Add Common Middleware Support (Validation, CORS, Logging, Error Handler, etc.)

📖 Description

Set up a robust collection of universal middleware functions that are reusable across all modules in a FastKit-style app. These middlewares should be plug-and-play, support TypeScript, and be easy to extend or replace.

This includes:

• 🧪 Validation (validateBody, validateParams, validateQuery)

• 🌐 CORS

• 📄 Request logging

• ❌ Global error handler

• 🧼 Input sanitization

• 🔄 Rate limiting

• 🔎 NotFound handler

🧠 Why This Is Important

• Standardizes request processing across all modules

• Prevents repetitive boilerplate code in every controller

• Helps debug and secure your app properly

• Encourages good architecture and scalable structure

• Every professional Express app needs these

##. 🧱 Folder Structure

src/
└── middlewares/
    │  
    ├── common/
    │   ├── validateBody.ts
    │   ├── validateParams.ts
    │   ├── validateQuery.ts
    │   ├── sanitizeInput.ts
    │   ├── cors.ts
    │   ├── requestLogger.ts
    │   ├── rateLimiter.ts
    │   ├── errorHandler.ts
    │   └── notFoundHandler.ts

✅ Tasks

🔐 Auth Middlewares

• verifyToken: Decode JWT, attach authId

• allowRoles('admin'): Role-based access control

🧪 Validation Middlewares

• validateBody(schema): Validate req.body with Zod or Joi

• validateParams(schema): Validate route params

• validateQuery(schema): Validate query strings

• sanitizeInput: Remove harmful tags/scripts

🌐 System-Level Middlewares

• cors.ts: Setup CORS with whitelist

• requestLogger.ts: Logs method, path, status, duration

• rateLimiter.ts: Prevent abuse (optional, with express-rate-limit)

• notFoundHandler.ts: Catch unknown routes

• errorHandler.ts: Catch & respond with formatted error

##✨ Usage Example

// file.route.ts

router.post(
  '/files',
  validateBody(createFileSchema),
  sanitizeInput,
  fileController.create
);

// app.ts or main.ts

app.use(corsMiddleware);
app.use(requestLogger);
app.use(express.json());
app.use(rateLimiter);
app.use('/api/v1', mainRouter);
app.use(notFoundHandler);
app.use(errorHandler);

🚀 Expected Outcome

• 🔄 All requests validated, sanitized, and logged

• 🔐 Unauthorized access blocked cleanly

• ❌ Invalid routes handled with friendly error

• 💥 All errors go through one handler

• 🔒 Easy to reuse in microservices or monorepos

🧠 Bonus Suggestions

• ✅ Auto add API version headers (X-API-Version)

• ⏱ Log response time using morgan or custom logger

• 🧪 Add test coverage for each middleware

• 📦 Export as reusable NPM package