Merge branch 'reduce-code-duplication'

5 files changed, 180 insertions, 270 deletions

diff --git a/ios/MullvadVPN.xcodeproj/project.pbxproj b/ios/MullvadVPN.xcodeproj/project.pbxproj
index c73d0c820c..3e7b6261aa 100644
--- a/ios/MullvadVPN.xcodeproj/project.pbxproj
+++ b/ios/MullvadVPN.xcodeproj/project.pbxproj
@@ -309,7 +309,6 @@
 		58FBFBEA291622580020E046 /* MullvadREST.framework in Frameworks */ = {isa = PBXBuildFile; fileRef = 06799ABC28F98E1D00ACD94E /* MullvadREST.framework */; };
 		58FBFBF1291630700020E046 /* DurationTests.swift in Sources */ = {isa = PBXBuildFile; fileRef = 58FBFBF0291630700020E046 /* DurationTests.swift */; };
 		58FC040A27B3EE03001C21F0 /* TunnelMonitor.swift in Sources */ = {isa = PBXBuildFile; fileRef = 58FC040927B3EE03001C21F0 /* TunnelMonitor.swift */; };
-		58FD5BE724192A2C00112C88 /* StoreReceipt.swift in Sources */ = {isa = PBXBuildFile; fileRef = 58FD5BE624192A2B00112C88 /* StoreReceipt.swift */; };
 		58FD5BF024238EB300112C88 /* SKProduct+Formatting.swift in Sources */ = {isa = PBXBuildFile; fileRef = 58FD5BEF24238EB300112C88 /* SKProduct+Formatting.swift */; };
 		58FD5BF42428C67600112C88 /* InAppPurchaseButton.swift in Sources */ = {isa = PBXBuildFile; fileRef = 58FD5BF32428C67600112C88 /* InAppPurchaseButton.swift */; };
 		58FEEB46260A028D00A621A8 /* GeoJSON.swift in Sources */ = {isa = PBXBuildFile; fileRef = 58FEEB45260A028D00A621A8 /* GeoJSON.swift */; };
@@ -802,7 +801,6 @@
 		58FBFBE8291622580020E046 /* ExponentialBackoffTests.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = ExponentialBackoffTests.swift; sourceTree = "<group>"; };
 		58FBFBF0291630700020E046 /* DurationTests.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = DurationTests.swift; sourceTree = "<group>"; };
 		58FC040927B3EE03001C21F0 /* TunnelMonitor.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = TunnelMonitor.swift; sourceTree = "<group>"; };
-		58FD5BE624192A2B00112C88 /* StoreReceipt.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = StoreReceipt.swift; sourceTree = "<group>"; };
 		58FD5BEF24238EB300112C88 /* SKProduct+Formatting.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = "SKProduct+Formatting.swift"; sourceTree = "<group>"; };
 		58FD5BF32428C67600112C88 /* InAppPurchaseButton.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = InAppPurchaseButton.swift; sourceTree = "<group>"; };
 		58FEEB45260A028D00A621A8 /* GeoJSON.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = GeoJSON.swift; sourceTree = "<group>"; };
@@ -1107,7 +1105,6 @@
 				5846227626E22A7C0035F7C2 /* StorePaymentManagerDelegate.swift */,
 				58FB865426E8BF3100F188BC /* StorePaymentManagerError.swift */,
 				5846227226E22A160035F7C2 /* StorePaymentObserver.swift */,
-				58FD5BE624192A2B00112C88 /* StoreReceipt.swift */,
 				5846227026E229F20035F7C2 /* StoreSubscription.swift */,
 			);
 			path = StorePaymentManager;
@@ -2239,7 +2236,6 @@
 				58677712290976FB006F721F /* SettingsInteractor.swift in Sources */,
 				58CE5E66224146200008646E /* LoginViewController.swift in Sources */,
 				58EF580B25D69D7A00AEBA94 /* ProblemReportSubmissionOverlayView.swift in Sources */,
-				58FD5BE724192A2C00112C88 /* StoreReceipt.swift in Sources */,
 				5892A45E265FABFF00890742 /* EmptyTableViewHeaderFooterView.swift in Sources */,
 				580909D32876D09A0078138D /* RevokedDeviceViewController.swift in Sources */,
 				5835B7CC233B76CB0096D79F /* TunnelManager.swift in Sources */,
diff --git a/ios/MullvadVPN/DisplayChainedError.swift b/ios/MullvadVPN/DisplayChainedError.swift
index 4bfa351f4f..c1ef9b463e 100644
--- a/ios/MullvadVPN/DisplayChainedError.swift
+++ b/ios/MullvadVPN/DisplayChainedError.swift
@@ -113,7 +113,7 @@ extension StorePaymentManagerError: DisplayChainedError {
         case .noAccountSet:
             return NSLocalizedString(
