Add chat history support

README.md

@@ -124,6 +124,32 @@ print $chat->sendMessage('in Go');
 // This code will print "Hello World!" to the standard output.
 ```
 
+### Chat Session with History
+
+```php
+use GeminiAPI\Laravel\Facades\Gemini;
+
+$history = [
+    [
+        'message' => 'Hello World in PHP',
+        'role' => 'user',
+    ],
+    [
+        'message' => <<<MESSAGE
+            echo "Hello World!";
+
+            This code will print "Hello World!" to the standard output.
+            MESSAGE,
+        'role' => 'model',
+    ],
+];
+$chat = Gemini::startChat($history);
+
+print $chat->sendMessage('in Go');
+// fmt.Println("Hello World!")
+// This code will print "Hello World!" to the standard output.
+```
+
 ### Tokens counting
 
 ```php

composer.json

@@ -22,7 +22,7 @@
   ],
   "require": {
     "php": "^8.1",
-    "gemini-api-php/client": "^1.1",
+    "gemini-api-php/client": "^1.2",
     "illuminate/support": "^9.0 || ^10.0 || ^11.0",
     "psr/container": "^1.0 || ^2.0",
     "psr/http-client": "^1.0"

src/ChatSession.php

@@ -5,6 +5,7 @@
 namespace GeminiAPI\Laravel;
 
 use GeminiAPI\ChatSession as ApiChatSession;
+use GeminiAPI\Resources\Content;
 use GeminiAPI\Resources\Parts\TextPart;
 use Psr\Http\Client\ClientExceptionInterface;
 
@@ -24,4 +25,21 @@ public function sendMessage(string $text): string
             ->sendMessage(new TextPart($text))
             ->text();
     }
+
+    /**
+     * @return array<int, array{
+     *     message: string,
+     *     role: string,
+     * }>
+     */
+    public function history(): array
+    {
+        return array_map(
+            static fn (Content $content): array => [
+                'message' => $content->parts[0] instanceof TextPart ? $content->parts[0]->text : '',
+                'role' => $content->role->value,
+            ],
+            $this->chatSession->history(),
+        );
+    }
 }

src/Gemini.php

@@ -7,14 +7,26 @@
 use GeminiAPI\ClientInterface;
 use GeminiAPI\Enums\MimeType;
 use GeminiAPI\Enums\ModelName;
+use GeminiAPI\Enums\Role;
 use GeminiAPI\Laravel\Contracts\GeminiContract;
 use GeminiAPI\Laravel\Exceptions\InvalidArgumentException;
 use GeminiAPI\Laravel\Exceptions\InvalidMimeType;
+use GeminiAPI\Resources\Content;
 use GeminiAPI\Resources\Model;
 use GeminiAPI\Resources\Parts\ImagePart;
 use GeminiAPI\Resources\Parts\TextPart;
 use Psr\Http\Client\ClientExceptionInterface;
 
+use function array_map;
+use function base64_encode;
+use function file_get_contents;
+use function in_array;
+use function is_file;
+use function is_null;
+use function is_readable;
+use function is_string;
+use function sprintf;
+
 class Gemini implements GeminiContract
 {
     public function __construct(
@@ -114,12 +126,38 @@ public function generateTextUsingImage(
         return $response->text();
     }
 
-    public function startChat(): ChatSession
+    /**
+     * @param array<int, array{
+     *   message: string,
+     *   role: string,
+     * }> $history
+     *
+     * @throws InvalidArgumentException
+     */
+    public function startChat(array $history = []): ChatSession
     {
         $chatSession = $this->client
             ->generativeModel(ModelName::GeminiPro)
             ->startChat();
 
+        if (! empty($history)) {
+            $contents = array_map(
+                static function (array $message): Content {
+                    if (empty($message['message']) || empty($message['role'])) {
+                        throw new InvalidArgumentException('Invalid message in the chat history');
+                    }
+
+                    if (! is_string($message['message']) || ! in_array($message['role'], ['user', 'model'], true)) {
+                        throw new InvalidArgumentException('Invalid message in the chat history');
+                    }
+
+                    return Content::text($message['message'], Role::from($message['role']));
+                },
+                $history,
+            );
+            $chatSession = $chatSession->withHistory($contents);
+        }
+
         return new ChatSession($chatSession);
     }