refactoring: TypeScript migration, security fixes,

server/src/middleware/validate.ts

@@ -0,0 +1,26 @@
+import { Request, Response, NextFunction } from 'express';
+
+function maxLength(field: string, max: number) {
+  return (req: Request, res: Response, next: NextFunction): void => {
+    if (req.body[field] && typeof req.body[field] === 'string' && req.body[field].length > max) {
+      res.status(400).json({ error: `${field} must be ${max} characters or less` });
+      return;
+    }
+    next();
+  };
+}
+
+function validateStringLengths(maxLengths: Record<string, number>) {
+  return (req: Request, res: Response, next: NextFunction): void => {
+    for (const [field, max] of Object.entries(maxLengths)) {
+      const value = req.body[field];
+      if (value && typeof value === 'string' && value.length > max) {
+        res.status(400).json({ error: `${field} must be ${max} characters or less` });
+        return;
+      }
+    }
+    next();
+  };
+}
+
+export { maxLength, validateStringLengths };