Encapsulate session handling from protocol to new SessionManager (#247)

src/Server/Session/SessionManager.php

@@ -0,0 +1,69 @@
+<?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\Session;
+
+use Psr\Log\LoggerInterface;
+use Psr\Log\NullLogger;
+use Symfony\Component\Uid\Uuid;
+
+/**
+ * Default implementation of SessionManagerInterface.
+ *
+ * @author Kyrian Obikwelu <koshnawaza@gmail.com>
+ */
+class SessionManager implements SessionManagerInterface
+{
+    public function __construct(
+        private readonly SessionStoreInterface $store,
+        private readonly LoggerInterface $logger = new NullLogger(),
+    ) {
+    }
+
+    public function create(): SessionInterface
+    {
+        return new Session($this->store, Uuid::v4());
+    }
+
+    public function createWithId(Uuid $id): SessionInterface
+    {
+        return new Session($this->store, $id);
+    }
+
+    public function exists(Uuid $id): bool
+    {
+        return $this->store->exists($id);
+    }
+
+    public function destroy(Uuid $id): bool
+    {
+        return $this->store->destroy($id);
+    }
+
+    /**
+     * Run garbage collection on expired sessions.
+     * Uses the session store's internal TTL configuration.
+     */
+    public function gc(): void
+    {
+        if (random_int(0, 100) > 1) {
+            return;
+        }
+
+        $deletedSessions = $this->store->gc();
+        if (!empty($deletedSessions)) {
+            $this->logger->debug('Garbage collected expired sessions.', [
+                'count' => \count($deletedSessions),
+                'session_ids' => array_map(static fn (Uuid $id) => $id->toRfc4122(), $deletedSessions),
+            ]);
+        }
+    }
+}