Implementation

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
<plist version="1.0">
<dict>
    <key>com.apple.developer.in-app-payments</key>
    <array>
        <string>merchant.com.yourcompany.yourapp</string>
    </array>
</dict>
</plist>

<key>NSFaceIDUsageDescription</key>
<string>Use Face ID to authenticate Apple Pay transactions</string>
<key>NSContactsUsageDescription</key>
<string>Access contacts for shipping and billing information</string>

import UIKit
import PXPCheckoutSDK

class CheckoutViewController: UIViewController {
    
    private var checkout: PxpCheckout?
    private var applePayComponent: ApplePayButtonComponent?
    
    override func viewDidLoad() {
        super.viewDidLoad()
        initializeSDK()
    }
    
    private func initializeSDK() {
        let checkoutConfig = CheckoutConfig(
            environment: .test, // or .live for production
            session: SessionConfig(
                sessionId: "your-session-id",
                allowedFundingTypes: AllowedFundingTypes(
                    wallets: WalletFundingTypes(
                        applePay: ApplePayFundingType(
                            merchantId: "merchant.com.yourcompany.yourapp"
                        )
                    )
                )
            ),
            ownerId: "your-owner-id",
            ownerType: .merchant,
            merchantShopperId: "shopper-\(Int(Date().timeIntervalSince1970))",
            transactionData: TransactionData(
                amount: 25.00,
                currency: "USD",
                entryType: .mobileApp,
                intent: .capture,
                merchantTransactionId: "txn-\(Int(Date().timeIntervalSince1970))",
                merchantTransactionDate: Date(),
                shopper: ShopperData(
                    email: "customer@example.com"
                )
            )
        )
        
        do {
            checkout = try PxpCheckout.initialize(config: checkoutConfig)
            print("PXP Checkout SDK initialised successfully")
        } catch {
            print("Failed to initialise PXP Checkout SDK: \(error)")
        }
    }
}

private func createApplePayConfiguration() -> ApplePayButtonComponentConfig {
    let config = ApplePayButtonComponentConfig()
    
    // Basic configuration
    config.merchantDisplayName = "Your Store"
    config.paymentDescription = "Purchase from Your Store"
    config.currencyCode = "USD"
    config.countryCode = "US"
    config.supportedNetworks = [.visa, .masterCard, .amex]
    config.merchantCapabilities = [.threeDSecure, .emv]
    
    // Button styling
    config.buttonType = .buy
    config.buttonStyle = .black
    config.buttonRadius = 8.0
    
    // Payment items
    config.totalPaymentItem = ApplePayPaymentSummaryItem(
        amount: 25.00,
        label: "Total",
        type: .final
    )
    
    config.paymentItems = [
        ApplePayPaymentSummaryItem(amount: 20.00, label: "Product", type: .final),
        ApplePayPaymentSummaryItem(amount: 3.00, label: "Tax", type: .final),
        ApplePayPaymentSummaryItem(amount: 2.00, label: "Shipping", type: .final)
    ]
    
    // Contact fields
    config.requiredBillingContactFields = [.postalAddress, .name, .emailAddress]
    config.requiredShippingContactFields = [.postalAddress, .name, .phoneNumber]
    
    // Shipping methods
    config.shippingMethods = [
        ApplePayShippingMethod(
            amount: 2.00,
            detail: "5-7 business days",
            identifier: "standard",
            label: "Standard Shipping"
        ),
        ApplePayShippingMethod(
            amount: 5.00,
            detail: "2-3 business days",
            identifier: "express",
            label: "Express Shipping"
        )
    ]
    
    // Event handlers
    config.onPreAuthorisation = { [weak self] in
        return await self?.handlePreAuthorisation()
    }
    
    config.onPostAuthorisation = { [weak self] result in
        self?.handlePostAuthorisation(result)
    }
    
    config.onError = { [weak self] error in
        self?.handleError(error)
    }
    
    config.onCancel = { [weak self] error in
        self?.handleCancellation(error)
    }
    
    return config
}

@IBOutlet weak var paymentSummaryView: UIView!
@IBOutlet weak var applePayContainer: UIView!
@IBOutlet weak var errorMessageLabel: UILabel!
@IBOutlet weak var successMessageLabel: UILabel!

override func viewDidLoad() {
    super.viewDidLoad()
    setupUI()
    initializeSDK()
}

private func setupUI() {
    // Configure payment summary
    setupPaymentSummary()
    
    // Configure Apple Pay container
    applePayContainer.layer.cornerRadius = 8
    applePayContainer.backgroundColor = .systemBackground
    
    // Hide message labels initially
    errorMessageLabel.isHidden = true
    successMessageLabel.isHidden = true
}

private func setupPaymentSummary() {
    // Create payment summary views
    let stackView = UIStackView()
    stackView.axis = .vertical
    stackView.spacing = 8
    stackView.translatesAutoresizingMaskIntoConstraints = false
    
