Email MCP Server

import express from 'express'; import bodyParser from 'body-parser'; import cors from 'cors'; import { spawn } from 'child_process'; import { Server } from '@modelcontextprotocol/sdk/server/index.js'; import { SSEServerTransport } from '@modelcontextprotocol/sdk/server/sse.js'; import { getVersion } from '../lib/getVersion.js'; import { onSignals } from '../lib/onSignals.js'; import { serializeCorsOrigin } from '../lib/serializeCorsOrigin.js'; const setResponseHeaders = ({ res, headers, }) => Object.entries(headers).forEach(([key, value]) => { res.setHeader(key, value); }); export async function stdioToSse(args) { const { stdioCmd, port, baseUrl, ssePath, messagePath, logger, corsOrigin, healthEndpoints, headers, } = args; logger.info(` - Headers: ${Object(headers).length ? JSON.stringify(headers) : '(none)'}`); logger.info(` - port: ${port}`); logger.info(` - stdio: ${stdioCmd}`); if (baseUrl) { logger.info(` - baseUrl: ${baseUrl}`); } logger.info(` - ssePath: ${ssePath}`); logger.info(` - messagePath: ${messagePath}`); logger.info(` - CORS: ${corsOrigin ? `enabled (${serializeCorsOrigin({ corsOrigin })})` : 'disabled'}`); logger.info(` - Health endpoints: ${healthEndpoints.length ? healthEndpoints.join(', ') : '(none)'}`); onSignals({ logger }); const child = spawn(stdioCmd, { shell: true }); child.on('exit', (code, signal) => { logger.error(`Child exited: code=${code}, signal=${signal}`); process.exit(code ?? 1); }); const server = new Server({ name: 'supergateway', version: getVersion() }, { capabilities: {} }); const sessions = {}; const app = express(); if (corsOrigin) { app.use(cors({ origin: corsOrigin })); } app.use((req, res, next) => { if (req.path === messagePath) return next(); return bodyParser.json()(req, res, next); }); for (const ep of healthEndpoints) { app.get(ep, (_req, res) => { setResponseHeaders({ res, headers, }); res.send('ok'); }); } app.get(ssePath, async (req, res) => { logger.info(`New SSE connection from ${req.ip}`); setResponseHeaders({ res, headers, }); const sseTransport = new SSEServerTransport(`${baseUrl}${messagePath}`, res); await server.connect(sseTransport); const sessionId = sseTransport.sessionId; if (sessionId) { sessions[sessionId] = { transport: sseTransport, response: res }; } sseTransport.onmessage = (msg) => { logger.info(`SSE → Child (session ${sessionId}): ${JSON.stringify(msg)}`); child.stdin.write(JSON.stringify(msg) + '\n'); }; sseTransport.onclose = () => { logger.info(`SSE connection closed (session ${sessionId})`); delete sessions[sessionId]; }; sseTransport.onerror = (err) => { logger.error(`SSE error (session ${sessionId}):`, err); delete sessions[sessionId]; }; req.on('close', () => { logger.info(`Client disconnected (session ${sessionId})`); delete sessions[sessionId]; }); }); // @ts-ignore app.post(messagePath, async (req, res) => { const sessionId = req.query.sessionId; setResponseHeaders({ res, headers, }); if (!sessionId) { return res.status(400).send('Missing sessionId parameter'); } const session = sessions[sessionId]; if (session?.transport?.handlePostMessage) { logger.info(`POST to SSE transport (session ${sessionId})`); await session.transport.handlePostMessage(req, res); } else { res.status(503).send(`No active SSE connection for session ${sessionId}`); } }); app.listen(port, () => { logger.info(`Listening on port ${port}`); logger.info(`SSE endpoint: http://localhost:${port}${ssePath}`); logger.info(`POST messages: http://localhost:${port}${messagePath}`); }); let buffer = ''; child.stdout.on('data', (chunk) => { buffer += chunk.toString('utf8'); const lines = buffer.split(/\r?\n/); buffer = lines.pop() ?? ''; lines.forEach((line) => { if (!line.trim()) return; try { const jsonMsg = JSON.parse(line); logger.info('Child → SSE:', jsonMsg); for (const [sid, session] of Object.entries(sessions)) { try { session.transport.send(jsonMsg); } catch (err) { logger.error(`Failed to send to session ${sid}:`, err); delete sessions[sid]; } } } catch { logger.error(`Child non-JSON: ${line}`); } }); }); child.stderr.on('data', (chunk) => { logger.error(`Child stderr: ${chunk.toString('utf8')}`); }); }