refactor: enhance authentication middleware to validate user existence and status before proceeding

nest-backend/src/middleware/auth.ts

@@ -1,5 +1,6 @@
 import { Request, Response, NextFunction } from 'express';
 import jwt from 'jsonwebtoken';
+import prisma from '../lib/prisma.js';
 
 export interface JwtPayload {
   userId: string;
@@ -15,7 +16,7 @@ declare global {
   }
 }
 
-export function authenticate(req: Request, res: Response, next: NextFunction): void {
+export async function authenticate(req: Request, res: Response, next: NextFunction): Promise<void> {
   const header = req.headers.authorization;
   if (!header?.startsWith('Bearer ')) {
     res.status(401).json({ error: 'Missing or invalid Authorization header' });
@@ -25,7 +26,21 @@ export function authenticate(req: Request, res: Response, next: NextFunction): v
   const token = header.slice(7);
   try {
     const payload = jwt.verify(token, process.env.JWT_SECRET!) as JwtPayload;
-    req.user = payload;
+    const user = await prisma.user.findUnique({
+      where: { id: payload.userId },
+      select: { id: true, role: true, isAdmin: true, isBanned: true },
+    });
+
+    if (!user || user.isBanned) {
+      res.status(401).json({ error: 'Token user no longer exists or is banned. Please login again.' });
+      return;
+    }
+
+    req.user = {
+      userId: user.id,
+      role: user.role,
+      isAdmin: user.isAdmin,
+    };
     next();
   } catch {
     res.status(401).json({ error: 'Token expired or invalid' });