ModelClient;
+use PhpLlm\LlmChain\Platform\ResponseConverter;
+use Symfony\Component\HttpClient\Chunk\ServerSentEvent;
+use Symfony\Component\HttpClient\EventSourceHttpClient;
+use Symfony\Component\HttpClient\Exception\JsonException;
+use Symfony\Contracts\HttpClient\Exception\ClientExceptionInterface;
+use Symfony\Contracts\HttpClient\Exception\DecodingExceptionInterface;
+use Symfony\Contracts\HttpClient\Exception\RedirectionExceptionInterface;
+use Symfony\Contracts\HttpClient\Exception\ServerExceptionInterface;
+use Symfony\Contracts\HttpClient\Exception\TransportExceptionInterface;
+use Symfony\Contracts\HttpClient\HttpClientInterface;
+use Symfony\Contracts\HttpClient\ResponseInterface;
+use Webmozart\Assert\Assert;
+
+final readonly class ModelHandler implements ModelClient, ResponseConverter
+{
+    private EventSourceHttpClient $httpClient;
+
+    public function __construct(
+        HttpClientInterface $httpClient,
+        #[\SensitiveParameter] private string $apiKey,
+    ) {
+        $this->httpClient = $httpClient instanceof EventSourceHttpClient ? $httpClient : new EventSourceHttpClient($httpClient);
+    }
+
+    public function supports(Model $model, array|string|object $input): bool
+    {
+        return $model instanceof GoogleModel && $input instanceof MessageBagInterface;
+    }
+
+    /**
+     * @throws TransportExceptionInterface
+     */
+    public function request(Model $model, object|array|string $input, array $options = []): ResponseInterface
+    {
+        Assert::isInstanceOf($input, MessageBagInterface::class);
+
+        $body = new GoogleRequestBodyProducer($input);
+
+        return $this->httpClient->request('POST', sprintf('https://generativelanguage.googleapis.com/v1beta/models/%s:generateContent', $model->getVersion()), [
+            'headers' => [
+                'x-goog-api-key' => $this->apiKey,
+            ],
+            'json' => $body,
+        ]);
+    }
+
+    /**
+     * @throws TransportExceptionInterface
+     * @throws ServerExceptionInterface
+     * @throws RedirectionExceptionInterface
+     * @throws DecodingExceptionInterface
+     * @throws ClientExceptionInterface
+     */
+    public function convert(ResponseInterface $response, array $options = []): LlmResponse
+    {
+        if ($options['stream'] ?? false) {
+            return new StreamResponse($this->convertStream($response));
+        }
+
+        $data = $response->toArray();
+
+        if (!isset($data['candidates'][0]['content']['parts'][0]['text'])) {
+            throw new RuntimeException('Response does not contain any content');
+        }
+
+        return new TextResponse($data['candidates'][0]['content']['parts'][0]['text']);
+    }
+
+    private function convertStream(ResponseInterface $response): \Generator
+    {
+        foreach ((new EventSourceHttpClient())->stream($response) as $chunk) {
+            if (!$chunk instanceof ServerSentEvent || '[DONE]' === $chunk->getData()) {
+                continue;
+            }
+
+            try {
+                $data = $chunk->getArrayData();
+            } catch (JsonException) {
+                // try catch only needed for Symfony 6.4
+                continue;
+            }
+
+            if (!isset($data['candidates'][0]['content']['parts'][0]['text'])) {
+                continue;
+            }
+
+            yield $data['candidates'][0]['content']['parts'][0]['text'];
+        }
+    }
+}

src/Bridge/Google/PlatformFactory.php

@@ -0,0 +1,23 @@
+<?php
+
+declare(strict_types=1);
+
+namespace PhpLlm\LlmChain\Bridge\Google;
+
+use PhpLlm\LlmChain\Platform;
+use Symfony\Component\HttpClient\EventSourceHttpClient;
+use Symfony\Contracts\HttpClient\HttpClientInterface;
+
+final readonly class PlatformFactory
+{
+    public static function create(
+        #[\SensitiveParameter]
+        string $apiKey,
+        ?HttpClientInterface $httpClient = null,
+    ): Platform {
+        $httpClient = $httpClient instanceof EventSourceHttpClient ? $httpClient : new EventSourceHttpClient($httpClient);
+        $responseHandler = new ModelHandler($httpClient, $apiKey);
+
+        return new Platform([$responseHandler], [$responseHandler]);
+    }
+}

src/Model/Message/AssistantMessage.php

@@ -50,4 +50,9 @@ public function jsonSerialize(): array
 
         return $array;
     }
+
+    public function accept(MessageVisitor $visitor): array
+    {
+        return $visitor->visitAssistantMessage($this);
+    }
 }

src/Model/Message/Content/Audio.php

@@ -32,4 +32,9 @@ public function jsonSerialize(): array
             ],
         ];
     }
+
+    public function accept(ContentVisitor $visitor): array
+    {
+        return $visitor->visitAudio($this);
+    }
 }

src/Model/Message/Content/Content.php

@@ -6,4 +6,5 @@
 
 interface Content extends \JsonSerializable
 {
+    public function accept(ContentVisitor $visitor): array;
 }

src/Model/Message/Content/ContentVisitor.php

@@ -0,0 +1,12 @@
+<?php
+
+namespace PhpLlm\LlmChain\Model\Message\Content;
+
+interface ContentVisitor
+{
+    public function visitAudio(Audio $content): array;
+
+    public function visitImage(Image $content): array;
+
+    public function visitText(Text $content): array;
+}

src/Model/Message/Content/Image.php

@@ -41,4 +41,9 @@ private function fromFile(string $filePath): string
 
         return sprintf('data:image/%s;base64,%s', $type, base64_encode($data));
     }
+
+    public function accept(ContentVisitor $visitor): array
+    {
+        return $visitor->visitImage($this);
+    }
 }

src/Model/Message/Content/Text.php

@@ -18,4 +18,9 @@ public function jsonSerialize(): array
     {
         return ['type' => 'text', 'text' => $this->text];
     }
+
+    public function accept(ContentVisitor $visitor): array
+    {
+        return $visitor->visitText($this);
+    }
 }

src/Model/Message/MessageInterface.php

@@ -7,4 +7,6 @@
 interface MessageInterface extends \JsonSerializable
 {
     public function getRole(): Role;
+
+    public function accept(MessageVisitor $visitor): array;
 }