Introduce schema component

src/Schema/Notification/CancelledNotification.php

@@ -0,0 +1,67 @@
+<?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\Schema\Notification;
+
+use Mcp\Exception\InvalidArgumentException;
+use Mcp\Schema\JsonRpc\Notification;
+
+/**
+ * This notification can be sent by either side to indicate that it is cancelling a previously-issued request.
+ *
+ * The request SHOULD still be in-flight, but due to communication latency, it is always possible that this notification MAY arrive after the request has already finished.
+ *
+ * This notification indicates that the result will be unused, so any associated processing SHOULD cease.
+ *
+ * A client MUST NOT attempt to cancel its `initialize` request.
+ *
+ * @author Kyrian Obikwelu <koshnawaza@gmail.com>
+ */
+class CancelledNotification extends Notification
+{
+    /**
+     * @param string                $requestId The ID of the request that is being cancelled. This MUST correspond to the ID of a request previously issued in the same direction.
+     * @param ?string               $reason    An optional string describing the reason for the cancellation. This MAY be logged or presented to the user.
+     * @param ?array<string, mixed> $_meta     additional metadata about the notification
+     */
+    public function __construct(
+        public readonly string $requestId,
+        public readonly ?string $reason = null,
+        public readonly ?array $_meta = null,
+    ) {
+        $params = [
+            'requestId' => $this->requestId,
+        ];
+        if (null !== $this->reason) {
+            $params['reason'] = $this->reason;
+        }
+        if (null !== $_meta) {
+            $params['_meta'] = $_meta;
+        }
+
+        parent::__construct('notifications/cancelled', $params);
+    }
+
+    public static function fromNotification(Notification $notification): self
+    {
+        if ('notifications/cancelled' !== $notification->method) {
+            throw new InvalidArgumentException('Notification is not a notifications/cancelled notification');
+        }
+
+        $params = $notification->params;
+
+        if (!isset($params['requestId']) || !\is_string($params['requestId'])) {
+            throw new InvalidArgumentException('Missing or invalid requestId parameter for notifications/cancelled notification');
+        }
+
+        return new self($params['requestId'], $params['reason'] ?? null, $params['_meta'] ?? null);
+    }
+}