feat: add completion/complete handler, centralize provider logic, and move completion capability (#97)

src/Server/Handler/Request/CompletionCompleteHandler.php

@@ -0,0 +1,52 @@
+<?php
+
+/*
+ * This file is part of the official PHP MCP SDK.
+ *
+ * A collaboration between Symfony and the PHP Foundation.
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace Mcp\Server\Handler\Request;
+
+use Mcp\Capability\Completion\CompleterInterface;
+use Mcp\Exception\ExceptionInterface;
+use Mcp\Schema\JsonRpc\Error;
+use Mcp\Schema\JsonRpc\HasMethodInterface;
+use Mcp\Schema\JsonRpc\Response;
+use Mcp\Schema\Request\CompletionCompleteRequest;
+use Mcp\Server\Handler\MethodHandlerInterface;
+use Mcp\Server\Session\SessionInterface;
+
+/**
+ * Handles completion/complete requests.
+ *
+ * @author Kyrian Obikwelu <koshnawaza@gmail.com>
+ */
+final class CompletionCompleteHandler implements MethodHandlerInterface
+{
+    public function __construct(
+        private readonly CompleterInterface $completer,
+    ) {
+    }
+
+    public function supports(HasMethodInterface $message): bool
+    {
+        return $message instanceof CompletionCompleteRequest;
+    }
+
+    public function handle(CompletionCompleteRequest|HasMethodInterface $message, SessionInterface $session): Response|Error
+    {
+        \assert($message instanceof CompletionCompleteRequest);
+
+        try {
+            $result = $this->completer->complete($message);
+        } catch (ExceptionInterface) {
+            return Error::forInternalError('Error while handling completion request', $message->getId());
+        }
+
+        return new Response($message->getId(), $result);
+    }
+}