#Best Practices

// Classes: UpperCamelCase
class UserProfile {}

// Variables, functions: lowerCamelCase
String userName = 'Alice';
void calculateTotal() {}

// Constants: lowerCamelCase
const maxRetries = 3;
const apiEndpoint = 'https://api.example.com';

// Private members: _leadingUnderscore
class BankAccount {
  double _balance;
}

// Libraries: lowercase_with_underscores
import 'package:my_app/user_service.dart';

// Good
String getName() => 'Alice';
List<int> getNumbers() => [1, 2, 3];

// Avoid
getName() => 'Alice';  // Type unclear

// Good
final name = 'Alice';
final numbers = [1, 2, 3];

// Less preferred
var name = 'Alice';

// Always handle nulls safely
String? getName() => null;

void main() {
  // Good
  String name = getName() ?? 'Guest';
  
  // Good
  String? maybeName = getName();
  if (maybeName != null) {
    print(maybeName.toUpperCase());
  }
  
  // Avoid
  // String name = getName()!;  // Risky!
}

// Good - single responsibility
bool isValidEmail(String email) {
  return email.contains('@') && email.contains('.');
}

bool isAdult(int age) {
  return age >= 18;
}

// Avoid - doing too much
void processUser(Map user) {
  // 100 lines of code...
}

// Good
void createUser({
  required String name,
  required String email,
  int age = 0,
}) {}

// Less clear
void createUser(String name, String email, int age) {}

// Good
var list = <int>[];
var map = <String, int>{};
var set = <String>{};

// Avoid
var list = List<int>();
var map = Map<String, int>();

// Good
var numbers = [
  1,
  2,
  if (includeThree) 3,
  for (var i in extras) i,
];

// Avoid
var numbers = [1, 2];
if (includeThree) numbers.add(3);
for (var i in extras) numbers.add(i);

// Good
class Point {
  final double x, y;
  Point(this.x, this.y);
}

// Avoid
class Point {
  final double x, y;
  Point(double x, double y) {
    this.x = x;
    this.y = y;
  }
}

// Good
class Car {
  final Engine engine;
  Car(this.engine);
}

// Less flexible
class Car extends Engine {}

// Good
Future<String> fetchData() async {
  var response = await http.get(url);
  return response.body;
}

// Avoid
Future<String> fetchData() {
  return http.get(url).then((response) {
    return response.body;
  });
}

Future<void> loadData() async {
  try {
    var data = await fetchData();
    processData(data);
  } catch (e) {
    print('Error: $e');
  }
}

// Good - created once
const icon = Icon(Icons.home);

// Less efficient - created every time
final icon = Icon(Icons.home);

// Good - extract to const
class MyWidget extends StatelessWidget {
  static const title = Text('Hello');
  
  @override
  Widget build(BuildContext context) {
    return title;
  }
}

/// Calculates the area of a circle.
///
/// The [radius] must be positive.
/// Returns the area as a double.
double calculateCircleArea(double radius) {
  assert(radius > 0, 'Radius must be positive');
  return 3.14159 * radius * radius;
}

import 'package:test/test.dart';

void main() {
  test('addition works', () {
    expect(2 + 2, equals(4));
  });
  
  test('string contains substring', () {
    expect('Hello, World', contains('World'));
  });
}