    // Add line items
    stackView.addArrangedSubview(createLineItem(label: "Premium T-Shirt", amount: "$20.00"))
    stackView.addArrangedSubview(createLineItem(label: "Sales Tax", amount: "$3.00"))
    stackView.addArrangedSubview(createLineItem(label: "Shipping", amount: "$2.00"))
    
    // Add separator
    let separator = UIView()
    separator.backgroundColor = .separator
    separator.heightAnchor.constraint(equalToConstant: 1).isActive = true
    stackView.addArrangedSubview(separator)
    
    // Add total
    let totalView = createLineItem(label: "Total", amount: "$25.00", isTotal: true)
    stackView.addArrangedSubview(totalView)
    
    paymentSummaryView.addSubview(stackView)
    
    NSLayoutConstraint.activate([
        stackView.topAnchor.constraint(equalTo: paymentSummaryView.topAnchor, constant: 16),
        stackView.leadingAnchor.constraint(equalTo: paymentSummaryView.leadingAnchor, constant: 16),
        stackView.trailingAnchor.constraint(equalTo: paymentSummaryView.trailingAnchor, constant: -16),
        stackView.bottomAnchor.constraint(equalTo: paymentSummaryView.bottomAnchor, constant: -16)
    ])
}

private func createLineItem(label: String, amount: String, isTotal: Bool = false) -> UIView {
    let containerView = UIView()
    
    let labelView = UILabel()
    labelView.text = label
    labelView.font = isTotal ? .systemFont(ofSize: 18, weight: .semibold) : .systemFont(ofSize: 16)
    labelView.translatesAutoresizingMaskIntoConstraints = false
    
    let amountLabel = UILabel()
    amountLabel.text = amount
    amountLabel.font = isTotal ? .systemFont(ofSize: 18, weight: .semibold) : .systemFont(ofSize: 16)
    amountLabel.textAlignment = .right
    amountLabel.translatesAutoresizingMaskIntoConstraints = false
    
    containerView.addSubview(labelView)
    containerView.addSubview(amountLabel)
    
    NSLayoutConstraint.activate([
        labelView.leadingAnchor.constraint(equalTo: containerView.leadingAnchor),
        labelView.centerYAnchor.constraint(equalTo: containerView.centerYAnchor),
        labelView.topAnchor.constraint(equalTo: containerView.topAnchor),
        labelView.bottomAnchor.constraint(equalTo: containerView.bottomAnchor),
        
        amountLabel.trailingAnchor.constraint(equalTo: containerView.trailingAnchor),
        amountLabel.centerYAnchor.constraint(equalTo: containerView.centerYAnchor),
        amountLabel.leadingAnchor.constraint(greaterThanOrEqualTo: labelView.trailingAnchor, constant: 8)
    ])
    
    return containerView
}

import SwiftUI
import PXPCheckoutSDK

struct CheckoutView: View {
    @State private var applePayComponent: ApplePayButtonComponent?
    @State private var checkout: PxpCheckout?
    @State private var errorMessage: String = ""
    @State private var successMessage: String = ""
    @State private var showingError = false
    @State private var showingSuccess = false
    
    var body: some View {
        VStack(spacing: 20) {
            Text("Complete your purchase")
                .font(.largeTitle)
                .fontWeight(.bold)
            
            // Payment summary
            VStack(spacing: 12) {
                HStack {
                    Text("Premium T-Shirt")
                    Spacer()
                    Text("$20.00")
                }
                
                HStack {
                    Text("Sales Tax")
                    Spacer()
                    Text("$3.00")
                }
                
                HStack {
                    Text("Shipping")
                    Spacer()
                    Text("$2.00")
                }
                
                Divider()
                
                HStack {
                    Text("Total")
                        .fontWeight(.semibold)
                    Spacer()
                    Text("$25.00")
                        .fontWeight(.semibold)
                }
                .font(.title3)
            }
            .padding()
            .background(Color(.systemGray6))
            .cornerRadius(12)
            
            // Error/Success Messages
            if showingError {
                Text(errorMessage)
                    .foregroundColor(.red)
                    .padding()
                    .background(Color.red.opacity(0.1))
                    .cornerRadius(8)
            }
            
            if showingSuccess {
                Text(successMessage)
                    .foregroundColor(.green)
                    .padding()
                    .background(Color.green.opacity(0.1))
                    .cornerRadius(8)
            }
            
            // Apple Pay button container
            ApplePayButtonView(
                onComponentCreated: { component in
                    self.applePayComponent = component
                }
            )
            .frame(height: 50)
            .cornerRadius(8)
            
            Text("Or pay with credit card")
                .foregroundColor(.secondary)
                .font(.caption)
            
            Spacer()
        }
        .padding()
        .onAppear {
            initializeSDK()
        }
    }
    
    private func initializeSDK() {
        // Initialise SDK (same as UIKit example)
    }
}

private func createAndMountApplePayComponent() {
    guard let checkout = checkout else {
        print("Checkout SDK not initialized")
        return
    }
    
    do {
        let config = createApplePayConfiguration()
        applePayComponent = try checkout.create(.applePayButton, componentConfig: config)
        
        if let componentView = applePayComponent?.render() {
            mountComponent(componentView)
        }
        
        print("Apple Pay component created and mounted successfully")
        
