MCPX MCP Gateway

import type { NextFunction, Request, Response } from "express"; import { HubConnectionError, HubService } from "../services/hub.js"; import { Logger } from "winston"; export type HubConnectionGuard = ( rq: Request, rs: Response, f: NextFunction, ) => void; export const noOpHubConnectionGuard: HubConnectionGuard = ( _req: Request, _res: Response, next: NextFunction, ): void => { next(); }; export type HubConnectionCheckResult = | { allowed: true } | { allowed: false; status: string; connectionError: HubConnectionError | undefined; }; /** * Checks if connection should be allowed based on hub authentication status. * Pure logic that can be reused in both Express middleware and Socket.IO handlers. */ export function checkHubConnection( hubService: HubService, enforceConnection: boolean, ): HubConnectionCheckResult { if (!enforceConnection) { return { allowed: true }; } const { status, connectionError } = hubService.status; if (status === "authenticated") { return { allowed: true }; } return { allowed: false, status, connectionError, }; } /** * Builds an Express middleware that enforces hub connection for routes. * - When enforceConnection is false: allows all requests * - When enforceConnection is true and hub is authenticated: allows requests * - When enforceConnection is true and hub is not authenticated: returns 503 */ export function makeHubConnectionGuard( hubService: HubService, enforceConnection: boolean, logger: Logger, ): HubConnectionGuard { if (!enforceConnection) { logger.info("Hub connection enforcement is disabled"); return noOpHubConnectionGuard; } logger.info("Hub connection enforcement is enabled"); return function (req: Request, res: Response, next: NextFunction): void { const result = checkHubConnection(hubService, enforceConnection); if (result.allowed) { next(); return; } logger.debug("Blocking request - hub not connected", { path: req.path, status: result.status, connectionError: result.connectionError?.toJSON(), }); res.status(503).json({ error: "Service Unavailable", message: "Server requires active hub connection", hubStatus: result.status, connectionError: result.connectionError?.toJSON(), }); }; }