                 "NO_ACCOUNT_SET_ERROR",
-                tableName: "AppStorePaymentManager",
+                tableName: "StorePaymentManager",
                 value: "Internal error: account is not set.",
                 comment: ""
             )
@@ -125,7 +125,7 @@ extension StorePaymentManagerError: DisplayChainedError {
                 return String(
                     format: NSLocalizedString(
                         "INVALID_ACCOUNT_ERROR",
-                        tableName: "AppStorePaymentManager",
+                        tableName: "StorePaymentManager",
                         value: "Cannot add credit to invalid account.",
                         comment: ""
                     ), reason
@@ -136,7 +136,7 @@ extension StorePaymentManagerError: DisplayChainedError {
                 return String(
                     format: NSLocalizedString(
                         "VALIDATE_ACCOUNT_ERROR",
-                        tableName: "AppStorePaymentManager",
+                        tableName: "StorePaymentManager",
                         value: "Failed to validate account token: %@",
                         comment: ""
                     ), reason
@@ -147,7 +147,7 @@ extension StorePaymentManagerError: DisplayChainedError {
             if readReceiptError is StoreReceiptNotFound {
                 return NSLocalizedString(
                     "RECEIPT_NOT_FOUND_ERROR",
-                    tableName: "AppStorePaymentManager",
+                    tableName: "StorePaymentManager",
                     value: "AppStore receipt is not found on disk.",
                     comment: ""
                 )
@@ -155,7 +155,7 @@ extension StorePaymentManagerError: DisplayChainedError {
                 return String(
                     format: NSLocalizedString(
                         "REFRESH_RECEIPT_ERROR",
-                        tableName: "AppStorePaymentManager",
+                        tableName: "StorePaymentManager",
                         value: "Cannot refresh the AppStore receipt: %@",
                         comment: ""
                     ),
@@ -165,7 +165,7 @@ extension StorePaymentManagerError: DisplayChainedError {
                 return String(
                     format: NSLocalizedString(
                         "READ_RECEIPT_ERROR",
-                        tableName: "AppStorePaymentManager",
+                        tableName: "StorePaymentManager",
                         value: "Cannot read the AppStore receipt from disk: %@",
                         comment: ""
                     ),
@@ -177,13 +177,13 @@ extension StorePaymentManagerError: DisplayChainedError {
             let reason = restError.errorChainDescription ?? ""
             let errorFormat = NSLocalizedString(
                 "SEND_RECEIPT_ERROR",
-                tableName: "AppStorePaymentManager",
+                tableName: "StorePaymentManager",
                 value: "Failed to send the receipt to server: %@",
                 comment: ""
             )
             let recoverySuggestion = NSLocalizedString(
                 "SEND_RECEIPT_RECOVERY_SUGGESTION",
-                tableName: "AppStorePaymentManager",
+                tableName: "StorePaymentManager",
                 value: "Please retry by using the \"Restore purchases\" button.",
                 comment: ""
             )
diff --git a/ios/MullvadVPN/StorePaymentManager/SendStoreReceiptOperation.swift b/ios/MullvadVPN/StorePaymentManager/SendStoreReceiptOperation.swift
index 0b360a7184..73e9788c2b 100644
--- a/ios/MullvadVPN/StorePaymentManager/SendStoreReceiptOperation.swift
+++ b/ios/MullvadVPN/StorePaymentManager/SendStoreReceiptOperation.swift
@@ -11,29 +11,32 @@ import MullvadLogging
 import MullvadREST
 import MullvadTypes
 import Operations
+import StoreKit
 