    } catch {
        print("Failed to create Apple Pay component: \(error)")
        showError("Apple Pay is not available on this device")
    }
}

private func mountComponent(_ componentView: UIView) {
    // Clear any existing subviews
    applePayContainer.subviews.forEach { $0.removeFromSuperview() }
    
    // Add the component view
    applePayContainer.addSubview(componentView)
    componentView.translatesAutoresizingMaskIntoConstraints = false
    
    NSLayoutConstraint.activate([
        componentView.topAnchor.constraint(equalTo: applePayContainer.topAnchor),
        componentView.leadingAnchor.constraint(equalTo: applePayContainer.leadingAnchor),
        componentView.trailingAnchor.constraint(equalTo: applePayContainer.trailingAnchor),
        componentView.bottomAnchor.constraint(equalTo: applePayContainer.bottomAnchor)
    ])
}

struct ApplePayButtonView: UIViewRepresentable {
    let onComponentCreated: (ApplePayButtonComponent) -> Void
    
    func makeUIView(context: Context) -> UIView {
        let containerView = UIView()
        
        // Create checkout and component
        let checkoutConfig = CheckoutConfig(
            environment: .test,
            session: SessionConfig(sessionId: "your-session-id"),
            // ... other configuration
        )
        
        do {
            let checkout = try PxpCheckout.initialize(config: checkoutConfig)
            let config = createApplePayConfiguration()
            let component = try checkout.create(.applePayButton, componentConfig: config)
            
            if let componentView = component.render() {
                containerView.addSubview(componentView)
                componentView.translatesAutoresizingMaskIntoConstraints = false
                
                NSLayoutConstraint.activate([
                    componentView.topAnchor.constraint(equalTo: containerView.topAnchor),
                    componentView.leadingAnchor.constraint(equalTo: containerView.leadingAnchor),
                    componentView.trailingAnchor.constraint(equalTo: containerView.trailingAnchor),
                    componentView.bottomAnchor.constraint(equalTo: containerView.bottomAnchor)
                ])
            }
            
            onComponentCreated(component)
        } catch {
            print("Failed to create Apple Pay component: \(error)")
        }
        
        return containerView
    }
    
    func updateUIView(_ uiView: UIView, context: Context) {
        // Updates handled by the component
    }
    
    private func createApplePayConfiguration() -> ApplePayButtonComponentConfig {
        // Same configuration as previous examples
    }
}

// MARK: - Event Handlers

private func handlePreAuthorisation() async -> ApplePayTransactionInitData? {
    print("Pre-authorisation started")
    
    DispatchQueue.main.async {
        self.showMessage("Processing payment...", type: .info)
    }
    
    return ApplePayTransactionInitData(
        riskScreeningData: RiskScreeningData(
            performRiskScreening: true,
            deviceSessionId: await getDeviceSessionId()
        )
    )
}

private func handlePostAuthorisation(_ result: BaseSubmitResult) {
    DispatchQueue.main.async {
        if let authorizedResult = result as? AuthorisedSubmitResult {
            self.showMessage("Payment successful! Redirecting...", type: .success)
            print("Transaction ID: \(authorizedResult.provider.code)")
            
            // Navigate to success screen after delay
            DispatchQueue.main.asyncAfter(deadline: .now() + 2.0) {
                self.navigateToSuccessScreen(transactionId: authorizedResult.provider.code)
            }
            
        } else if let declinedResult = result as? DeclinedSubmitResult {
            self.showMessage("Payment was declined: \(declinedResult.errorReason)", type: .error)
            
        } else if let failedResult = result as? FailedSubmitResult {
            self.showMessage("Payment failed: \(failedResult.errorReason)", type: .error)
        }
    }
}

private func handleError(_ error: Error) {
    print("Apple Pay error: \(error)")
    
    DispatchQueue.main.async {
        if let pkError = error as? PKPaymentError {
            self.handlePKPaymentError(pkError)
        } else if let validationError = error as? ApplePayValidationException {
            self.showMessage("Validation error: \(validationError.localizedDescription)", type: .error)
        } else {
            self.showMessage("Payment error: \(error.localizedDescription)", type: .error)
        }
    }
}

private func handlePKPaymentError(_ error: PKPaymentError) {
    switch error.code {
    case .paymentNotAllowed:
        showMessage("Payment not allowed. Please check your settings.", type: .error)
    case .paymentNetworkNotSupported:
        showMessage("Card network not supported. Please use a different card.", type: .error)
    case .deviceCannotMakePayments:
        showMessage("Apple Pay is not available on this device.", type: .error)
    default:
        showMessage("Payment error occurred. Please try again.", type: .error)
    }
}

private func handleCancellation(_ error: Error?) {
    print("Payment cancelled by user")
    DispatchQueue.main.async {
        self.showMessage("Payment was cancelled", type: .info)
    }
}

