Best Practices

// ✅ Good: Explicit types
interface UserData {
  name: string;
  email: string;
  role: 'admin' | 'user';
}

const updateUser = async (userId: string, data: UserData): Promise<void> => {
  // Implementation
};

// ❌ Bad: Using 'any'
const updateUser = async (userId: any, data: any): Promise<any> => {
  // Implementation
};

// ✅ Good: Proper error handling
try {
  const result = await functionCall();
  return result;
} catch (error) {
  console.error('Operation failed:', error);
  throw new Error('User-friendly error message');
}

// ❌ Bad: No error handling
const result = await functionCall();
return result;

// ✅ Good: Memoization
const ExpensiveComponent = React.memo(({ data }) => {
  const processedData = useMemo(() => {
    return expensiveCalculation(data);
  }, [data]);

  return <div>{processedData}</div>;
});

// ❌ Bad: No optimization
const ExpensiveComponent = ({ data }) => {
  const processedData = expensiveCalculation(data); // Runs on every render
  return <div>{processedData}</div>;
};

// ✅ Good: Check permissions
const deleteSubscription = functions.https.onCall(async (data, context) => {
  if (!context.auth) {
    throw new functions.https.HttpsError('unauthenticated', 'Must be logged in');
  }

  const isOwner = await checkSubscriptionOwnership(
    context.auth.uid,
    data.subscriptionId
  );

  if (!isOwner) {
    throw new functions.https.HttpsError('permission-denied', 'Not authorized');
  }

  // Proceed with deletion
});

// ❌ Bad: No permission checks
const deleteSubscription = functions.https.onCall(async (data, context) => {
  await admin.firestore().collection('subscriptions').doc(data.subscriptionId).delete();
});

// ✅ Good: Small, focused functions with clear names
const validateEmail = (email: string): boolean => {
  const emailRegex = /^[^\s@]+@[^\s@]+\.[^\s@]+$/;
  return emailRegex.test(email);
};

const sendWelcomeEmail = async (userEmail: string): Promise<void> => {
  if (!validateEmail(userEmail)) {
    throw new Error('Invalid email address');
  }
  // Send email logic
};

// ❌ Bad: Large function doing multiple things
const processUser = async (data: any) => {
  // Validation
  if (!data.email || !/^[^\s@]+@[^\s@]+\.[^\s@]+$/.test(data.email)) {
    throw new Error('Invalid email');
  }
  // Database operation
  await db.collection('users').doc(data.id).set(data);
  // Send email
  await emailService.send(data.email, 'Welcome!');
  // Log event
  console.log('User processed:', data.id);
};