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// StoreKitPurchaseTracker.swift
// FlintCore-iOS
// Created by Marc Palmer on 16/02/2018.
// Copyright © 2018 Montana Floss Co. Ltd. All rights reserved.
import Foundation
#if os(iOS) || os(tvOS) || os(macOS)
import StoreKit
/// A basic StoreKit In-App Purchase checker that uses only the payment queue and *local storage*
/// to cache the list of purchase statuses. *It does not validate receipts*.
/// The local storage is unprotected if the user unlocks the device, and as such may be
/// subject to relatively easy editing by the determined cheapskate user to unlock features.
/// - note: ⚠️⚠️⚠️ Do not use this implementation if you insist on cryprographically verifying
/// purchases.
/// - note: ⚠️⚠️⚠️ It is our view that we should rely on the security of Apple's platform and not
/// be overly concerned with users performing hacks and workarounds. People that go to the effort of
/// jailbreaking, re-signing apps or applying other patching or data editing mechanisms
/// are unlikely to have paid you any money anyway.
/// If this isn't good enough for you, you will need to add your own app-specific logic to verify this so there isn't a
/// single point of verification, and to check receipts. You may not want to use Flint
/// for purchase verification at all if it transpires that the Swift call sites for
/// conditional requests are easily circumvented.
/// - note: In-App Purchases APIs are not available on watchOS as of watchOS 5. Any
/// Feature that requires a purchase will not be enabled on watchOS.
@available(iOS 3, tvOS 9, macOS 10.7, *)
open class StoreKitPurchaseTracker: NSObject, PurchaseTracker {
private let purchaseStore: SimplePurchaseStore
private var observers = ObserverSet<PurchaseTrackerObserver>()
private var purchases: [String:PurchaseStatus]
private let logger: ContextSpecificLogger?
struct PurchaseStatus: Codable {
let productID: String
let isPurchased: Bool
let date: Date
/// Instantiate the StoreKit purchase tracker, storing the status of purchases
/// in the container specified by `appGroupIndentifier`.
/// - param appGroupIdentifier: If nil, the information about purchases will be stored
/// in the app's container. This will not be accessible to other parts of your app, e.g.
/// app extensions. So if you have extensions you must create an app group container all
/// extensions use and specify its identifier here.
public init(appGroupIdentifier: String?) throws {
logger = Logging.development?.contextualLogger(activity: "StoreKit Purchases", topicPath: FlintInternal.coreLoggingTopic.appending("Purchases"))
purchaseStore = try SimplePurchaseStore(appGroupIdentifier: appGroupIdentifier)
purchases = [:]
logger?.debug("Loading purchases")
purchaseStore.load().forEach { purchases[$0.productID] = $0 }
deinit {
public func addObserver(_ observer: PurchaseTrackerObserver) {
let queue = SmartDispatchQueue(queue: .main)
observers.add(observer, using: queue)
public func removeObserver(_ observer: PurchaseTrackerObserver) {
/// Called to see if a specific product has been purchased
public func isPurchased(_ product: NonConsumableProduct) -> Bool? {
if let productStatus = purchases[product.productID] {
return productStatus.isPurchased
} else {
return nil
public func isSubscriptionActive(_ product: SubscriptionProduct) -> Bool? {
return nil
public func isFeatureEnabledByPastPurchases(_ feature: FeatureDefinition.Type) -> Bool {
return false
/// Indicate the purchase was successful, and store this fact
func didPurchase(_ productID: String, date: Date) throws {
logger?.debug("Recording purchase of iTunes product ID: \(productID)")
// Only update status if it is newer than the old status
if let existingPurchase = purchases[productID] {
guard < date else {
purchases[productID] = PurchaseStatus(productID: productID, isPurchased: true, date: date)
notifyChange(productID: productID, isPurchased: true)
try save()
/// Indicate the purchase is no longer valid, and store this fact
func didInvalidatePurchase(_ productID: String) throws {
logger?.debug("Recording invalidation of purchase of iTunes product ID: \(productID)")
purchases.removeValue(forKey: productID)
notifyChange(productID: productID, isPurchased: false)
try save()
private func notifyChange(productID: String, isPurchased: Bool) {
observers.notifySync { observer in
observer.purchaseStatusDidChange(productID: productID, isPurchased: false)
private func save() throws {
logger?.debug("Saving purchases")
try Array(purchases.values))
extension StoreKitPurchaseTracker: SKPaymentTransactionObserver {
/// A naïve implementation that assumes all success and restores enable a purchase,
/// and all failures and deferred remove them. This only works for one-time purchases
public func paymentQueue(_ queue: SKPaymentQueue, updatedTransactions transactions: [SKPaymentTransaction]) {
for transaction in transactions {
logger?.debug("Transaction updated, status: \(transaction.transactionState.rawValue) id: \(transaction.transactionIdentifier != nil ? transaction.transactionIdentifier! : "nil") for payment of product \(transaction.payment.productIdentifier) with quantity \(transaction.payment.quantity)")
let productID = transaction.payment.productIdentifier
guard let product = Product.productByID(productID) else {
logger?.error("Transaction updated for product ID not registered as a Product, will not store the fact this is purchased: \(productID)")
// Make sure we don't do this for products that can't be supported, but don't crash
guard product is NonConsumableProduct else {
logger?.error("Transaction updated for product ID that is not a non-consumable, will not store the fact this is purchased: \(productID)")
/// !!! TODO: At least salt and hash the product IDs to make it harder to hack?
switch transaction.transactionState {
case .purchased, .restored:
do {
guard let date = transaction.transactionDate else {
logger?.error("Failed to save purchase confirmation for \(productID), there was no transactionDate")
try didPurchase(productID, date: date)
} catch let error {
logger?.error("Failed to save purchase confirmation for \(productID): \(error)")
case .failed, .deferred:
do {
try didInvalidatePurchase(productID)
} catch let error {
logger?.error("Failed to save purchase invalidation for \(productID): \(error)")