// MARK: - Helper methods

private func getDeviceSessionId() async -> String {
    return UIDevice.current.identifierForVendor?.uuidString ?? "unknown-device"
}

private func showMessage(_ message: String, type: MessageType) {
    errorMessageLabel.isHidden = true
    successMessageLabel.isHidden = true
    
    switch type {
    case .error:
        errorMessageLabel.text = message
        errorMessageLabel.isHidden = false
    case .success:
        successMessageLabel.text = message
        successMessageLabel.isHidden = false
    case .info:
        successMessageLabel.text = message
        successMessageLabel.textColor = .systemBlue
        successMessageLabel.isHidden = false
    }
}

private func navigateToSuccessScreen(transactionId: String) {
    let storyboard = UIStoryboard(name: "Main", bundle: nil)
    if let successVC = storyboard.instantiateViewController(withIdentifier: "SuccessViewController") as? SuccessViewController {
        successVC.transactionId = transactionId
        navigationController?.pushViewController(successVC, animated: true)
    }
}

enum MessageType {
    case error, success, info
}

private func setupAdvancedEventHandlers() {
    guard let config = applePayComponent?.config else { return }
    
    // Shipping contact selection
    config.onShippingContactSelected = { [weak self] contact in
        guard let self = self else { return PKPaymentRequestShippingContactUpdate(errors: []) }
        
        print("Shipping contact selected: \(contact)")
        
        // Calculate shipping and tax based on address
        let shippingCost = self.calculateShippingCost(for: contact.postalAddress)
        let tax = self.calculateTax(for: contact.postalAddress)
        let newTotal = 20.00 + shippingCost + tax
        
        return PKPaymentRequestShippingContactUpdate(
            errors: [],
            shippingMethods: [
                PKShippingMethod(
                    label: "Standard Shipping",
                    amount: NSDecimalNumber(value: shippingCost),
                    type: .final,
                    identifier: "standard",
                    detail: "5-7 business days"
                )
            ],
            paymentSummaryItems: [
                PKPaymentSummaryItem(label: "Premium T-Shirt", amount: NSDecimalNumber(value: 20.00)),
                PKPaymentSummaryItem(label: "Sales Tax", amount: NSDecimalNumber(value: tax)),
                PKPaymentSummaryItem(label: "Shipping", amount: NSDecimalNumber(value: shippingCost)),
                PKPaymentSummaryItem(label: "Your Store Name", amount: NSDecimalNumber(value: newTotal))
            ]
        )
    }
    
    // Shipping method selection
    config.onShippingMethodSelected = { [weak self] method in
        guard let self = self else { return PKPaymentRequestShippingMethodUpdate(paymentSummaryItems: []) }
        
        print("Shipping method selected: \(method)")
        
        let baseAmount = 20.00
        let tax = 3.00
        let shippingCost = method.amount.doubleValue
        let newTotal = baseAmount + tax + shippingCost
        
        return PKPaymentRequestShippingMethodUpdate(
            paymentSummaryItems: [
                PKPaymentSummaryItem(label: "Premium T-Shirt", amount: NSDecimalNumber(value: baseAmount)),
                PKPaymentSummaryItem(label: "Sales Tax", amount: NSDecimalNumber(value: tax)),
                PKPaymentSummaryItem(label: "Shipping", amount: method.amount),
                PKPaymentSummaryItem(label: "Your Store Name", amount: NSDecimalNumber(value: newTotal))
            ]
        )
    }
    
    // Payment method selection (iOS 15.0+)
    if #available(iOS 15.0, *) {
        config.onPaymentMethodSelected = { paymentMethod in
            print("Payment method selected: \(paymentMethod)")
            
            return PKPaymentRequestPaymentMethodUpdate(
                paymentSummaryItems: [
                    PKPaymentSummaryItem(label: "Premium T-Shirt", amount: NSDecimalNumber(value: 20.00)),
                    PKPaymentSummaryItem(label: "Sales Tax", amount: NSDecimalNumber(value: 3.00)),
                    PKPaymentSummaryItem(label: "Shipping", amount: NSDecimalNumber(value: 2.00)),
                    PKPaymentSummaryItem(label: "Your Store Name", amount: NSDecimalNumber(value: 25.00))
                ]
            )
        }
        
        // Coupon code handling
        config.onCouponCodeChanged = { [weak self] couponCode in
            guard let self = self else { return PKPaymentRequestCouponCodeUpdate(paymentSummaryItems: []) }
            
            print("Coupon code changed: \(couponCode)")
            
            let discount = self.calculateDiscount(for: couponCode)
            let newTotal = 25.00 - discount
            
            return PKPaymentRequestCouponCodeUpdate(
                errors: discount > 0 ? [] : [PKPaymentError(.couponCodeInvalid)],
                paymentSummaryItems: [
                    PKPaymentSummaryItem(label: "Premium T-Shirt", amount: NSDecimalNumber(value: 20.00)),
                    PKPaymentSummaryItem(label: "Sales Tax", amount: NSDecimalNumber(value: 3.00)),
                    PKPaymentSummaryItem(label: "Shipping", amount: NSDecimalNumber(value: 2.00)),
                    PKPaymentSummaryItem(label: "Discount", amount: NSDecimalNumber(value: -discount)),
                    PKPaymentSummaryItem(label: "Your Store Name", amount: NSDecimalNumber(value: newTotal))
                ]
            )
        }
    }
}

