/**
* HTTP Streamable Transport Handler
* Implements the MCP HTTP Streamable transport specification
*/
import { Request, Response, Router } from 'express';
import { MCPProtocolHandler } from '../protocol/index.js';
import { MCPRequest, MCPMessage } from '../types.js';
import { logger } from '../logger.js';
export function createHttpTransport(protocolHandler: MCPProtocolHandler): Router {
const router = Router();
/**
* Handle POST requests - main MCP endpoint
* Supports both single requests and batch requests
*/
router.post('/', async (req: Request, res: Response) => {
const sessionId = req.headers['mcp-session-id'] as string | undefined;
const session = protocolHandler.getOrCreateSession(sessionId);
// Set session ID header
res.setHeader('Mcp-Session-Id', session.id);
const body = req.body;
// Check if it's a batch request
if (Array.isArray(body)) {
await handleBatchRequest(body, session, protocolHandler, res);
} else {
await handleSingleRequest(body, session, protocolHandler, req, res);
}
});
/**
* Handle GET requests - server info
*/
router.get('/', (_req: Request, res: Response) => {
res.json({
name: 'MCP Gateway',
version: '1.0.0',
protocol: '2024-11-05',
transports: ['http', 'sse'],
});
});
/**
* Handle DELETE requests - close session
*/
router.delete('/', (req: Request, res: Response) => {
const sessionId = req.headers['mcp-session-id'] as string | undefined;
if (sessionId) {
const session = protocolHandler.getSession(sessionId);
if (session) {
logger.info(`Session ${sessionId} closed by client`);
}
}
res.status(204).send();
});
return router;
}
/**
* Handle a single MCP request
*/
async function handleSingleRequest(
body: MCPMessage,
session: ReturnType<MCPProtocolHandler['getOrCreateSession']>,
protocolHandler: MCPProtocolHandler,
_req: Request,
res: Response
): Promise<void> {
try {
const response = await protocolHandler.handleMessage(body, session);
if (response === null) {
// It was a notification, no response needed
res.status(202).json({ status: 'accepted' });
return;
}
// Always return JSON for HTTP Streamable transport
// Cursor and other clients expect plain JSON, not SSE format
res.json(response);
} catch (error) {
logger.error('Error handling request', { error });
const errorResponse = {
jsonrpc: '2.0',
id: (body as MCPRequest).id ?? null,
error: {
code: -32603,
message: error instanceof Error ? error.message : 'Internal error',
},
};
res.status(500).json(errorResponse);
}
}
/**
* Handle a batch of MCP requests
*/
async function handleBatchRequest(
messages: MCPMessage[],
session: ReturnType<MCPProtocolHandler['getOrCreateSession']>,
protocolHandler: MCPProtocolHandler,
res: Response
): Promise<void> {
const responses: unknown[] = [];
for (const message of messages) {
try {
const response = await protocolHandler.handleMessage(message, session);
if (response !== null) {
responses.push(response);
}
} catch (error) {
responses.push({
jsonrpc: '2.0',
id: (message as MCPRequest).id ?? null,
error: {
code: -32603,
message: error instanceof Error ? error.message : 'Internal error',
},
});
}
}
res.json(responses);
}
