/**
* Entry point for running the Value Picker MCP server.
*
* Transport selection:
* --stdio Force STDIO mode
* --http Force Streamable HTTP mode
* (default) Auto-detect: STDIO when stdin is piped, HTTP when interactive
*
* IMPORTANT: In STDIO mode, stdout is reserved for JSON-RPC messages.
* ALL console output is suppressed to avoid corrupting the protocol.
*/
import { StdioServerTransport } from "@modelcontextprotocol/sdk/server/stdio.js";
import { createMcpExpressApp } from "@modelcontextprotocol/sdk/server/express.js";
import type { McpServer } from "@modelcontextprotocol/sdk/server/mcp.js";
import { StreamableHTTPServerTransport } from "@modelcontextprotocol/sdk/server/streamableHttp.js";
import { createServer as createNetServer } from "node:net";
import cors from "cors";
import type { Request, Response } from "express";
import { createServer } from "./server.js";
/**
* Determine transport mode:
* 1. Explicit --stdio flag → STDIO
* 2. Explicit --http flag → HTTP
* 3. Auto-detect: stdin is piped (not a TTY) → STDIO, otherwise HTTP
*/
function resolveTransport(): "stdio" | "http" {
if (process.argv.includes("--stdio")) return "stdio";
if (process.argv.includes("--http")) return "http";
// When a client (Claude Desktop, MCP sandbox) spawns this process,
// stdin is a pipe, not a TTY.
return process.stdin.isTTY ? "http" : "stdio";
}
const transport = resolveTransport();
/**
* In STDIO mode, suppress ALL console output.
* stdout is reserved for JSON-RPC, and the sandbox may also capture stderr.
*/
if (transport === "stdio") {
const noop = () => {};
console.log = noop;
console.info = noop;
console.warn = noop;
console.error = noop;
console.debug = noop;
}
/**
* Find an available port. Tries the preferred port first, then falls back
* to an OS-assigned ephemeral port.
*/
function findAvailablePort(preferred: number): Promise<number> {
return new Promise((resolve, reject) => {
const srv = createNetServer();
srv.once("error", (err: NodeJS.ErrnoException) => {
if (err.code === "EADDRINUSE") {
// Preferred port is taken — let the OS assign one
srv.listen(0, "0.0.0.0", () => {
const addr = srv.address();
const port = typeof addr === "object" && addr ? addr.port : 0;
srv.close(() => resolve(port));
});
} else {
reject(err);
}
});
srv.listen(preferred, "0.0.0.0", () => {
const addr = srv.address();
const port = typeof addr === "object" && addr ? addr.port : preferred;
srv.close(() => resolve(port));
});
});
}
export async function startStreamableHTTPServer(
createServer: () => McpServer,
): Promise<void> {
const preferredPort = parseInt(process.env.PORT ?? "3456", 10);
const port = await findAvailablePort(preferredPort);
const app = createMcpExpressApp({ host: "0.0.0.0" });
app.use(cors());
app.all("/mcp", async (req: Request, res: Response) => {
const server = createServer();
const transport = new StreamableHTTPServerTransport({
sessionIdGenerator: undefined,
});
res.on("close", () => {
transport.close().catch(() => {});
server.close().catch(() => {});
});
try {
await server.connect(transport);
await transport.handleRequest(req, res, req.body);
} catch (error) {
console.error("MCP error:", error);
if (!res.headersSent) {
res.status(500).json({
jsonrpc: "2.0",
error: { code: -32603, message: "Internal server error" },
id: null,
});
}
}
});
const httpServer = app.listen(port, (err) => {
if (err) {
console.error("Failed to start server:", err);
process.exit(1);
}
console.log(`Value Picker MCP server listening on http://localhost:${port}/mcp`);
});
const shutdown = () => {
httpServer.close(() => process.exit(0));
};
process.on("SIGINT", shutdown);
process.on("SIGTERM", shutdown);
}
export async function startStdioServer(
createServer: () => McpServer,
): Promise<void> {
const server = createServer();
const stdioTransport = new StdioServerTransport();
await server.connect(stdioTransport);
}
async function main() {
if (transport === "stdio") {
await startStdioServer(createServer);
} else {
await startStreamableHTTPServer(createServer);
}
}
main().catch((e) => {
console.error(e);
process.exit(1);
});