// MARK: - Calculation methods

private func calculateShippingCost(for address: CNPostalAddress?) -> Double {
    guard let address = address else { return 5.00 }
    
    // Simple shipping calculation based on state/country
    if address.isoCountryCode == "US" {
        return address.state == "CA" ? 7.99 : 4.99
    }
    return 15.99 // International shipping
}

private func calculateTax(for address: CNPostalAddress?) -> Double {
    guard let address = address, address.isoCountryCode == "US" else { return 0.00 }
    
    let taxRates: [String: Double] = [
        "CA": 0.0875, // California
        "NY": 0.08,   // New York
        "TX": 0.0625  // Texas
    ]
    
    let rate = taxRates[address.state] ?? 0.06
    return 20.00 * rate
}

private func calculateDiscount(for couponCode: String) -> Double {
    let validCoupons: [String: Double] = [
        "SAVE10": 2.50,
        "SAVE20": 5.00,
        "WELCOME": 3.00
    ]
    
    return validCoupons[couponCode.uppercased()] ?? 0.00
}

class CheckoutViewController: UIViewController {
    
    // MARK: - Lifecycle
    
    override func viewWillDisappear(_ animated: Bool) {
        super.viewWillDisappear(animated)
        
        // Clean up component if navigating away
        if isMovingFromParent || isBeingDismissed {
            cleanupComponent()
        }
    }
    
    deinit {
        cleanupComponent()
    }
    
    private func cleanupComponent() {
        applePayComponent?.unmount()
        applePayComponent = nil
        checkout = nil
        print("Apple Pay component cleaned up")
    }
    
    // MARK: - Error recovery
    
    private func retryComponentCreation() {
        cleanupComponent()
        
        DispatchQueue.main.asyncAfter(deadline: .now() + 1.0) {
            self.initializeSDK()
            self.createAndMountApplePayComponent()
        }
    }
}

// Custom button styling
config.buttonType = .buy
config.buttonStyle = .black
config.buttonRadius = 12.0

// Custom SwiftUI content
config.customContent = {
    return AnyView(
        HStack {
            Image(systemName: "applelogo")
                .foregroundColor(.white)
            Text("Buy with Apple Pay")
                .foregroundColor(.white)
                .fontWeight(.semibold)
        }
        .frame(maxWidth: .infinity, minHeight: 50)
        .background(
            LinearGradient(
                gradient: Gradient(colors: [Color.black, Color.gray]),
                startPoint: .leading,
                endPoint: .trailing
            )
        )
        .cornerRadius(12)
    )
}

// Comprehensive error handling
config.onError = { error in
    DispatchQueue.main.async {
        if let validationError = error as? ApplePayValidationException {
            self.handleValidationError(validationError)
        } else if let networkError = error as? URLError {
            self.handleNetworkError(networkError)
        } else {
            self.handleGenericError(error)
        }
    }
}

private func handleValidationError(_ error: ApplePayValidationException) {
    showMessage("Please check your payment information: \(error.localizedDescription)", type: .error)
}

private func handleNetworkError(_ error: URLError) {
    showMessage("Connection error. Please check your internet and try again.", type: .error)
}

private func handleGenericError(_ error: Error) {
    showMessage("An unexpected error occurred. Please try again.", type: .error)
}

import UIKit
import PXPCheckoutSDK
import PassKit

class CompleteCheckoutViewController: UIViewController {
    
    // MARK: - Outlets
    @IBOutlet weak var titleLabel: UILabel!
    @IBOutlet weak var paymentSummaryView: UIView!
    @IBOutlet weak var applePayContainer: UIView!
    @IBOutlet weak var errorMessageLabel: UILabel!
    @IBOutlet weak var successMessageLabel: UILabel!
    @IBOutlet weak var loadingIndicator: UIActivityIndicatorView!
    
    // MARK: - Properties
    private var checkout: PxpCheckout?
    private var applePayComponent: ApplePayButtonComponent?
    
