Add Combine publishers for SKRequest subclasses

2 files changed, 125 insertions, 0 deletions

diff --git a/ios/MullvadVPN.xcodeproj/project.pbxproj b/ios/MullvadVPN.xcodeproj/project.pbxproj
index e747d23f77..449a9f06cc 100644
--- a/ios/MullvadVPN.xcodeproj/project.pbxproj
+++ b/ios/MullvadVPN.xcodeproj/project.pbxproj
@@ -122,6 +122,7 @@
 		58D0C7A223F1CECF00FE9BA7 /* MullvadVPNScreenshots.swift in Sources */ = {isa = PBXBuildFile; fileRef = 58D0C7A023F1CECF00FE9BA7 /* MullvadVPNScreenshots.swift */; };
 		58EC4E6C23915325003F5C5B /* Bundle+MullvadVersion.swift in Sources */ = {isa = PBXBuildFile; fileRef = 58EC4E6B23915325003F5C5B /* Bundle+MullvadVersion.swift */; };
 		58F19E35228C15BA00C7710B /* SpinnerActivityIndicatorView.swift in Sources */ = {isa = PBXBuildFile; fileRef = 58F19E34228C15BA00C7710B /* SpinnerActivityIndicatorView.swift */; };
+		58FD5BE92419406000112C88 /* SKRequestPublisher.swift in Sources */ = {isa = PBXBuildFile; fileRef = 58FD5BE82419406000112C88 /* SKRequestPublisher.swift */; };
 /* End PBXBuildFile section */
 
 /* Begin PBXContainerItemProxy section */
@@ -258,6 +259,7 @@
 		58F19E34228C15BA00C7710B /* SpinnerActivityIndicatorView.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = SpinnerActivityIndicatorView.swift; sourceTree = "<group>"; };
 		58FBDAA422A52BDA00EB69A3 /* PacketTunnel-Bridging-Header.h */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.c.h; path = "PacketTunnel-Bridging-Header.h"; sourceTree = "<group>"; };
 		58FBDAAA22A52DC500EB69A3 /* MullvadVPN-Bridging-Header.h */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.c.h; path = "MullvadVPN-Bridging-Header.h"; sourceTree = "<group>"; };
+		58FD5BE82419406000112C88 /* SKRequestPublisher.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = SKRequestPublisher.swift; sourceTree = "<group>"; };
 /* End PBXFileReference section */
 