 class SendStoreReceiptOperation: ResultOperation<
     REST.CreateApplePaymentResponse,
     StorePaymentManagerError
-> {
+>, SKRequestDelegate {
     private let apiProxy: REST.APIProxy
-    private let accountToken: String
+    private let accountNumber: String
+
     private let forceRefresh: Bool
     private let receiptProperties: [String: Any]?
-    private var fetchReceiptTask: Cancellable?
+    private var refreshRequest: SKReceiptRefreshRequest?
+
     private var submitReceiptTask: Cancellable?
 
     private let logger = Logger(label: "SendStoreReceiptOperation")
 
     init(
         apiProxy: REST.APIProxy,
-        accountToken: String,
+        accountNumber: String,
         forceRefresh: Bool,
         receiptProperties: [String: Any]?,
         completionHandler: @escaping CompletionHandler
     ) {
         self.apiProxy = apiProxy
-        self.accountToken = accountToken
+        self.accountNumber = accountNumber
         self.forceRefresh = forceRefresh
         self.receiptProperties = receiptProperties
 
@@ -45,42 +48,98 @@ class SendStoreReceiptOperation: ResultOperation<
     }
 
     override func operationDidCancel() {
-        fetchReceiptTask?.cancel()
-        fetchReceiptTask = nil
+        refreshRequest?.cancel()
+        refreshRequest = nil
 
         submitReceiptTask?.cancel()
         submitReceiptTask = nil
     }
 
     override func main() {
-        fetchReceiptTask = StoreReceipt.fetch(
-            forceRefresh: forceRefresh,
-            receiptProperties: receiptProperties
-        ) { completion in
-            switch completion {
-            case let .success(receiptData):
-                self.sendReceipt(receiptData)
+        // Pull receipt from AppStore if requested.
+        guard !forceRefresh else {
+            startRefreshRequest()
+            return
+        }
 
-            case let .failure(error):
+        // Read AppStore receipt from disk.
+        do {
+            let data = try readReceiptFromDisk()
+
+            sendReceipt(data)
+        } catch is StoreReceiptNotFound {
+            // Pull receipt from AppStore if it's not cached locally.
+            startRefreshRequest()
+        } catch {
+            logger.error(
+                error: error,
+                message: "Failed to read the AppStore receipt."
+            )
+            finish(completion: .failure(.readReceipt(error)))
+        }
+    }
+
+    // - MARK: SKRequestDelegate
+
+    func requestDidFinish(_ request: SKRequest) {
+        dispatchQueue.async {
+            do {
+                let data = try self.readReceiptFromDisk()
+
+                self.sendReceipt(data)
+            } catch {
                 self.logger.error(
                     error: error,
-                    message: "Failed to fetch the AppStore receipt."
+                    message: "Failed to read the AppStore receipt after refresh."
                 )
                 self.finish(completion: .failure(.readReceipt(error)))
-
-            case .cancelled:
-                self.finish(completion: .cancelled)
             }
         }
     }
 
+    func request(_ request: SKRequest, didFailWithError error: Error) {
+        dispatchQueue.async {
+            self.logger.error(
+                error: error,
+                message: "Failed to refresh the AppStore receipt."
+            )
+            self.finish(completion: .failure(.readReceipt(error)))
+        }
+    }
+
+    // MARK: - Private
+
+    private func startRefreshRequest() {
+        let refreshRequest = SKReceiptRefreshRequest(receiptProperties: receiptProperties)
+        refreshRequest.delegate = self
+        refreshRequest.start()
+
+        self.refreshRequest = refreshRequest
+    }
+
+    private func readReceiptFromDisk() throws -> Data {
+        guard let appStoreReceiptURL = Bundle.main.appStoreReceiptURL else {
+            throw StoreReceiptNotFound()
+        }
+
+        do {
+            return try Data(contentsOf: appStoreReceiptURL)
+        } catch let error as CocoaError
+            where error.code == .fileReadNoSuchFile || error.code == .fileNoSuchFile
+        {
+            throw StoreReceiptNotFound()
+        } catch {
+            throw error
+        }
+    }
+
     private func sendReceipt(_ receiptData: Data) {
         submitReceiptTask = apiProxy.createApplePayment(
-            accountNumber: accountToken,
+            accountNumber: accountNumber,
             receiptString: receiptData,
             retryStrategy: .noRetry
-        ) { result in
-            switch result {
+        ) { completion in
+            switch completion {
             case let .success(response):
                 self.logger.info(
                     """
@@ -105,3 +164,9 @@ class SendStoreReceiptOperation: ResultOperation<
         }
     }
 }
+
+struct StoreReceiptNotFound: LocalizedError {
+    var errorDescription: String? {
+        return "AppStore receipt file does not exist on disk."
+    }
+}
diff --git a/ios/MullvadVPN/StorePaymentManager/StorePaymentManager.swift b/ios/MullvadVPN/StorePaymentManager/StorePaymentManager.swift
index 61b626cd33..fa8963f5b6 100644
--- a/ios/MullvadVPN/StorePaymentManager/StorePaymentManager.swift
+++ b/ios/MullvadVPN/StorePaymentManager/StorePaymentManager.swift
@@ -13,7 +13,7 @@ import MullvadTypes
 import Operations
 import StoreKit
 