    // MARK: - Lifecycle
    override func viewDidLoad() {
        super.viewDidLoad()
        setupUI()
        initializeSDK()
    }
    
    override func viewWillDisappear(_ animated: Bool) {
        super.viewWillDisappear(animated)
        if isMovingFromParent || isBeingDismissed {
            cleanupComponent()
        }
    }
    
    deinit {
        cleanupComponent()
    }
    
    // MARK: - Setup
    private func setupUI() {
        titleLabel.text = "Complete your purchase"
        titleLabel.font = UIFont.systemFont(ofSize: 28, weight: .bold)
        
        setupPaymentSummary()
        
        applePayContainer.layer.cornerRadius = 8
        applePayContainer.backgroundColor = .systemBackground
        
        errorMessageLabel.isHidden = true
        successMessageLabel.isHidden = true
        loadingIndicator.isHidden = true
        
        view.backgroundColor = .systemBackground
    }
    
    private func setupPaymentSummary() {
        paymentSummaryView.backgroundColor = UIColor.systemGray6
        paymentSummaryView.layer.cornerRadius = 12
        
        let stackView = UIStackView()
        stackView.axis = .vertical
        stackView.spacing = 12
        stackView.translatesAutoresizingMaskIntoConstraints = false
        
        // Add line items
        stackView.addArrangedSubview(createLineItem(label: "Premium T-Shirt", amount: "$20.00"))
        stackView.addArrangedSubview(createLineItem(label: "Sales Tax", amount: "$3.00"))
        stackView.addArrangedSubview(createLineItem(label: "Shipping", amount: "$2.00"))
        
        // Add separator
        let separator = UIView()
        separator.backgroundColor = .separator
        separator.heightAnchor.constraint(equalToConstant: 1).isActive = true
        stackView.addArrangedSubview(separator)
        
        // Add total
        stackView.addArrangedSubview(createLineItem(label: "Total", amount: "$25.00", isTotal: true))
        
        paymentSummaryView.addSubview(stackView)
        
        NSLayoutConstraint.activate([
            stackView.topAnchor.constraint(equalTo: paymentSummaryView.topAnchor, constant: 16),
            stackView.leadingAnchor.constraint(equalTo: paymentSummaryView.leadingAnchor, constant: 16),
            stackView.trailingAnchor.constraint(equalTo: paymentSummaryView.trailingAnchor, constant: -16),
            stackView.bottomAnchor.constraint(equalTo: paymentSummaryView.bottomAnchor, constant: -16)
        ])
    }
    
    private func createLineItem(label: String, amount: String, isTotal: Bool = false) -> UIView {
        let containerView = UIView()
        
        let labelView = UILabel()
        labelView.text = label
        labelView.font = isTotal ? .systemFont(ofSize: 18, weight: .semibold) : .systemFont(ofSize: 16)
        labelView.translatesAutoresizingMaskIntoConstraints = false
        
        let amountLabel = UILabel()
        amountLabel.text = amount
        amountLabel.font = isTotal ? .systemFont(ofSize: 18, weight: .semibold) : .systemFont(ofSize: 16)
        amountLabel.textAlignment = .right
        amountLabel.translatesAutoresizingMaskIntoConstraints = false
        
        containerView.addSubview(labelView)
        containerView.addSubview(amountLabel)
        
        NSLayoutConstraint.activate([
            labelView.leadingAnchor.constraint(equalTo: containerView.leadingAnchor),
            labelView.centerYAnchor.constraint(equalTo: containerView.centerYAnchor),
            labelView.topAnchor.constraint(equalTo: containerView.topAnchor),
            labelView.bottomAnchor.constraint(equalTo: containerView.bottomAnchor),
            
            amountLabel.trailingAnchor.constraint(equalTo: containerView.trailingAnchor),
            amountLabel.centerYAnchor.constraint(equalTo: containerView.centerYAnchor),
            amountLabel.leadingAnchor.constraint(greaterThanOrEqualTo: labelView.trailingAnchor, constant: 8)
        ])
        
        return containerView
    }
    
    // MARK: - SDK Initialisation
    private func initializeSDK() {
        let checkoutConfig = CheckoutConfig(
            environment: .test,
            session: SessionConfig(
                sessionId: "your-session-id",
                allowedFundingTypes: AllowedFundingTypes(
                    wallets: WalletFundingTypes(
                        applePay: ApplePayFundingType(
                            merchantId: "merchant.com.yourcompany.yourapp"
                        )
                    )
                )
            ),
            ownerId: "your-owner-id",
            ownerType: .merchant,
            merchantShopperId: "shopper-\(Int(Date().timeIntervalSince1970))",
            transactionData: TransactionData(
                amount: 25.00,
                currency: "USD",
                entryType: .mobileApp,
                intent: .capture,
                merchantTransactionId: "txn-\(Int(Date().timeIntervalSince1970))",
                merchantTransactionDate: Date(),
                shopper: ShopperData(
                    email: "customer@example.com"
                )
            )
        )
        
        do {
            checkout = try PxpCheckout.initialize(config: checkoutConfig)
            createAndMountApplePayComponent()
        } catch {
            print("Failed to initialize SDK: \(error)")
            showMessage("Failed to initialize payment system", type: .error)
        }
    }
    
    private func createAndMountApplePayComponent() {
        guard let checkout = checkout else { return }
        
        // Check if Apple Pay is available
        guard PKPaymentAuthorizationController.canMakePayments() else {
            showMessage("Apple Pay is not available on this device", type: .error)
            return
        }
        
        do {
            let config = createApplePayConfiguration()
            applePayComponent = try checkout.create(.applePayButton, componentConfig: config)
            
            if let componentView = applePayComponent?.render() {
                mountComponent(componentView)
            }
            
