Build a robust file upload service that handles file validation, storage, and provides APIs for uploading and retrieving files with support for multiple file types.

Project Checklist

• Create upload endpoint accepting multipart/form-data
• Implement file type and size validation
• Store files securely with unique naming
• Create endpoint to retrieve uploaded files
• Add file metadata storage (name, size, type, upload date)
• Implement file deletion endpoint

Bonus Project Checklist Items

• Add image resizing/optimization
• Implement progress tracking for large uploads
• Add virus scanning integration
• Create thumbnail generation for images
• Implement CDN integration
• Add file sharing with expiration links

Inspiration (Any companies/libraries similar)

• AWS S3
• Cloudinary
• Imgur API

Hint/Code snippet to start

const multer = require('multer');
const upload = multer({
  dest: 'uploads/',
  limits: { fileSize: 5 * 1024 * 1024 },
  fileFilter: (req, file, cb) => {
    const allowedTypes = /jpeg|jpg|png|gif|pdf/;
    cb(null, allowedTypes.test(file.mimetype));
  }
});

app.post('/upload', upload.single('file'), (req, res) => {
  res.json({ fileId: req.file.filename, url: `/files/${req.file.filename}` });
});