chore: add start server for Railway

package.json

@@ -3,10 +3,14 @@
   "private": true,
   "version": "0.0.0",
   "type": "module",
+  "engines": {
+    "node": ">=20"
+  },
   "scripts": {
     "dev": "vite",
     "build": "tsc -b && vite build",
     "lint": "eslint .",
+    "start": "node server.mjs",
     "preview": "vite preview",
     "typecheck": "tsc -b",
     "test": "vitest run",

server.mjs

@@ -0,0 +1,111 @@
+import http from 'node:http'
+import fs from 'node:fs'
+import path from 'node:path'
+
+const HOST = process.env.HOST ?? '0.0.0.0'
+const PORT = Number(process.env.PORT ?? '3000')
+
+const DIST_DIR = path.join(process.cwd(), 'dist')
+
+const MIME_TYPES = {
+  '.html': 'text/html; charset=utf-8',
+  '.js': 'text/javascript; charset=utf-8',
+  '.css': 'text/css; charset=utf-8',
+  '.json': 'application/json; charset=utf-8',
+  '.map': 'application/json; charset=utf-8',
+  '.txt': 'text/plain; charset=utf-8',
+  '.svg': 'image/svg+xml',
+  '.png': 'image/png',
+  '.jpg': 'image/jpeg',
+  '.jpeg': 'image/jpeg',
+  '.gif': 'image/gif',
+  '.webp': 'image/webp',
+  '.ico': 'image/x-icon',
+  '.woff': 'font/woff',
+  '.woff2': 'font/woff2',
+  '.ttf': 'font/ttf',
+  '.otf': 'font/otf',
+  '.eot': 'application/vnd.ms-fontobject',
+}
+
+function sendText(res, statusCode, text) {
+  res.writeHead(statusCode, { 'Content-Type': 'text/plain; charset=utf-8' })
+  res.end(text)
+}
+
+function sendFile(res, filePath, statusCode = 200) {
+  const ext = path.extname(filePath).toLowerCase()
+  const contentType = MIME_TYPES[ext] ?? 'application/octet-stream'
+
+  const headers = { 'Content-Type': contentType }
+
+  // Cache hashed build artifacts aggressively; keep index.html fresh for updates.
+  const base = path.basename(filePath)
+  if (base === 'index.html') {
+    headers['Cache-Control'] = 'no-cache'
+  } else if (/-[A-Za-z0-9]{6,}\./.test(base)) {
+    headers['Cache-Control'] = 'public, max-age=31536000, immutable'
+  } else {
+    headers['Cache-Control'] = 'public, max-age=3600'
+  }
+
+  res.writeHead(statusCode, headers)
+  fs.createReadStream(filePath).pipe(res)
+}
+
+const server = http.createServer((req, res) => {
+  if (!req.url) return sendText(res, 400, 'Bad Request')
+
+  if (req.method !== 'GET' && req.method !== 'HEAD') {
+    res.setHeader('Allow', 'GET, HEAD')
+    return sendText(res, 405, 'Method Not Allowed')
+  }
+
+  let url
+  try {
+    url = new URL(req.url, `http://${req.headers.host ?? 'localhost'}`)
+  } catch {
+    return sendText(res, 400, 'Bad Request')
+  }
+
+  let pathname = decodeURIComponent(url.pathname)
+  if (pathname === '/') pathname = '/index.html'
+
+  // Prevent directory traversal
+  const filePath = path.normalize(path.join(DIST_DIR, pathname))
+  if (!filePath.startsWith(DIST_DIR)) return sendText(res, 403, 'Forbidden')
+
+  fs.stat(filePath, (err, stat) => {
+    if (!err && stat.isFile()) {
+      if (req.method === 'HEAD') {
+        const ext = path.extname(filePath).toLowerCase()
+        res.writeHead(200, { 'Content-Type': MIME_TYPES[ext] ?? 'application/octet-stream' })
+        return res.end()
+      }
+      return sendFile(res, filePath)
+    }
+
+    // If the request looks like an asset (has an extension), don't SPA-fallback.
+    if (path.extname(pathname)) return sendText(res, 404, 'Not Found')
+
+    const indexPath = path.join(DIST_DIR, 'index.html')
+    fs.stat(indexPath, (indexErr, indexStat) => {
+      if (indexErr || !indexStat.isFile()) {
+        return sendText(res, 500, 'Missing dist/index.html. Run `npm run build` before starting the server.')
+      }
+      if (req.method === 'HEAD') {
+        res.writeHead(200, { 'Content-Type': 'text/html; charset=utf-8' })
+        return res.end()
+      }
+      return sendFile(res, indexPath)
+    })
+  })
+})
+
+server.listen(PORT, HOST, () => {
+  console.log(`building-viz server listening on http://${HOST}:${PORT}`)
+})
+
+process.on('SIGTERM', () => {
+  server.close(() => process.exit(0))
+})