Refactor AudioPlayer to use an AudioPlayerRateManager protocol for managing rate/defaultRate state management. Implements a LegacyAudioPlayerRateManager implementation with existing (pre-iOS 16) behavior.

ios/App/Shared/player/AudioPlayer.swift

@@ -29,9 +29,7 @@ class AudioPlayer: NSObject {
     internal let logger = AppLogger(category: "AudioPlayer")
 
     private var status: PlayerStatus
-    internal var rate: Float
+    internal var rateManager: AudioPlayerRateManager
-
-    private var tmpRate: Float = 1.0
     
     private var playerContext = 0
     private var playerItemContext = 0
@@ -64,11 +62,13 @@ class AudioPlayer: NSObject {
         self.audioPlayer.automaticallyWaitsToMinimizeStalling = true
         self.sessionId = sessionId
         self.status = .uninitialized
-        self.rate = 0.0
+        self.rateManager = LegacyAudioPlayerRateManager(audioPlayer: self.audioPlayer, defaultRate: playbackRate)
-        self.tmpRate = playbackRate
         
         super.init()
         
+        self.rateManager.rateChangedCompletion = self.updateNowPlaying
+        self.rateManager.defaultRateChangedCompletion = self.setupTimeObservers
+        
         initAudioSession()
         setupRemoteTransportControls()
         
@@ -81,7 +81,6 @@ class AudioPlayer: NSObject {
         
         // Listen to player events
         self.setupAudioSessionNotifications()
-        self.audioPlayer.addObserver(self, forKeyPath: #keyPath(AVPlayer.rate), options: .new, context: &playerContext)
         self.audioPlayer.addObserver(self, forKeyPath: #keyPath(AVPlayer.currentItem), options: .new, context: &playerContext)
         
         for track in playbackSession.audioTracks {
@@ -150,7 +149,6 @@ class AudioPlayer: NSObject {
         }
         
         // Remove observers
-        self.audioPlayer.removeObserver(self, forKeyPath: #keyPath(AVPlayer.rate), context: &playerContext)
         self.audioPlayer.removeObserver(self, forKeyPath: #keyPath(AVPlayer.currentItem), context: &playerContext)
         self.removeTimeObservers()
         
@@ -332,7 +330,7 @@ class AudioPlayer: NSObject {
         self.markAudioSessionAs(active: true)
         DispatchQueue.runOnMainQueue {
             self.audioPlayer.play()
-            self.audioPlayer.rate = self.tmpRate
+            self.rateManager.handlePlayEvent()
         }
         self.status = .playing
 
@@ -424,25 +422,8 @@ class AudioPlayer: NSObject {
         }
     }
     
-    public func setPlaybackRate(_ rate: Float, observed: Bool = false) {
+    public func setPlaybackRate(_ rate: Float) {
-        let playbackSpeedChanged = rate > 0.0 && rate != self.tmpRate && !(observed && rate == 1)
+        self.rateManager.setPlaybackRate(rate)
-        
-        if self.audioPlayer.rate != rate {
-            logger.log("setPlaybakRate rate changed from \(self.audioPlayer.rate) to \(rate)")
-            DispatchQueue.runOnMainQueue {
-                self.audioPlayer.rate = rate
-            }
-        }
-        
-        self.rate = rate
-        self.updateNowPlaying()
-        
-        if playbackSpeedChanged {
-            self.tmpRate = rate
-            
-            // Setup the time observer again at the new rate
-            self.setupTimeObservers()
-        }
     }
     
     public func setChapterTrack() {
@@ -706,24 +687,21 @@ class AudioPlayer: NSObject {
             NowPlayingInfo.shared.update(
                 duration: currentChapter.getRelativeChapterEndTime(),
                 currentTime: currentChapter.getRelativeChapterCurrentTime(sessionCurrentTime: session.currentTime),
-                rate: rate,
+                rate: self.rateManager.rate,
-                defaultRate: tmpRate,
+                defaultRate: self.rateManager.defaultRate,
                 chapterName: currentChapter.title,
                 chapterNumber: (session.chapters.firstIndex(of: currentChapter) ?? 0) + 1,
                 chapterCount: session.chapters.count
             )
         } else if let duration = self.getDuration(), let currentTime = self.getCurrentTime() {
-            NowPlayingInfo.shared.update(duration: duration, currentTime: currentTime, rate: rate, defaultRate: tmpRate)
+            NowPlayingInfo.shared.update(duration: duration, currentTime: currentTime, rate: self.rateManager.rate, defaultRate: self.rateManager.defaultRate)
         }
     }
     