        } catch {
            print("Failed to create Apple Pay component: \(error)")
            showMessage("Apple Pay is not available", type: .error)
        }
    }
    
    private func createApplePayConfiguration() -> ApplePayButtonComponentConfig {
        let config = ApplePayButtonComponentConfig()
        
        // Basic configuration
        config.merchantDisplayName = "Your Store Name"
        config.paymentDescription = "Premium T-Shirt Purchase"
        config.currencyCode = "USD"
        config.countryCode = "US"
        config.supportedNetworks = [.visa, .masterCard, .amex, .discover]
        config.merchantCapabilities = [.threeDSecure, .emv, .credit, .debit]
        
        // Button styling
        config.buttonType = .buy
        config.buttonStyle = .black
        config.buttonRadius = 8.0
        
        // Payment items
        config.totalPaymentItem = ApplePayPaymentSummaryItem(
            amount: 25.00,
            label: "Your Store Name",
            type: .final
        )
        
        config.paymentItems = [
            ApplePayPaymentSummaryItem(amount: 20.00, label: "Premium T-Shirt", type: .final),
            ApplePayPaymentSummaryItem(amount: 3.00, label: "Sales Tax", type: .final),
            ApplePayPaymentSummaryItem(amount: 2.00, label: "Shipping", type: .final)
        ]
        
        // Contact fields
        config.requiredBillingContactFields = [.postalAddress, .name, .emailAddress]
        config.requiredShippingContactFields = [.postalAddress, .name, .phoneNumber]
        
        // Shipping methods
        config.shippingMethods = [
            ApplePayShippingMethod(
                amount: 2.00,
                detail: "5-7 business days",
                identifier: "standard",
                label: "Standard Shipping"
            ),
            ApplePayShippingMethod(
                amount: 5.00,
                detail: "2-3 business days", 
                identifier: "express",
                label: "Express Shipping"
            )
        ]
        
        // Event handlers
        config.onPreAuthorisation = { [weak self] in
            return await self?.handlePreAuthorisation()
        }
        
        config.onPostAuthorisation = { [weak self] result in
            self?.handlePostAuthorisation(result)
        }
        
        config.onShippingContactSelected = { [weak self] contact in
            return self?.handleShippingContactSelected(contact) ?? PKPaymentRequestShippingContactUpdate(errors: [])
        }
        
        config.onShippingMethodSelected = { [weak self] method in
            return self?.handleShippingMethodSelected(method) ?? PKPaymentRequestShippingMethodUpdate(paymentSummaryItems: [])
        }
        
        config.onError = { [weak self] error in
            self?.handleError(error)
        }
        
        config.onCancel = { [weak self] error in
            self?.handleCancellation(error)
        }
        
        return config
    }
    
    private func mountComponent(_ componentView: UIView) {
        applePayContainer.subviews.forEach { $0.removeFromSuperview() }
        applePayContainer.addSubview(componentView)
        componentView.translatesAutoresizingMaskIntoConstraints = false
        
        NSLayoutConstraint.activate([
            componentView.topAnchor.constraint(equalTo: applePayContainer.topAnchor),
            componentView.leadingAnchor.constraint(equalTo: applePayContainer.leadingAnchor),
            componentView.trailingAnchor.constraint(equalTo: applePayContainer.trailingAnchor),
            componentView.bottomAnchor.constraint(equalTo: applePayContainer.bottomAnchor),
            componentView.heightAnchor.constraint(equalToConstant: 50)
        ])
    }
    
    // MARK: - Event Handlers
    private func handlePreAuthorisation() async -> ApplePayTransactionInitData? {
        DispatchQueue.main.async {
            self.showMessage("Processing payment...", type: .info)
            self.loadingIndicator.startAnimating()
            self.loadingIndicator.isHidden = false
        }
        
        return ApplePayTransactionInitData(
            riskScreeningData: RiskScreeningData(
                performRiskScreening: true,
                deviceSessionId: UIDevice.current.identifierForVendor?.uuidString ?? "unknown"
            )
        )
    }
    
    private func handlePostAuthorisation(_ result: BaseSubmitResult) {
        DispatchQueue.main.async {
            self.loadingIndicator.stopAnimating()
            self.loadingIndicator.isHidden = true
            
            if let authorizedResult = result as? AuthorisedSubmitResult {
                self.showMessage("Payment successful! Redirecting...", type: .success)
                print("Transaction ID: \(authorizedResult.provider.code)")
                
                DispatchQueue.main.asyncAfter(deadline: .now() + 2.0) {
                    self.navigateToSuccessScreen(transactionId: authorizedResult.provider.code)
                }
                
            } else if let declinedResult = result as? DeclinedSubmitResult {
                self.showMessage("Payment declined: \(declinedResult.errorReason)", type: .error)
                
