New queue playback solution

lib/just_audio_media_kit.dart

@@ -1,4 +1,4 @@
-/// package:media_kit bindings for just_audio to support Linux and Windows.
+/// `package:media_kit` bindings for `just_audio` to support Linux and Windows.
 library just_audio_media_kit;
 
 import 'dart:collection';
@@ -11,12 +11,12 @@ import 'package:media_kit/media_kit.dart';
 import 'package:universal_platform/universal_platform.dart';
 
 class JustAudioMediaKit extends JustAudioPlatform {
-  JustAudioMediaKit();
+  static final _logger = Logger('JustAudioMediaKit');
 
-  /// The internal MPV player's logLevel
+  /// The internal MPV player's logLevel.
   static MPVLogLevel mpvLogLevel = MPVLogLevel.error;
 
-  /// Sets the demuxer's cache size (in bytes)
+  /// Sets the demuxer's cache size (in bytes).
   static int bufferSize = 32 * 1024 * 1024;
 
   /// Sets the name of the underlying window & process for native backend. This is visible inside the Windows' volume mixer.
@@ -40,15 +40,22 @@ class JustAudioMediaKit extends JustAudioPlatform {
   /// This uses `scaletempo` under the hood & disables `audio-pitch-correction`.
   static bool pitch = true;
 
-  /// Enables gapless playback via the [`--prefetch-playlist`](https://mpv.io/manual/stable/#options-prefetch-playlist) in libmpv
+  /// Enables gapless playback via the [`--prefetch-playlist`](https://mpv.io/manual/stable/#options-prefetch-playlist) in libmpv.
   ///
   /// This is highly experimental. Use at your own risk.
   ///
   /// Check [mpv's docs](https://mpv.io/manual/stable/#options-prefetch-playlist) and
-  /// [the related issue](https://github.com/Pato05/just_audio_media_kit/issues/11) for more information
+  /// [the related issue](https://github.com/Pato05/just_audio_media_kit/issues/11) for more information.
+  ///
+  /// [prefetchPlaylistSize] can be changed to set the amount of items to prefetch.
   static bool prefetchPlaylist = false;
 
-  static final _logger = Logger('JustAudioMediaKit');
+  /// Max amount of items to prefetch in the playlist.
+  ///
+  /// Does nothing, if [prefetchPlaylist] is set to false. Default is 2.
+  /// It is not recommended to change this, because libmpv doesn't prefetch more than 2 items.
+  static int prefetchPlaylistSize = 2;
+
   final _players = HashMap<String, MediaKitPlayer>();
 
   /// Players that are disposing (player id -> future that completes when the player is disposed)
@@ -57,7 +64,7 @@ class JustAudioMediaKit extends JustAudioPlatform {
   /// Initializes the plugin if the platform we're running on is marked
   /// as true, otherwise it will leave everything unchanged.
   ///
-  /// Can also be safely called from Web, even though it'll have no effect
+  /// Can also be safely called from Web, even though it'll have no effect.
   static void ensureInitialized({
     bool linux = true,
     bool windows = true,
@@ -69,14 +76,14 @@ class JustAudioMediaKit extends JustAudioPlatform {
     /// The name of the library is generally `libmpv.so` on GNU/Linux and `libmpv-2.dll` on Windows.
     String? libmpv,
   }) {
-    if ((UniversalPlatform.isLinux && linux) ||
+    if (!((UniversalPlatform.isLinux && linux) ||
         (UniversalPlatform.isWindows && windows) ||
         (UniversalPlatform.isAndroid && android) ||
         (UniversalPlatform.isIOS && iOS) ||
-        (UniversalPlatform.isMacOS && macOS)) {
-      registerWith();
-      MediaKit.ensureInitialized(libmpv: libmpv);
-    }
+        (UniversalPlatform.isMacOS && macOS))) return;
+
+    registerWith();
+    MediaKit.ensureInitialized(libmpv: libmpv);
   }
 
   /// Registers the plugin with [JustAudioPlatform]
@@ -88,32 +95,37 @@ class JustAudioMediaKit extends JustAudioPlatform {
   Future<AudioPlayerPlatform> init(InitRequest request) async {
     if (_players.containsKey(request.id)) {
       throw PlatformException(
-          code: 'error', message: 'Player ${request.id} already exists!');
+        code: 'error',
+        message: 'Player ${request.id} already exists!',
+      );
     }
 
     _logger.fine('instantiating new player ${request.id}');
     final player = MediaKitPlayer(request.id);
     _players[request.id] = player;
     await player.ready();
     _logger.fine('player ready! (players: $_players)');
+
     return player;
   }
 
   @override
-  Future<DisposePlayerResponse> disposePlayer(
-      DisposePlayerRequest request) async {
+  Future<DisposePlayerResponse> disposePlayer(request) async {
     _logger.fine('disposing player ${request.id}');
 
     // temporary workaround because disposePlayer is called more than once
     if (_disposingPlayers.containsKey(request.id)) {
       _logger.fine('disposePlayer() called more than once!');
       await _disposingPlayers[request.id]!;
+
       return DisposePlayerResponse();
     }
 
     if (!_players.containsKey(request.id)) {
       throw PlatformException(
-          code: 'error', message: 'Player ${request.id} doesn\'t exist.');
+        code: 'error',
+        message: 'Player ${request.id} doesn\'t exist.',
+      );
     }
 
     final future = _players[request.id]!.release();
@@ -123,17 +135,19 @@ class JustAudioMediaKit extends JustAudioPlatform {
     _disposingPlayers.remove(request.id);
 
     _logger.fine('player ${request.id} disposed!');
+
     return DisposePlayerResponse();
   }
 
   @override
-  Future<DisposeAllPlayersResponse> disposeAllPlayers(
-      DisposeAllPlayersRequest request) async {
+  Future<DisposeAllPlayersResponse> disposeAllPlayers(request) async {
     _logger.fine('disposing of all players...');
+
     if (_players.isNotEmpty) {
       await Future.wait(_players.values.map((e) => e.release()));
       _players.clear();
     }
+
     return DisposeAllPlayersResponse();
   }
 }