import express from "express";
import type { Request, Response } from "express";
import { StreamableHTTPServerTransport } from "@modelcontextprotocol/sdk/server/streamableHttp.js";
import { buildMermaidMcpServer } from "./server.js";
const app = express();
app.use(express.json());
const PORT = process.env.PORT || 3000;
// Health check endpoint
app.get("/health", (_req: Request, res: Response) => {
res.json({ status: "ok", service: "mermaid-mcp" });
});
// MCP endpoint using StreamableHTTPServerTransport
app.post("/mcp", async (req: Request, res: Response) => {
const server = buildMermaidMcpServer();
try {
const transport = new StreamableHTTPServerTransport({
sessionIdGenerator: undefined
});
await server.connect(transport);
await transport.handleRequest(req, res, req.body);
res.on("close", () => {
// Only log in debug mode
if (process.env.DEBUG) {
console.log("MCP request completed");
}
transport.close();
server.close();
});
} catch (error) {
console.error("Error handling MCP request:", error);
if (!res.headersSent) {
res.status(500).json({
jsonrpc: "2.0",
error: {
code: -32603,
message: "Internal server error"
},
id: null
});
}
}
});
// Reject GET requests
app.get("/mcp", async (_req: Request, res: Response) => {
if (process.env.DEBUG) {
console.log("Rejected GET request to /mcp");
}
res.writeHead(405).end(
JSON.stringify({
jsonrpc: "2.0",
error: {
code: -32000,
message: "Method not allowed."
},
id: null
})
);
});
// Reject DELETE requests
app.delete("/mcp", async (_req: Request, res: Response) => {
if (process.env.DEBUG) {
console.log("Rejected DELETE request to /mcp");
}
res.writeHead(405).end(
JSON.stringify({
jsonrpc: "2.0",
error: {
code: -32000,
message: "Method not allowed."
},
id: null
})
);
});
// Start server
const server = app.listen(PORT, () => {
console.log(`Mermaid MCP HTTP server listening on port ${PORT}`);
console.log(`Health check: http://localhost:${PORT}/health`);
console.log(`MCP endpoint: http://localhost:${PORT}/mcp`);
});
// Handle port conflicts and other listen errors
server.on("error", (error: NodeJS.ErrnoException) => {
if (error.code === "EADDRINUSE") {
console.error(`❌ Error: Port ${PORT} is already in use.`);
console.error(`Please stop the other server or set a different PORT environment variable.`);
console.error(`Example: PORT=3001 npm run start:http`);
} else {
console.error(`❌ Server error:`, error);
}
process.exit(1);
});
// Handle server shutdown
process.on("SIGINT", async () => {
console.log("Shutting down server...");
server.close(() => {
console.log("Server closed");
process.exit(0);
});
});
