Add ResultOperation

2 files changed, 82 insertions, 1 deletions

diff --git a/ios/MullvadVPN.xcodeproj/project.pbxproj b/ios/MullvadVPN.xcodeproj/project.pbxproj
index 266f67eafe..65cf355107 100644
--- a/ios/MullvadVPN.xcodeproj/project.pbxproj
+++ b/ios/MullvadVPN.xcodeproj/project.pbxproj
@@ -273,6 +273,7 @@
 		58F559102697002100F630D0 /* HeaderBar.strings in Resources */ = {isa = PBXBuildFile; fileRef = 58F559092697002100F630D0 /* HeaderBar.strings */; };
 		58F61F4F2692F21C00DCFC2B /* WireguardKeys.strings in Resources */ = {isa = PBXBuildFile; fileRef = 58F61F4D2692F21C00DCFC2B /* WireguardKeys.strings */; };
 		58F7CA882692E34000FC59FD /* WireguardKeysContentView.swift in Sources */ = {isa = PBXBuildFile; fileRef = 58F7CA872692E34000FC59FD /* WireguardKeysContentView.swift */; };
+		58F7D26527EB50A300E4D821 /* ResultOperation.swift in Sources */ = {isa = PBXBuildFile; fileRef = 58F7D26427EB50A300E4D821 /* ResultOperation.swift */; };
 		58F840B22464491D0044E708 /* ChainedError.swift in Sources */ = {isa = PBXBuildFile; fileRef = 58F840B12464491D0044E708 /* ChainedError.swift */; };
 		58F840B32464491D0044E708 /* ChainedError.swift in Sources */ = {isa = PBXBuildFile; fileRef = 58F840B12464491D0044E708 /* ChainedError.swift */; };
 		58F8AC0E25D3F8CE002BE0ED /* ProblemReportReviewViewController.swift in Sources */ = {isa = PBXBuildFile; fileRef = 58F8AC0D25D3F8CE002BE0ED /* ProblemReportReviewViewController.swift */; };
@@ -548,6 +549,7 @@
 		58F5590A2697002100F630D0 /* en */ = {isa = PBXFileReference; lastKnownFileType = text.plist.strings; name = en; path = en.lproj/HeaderBar.strings; sourceTree = "<group>"; };
 		58F61F4E2692F21C00DCFC2B /* en */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = text.plist.strings; name = en; path = en.lproj/WireguardKeys.strings; sourceTree = "<group>"; };
 		58F7CA872692E34000FC59FD /* WireguardKeysContentView.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = WireguardKeysContentView.swift; sourceTree = "<group>"; };
+		58F7D26427EB50A300E4D821 /* ResultOperation.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = ResultOperation.swift; sourceTree = "<group>"; };
 		58F840B12464491D0044E708 /* ChainedError.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = ChainedError.swift; sourceTree = "<group>"; };
 		58F8AC0D25D3F8CE002BE0ED /* ProblemReportReviewViewController.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = ProblemReportReviewViewController.swift; sourceTree = "<group>"; };
 		58FAEDEB245059F000CB0F5B /* KeychainAttributes.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = KeychainAttributes.swift; sourceTree = "<group>"; };
@@ -632,9 +634,10 @@
 				580EE22324B3243100F9D8A1 /* AsyncBlockOperation.swift */,
 				58E973DD24850EB600096F90 /* AsyncOperation.swift */,
 				580EE20524B3222200F9D8A1 /* ExclusivityController.swift */,
+				5840BE34279EDB16002836BA /* OperationCompletion.swift */,
 				5820675D26E6839900655B05 /* PresentAlertOperation.swift */,
 				5846226426E0D9630035F7C2 /* ProductsRequestOperation.swift */,
-				5840BE34279EDB16002836BA /* OperationCompletion.swift */,
+				58F7D26427EB50A300E4D821 /* ResultOperation.swift */,
 			);
 			path = Operations;
 			sourceTree = "<group>";
@@ -1290,6 +1293,7 @@
 				585DA87D26B0254000B8C587 /* RelayCacheIO.swift in Sources */,
 				582AD44027BE616E002A6BFC /* CodingErrors+ChainedError.swift in Sources */,
 				58F2E148276A307400A79513 /* MapConnectionStatusOperation.swift in Sources */,
+				58F7D26527EB50A300E4D821 /* ResultOperation.swift in Sources */,
 				58BA693123EADA6A009DC256 /* SimulatorTunnelProvider.swift in Sources */,
 				58F1311327E09B00007AC5BC /* Cancellable.swift in Sources */,
 				587C575326D2615F005EF767 /* PacketTunnelOptions.swift in Sources */,
diff --git a/ios/MullvadVPN/Operations/ResultOperation.swift b/ios/MullvadVPN/Operations/ResultOperation.swift
new file mode 100644
index 0000000000..ba2cd59c4e
--- /dev/null
+++ b/ios/MullvadVPN/Operations/ResultOperation.swift
@@ -0,0 +1,77 @@
+//
+//  ResultOperation.swift
+//  MullvadVPN
+//
+//  Created by pronebird on 23/03/2022.
+//  Copyright © 2022 Mullvad VPN AB. All rights reserved.
+//
+
+import Foundation
+
+/// Base class for operations producing result.
+class ResultOperation<Success, Failure: Error>: AsyncOperation {
+    typealias Completion = OperationCompletion<Success, Failure>
+    typealias CompletionHandler = (Completion) -> Void
+
+    private let stateLock = NSLock()
+    private var completionValue: Completion?
+    private let completionQueue: DispatchQueue?
+    private var completionHandler: CompletionHandler?
+
+    var completion: Completion? {
+        stateLock.lock()
+        defer { stateLock.unlock() }
+        return completionValue
+    }
+
+    init(completionQueue: DispatchQueue?, completionHandler: CompletionHandler?) {
+        self.completionQueue = completionQueue
+        self.completionHandler = completionHandler
+
+        super.init()
+    }
+
+    override func finish() {
+        // Propagate cancellation if finish() is called directly from start().
+        if isCancelled {
+            finish(completion: .cancelled)
+        } else {
+            preconditionFailure("Use finish(completion:) to finish operation.")
+        }
+    }
+
+    func finish(completion: Completion) {
+        stateLock.lock()
+
+        // Bail if operation is already finishing.
+        guard completionValue == nil else {
+            stateLock.unlock()
+            return
+        }
+
+        // Store completion value.
+        completionValue = completion
+
+        // Copy completion handler.
+        let completionHandler: CompletionHandler? = self.completionHandler
+
+        // Unset completion handler.
+        self.completionHandler = nil
+
+        stateLock.unlock()
+
+        let block = {
+            // Call completion handler.
+            completionHandler?(completion)
+
+            // Finish operation.
+            super.finish()
+        }
+
+        if let completionQueue = completionQueue {
+            completionQueue.async(execute: block)
+        } else {
+            block()
+        }
+    }
+}