Accept in-app payments

@_spi(EmbeddedPaymentElementPrivateBeta) import StripePaymentSheet

class MyCheckoutVC: UIViewController {

    func createEmbeddedPaymentElement() async throws -> EmbeddedPaymentElement {
        let intentConfig = PaymentSheet.IntentConfiguration(
          mode: .payment(amount: 1099, currency: "USD")
        ) { [weak self] _, _, intentCreationCallback in
          self?.handleConfirm(intentCreationCallback)
        }
        var configuration = EmbeddedPaymentElement.Configuration()
        configuration.returnURL = "your-app://stripe-redirect" // Use the return url you set up in the previous step
        let embeddedPaymentElement = try await EmbeddedPaymentElement.create(intentConfiguration: intentConfig, configuration: configuration)
        embeddedPaymentElement.presentingViewController = self
        embeddedPaymentElement.delegate = self
        return embeddedPaymentElement
    }

    func handleConfirm(_ intentCreationCallback: @escaping (Result<String, Error>) -> Void) {
      // ...explained later
    }
}

class MyCheckoutVC: UIViewController {
    // ...
    private(set) var embeddedPaymentElement: EmbeddedPaymentElement?

    private lazy var checkoutButton: UIButton = {
        let checkoutButton = UIButton(type: .system)
        checkoutButton.backgroundColor = .systemBlue
        checkoutButton.layer.cornerRadius = 5.0
        checkoutButton.clipsToBounds = true
        checkoutButton.setTitle("Checkout", for: .normal)
        checkoutButton.setTitleColor(.white, for: .normal)
        checkoutButton.translatesAutoresizingMaskIntoConstraints = false
        checkoutButton.isEnabled = embeddedPaymentElement?.paymentOption != nil
        checkoutButton.addTarget(self, action: #selector(didTapConfirmButton), for: .touchUpInside)
        return checkoutButton
    }()
    // ...
    @objc func didTapConfirmButton() {
        // ...explained later
    }

    override func viewDidLoad() {
        super.viewDidLoad()
        Task { @MainActor in
            do {
                // Create a UIScrollView
                let scrollView = UIScrollView()
                scrollView.translatesAutoresizingMaskIntoConstraints = false
                self.view.addSubview(scrollView)

	       // Create the Mobile Embedded Payment Element
                let embeddedPaymentElement = try await createEmbeddedPaymentElement()
                embeddedPaymentElement.delegate = self
                embeddedPaymentElement.presentingViewController = self
                self.embeddedPaymentElement = embeddedPaymentElement

                // Add its view to the scroll view
                scrollView.addSubview(embeddedPaymentElement.view)

	       // Add your own checkout button to the scroll view
                scrollView.addSubview(checkoutButton)

                // Set up layout constraints
                embeddedPaymentElement.view.translatesAutoresizingMaskIntoConstraints = false
                NSLayoutConstraint.activate([
                    scrollView.topAnchor.constraint(equalTo: view.safeAreaLayoutGuide.topAnchor),
                    scrollView.bottomAnchor.constraint(equalTo: view.safeAreaLayoutGuide.bottomAnchor),
                    scrollView.leadingAnchor.constraint(equalTo: view.safeAreaLayoutGuide.leadingAnchor),
                    scrollView.trailingAnchor.constraint(equalTo: view.safeAreaLayoutGuide.trailingAnchor),

                    embeddedPaymentElement.view.topAnchor.constraint(equalTo: scrollView.topAnchor),
                    embeddedPaymentElement.view.leadingAnchor.constraint(equalTo: scrollView.leadingAnchor),
                    embeddedPaymentElement.view.trailingAnchor.constraint(equalTo: scrollView.trailingAnchor),
                    checkoutButton.topAnchor.constraint(equalTo: embeddedPaymentElement.view.bottomAnchor, constant: 4.0),
                    checkoutButton.leadingAnchor.constraint(equalTo: scrollView.safeAreaLayoutGuide.leadingAnchor, constant: 4.0),
                    checkoutButton.trailingAnchor.constraint(equalTo: scrollView.safeAreaLayoutGuide.trailingAnchor, constant: -4.0),
                ])

            } catch {
                // handle view not being added to view
            }
        }
    }
}

extension MyCheckoutVC: EmbeddedPaymentElementDelegate {
    func embeddedPaymentElementDidUpdateHeight(embeddedPaymentElement: StripePaymentSheet.EmbeddedPaymentElement) {
        // Handle layout appropriately
        self.view.setNeedsLayout()
        self.view.layoutIfNeeded()
    }
}

class MyCheckoutVC: UIViewController {
    override func viewDidLoad() {
        // This is only for testing purposes:
        #if DEBUG
        Timer.scheduledTimer(withTimeInterval: 5.0, repeats: true) { [weak self] _ in
            Task { @MainActor in
                self?.embeddedPaymentElement?.testHeightChange()
            }
        }
        #endif
    }
}

extension MyCheckoutVC: EmbeddedPaymentElementDelegate {
  func embeddedPaymentElementDidUpdatePaymentOption(embeddedPaymentElement: EmbeddedPaymentElement) {
    print("The payment option changed: \(embeddedPaymentElement.paymentOption)")
    checkoutButton.isEnabled = embeddedPaymentElement.paymentOption != nil
  }
}

extension MyCheckoutVC {
    func update() {
        Task { @MainActor in
            var updatedIntentConfig = oldIntentConfig
            updatedIntentConfig.mode = PaymentSheet.IntentConfiguration.Mode.payment(amount: 999, currency: "USD")

            let result = await embeddedPaymentElement?.update(intentConfiguration: updatedIntentConfig)
            switch result {
            case .canceled, nil:
                // Do nothing; this happens when a subsequent `update` call cancels this one
                break
            case .failed(let error):
                // Display error to user in an alert, let users retry
            case .succeeded:
                // Update your UI in case the payment option changed
            }
        }
    }
}

extension MyCheckoutVC {
    @objc func didTapConfirmButton() {
        Task { @MainActor in
            guard let embeddedPaymentElement else { return }
            self.view.isUserInteractionEnabled = false // Disable user interaction, show a spinner, and so on before calling confirm
            let result = await embeddedPaymentElement.confirm()
            switch result {
            case .completed:
                // Payment completed - show a confirmation screen.
            case .failed(let error):
                self.view.isUserInteractionEnabled = true
                // Encountered an unrecoverable error. You can display the error to the user, log it, etc.
            case .canceled:
                self.view.isUserInteractionEnabled = true
                // Customer canceled - you should probably do nothing.
                break
            }
        }
    }
}

extension MyCheckoutVC {
    func handleConfirm(_ intentCreationCallback: @escaping (Result<String, Error>)-> Void) {
        // Make a request to your own server and receive a client secret or an error.
        let myServerResponse: Result<String, Error> = ...
        switch myServerResponse {
        case .success(let clientSecret):
          // Call the `intentCreationCallback` with the client secret
          intentCreationCallback(.success(clientSecret))
        case .failure(let error):
          // Call the `intentCreationCallback` with the error
          intentCreationCallback(.failure(error))
        }
    }
}