PaymentFlowNavigator.kt

class PaymentFlowNavigator private constructor(
  private var shippingInfo: ShippingInfo? = null,
  savedState: SavedState?
): StackNavigator(savedState),
   ShippingInfoScreen.Events,
   PaymentInfoScreen.Events,
   ConfirmationScreen.Events {
   
  override fun initialStack() = listOf(ShoppingCartScreen())

  override fun onProvideShippingInfoClicked() {
    push(ShippingInfoScreen(this))
  }
  
  override fun onShippingInfo(shippingInfo: ShippingInfo) {
    this.shippingInfo = shippingInfo
    push(PaymentInfoScreen(this))
  }
  
  override fun onPaymentInfo(paymentInfo: PaymentInfo) {
    push(ConfirmationScreen(shippingInfo, paymentInfo, this))
  }
  
  override fun onConfirmed() {
    finish()
  }
     
  override fun saveInstanceState() : SavedState {
    return super.saveInstanceState().also {
      it.shippingInfo = shippingInfo
    }  
  }
     
  companion object {
   
    fun create() = PaymentFlowNavigator(null, null)
    
    fun from(savedState: SavedState) = PaymentFlowNavigator(savedState.shippingInfo, savedState)
  }
}