snapshot

Signed-off-by: Joseph Mattello <mail@joemattiello.com>

SideStoreApp/Sources/SideStoreUIKit/Components/BackgroundTaskManager.swift

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+//
+//  BackgroundTaskManager.swift
+//  AltStore
+//
+//  Created by Riley Testut on 6/19/19.
+//  Copyright © 2019 Riley Testut. All rights reserved.
+//
+
+import AVFoundation
+
+public final class BackgroundTaskManager {
+	public 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() {
+        audioEngine = AVAudioEngine()
+        audioEngine.mainMixerNode.outputVolume = 0.0
+
+        player = AVAudioPlayerNode()
+        audioEngine.attach(player)
+
+        do {
+            let audioFileURL = Bundle.main.url(forResource: "Silence", withExtension: "m4a")!
+
+            audioFile = try AVAudioFile(forReading: audioFileURL)
+            audioEngine.connect(player, to: audioEngine.mainMixerNode, format: audioFile.processingFormat)
+        } catch {
+            fatalError("Error. \(error)")
+        }
+
+        audioEngineQueue = DispatchQueue(label: "com.altstore.BackgroundTaskManager")
+    }
+}
+
+public extension BackgroundTaskManager {
+    func performExtendedBackgroundTask(taskHandler: @escaping ((Result<Void, Error>, @escaping () -> Void) -> Void)) {
+        func finish() {
+            player.stop()
+            audioEngine.stop()
+
+            isPlaying = false
+        }
+
+        audioEngineQueue.sync {
+            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() {
+        player.scheduleFile(audioFile, at: nil) {
+            self.audioEngineQueue.async {
+                guard self.isPlaying else { return }
+                self.scheduleAudioFile()
+            }
+        }
+    }
+}