File Upload Handler with Validation

javascript Copy Code

const multer = require('multer');
const path = require('path');
const crypto = require('crypto');

const ALLOWED_TYPES = {
    'image/jpeg': '.jpg',
    'image/png': '.png',
    'image/webp': '.webp',
    'application/pdf': '.pdf'
};

const MAX_SIZE = 5 * 1024 * 1024; // 5MB

const storage = multer.diskStorage({
    destination: (req, file, cb) => {
        cb(null, path.join(__dirname, '../uploads'));
    },
    filename: (req, file, cb) => {
        const uniqueId = crypto.randomBytes(16).toString('hex');
        const ext = ALLOWED_TYPES[file.mimetype] || path.extname(file.originalname);
        cb(null, `${Date.now()}-${uniqueId}${ext}`);
    }
});

const fileFilter = (req, file, cb) => {
    if (ALLOWED_TYPES[file.mimetype]) {
        cb(null, true);
    } else {
        cb(new Error(`File type ${file.mimetype} not allowed. Accepted: ${Object.keys(ALLOWED_TYPES).join(', ')}`), false);
    }
};

const upload = multer({
    storage,
    fileFilter,
    limits: { fileSize: MAX_SIZE, files: 5 }
});

const handleUploadError = (err, req, res, next) => {
    if (err instanceof multer.MulterError) {
        if (err.code === 'LIMIT_FILE_SIZE') {
            return res.status(400).json({ error: 'File too large (max 5MB)' });
        }
        return res.status(400).json({ error: err.message });
    }
    if (err) return res.status(400).json({ error: err.message });
    next();
};

module.exports = { upload, handleUploadError };

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