final class IAPManager: NSObject, SKProductsRequestDelegate, SKPaymentTransactionObserver {
    static let shared = IAPManager()

    private var products = [SKProduct]()

    private var productBeingPurchased: SKProduct?

    enum Product: String, CaseIterable {
        case removeAds = "JokesRUs.RemoveAds"
        case summerIcon = "JokesRUs.Icons.Summer"
        case tacoIcon = "JokesRUs.Icons.Taco"
        case pizzaIcon = "JokesRUs.Icons.Pizza"
        case hotdogIcon = "JokesRUs.Icons.HotDog"
        case hamburgerIcon = "JokesRUs.Icons.Hamburger"
        case doughnutIcon = "JokesRUs.Icons.Doughnut"
    }
    let group = DispatchGroup()
    
    public func fetchProducts() {
        let request = SKProductsRequest(productIdentifiers: Set(Product.allCases.compactMap(({ $0.rawValue }))))
        request.delegate = self
        request.start()
    }
    func productsRequest(_ request: SKProductsRequest, didReceive response: SKProductsResponse) {
        products = response.products
    }
    func request(_ request: SKRequest, didFailWithError error: Error) {
        guard request is SKProductsRequest else {
            return
        }

        print("Product fetch request failed")
    }
    public func purchase(product: Product, completion: @escaping () -> Void) {
        guard SKPaymentQueue.canMakePayments() else {
            return
        }
        guard let storeKitProduct = products.first(where: { $0.productIdentifier == product.rawValue }) else {
            return
        }
        Utilities.purchaseFailed = Bool()
        group.enter()
        DispatchQueue.main.async {
            let paymentRequest = SKPayment(product: storeKitProduct)
            SKPaymentQueue.default().add(self)
            SKPaymentQueue.default().add(paymentRequest)
            self.group.leave()
        }
        group.notify(queue: .main) {
            completion()
        }
    }
    public func restore(completion: @escaping () -> Void) {
        group.enter()
        DispatchQueue.main.async {
            SKPaymentQueue.default().restoreCompletedTransactions()
            self.group.leave()
        }
        group.notify(queue: .main) {
            completion()
        }
    }
    
    func paymentQueue(_ queue: SKPaymentQueue, updatedTransactions transactions: [SKPaymentTransaction]) {
        transactions.forEach({ transaction in
            switch transaction.transactionState {
            case .purchasing:
                //No op
                break
            case .purchased:
                handlePurchase(transaction.payment.productIdentifier)
                Utilities.purchaseFailed = false
                SKPaymentQueue.default().finishTransaction(transaction)
                break
            case .failed:
                Utilities.purchaseFailed = true
                Utilities.restoredPurchases = false
                SKPaymentQueue.default().finishTransaction(transaction)
                break
            case .restored:
                print("purchases restored")
                handlePurchase(transaction.payment.productIdentifier)
                Utilities.restoredPurchases = true
                SKPaymentQueue.default().finishTransaction(transaction)
                break
            case .deferred:
                break
            @unknown default:
                break
            }
        })
}