            } else if let failedResult = result as? FailedSubmitResult {
                self.showMessage("Payment failed: \(failedResult.errorReason)", type: .error)
            }
        }
    }
    
    private func handleShippingContactSelected(_ contact: PKContact) -> PKPaymentRequestShippingContactUpdate {
        let shippingCost = calculateShippingCost(for: contact.postalAddress)
        let tax = calculateTax(for: contact.postalAddress)
        let newTotal = 20.00 + shippingCost + tax
        
        return PKPaymentRequestShippingContactUpdate(
            errors: [],
            shippingMethods: [
                PKShippingMethod(
                    label: "Standard Shipping",
                    amount: NSDecimalNumber(value: shippingCost),
                    type: .final,
                    identifier: "standard",
                    detail: "5-7 business days"
                )
            ],
            paymentSummaryItems: [
                PKPaymentSummaryItem(label: "Premium T-Shirt", amount: NSDecimalNumber(value: 20.00)),
                PKPaymentSummaryItem(label: "Sales Tax", amount: NSDecimalNumber(value: tax)),
                PKPaymentSummaryItem(label: "Shipping", amount: NSDecimalNumber(value: shippingCost)),
                PKPaymentSummaryItem(label: "Your Store Name", amount: NSDecimalNumber(value: newTotal))
            ]
        )
    }
    
    private func handleShippingMethodSelected(_ method: PKShippingMethod) -> PKPaymentRequestShippingMethodUpdate {
        let baseAmount = 20.00
        let tax = 3.00
        let shippingCost = method.amount.doubleValue
        let newTotal = baseAmount + tax + shippingCost
        
        return PKPaymentRequestShippingMethodUpdate(
            paymentSummaryItems: [
                PKPaymentSummaryItem(label: "Premium T-Shirt", amount: NSDecimalNumber(value: baseAmount)),
                PKPaymentSummaryItem(label: "Sales Tax", amount: NSDecimalNumber(value: tax)),
                PKPaymentSummaryItem(label: "Shipping", amount: method.amount),
                PKPaymentSummaryItem(label: "Your Store Name", amount: NSDecimalNumber(value: newTotal))
            ]
        )
    }
    
    private func handleError(_ error: Error) {
        DispatchQueue.main.async {
            self.loadingIndicator.stopAnimating()
            self.loadingIndicator.isHidden = true
            
            if let pkError = error as? PKPaymentError {
                self.handlePKPaymentError(pkError)
            } else if let validationError = error as? ApplePayValidationException {
                self.showMessage("Validation error: \(validationError.localizedDescription)", type: .error)
            } else {
                self.showMessage("Payment error: \(error.localizedDescription)", type: .error)
            }
        }
    }
    
    private func handlePKPaymentError(_ error: PKPaymentError) {
        switch error.code {
        case .paymentNotAllowed:
            showMessage("Payment not allowed. Please check your settings.", type: .error)
        case .paymentNetworkNotSupported:
            showMessage("Card not supported. Please use a different card.", type: .error)
        case .deviceCannotMakePayments:
            showMessage("Apple Pay is not available on this device.", type: .error)
        default:
            showMessage("Payment error occurred. Please try again.", type: .error)
        }
    }
    
    private func handleCancellation(_ error: Error?) {
        DispatchQueue.main.async {
            self.loadingIndicator.stopAnimating()
            self.loadingIndicator.isHidden = true
            self.showMessage("Payment was cancelled", type: .info)
        }
    }
    
    // MARK: - Helper Methods
    private func showMessage(_ message: String, type: MessageType) {
        errorMessageLabel.isHidden = true
        successMessageLabel.isHidden = true
        
        switch type {
        case .error:
            errorMessageLabel.text = message
            errorMessageLabel.isHidden = false
        case .success:
            successMessageLabel.text = message
            successMessageLabel.textColor = .systemGreen
            successMessageLabel.isHidden = false
        case .info:
            successMessageLabel.text = message
            successMessageLabel.textColor = .systemBlue
            successMessageLabel.isHidden = false
        }
    }
    
    private func calculateShippingCost(for address: CNPostalAddress?) -> Double {
        guard let address = address else { return 5.00 }
        return address.isoCountryCode == "US" ? (address.state == "CA" ? 7.99 : 4.99) : 15.99
    }
    
    private func calculateTax(for address: CNPostalAddress?) -> Double {
        guard let address = address, address.isoCountryCode == "US" else { return 0.00 }
        
        let taxRates: [String: Double] = ["CA": 0.0875, "NY": 0.08, "TX": 0.0625]
        let rate = taxRates[address.state] ?? 0.06
        return 20.00 * rate
    }
    
    private func navigateToSuccessScreen(transactionId: String) {
        let alert = UIAlertController(
            title: "Payment Successful",
            message: "Transaction ID: \(transactionId)",
            preferredStyle: .alert
        )
        alert.addAction(UIAlertAction(title: "OK", style: .default) { _ in
            self.navigationController?.popViewController(animated: true)
        })
        present(alert, animated: true)
    }
    
    private func cleanupComponent() {
        applePayComponent?.unmount()
        applePayComponent = nil
        checkout = nil
    }
    
    enum MessageType {
        case error, success, info
    }
}