 /* Begin PBXFrameworksBuildPhase section */
@@ -396,6 +398,7 @@
 				58CCA01122424D11004F3011 /* SettingsViewController.swift */,
 				58BA693023EADA6A009DC256 /* SimulatorTunnelProvider.swift */,
 				587A01FB23F1F0BE00B68763 /* SimulatorTunnelProviderHost.swift */,
+				58FD5BE82419406000112C88 /* SKRequestPublisher.swift */,
 				58F19E34228C15BA00C7710B /* SpinnerActivityIndicatorView.swift */,
 				581CBCED229826FD00727D7F /* StaticTableViewDataSource.swift */,
 				5862805322428EF100F5A6E1 /* TranslucentButtonBlurView.swift */,
@@ -711,6 +714,7 @@
 				58EC4E6C23915325003F5C5B /* Bundle+MullvadVersion.swift in Sources */,
 				58BA693123EADA6A009DC256 /* SimulatorTunnelProvider.swift in Sources */,
 				58A1AA8C23F5584C009F7EA6 /* ConnectionPanelView.swift in Sources */,
+				58FD5BE92419406000112C88 /* SKRequestPublisher.swift in Sources */,
 				582BB1B52295780F0055B6EF /* AccountExpiry.swift in Sources */,
 				582BB1B3229574F40055B6EF /* SettingsAccountCell.swift in Sources */,
 				58CCA010224249A1004F3011 /* ConnectViewController.swift in Sources */,
diff --git a/ios/MullvadVPN/SKRequestPublisher.swift b/ios/MullvadVPN/SKRequestPublisher.swift
new file mode 100644
index 0000000000..1e2786eb6e
--- /dev/null
+++ b/ios/MullvadVPN/SKRequestPublisher.swift
@@ -0,0 +1,121 @@
+//
+//  SKRequestPublisher.swift
+//  MullvadVPN
+//
+//  Created by pronebird on 11/03/2020.
+//  Copyright © 2020 Mullvad VPN AB. All rights reserved.
+//
+
+import Combine
+import Foundation
+import StoreKit
+
+/// A protocol that formalizes the interface of all of the subclasses of
+/// `SKRequestSubscription<Output>`
+protocol SKRequestSubscriptionProtocol: Subscription {
+    associatedtype Output
+    associatedtype Failure: Error
+
+    init<S: Subscriber>(request: SKRequest, subscriber: S)
+        where S.Input == Output, S.Failure == Failure
+}
+
+/// A base implementation of subscription that handles the `SKRequest`.
+class SKRequestSubscription<Output>: NSObject, Subscription, SKRequestDelegate,
+    SKRequestSubscriptionProtocol
+{
+    typealias Failure = Error
+
+    private let request: SKRequest
+    fileprivate let subscriber: AnySubscriber<Output, Failure>
+
+    required init<S: Subscriber>(request: SKRequest, subscriber: S)
+        where S.Input == Output, S.Failure == Failure
+    {
+        self.request = request
+        self.subscriber = AnySubscriber(subscriber)
+
+        super.init()
+        request.delegate = self
+    }
+
+    func request(_ demand: Subscribers.Demand) {
+        request.start()
+    }
+
+    func cancel() {
+        request.cancel()
+    }
+
+    // MARK: - SKRequestDelegate
+
+    func request(_ request: SKRequest, didFailWithError error: Error) {
+        subscriber.receive(completion: .failure(error))
+    }
+
+    func requestDidFinish(_ request: SKRequest) {
+        subscriber.receive(completion: .finished)
+    }
+}
+
+/// A subscription that emits the `SKProductsResponse` upon request completion
+class SKProductsRequestSubscription: SKRequestSubscription<SKProductsResponse>,
+    SKProductsRequestDelegate
+{
+
+    // MARK: - SKProductsRequestDelegate
+
+    func productsRequest(_ request: SKProductsRequest, didReceive response: SKProductsResponse) {
+        _ = self.subscriber.receive(response)
+    }
+
+}
+
+/// A subscription for requesting the AppStore receipt refresh
+class SKRefreshRequestSubscription: SKRequestSubscription<()> {
+    override func requestDidFinish(_ request: SKRequest) {
+        // Emit void so that publishers using this subscription could be chained
+        _ = self.subscriber.receive(())
+
+        super.requestDidFinish(request)
+    }
+}
+
+/// A base implementation of publisher that runs `SKRequest`s
+class SKRequestPublisher<SubscriptionType>: Publisher
+    where SubscriptionType: SKRequestSubscriptionProtocol
+{
+    typealias Output = SubscriptionType.Output
+    typealias Failure = SubscriptionType.Failure
+
+    fileprivate let request: SKRequest
+
+    init(request: SKRequest) {
+        self.request = request
+    }
+
+    func receive<S>(subscriber: S) where S : Subscriber, Failure == S.Failure, Output == S.Input {
+        let subscription = SubscriptionType(request: request, subscriber: subscriber)
+
+        subscriber.receive(subscription: subscription)
+    }
+
+}
+
+protocol SKRequestPublishing {
+    associatedtype SubscriptionType: SKRequestSubscriptionProtocol
+
+    var publisher: SKRequestPublisher<SubscriptionType> { get }
+}
+
+extension SKProductsRequest: SKRequestPublishing {
+    var publisher: SKRequestPublisher<SKProductsRequestSubscription> {
+        return .init(request: self)
+    }
+}
+
+extension SKReceiptRefreshRequest: SKRequestPublishing {
+    var publisher: SKRequestPublisher<SKRefreshRequestSubscription> {
+        return .init(request: self)
+    }
+}