feat: support dynamic base path in Express server via proxy headers

drills/flat-stack-presejpacky/server.ts

@@ -1,6 +1,7 @@
 import express from 'express';
 import path from 'path';
 import { fileURLToPath } from 'url';
+import fs from 'fs';
 
 const __filename = fileURLToPath(import.meta.url);
 const __dirname = path.dirname(__filename);
@@ -8,12 +9,44 @@ const __dirname = path.dirname(__filename);
 const app = express();
 const PORT = process.env.PORT || 3000;
 
+// Middleware to strip base path prefix from request headers if present
+app.use((req, res, next) => {
+  const prefix = (req.headers['x-forwarded-prefix'] as string) || (req.headers['x-base-path'] as string) || '';
+  const cleanPrefix = prefix.endsWith('/') ? prefix.slice(0, -1) : prefix;
+
+  if (cleanPrefix && req.url.startsWith(cleanPrefix)) {
+    req.url = req.url.substring(cleanPrefix.length);
+    if (!req.url.startsWith('/')) {
+      req.url = '/' + req.url;
+    }
+  }
+  next();
+});
+
 // Serve static files from the 'dist' directory
 app.use(express.static(path.join(__dirname, 'dist')));
 
-// Fallback to index.html for Single Page Application routing
+// Fallback to index.html for Single Page Application routing, injecting base path from headers
 app.get('*', (req, res) => {
-  res.sendFile(path.join(__dirname, 'dist', 'index.html'));
+  const indexPath = path.join(__dirname, 'dist', 'index.html');
+  fs.readFile(indexPath, 'utf8', (err, html) => {
+    if (err) {
+      return res.status(500).send('Error reading index.html');
+    }
+
+    const prefix = (req.headers['x-forwarded-prefix'] as string) || (req.headers['x-base-path'] as string) || '';
+    const cleanPrefix = prefix.endsWith('/') ? prefix.slice(0, -1) : prefix;
+
+    // Dynamically prefix asset URLs in index.html with the base path
+    let modifiedHtml = html;
+    if (cleanPrefix) {
+      modifiedHtml = html
+        .replace(/(href|src)="\/assets\//g, `$1="${cleanPrefix}/assets/`)
+        .replace(/(href|src)="\/vite.svg"/g, `$1="${cleanPrefix}/vite.svg"`);
+    }
+
+    res.send(modifiedHtml);
+  });
 });
 
 app.listen(PORT, () => {