type Booking = {
  items: { 
    product: Product, 
    discount?: Discount 
  }[];
  customer: Customer;
  status: string;
  paymentDate?: DateTime;
}

export type Discount = {
  type: 'percentage' | 'fixed';
  value: number;
}

export type Customer = {
  id: CustomerId;
  email: Email;
  address: string;
};

export type Discount = {
  type: "percentage" | "fixed" | "free";
  value: number;
};

export type Product = RoomProduct | ServiceProduct;

type RoomProduct = {
  id: ProductId;
  name: string;
  type: "room";
  unitPrice: number;
  details: { from: BookingTime; to: BookingTime; roomId: RoomId };
};

type ServiceProduct = {
  id: ProductId;
  name: string;
  type: "service";
  unitPrice: number;
  details: { serviceId: ServiceId; count: number };
};

export type Booking = DraftBooking | ValidatedBooking | PaidBooking;

type DraftBooking = {
  items: BookingItem[];
  customer?: {
    email?: string;
    address?: string;
  };
  status: "draft";
};

type ValidatedBooking = {
  items: NonEmptyArray<BookingItem>;
  customer: Customer;
  status: "validated";
};

type PaidBooking = {
  // ...
  paymentDate: DateTime;
};