[AltStore] Extends background fetch time until finished refreshing apps

Plays silent audio in background

AltStore/AppDelegate.swift

@@ -91,81 +91,90 @@ extension AppDelegate
             }
         }
         
-        // Wait a few seconds so we have a chance to discover nearby AltServers.
-        DispatchQueue.main.asyncAfter(deadline: .now() + 3.0) {
-            
-            func finish(_ result: Result<[String: Result<InstalledApp, Error>], Error>)
+        BackgroundTaskManager.shared.performExtendedBackgroundTask { (taskResult, taskCompletionHandler) in
+            if let error = taskResult.error
             {
-                ServerManager.shared.stopDiscovering()
+                print("Error starting extended background task.", error)
+            }
+            
+            // Wait a few seconds so we have a chance to discover nearby AltServers.
+            DispatchQueue.main.asyncAfter(deadline: .now() + 3.0) {
                 
-                let content = UNMutableNotificationContent()
-                var shouldPresentAlert = true
-                
-                do
+                func finish(_ result: Result<[String: Result<InstalledApp, Error>], Error>)
                 {
-                    let results = try result.get()
-                    shouldPresentAlert = !results.isEmpty
+                    ServerManager.shared.stopDiscovering()
                     
-                    for (_, result) in results
+                    let content = UNMutableNotificationContent()
+                    var shouldPresentAlert = true
+                    
+                    do
                     {
-                        guard case let .failure(error) = result else { continue }
-                        throw error
+                        let results = try result.get()
+                        shouldPresentAlert = !results.isEmpty
+                        
+                        for (_, result) in results
+                        {
+                            guard case let .failure(error) = result else { continue }
+                            throw error
+                        }
+                        
+                        content.title = NSLocalizedString("Refreshed all apps!", comment: "")
+                    }
+                    catch
+                    {
+                        print("Failed to refresh apps in background.", error)
+                        
+                        content.title = NSLocalizedString("Failed to Refresh Apps", comment: "")
+                        content.body = error.localizedDescription
+                        
+                        shouldPresentAlert = true
                     }
                     
-                    content.title = NSLocalizedString("Refreshed all apps!", comment: "")
-                }
-                catch
-                {
-                    print("Failed to refresh apps in background.", error)
-                    
-                    content.title = NSLocalizedString("Failed to Refresh Apps", comment: "")
-                    content.body = error.localizedDescription
-                    
-                    shouldPresentAlert = true
-                }
-                
-                if shouldPresentAlert
-                {
-                    let trigger = UNTimeIntervalNotificationTrigger(timeInterval: 0.01, repeats: false)
-                    
-                    let request = UNNotificationRequest(identifier: UUID().uuidString, content: content, trigger: trigger)
-                    UNUserNotificationCenter.current().add(request) { (error) in
-                        if let error = error {
-                            print(error)
+                    if shouldPresentAlert
+                    {
+                        let trigger = UNTimeIntervalNotificationTrigger(timeInterval: 0.01, repeats: false)
+                        
+                        let request = UNNotificationRequest(identifier: UUID().uuidString, content: content, trigger: trigger)
+                        UNUserNotificationCenter.current().add(request) { (error) in
+                            if let error = error {
+                                print(error)
+                            }
                         }
                     }
-                }
-                
-                switch result
-                {
-                case .failure(ConnectionError.serverNotFound): completionHandler(.newData)
-                case .failure: completionHandler(.failed)
-                case .success: completionHandler(.newData)
-                }
-            }
-            
-            let group = AppManager.shared.refresh(installedApps, presentingViewController: nil)
-            group.beginInstallationHandler = { (installedApp) in
-                guard installedApp.app.identifier == App.altstoreAppID else { return }
-                
-                // We're starting to install AltStore, which means the app is about to quit.
-                // So, we say we were successful even though we technically don't know 100% yet.
-                // Also since AltServer has already received the app, it can finish installing even if we're no longer running in background.
-                
-                if let error = group.error
-                {
-                    finish(.failure(error))
-                }
-                else
-                {
-                    var results = group.results
-                    results[installedApp.app.identifier] = .success(installedApp)
                     