-class StorePaymentManager: NSObject, SKPaymentTransactionObserver {
+final class StorePaymentManager: NSObject, SKPaymentTransactionObserver {
     private enum OperationCategory {
         static let sendStoreReceipt = "StorePaymentManager.sendStoreReceipt"
         static let productsRequest = "StorePaymentManager.productsRequest"
@@ -124,67 +124,38 @@ class StorePaymentManager: NSObject, SKPaymentTransactionObserver {
         return operation
     }
 
-    func addPayment(_ payment: SKPayment, for accountToken: String) {
-        var task: Cancellable?
-        let backgroundTaskIdentifier = UIApplication.shared
-            .beginBackgroundTask(withName: "Validate account token") {
-                task?.cancel()
-            }
-
+    func addPayment(_ payment: SKPayment, for accountNumber: String) {
         // Validate account token before adding new payment to the queue.
-        task = accountsProxy.getAccountData(
-            accountNumber: accountToken,
-            retryStrategy: .default
-        ) { completion in
-            dispatchPrecondition(condition: .onQueue(.main))
-
-            switch completion {
-            case .success:
-                self.associateAccountToken(accountToken, and: payment)
-                self.paymentQueue.add(payment)
-
-            case let .failure(error):
-                let event = StorePaymentEvent.failure(
-                    StorePaymentFailure(
-                        transaction: nil,
-                        payment: payment,
-                        accountNumber: accountToken,
-                        error: .validateAccount(error)
-                    )
-                )
-
-                self.observerList.forEach { observer in
-                    observer.storePaymentManager(self, didReceiveEvent: event)
-                }
-
-            case .cancelled:
+        validateAccount(accountNumber: accountNumber) { error in
+            if let error = error {
                 let event = StorePaymentEvent.failure(
                     StorePaymentFailure(
                         transaction: nil,
                         payment: payment,
-                        accountNumber: accountToken,
-                        error: .validateAccount(.network(URLError(.cancelled)))
+                        accountNumber: accountNumber,
+                        error: error
                     )
                 )
 
                 self.observerList.forEach { observer in
                     observer.storePaymentManager(self, didReceiveEvent: event)
                 }
+            } else {
+                self.associateAccountToken(accountNumber, and: payment)
+                self.paymentQueue.add(payment)
             }
-
-            UIApplication.shared.endBackgroundTask(backgroundTaskIdentifier)
         }
     }
 
     func restorePurchases(
-        for accountToken: String,
+        for accountNumber: String,
         completionHandler: @escaping (OperationCompletion<
             REST.CreateApplePaymentResponse,
             StorePaymentManagerError
         >) -> Void
     ) -> Cancellable {
         return sendStoreReceipt(
-            accountToken: accountToken,
+            accountNumber: accountNumber,
             forceRefresh: true,
             completionHandler: completionHandler
         )
@@ -209,18 +180,59 @@ class StorePaymentManager: NSObject, SKPaymentTransactionObserver {
         }
     }
 
+    private func validateAccount(
+        accountNumber: String,
+        completionHandler: @escaping (StorePaymentManagerError?) -> Void
+    ) {
+        let accountOperation = ResultBlockOperation<
+            REST.AccountData,
+            REST.Error
+        >(dispatchQueue: .main) { op in
+            let task = self.accountsProxy.getAccountData(
+                accountNumber: accountNumber,
+                retryStrategy: .default
+            ) { completion in
+                op.finish(completion: completion)
+            }
+
+            op.addCancellationBlock {
+                task.cancel()
+            }
+        }
+
+        accountOperation.addObserver(BackgroundObserver(
+            application: .shared,
+            name: "Validate account number",
+            cancelUponExpiration: false
+        ))
+
+        accountOperation.completionQueue = .main
+        accountOperation.completionHandler = { completion in
+            var error: REST.Error?
+
+            if case .cancelled = completion {
+                error = .network(URLError(.cancelled))
+            } else {
+                error = completion.error
+            }
+
+            completionHandler(error.map { .validateAccount($0) })
+        }
+
+        operationQueue.addOperation(accountOperation)
+    }
+
     private func sendStoreReceipt(
-        accountToken: String,
+        accountNumber: String,
         forceRefresh: Bool,
         completionHandler: @escaping (OperationCompletion<
             REST.CreateApplePaymentResponse,
             StorePaymentManagerError
-        >)
-            -> Void
+        >) -> Void
     ) -> Cancellable {
         let operation = SendStoreReceiptOperation(
             apiProxy: apiProxy,
-            accountToken: accountToken,
+            accountNumber: accountNumber,
             forceRefresh: forceRefresh,
             receiptProperties: nil,
             completionHandler: completionHandler
@@ -234,9 +246,7 @@ class StorePaymentManager: NSObject, SKPaymentTransactionObserver {
             )
         )
 
