Add abstract Message

Author: paulbalandan

src/Message/Message.php

@@ -0,0 +1,56 @@
+<?php
+
+declare(strict_types=1);
+
+/**
+ * This file is part of the Nexus MCP SDK package.
+ *
+ * (c) 2025 John Paul E. Balandan, CPA <[email protected]>
+ *
+ * For the full copyright and license information, please view
+ * the LICENSE file that was distributed with this source code.
+ */
+
+namespace Nexus\Mcp\Message;
+
+/**
+ * A JSON-RPC message.
+ */
+abstract readonly class Message implements \JsonSerializable
+{
+    final public const string JSON_RPC_VERSION = '2.0';
+
+    /**
+     * @var non-empty-string
+     */
+    public string $jsonrpc;
+
+    public function __construct(string $jsonrpc)
+    {
+        if ('' === $jsonrpc) {
+            throw new \InvalidArgumentException('JSON-RPC version cannot be empty.');
+        }
+
+        if (self::JSON_RPC_VERSION !== $jsonrpc) {
+            throw new \InvalidArgumentException('Invalid JSON-RPC version.');
+        }
+
+        $this->jsonrpc = $jsonrpc;
+    }
+
+    /**
+     * Get the array representation of the message.
+     *
+     * @return array<string, mixed>
+     */
+    abstract public function toArray(): array;
+
+    /**
+     * @return array<string, mixed>
+     */
+    #[\Override]
+    public function jsonSerialize(): array
+    {
+        return $this->toArray();
+    }
+}

tests/Message/MessageTest.php

@@ -0,0 +1,51 @@
+<?php
+
+declare(strict_types=1);
+
+/**
+ * This file is part of the Nexus MCP SDK package.
+ *
+ * (c) 2025 John Paul E. Balandan, CPA <[email protected]>
+ *
+ * For the full copyright and license information, please view
+ * the LICENSE file that was distributed with this source code.
+ */
+
+namespace Nexus\Mcp\Tests\Message;
+
+use Nexus\Mcp\Message\Message;
+use PHPUnit\Framework\Attributes\CoversClass;
+use PHPUnit\Framework\TestCase;
+
+/**
+ * @internal
+ */
+#[CoversClass(Message::class)]
+final class MessageTest extends TestCase
+{
+    public function testMessageDoesNotAcceptInvalidJsonRpcVersion(): void
+    {
+        $this->expectException(\InvalidArgumentException::class);
+        $this->expectExceptionMessage('Invalid JSON-RPC version.');
+        $this->getMockBuilder(Message::class)->setConstructorArgs(['1.1'])->getMock();
+    }
+
+    public function testMessageDoesNotAcceptEmptyJsonRpcVersion(): void
+    {
+        $this->expectException(\InvalidArgumentException::class);
+        $this->expectExceptionMessage('JSON-RPC version cannot be empty.');
+        $this->getMockBuilder(Message::class)->setConstructorArgs([''])->getMock();
+    }
+
+    public function testMessageCanBeJsonSerialized(): void
+    {
+        $message = $this->getMockBuilder(Message::class)
+            ->setConstructorArgs([Message::JSON_RPC_VERSION])
+            ->onlyMethods(['toArray'])
+            ->getMock()
+        ;
+        $message->method('toArray')->willReturn(['jsonrpc' => Message::JSON_RPC_VERSION]);
+
+        self::assertSame('{"jsonrpc":"2.0"}', json_encode($message));
+    }
+}