-                    finish(.success(results))
+                    switch result
+                    {
+                    case .failure(ConnectionError.serverNotFound): completionHandler(.newData)
+                    case .failure: completionHandler(.failed)
+                    case .success: completionHandler(.newData)
+                    }
+                    
+                    taskCompletionHandler()
+                }
+                
+                let group = AppManager.shared.refresh(installedApps, presentingViewController: nil)
+                group.beginInstallationHandler = { (installedApp) in
+                    guard installedApp.app.identifier == App.altstoreAppID else { return }
+                    
+                    // We're starting to install AltStore, which means the app is about to quit.
+                    // So, we say we were successful even though we technically don't know 100% yet.
+                    // Also since AltServer has already received the app, it can finish installing even if we're no longer running in background.
+                    
+                    if let error = group.error
+                    {
+                        finish(.failure(error))
+                    }
+                    else
+                    {
+                        var results = group.results
+                        results[installedApp.app.identifier] = .success(installedApp)
+                        
+                        finish(.success(results))
+                    }
+                }
+                group.completionHandler = { (result) in
+                    finish(result)
                 }
-            }
-            group.completionHandler = { (result) in
-                finish(result)
             }
         }
     }

AltStore/Components/BackgroundTaskManager.swift

@@ -0,0 +1,102 @@
+//
+//  BackgroundTaskManager.swift
+//  AltStore
+//
+//  Created by Riley Testut on 6/19/19.
+//  Copyright © 2019 Riley Testut. All rights reserved.
+//
+
+import AVFoundation
+
+class BackgroundTaskManager
+{
+    static let shared = BackgroundTaskManager()
+    
+    private var isPlaying = false
+    
+    private let audioEngine: AVAudioEngine
+    private let player: AVAudioPlayerNode
+    private let audioFile: AVAudioFile
+    
+    private let audioEngineQueue: DispatchQueue
+    
+    private init()
+    {
+        self.audioEngine = AVAudioEngine()
+        self.audioEngine.mainMixerNode.outputVolume = 0.0
+        
+        self.player = AVAudioPlayerNode()
+        self.audioEngine.attach(self.player)
+        
+        do
+        {
+            let audioFileURL = Bundle.main.url(forResource: "Silence", withExtension: "m4a")!
+            
+            self.audioFile = try AVAudioFile(forReading: audioFileURL)
+            self.audioEngine.connect(self.player, to: self.audioEngine.mainMixerNode, format: self.audioFile.processingFormat)
+        }
+        catch
+        {
+            fatalError("Error. \(error)")
+        }
+        
+        self.audioEngineQueue = DispatchQueue(label: "com.altstore.BackgroundTaskManager")
+    }
+}
+
+extension BackgroundTaskManager
+{
+    func performExtendedBackgroundTask(taskHandler: @escaping ((Result<Void, Error>, @escaping () -> Void) -> Void))
+    {
+        func finish()
+        {
+            self.player.stop()
+            self.audioEngine.stop()
+            
+            self.isPlaying = false
+        }
+        
+        self.audioEngineQueue.async {
+            do
+            {
+                try AVAudioSession.sharedInstance().setCategory(.playback, options: .mixWithOthers)
+                try AVAudioSession.sharedInstance().setActive(true)
+                
+                // Schedule audio file buffers.
+                self.scheduleAudioFile()
+                self.scheduleAudioFile()
+                
+                let outputFormat = self.audioEngine.outputNode.outputFormat(forBus: 0)
+                self.audioEngine.connect(self.audioEngine.mainMixerNode, to: self.audioEngine.outputNode, format: outputFormat)
+                
+                try self.audioEngine.start()
+                self.player.play()
+                
+                self.isPlaying = true
+                
+                taskHandler(.success(())) {
+                    finish()
+                }
+            }
+            catch
+            {
+                taskHandler(.failure(error)) {
+                    finish()
+                }
+            }
+        }
+    }
+}
+
+private extension BackgroundTaskManager
+{
+    func scheduleAudioFile()
+    {
+        self.player.scheduleFile(self.audioFile, at: nil) {
+            self.audioEngineQueue.async {
+                guard self.isPlaying else { return }
+                self.scheduleAudioFile()
+            }
+        }
+    }
+}

AltStore/Info.plist

@@ -43,6 +43,7 @@
 	<true/>
 	<key>UIBackgroundModes</key>
 	<array>
+		<string>audio</string>
 		<string>fetch</string>
 	</array>
 	<key>UILaunchStoryboardName</key>