// Dish Interface
interface Dish {
    prepare(): void;
}

// Concrete Momo Class
class Momo implements Dish {
    prepare(): void {
        console.log("Preparing Momo");
    }
}

// Concrete Pizza Class
class Pizza implements Dish {
    prepare(): void {
        console.log("Preparing Pizza");
    }
}

// Waiter (Factory) Class
class Waiter {
    static orderDish(dishType: string): Dish | null {
        switch (dishType) {
            case 'Momo':
                return new Momo();
            case 'Pizza':
                return new Pizza();
            default:
                return null;
        }
    }
}

// Client Code
const dish1: Dish | null = Waiter.orderDish('Momo');
if (dish1) {
    dish1.prepare();  // Output: Preparing Momo
}

const dish2: Dish | null = Waiter.orderDish('Pizza');
if (dish2) {
    dish2.prepare();  // Output: Preparing Pizza
}