// 子系统1：库存服务
type InventoryService struct{}
func (i *InventoryService) Reserve(itemID string, qty int) error {
    fmt.Printf("库存：为商品 %s 预留 %d 件\n", itemID, qty)
    return nil
}

// 子系统2：订单服务
type OrderService struct{}
func (o *OrderService) Create(orderInfo map[string]interface{}) (string, error) {
    orderID := "ORDER-1001"
    fmt.Println("订单：已创建新订单，ID:", orderID)
    return orderID, nil
}

// 子系统3：支付服务
type PaymentService struct{}
func (p *PaymentService) Initiate(amount float64) (string, error) {
    payID := "PAY-9876"
    fmt.Printf("支付：发起金额 %.2f，支付ID: %s\n", amount, payID)
    return payID, nil
}

// 子系统4：通知服务
type NotificationService struct{}
func (n *NotificationService) Send(to string, msg string) {
    fmt.Printf("通知：发送消息给 %s -> %s\n", to, msg)
}

// 外观结构体
type OrderFacade struct {
    inventory   *InventoryService
    order       *OrderService
    payment     *PaymentService
    notification *NotificationService
}

// 初始化外观
func NewOrderFacade() *OrderFacade {
    return &OrderFacade{
        inventory:   &InventoryService{},
        order:       &OrderService{},
        payment:     &PaymentService{},
        notification: &NotificationService{},
    }
}

// 高层接口：一键下单
func (f *OrderFacade) PlaceOrder(itemID string, qty int, amount float64, user string) {
    f.inventory.Reserve(itemID, qty)
    orderInfo := map[string]interface{}{"item": itemID, "qty": qty}
    orderID, _ := f.order.Create(orderInfo)
    payID, _ := f.payment.Initiate(amount)
    msg := fmt.Sprintf("订单 %s 已创建，支付单 %s，请及时付款", orderID, payID)
    f.notification.Send(user, msg)
}

facade := NewOrderFacade()
facade.PlaceOrder("iPhone15", 1, 999.99, "alice@example.com")