-        operation.addCondition(
-            MutuallyExclusive(category: OperationCategory.sendStoreReceipt)
-        )
+        operation.addCondition(MutuallyExclusive(category: OperationCategory.sendStoreReceipt))
 
         operationQueue.addOperation(operation)
 
@@ -283,37 +293,31 @@ class StorePaymentManager: NSObject, SKPaymentTransactionObserver {
     private func didFailPurchase(transaction: SKPaymentTransaction) {
         paymentQueue.finishTransaction(transaction)
 
+        let paymentFailure: StorePaymentFailure
+
         if let accountToken = deassociateAccountToken(transaction.payment) {
-            let event = StorePaymentEvent.failure(
-                StorePaymentFailure(
-                    transaction: transaction,
-                    payment: transaction.payment,
-                    accountNumber: accountToken,
-                    error: .storePayment(transaction.error!)
-                )
+            paymentFailure = StorePaymentFailure(
+                transaction: transaction,
+                payment: transaction.payment,
+                accountNumber: accountToken,
+                error: .storePayment(transaction.error!)
             )
-
-            observerList.forEach { observer in
-                observer.storePaymentManager(self, didReceiveEvent: event)
-            }
         } else {
-            let event = StorePaymentEvent.failure(
-                StorePaymentFailure(
-                    transaction: transaction,
-                    payment: transaction.payment,
-                    accountNumber: nil,
-                    error: .noAccountSet
-                )
+            paymentFailure = StorePaymentFailure(
+                transaction: transaction,
+                payment: transaction.payment,
+                accountNumber: nil,
+                error: .noAccountSet
             )
+        }
 
-            observerList.forEach { observer in
-                observer.storePaymentManager(self, didReceiveEvent: event)
-            }
+        observerList.forEach { observer in
+            observer.storePaymentManager(self, didReceiveEvent: .failure(paymentFailure))
         }
     }
 
     private func didFinishOrRestorePurchase(transaction: SKPaymentTransaction) {
-        guard let accountToken = deassociateAccountToken(transaction.payment) else {
+        guard let accountNumber = deassociateAccountToken(transaction.payment) else {
             let event = StorePaymentEvent.failure(
                 StorePaymentFailure(
                     transaction: transaction,
@@ -329,35 +333,35 @@ class StorePaymentManager: NSObject, SKPaymentTransactionObserver {
             return
         }
 
-        _ = sendStoreReceipt(accountToken: accountToken, forceRefresh: false) { completion in
+        _ = sendStoreReceipt(accountNumber: accountNumber, forceRefresh: false) { completion in
+            var event: StorePaymentEvent?
+
             switch completion {
             case let .success(response):
                 self.paymentQueue.finishTransaction(transaction)
 
-                let event = StorePaymentEvent.finished(StorePaymentCompletion(
+                event = StorePaymentEvent.finished(StorePaymentCompletion(
                     transaction: transaction,
-                    accountNumber: accountToken,
+                    accountNumber: accountNumber,
                     serverResponse: response
                 ))
 
-                self.observerList.forEach { observer in
-                    observer.storePaymentManager(self, didReceiveEvent: event)
-                }
-
             case let .failure(error):
-                let event = StorePaymentEvent.failure(StorePaymentFailure(
+                event = StorePaymentEvent.failure(StorePaymentFailure(
                     transaction: transaction,
                     payment: transaction.payment,
-                    accountNumber: accountToken,
+                    accountNumber: accountNumber,
                     error: error
                 ))
 
