import PassKit

func canMakePayments() -> Bool {
    // Check device supports Apple Pay at all
    guard PKPaymentAuthorizationController.canMakePayments() else {
        return false
    }
    // Check user has cards for the networks you support
    return PKPaymentAuthorizationController.canMakePayments(
        usingNetworks: [.visa, .masterCard, .amex, .discover],
        capabilities: .threeDSecure
    )
}

import SwiftUI
import PassKit

struct CheckoutView: View {
    var body: some View {
        PayWithApplePayButton(.buy) {
            startPayment()
        }
        .payWithApplePayButtonStyle(.black)
        .frame(height: 48)
        .padding()
    }
}

let button = PKPaymentButton(
    paymentButtonType: .buy,
    paymentButtonStyle: .black
)
button.cornerRadius = 12
button.addTarget(self, action: #selector(startPayment), for: .touchUpInside)

func createPaymentRequest() -> PKPaymentRequest {
    let request = PKPaymentRequest()
    request.merchantIdentifier = "merchant.com.example.app"
    request.countryCode = "US"
    request.currencyCode = "USD"
    request.supportedNetworks = [.visa, .masterCard, .amex, .discover]
    request.merchantCapabilities = .threeDSecure

    request.paymentSummaryItems = [
        PKPaymentSummaryItem(label: "Widget", amount: 9.99),
        PKPaymentSummaryItem(label: "Shipping", amount: 4.99),
        PKPaymentSummaryItem(label: "My Store", amount: 14.98) // Total (last item)
    ]

    return request
}

request.requiredShippingContactFields = [.postalAddress, .emailAddress, .name]
request.requiredBillingContactFields = [.postalAddress]

request.shippingMethods = [
    PKShippingMethod(label: "Standard", amount: 4.99),
    PKShippingMethod(label: "Express", amount: 9.99),
]
request.shippingMethods?[0].identifier = "standard"
request.shippingMethods?[0].detail = "5-7 business days"
request.shippingMethods?[1].identifier = "express"
request.shippingMethods?[1].detail = "1-2 business days"

request.shippingType = .shipping // .delivery, .storePickup, .servicePickup

@MainActor
func startPayment() {
    let request = createPaymentRequest()
    let controller = PKPaymentAuthorizationController(paymentRequest: request)
    controller.delegate = self
    controller.present()
}

extension CheckoutCoordinator: PKPaymentAuthorizationControllerDelegate {
    func paymentAuthorizationController(
        _ controller: PKPaymentAuthorizationController,
        didAuthorizePayment payment: PKPayment,
        handler completion: @escaping (PKPaymentAuthorizationResult) -> Void
    ) {
        // Send payment.token.paymentData to your payment processor
        Task {
            do {
                try await paymentService.process(payment.token)
                completion(PKPaymentAuthorizationResult(status: .success, errors: nil))
            } catch {
                completion(PKPaymentAuthorizationResult(status: .failure, errors: [error]))
            }
        }
    }

    func paymentAuthorizationControllerDidFinish(
        _ controller: PKPaymentAuthorizationController
    ) {
        controller.dismiss()
    }
}

func paymentAuthorizationController(
    _ controller: PKPaymentAuthorizationController,
    didSelectShippingMethod shippingMethod: PKShippingMethod,
    handler completion: @escaping (PKPaymentRequestShippingMethodUpdate) -> Void
) {
    let updatedItems = recalculateItems(with: shippingMethod)
    let update = PKPaymentRequestShippingMethodUpdate(paymentSummaryItems: updatedItems)
    completion(update)
}

func addPassToWallet(data: Data) {
    guard let pass = try? PKPass(data: data) else { return }

    if let addController = PKAddPassesViewController(pass: pass) {
        addController.delegate = self
        present(addController, animated: true)
    }
}

import PassKit
import SwiftUI

struct AddPassButton: View {
    let passData: Data

    var body: some View {
        Button("Add to Wallet") {
            addPass()
        }
    }

    func addPass() {
        guard let pass = try? PKPass(data: passData) else { return }
        let library = PKPassLibrary()
        library.addPasses([pass]) { status in
            switch status {
            case .shouldReviewPasses:
                // Present review UI
                break
            case .didAddPasses:
                // Passes added successfully
                break
            case .didCancelAddPasses:
                break
            @unknown default:
                break
            }
        }
    }
}

let library = PKPassLibrary()

// Check if a specific pass is already in Wallet
let hasPass = library.containsPass(pass)

// Retrieve passes your app can access
let passes = library.passes()

// Check if pass library is available
guard PKPassLibrary.isPassLibraryAvailable() else { return }

// WRONG: Using StoreKit to sell a physical product
let product = try await Product.products(for: ["com.example.tshirt"])

// CORRECT: Use Apple Pay for physical goods
let request = PKPaymentRequest()
request.paymentSummaryItems = [
    PKPaymentSummaryItem(label: "T-Shirt", amount: 29.99),
    PKPaymentSummaryItem(label: "My Store", amount: 29.99)
]

// WRONG: Merchant ID scattered across the codebase
let request1 = PKPaymentRequest()
request1.merchantIdentifier = "merchant.com.example.app"
// ...elsewhere:
let request2 = PKPaymentRequest()
request2.merchantIdentifier = "merchant.com.example.app" // easy to get out of sync

// CORRECT: Centralize configuration
enum PaymentConfig {
    static let merchantIdentifier = "merchant.com.example.app"
    static let countryCode = "US"
    static let currencyCode = "USD"
    static let supportedNetworks: [PKPaymentNetwork] = [.visa, .masterCard, .amex]
}

// WRONG: No total item
request.paymentSummaryItems = [
    PKPaymentSummaryItem(label: "Widget", amount: 9.99)
]

// CORRECT: Last item is the total with your merchant name
request.paymentSummaryItems = [
    PKPaymentSummaryItem(label: "Widget", amount: 9.99),
    PKPaymentSummaryItem(label: "My Store", amount: 9.99) // Total
]

// WRONG: Show Apple Pay button without checking
PayWithApplePayButton(.buy) { startPayment() }

// CORRECT: Only show when available
if PKPaymentAuthorizationController.canMakePayments(
    usingNetworks: PaymentConfig.supportedNetworks
) {
    PayWithApplePayButton(.buy) { startPayment() }
} else {
    // Show alternative checkout or setup button
    Button("Set Up Apple Pay") { /* guide user */ }
}

// WRONG: Dismissing inside didAuthorizePayment
func paymentAuthorizationController(
    _ controller: PKPaymentAuthorizationController,
    didAuthorizePayment payment: PKPayment,
    handler completion: @escaping (PKPaymentAuthorizationResult) -> Void
) {
    controller.dismiss() // Too early -- causes blank sheet
    completion(.init(status: .success, errors: nil))
}

// CORRECT: Dismiss only in paymentAuthorizationControllerDidFinish
func paymentAuthorizationControllerDidFinish(
    _ controller: PKPaymentAuthorizationController
) {
    controller.dismiss()
}