     // MARK: - Observer
     public override func observeValue(forKeyPath keyPath: String?, of object: Any?, change: [NSKeyValueChangeKey : Any]?, context: UnsafeMutableRawPointer?) {
         if context == &playerContext {
-            if keyPath == #keyPath(AVPlayer.rate) {
+            if keyPath == #keyPath(AVPlayer.currentItem) {
-                logger.log("playerContext observer player rate")
-                self.setPlaybackRate(change?[.newKey] as? Float ?? 1.0, observed: true)
-            } else if keyPath == #keyPath(AVPlayer.currentItem) {
                 NotificationCenter.default.post(name: NSNotification.Name(PlayerEvents.update.rawValue), object: nil)
                 logger.log("WARNING: Item ended")
             }

ios/App/Shared/player/AudioPlayerRateManager.swift

@@ -0,0 +1,23 @@
+//
+//  AudioPlayerRateManager.swift
+//  Audiobookshelf
+//
+//  Created by Marke Hallowell on 4/14/24.
+//
+
+import Foundation
+import AVFoundation
+
+protocol AudioPlayerRateManager {
+    var rate: Float { get }
+    var defaultRate: Float { get }
+    var rateChangedCompletion: () -> Void { get set }
+    var defaultRateChangedCompletion: () -> Void { get set }
+    
+    init(audioPlayer: AVPlayer, defaultRate: Float)
+    
+    func setPlaybackRate(_ rate: Float)
+
+    // Callback for play events (e.g. LegacyAudioPlayerRateManager uses this set rate immediately after playback resumes)
+    func handlePlayEvent() -> Void
+}

ios/App/Shared/player/AudioPlayerSleepTimer.swift

@@ -22,7 +22,7 @@ extension AudioPlayer {
         // Return the player time until sleep
         var sleepTimeRemaining: Double? = nil
         if let chapterStopAt = self.sleepTimeChapterStopAt {
-            sleepTimeRemaining = (chapterStopAt - currentTime) / Double(self.rate > 0 ? self.rate : 1.0)
+            sleepTimeRemaining = (chapterStopAt - currentTime) / Double(self.rateManager.rate > 0 ? self.rateManager.rate : 1.0)
         } else if self.isCountdownSleepTimerSet() {
             sleepTimeRemaining = self.sleepTimeRemaining
         }

ios/App/Shared/player/LegacyAudioPlayerRateManager.swift

@@ -0,0 +1,84 @@
+//
+//  LegacyAudioPlayerRateManager.swift
+//  Audiobookshelf
+//
+//  Created by Marke Hallowell on 4/14/24.
+//
+
+import Foundation
+import AVFoundation
+
+class LegacyAudioPlayerRateManager: NSObject, AudioPlayerRateManager {
+    internal let logger = AppLogger(category: "AudioPlayer")
+    
+    internal var audioPlayer: AVPlayer
+    
+    internal var managerContext = 0
+    
+    // MARK: - AudioPlayerRateManager
+    public private(set) var defaultRate: Float
+    public private(set) var rate: Float
+    public var rateChangedCompletion: () -> Void
+    public var defaultRateChangedCompletion: () -> Void
+
+    required init(audioPlayer: AVPlayer, defaultRate: Float) {
+        self.rate = 0.0
+        self.defaultRate = defaultRate
+        self.audioPlayer = audioPlayer
+        self.rateChangedCompletion = {}
+        self.defaultRateChangedCompletion = {}
+        
+        super.init()
+        
+        self.audioPlayer.addObserver(self, forKeyPath: #keyPath(AVPlayer.rate), options: .new, context: &managerContext)
+    }
+    
+    public func setPlaybackRate(_ rate: Float) {
+        self.handlePlaybackRateChange(rate, observed: false)
+    }
+    
+    public func handlePlayEvent() {
+        DispatchQueue.runOnMainQueue {
+            self.audioPlayer.rate = self.defaultRate
+        }
+    }
+
+    // MARK: - Destructor
+    public func destroy() {
+        // Remove Observer
+        self.audioPlayer.removeObserver(self, forKeyPath: #keyPath(AVPlayer.rate), context: &managerContext)
+    }
+    
+    // MARK: - Internal
+    internal func handlePlaybackRateChange(_ rate: Float, observed: Bool = false) {
+        let playbackSpeedChanged = rate > 0.0 && rate != self.defaultRate && !(observed && rate == 1)
+        
+        if self.audioPlayer.rate != rate {
+            logger.log("setPlaybakRate rate changed from \(self.audioPlayer.rate) to \(rate)")
+            DispatchQueue.runOnMainQueue {
+                self.audioPlayer.rate = rate
+            }
+        }
+        
+        self.rate = rate
+        self.rateChangedCompletion()
+        
+        if playbackSpeedChanged {
+            self.defaultRate = rate
+            self.defaultRateChangedCompletion()
+        }
+    }
+    
+    // MARK: - Observer
+    public override func observeValue(forKeyPath keyPath: String?, of object: Any?, change: [NSKeyValueChangeKey : Any]?, context: UnsafeMutableRawPointer?) {
+        if context == &managerContext {
+            if keyPath == #keyPath(AVPlayer.rate) {
+                logger.log("playerContext observer player rate")
+                self.handlePlaybackRateChange(change?[.newKey] as? Float ?? 1.0, observed: true)
+            }
+        } else {
+            super.observeValue(forKeyPath: keyPath, of: object, change: change, context: context)
+            return
+        }
+    }
+}

ios/App/Shared/player/PlayerHandler.swift

@@ -38,7 +38,7 @@ class PlayerHandler {
     public static var paused: Bool {
         get {
             guard let player = player else { return true }
-            return player.rate == 0.0
+            return player.rateManager.rate == 0.0
         }
         set(paused) {
             if paused {