+            case .cancelled:
+                break
+            }
+
+            if let event = event {
                 self.observerList.forEach { observer in
                     observer.storePaymentManager(self, didReceiveEvent: event)
                 }
-
-            case .cancelled:
-                break
             }
         }
     }
diff --git a/ios/MullvadVPN/StorePaymentManager/StoreReceipt.swift b/ios/MullvadVPN/StorePaymentManager/StoreReceipt.swift
deleted file mode 100644
index 93731ba7f9..0000000000
--- a/ios/MullvadVPN/StorePaymentManager/StoreReceipt.swift
+++ /dev/null
@@ -1,155 +0,0 @@
-//
-//  StoreReceipt.swift
-//  MullvadVPN
-//
-//  Created by pronebird on 11/03/2020.
-//  Copyright © 2020 Mullvad VPN AB. All rights reserved.
-//
-
-import Foundation
-import MullvadREST
-import MullvadTypes
-import Operations
-import StoreKit
-
-struct StoreReceiptNotFound: LocalizedError {
-    var errorDescription: String? {
-        return "AppStore receipt file does not exist on disk."
-    }
-}
-
-enum StoreReceipt {
-    /// Internal operation queue.
-    private static let operationQueue: OperationQueue = {
-        let queue = AsyncOperationQueue()
-        queue.name = "StoreReceiptQueue"
-        queue.maxConcurrentOperationCount = 1
-        return queue
-    }()
-
-    /// Read AppStore receipt from disk or refresh it from AppStore if it's missing.
-    /// This call may trigger a sign in with AppStore prompt to appear.
-    static func fetch(
-        forceRefresh: Bool = false,
-        receiptProperties: [String: Any]? = nil,
-        completionHandler: @escaping (OperationCompletion<Data, Error>) -> Void
-    ) -> Cancellable {
-        let operation = FetchAppStoreReceiptOperation(
-            forceRefresh: forceRefresh,
-            receiptProperties: receiptProperties,
-            completionHandler: completionHandler
-        )
-
-        operation.addObserver(
-            BackgroundObserver(
-                application: .shared,
-                name: "Fetch AppStore receipt",
-                cancelUponExpiration: true
-            )
-        )
-
-        operationQueue.addOperation(operation)
-
-        return operation
-    }
-}
-
-private class FetchAppStoreReceiptOperation: ResultOperation<Data, Error>, SKRequestDelegate {
-    private var request: SKReceiptRefreshRequest?
-    private let receiptProperties: [String: Any]?
-    private let forceRefresh: Bool
-
-    init(
-        forceRefresh: Bool,
-        receiptProperties: [String: Any]?,
-        completionHandler: @escaping (Completion) -> Void
-    ) {
-        self.forceRefresh = forceRefresh
-        self.receiptProperties = receiptProperties
-
-        super.init(
-            dispatchQueue: .main,
-            completionQueue: .main,
-            completionHandler: completionHandler
-        )
-    }
-
-    override func main() {
-        // Pull receipt from AppStore if requested.
-        guard !forceRefresh else {
-            startRefreshRequest()
-            return
-        }
-
-        // Read AppStore receipt from disk.
-        do {
-            let data = try readReceiptFromDisk()
-
-            finish(completion: .success(data))
-        } catch is StoreReceiptNotFound {
-            // Pull receipt from AppStore if it's not cached locally.
-            startRefreshRequest()
-        } catch {
-            finish(completion: .failure(error))
-        }
-    }
-
-    override func operationDidCancel() {
-        request?.cancel()
-    }
-
-    // - MARK: SKRequestDelegate
-
-    func requestDidFinish(_ request: SKRequest) {
-        dispatchQueue.async {
-            self.didFinishRefreshRequest(error: nil)
-        }
-    }
-
-    func request(_ request: SKRequest, didFailWithError error: Error) {
-        dispatchQueue.async {
-            self.didFinishRefreshRequest(error: error)
-        }
-    }
-
-    // - MARK: Private
-
-    private func startRefreshRequest() {
-        let request = SKReceiptRefreshRequest(receiptProperties: receiptProperties)
-        request.delegate = self
-        request.start()
-
-        self.request = request
-    }
-
-    private func didFinishRefreshRequest(error: Error?) {
-        guard !isCancelled else {
-            finish(completion: .cancelled)
-            return
-        }
-
-        if let error = error {
-            finish(completion: .failure(error))
-        } else {
-            let result = Result { try readReceiptFromDisk() }
-
-            finish(completion: OperationCompletion(result: result))
-        }
-    }
-
-    private func readReceiptFromDisk() throws -> Data {
-        guard let appStoreReceiptURL = Bundle.main.appStoreReceiptURL else {
-            throw StoreReceiptNotFound()
-        }
-
-        do {
-            return try Data(contentsOf: appStoreReceiptURL)
-        } catch let error as CocoaError
-            where error.code == .fileReadNoSuchFile || error.code == .fileNoSuchFile
-        {
-            throw StoreReceiptNotFound()
-        } catch {
-            throw error
-        }
-    }
-}