feat: empower input processor to change LLM and MessageBag (#184)

Author: chr-hertel

src/Chain.php

@@ -47,25 +47,18 @@ public function __construct(
      */
     public function call(MessageBagInterface $messages, array $options = []): ResponseInterface
     {
-        $llm = $this->llm;
-
-        if (array_key_exists('llm', $options)) {
-            if (!$options['llm'] instanceof LanguageModel) {
-                throw new InvalidArgumentException(sprintf('Option "llm" must be an instance of %s.', LanguageModel::class));
-            }
-
-            $llm = $options['llm'];
-            unset($options['llm']);
-        }
-
-        $input = new Input($llm, $messages, $options);
+        $input = new Input($this->llm, $messages, $options);
         array_map(fn (InputProcessor $processor) => $processor->processInput($input), $this->inputProcessor);
 
+        $llm = $input->llm;
+        $messages = $input->messages;
+        $options = $input->getOptions();
+
         if ($messages->containsImage() && !$llm->supportsImageInput()) {
             throw MissingModelSupport::forImageInput($llm::class);
         }
 
-        $response = $this->platform->request($llm, $messages, $options = $input->getOptions());
+        $response = $this->platform->request($llm, $messages, $options);
 
         if ($response instanceof AsyncResponse) {
             $response = $response->unwrap();

src/Chain/Input.php

@@ -13,8 +13,8 @@ final class Input
      * @param array<string, mixed> $options
      */
     public function __construct(
-        public readonly LanguageModel $llm,
-        public readonly MessageBagInterface $messages,
+        public LanguageModel $llm,
+        public MessageBagInterface $messages,
         private array $options,
     ) {
     }

src/Chain/LlmOverrideInputProcessor.php

@@ -0,0 +1,26 @@
+<?php
+
+declare(strict_types=1);
+
+namespace PhpLlm\LlmChain\Chain;
+
+use PhpLlm\LlmChain\Exception\InvalidArgumentException;
+use PhpLlm\LlmChain\Model\LanguageModel;
+
+final class LlmOverrideInputProcessor implements InputProcessor
+{
+    public function processInput(Input $input): void
+    {
+        $options = $input->getOptions();
+
+        if (!array_key_exists('llm', $options)) {
+            return;
+        }
+
+        if (!$options['llm'] instanceof LanguageModel) {
+            throw new InvalidArgumentException(sprintf('Option "llm" must be an instance of %s.', LanguageModel::class));
+        }
+
+        $input->llm = $options['llm'];
+    }
+}

tests/Chain/LlmOverrideInputProcessorTest.php

@@ -0,0 +1,66 @@
+<?php
+
+declare(strict_types=1);
+
+namespace PhpLlm\LlmChain\Tests\Chain;
+
+use PhpLlm\LlmChain\Bridge\Anthropic\Claude;
+use PhpLlm\LlmChain\Bridge\OpenAI\Embeddings;
+use PhpLlm\LlmChain\Bridge\OpenAI\GPT;
+use PhpLlm\LlmChain\Chain\Input;
+use PhpLlm\LlmChain\Chain\LlmOverrideInputProcessor;
+use PhpLlm\LlmChain\Exception\InvalidArgumentException;
+use PhpLlm\LlmChain\Model\Message\MessageBag;
+use PHPUnit\Framework\Attributes\CoversClass;
+use PHPUnit\Framework\Attributes\Small;
+use PHPUnit\Framework\Attributes\Test;
+use PHPUnit\Framework\Attributes\UsesClass;
+use PHPUnit\Framework\TestCase;
+
+#[CoversClass(LlmOverrideInputProcessor::class)]
+#[UsesClass(GPT::class)]
+#[UsesClass(Claude::class)]
+#[UsesClass(Input::class)]
+#[UsesClass(MessageBag::class)]
+#[Small]
+final class LlmOverrideInputProcessorTest extends TestCase
+{
+    #[Test]
+    public function processInputWithValidLlmOption(): void
+    {
+        $gpt = new GPT();
+        $claude = new Claude();
+        $input = new Input($gpt, new MessageBag(), ['llm' => $claude]);
+
+        $processor = new LlmOverrideInputProcessor();
+        $processor->processInput($input);
+
+        self::assertSame($claude, $input->llm);
+    }
+
+    #[Test]
+    public function processInputWithoutLlmOption(): void
+    {
+        $gpt = new GPT();
+        $input = new Input($gpt, new MessageBag(), []);
+
+        $processor = new LlmOverrideInputProcessor();
+        $processor->processInput($input);
+
+        self::assertSame($gpt, $input->llm);
+    }
+
+    #[Test]
+    public function processInputWithInvalidLlmOption(): void
+    {
+        self::expectException(InvalidArgumentException::class);
+        self::expectExceptionMessage('Option "llm" must be an instance of PhpLlm\LlmChain\Model\LanguageModel.');
+
+        $gpt = new GPT();
+        $model = new Embeddings();
+        $input = new Input($gpt, new MessageBag(), ['llm' => $model]);
+
+        $processor = new LlmOverrideInputProcessor();
+        $processor->processInput($input);
+    }
+}