Add missing handler for resource subscribe and unsubscribe (#220)

src/Server/Handler/Request/ResourceUnsubscribeHandler.php

@@ -0,0 +1,72 @@
+<?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\RegistryInterface;
+use Mcp\Exception\ResourceNotFoundException;
+use Mcp\Schema\JsonRpc\Error;
+use Mcp\Schema\JsonRpc\Request;
+use Mcp\Schema\JsonRpc\Response;
+use Mcp\Schema\Request\ResourceUnsubscribeRequest;
+use Mcp\Schema\Result\EmptyResult;
+use Mcp\Server\Resource\SubscriptionManagerInterface;
+use Mcp\Server\Session\SessionInterface;
+use Psr\Log\LoggerInterface;
+use Psr\Log\NullLogger;
+use Psr\SimpleCache\InvalidArgumentException;
+
+/**
+ * @implements RequestHandlerInterface<EmptyResult>
+ *
+ * @author Larry Sule-balogun <suleabimbola@gmail.com>
+ */
+final class ResourceUnsubscribeHandler implements RequestHandlerInterface
+{
+    public function __construct(
+        private readonly RegistryInterface $registry,
+        private readonly SubscriptionManagerInterface $subscriptionManager,
+        private readonly LoggerInterface $logger = new NullLogger(),
+    ) {
+    }
+
+    public function supports(Request $request): bool
+    {
+        return $request instanceof ResourceUnsubscribeRequest;
+    }
+
+    /**
+     * @throws InvalidArgumentException
+     */
+    public function handle(Request $request, SessionInterface $session): Response|Error
+    {
+        \assert($request instanceof ResourceUnsubscribeRequest);
+
+        $uri = $request->uri;
+
+        try {
+            $this->registry->getResource($uri);
+        } catch (ResourceNotFoundException $e) {
+            $this->logger->error('Resource not found', ['uri' => $uri]);
+
+            return Error::forResourceNotFound($e->getMessage(), $request->getId());
+        }
+
+        $this->logger->debug('Unsubscribing from resource', ['uri' => $uri]);
+
+        $this->subscriptionManager->unsubscribe($session, $uri);
+
+        return new Response(
+            $request->getId(),
+            new EmptyResult(),
+        );
+    }
+}