Patch data-races and minor changes in SyncPlay

8 files changed, 45 insertions, 72 deletions

diff --git a/MediaBrowser.Controller/SyncPlay/GroupStates/AbstractGroupState.cs b/MediaBrowser.Controller/SyncPlay/GroupStates/AbstractGroupState.cs
index bc2e22380..e5da0ef40 100644
--- a/MediaBrowser.Controller/SyncPlay/GroupStates/AbstractGroupState.cs
+++ b/MediaBrowser.Controller/SyncPlay/GroupStates/AbstractGroupState.cs
@@ -68,7 +68,7 @@ namespace MediaBrowser.Controller.SyncPlay.GroupStates
 
             if (playingItemRemoved && !context.PlayQueue.IsItemPlaying())
             {
-                Logger.LogDebug("HandleRequest: {0} in group {1}, play queue is empty.", request.Type, context.GroupId.ToString());
+                Logger.LogDebug("HandleRequest: {RequestType} in group {GroupId}, play queue is empty.", request.Type, context.GroupId.ToString());
 
                 IGroupState idleState = new IdleGroupState(Logger);
                 context.SetState(idleState);
@@ -84,7 +84,7 @@ namespace MediaBrowser.Controller.SyncPlay.GroupStates
 
             if (!result)
             {
-                Logger.LogError("HandleRequest: {0} in group {1}, unable to move item in play queue.", request.Type, context.GroupId.ToString());
+                Logger.LogError("HandleRequest: {RequestType} in group {GroupId}, unable to move item in play queue.", request.Type, context.GroupId.ToString());
                 return;
             }
 
@@ -100,7 +100,7 @@ namespace MediaBrowser.Controller.SyncPlay.GroupStates
 
             if (!result)
             {
-                Logger.LogError("HandleRequest: {0} in group {1}, unable to add items to play queue.", request.Type, context.GroupId.ToString());
+                Logger.LogError("HandleRequest: {RequestType} in group {GroupId}, unable to add items to play queue.", request.Type, context.GroupId.ToString());
                 return;
             }
 
@@ -203,18 +203,14 @@ namespace MediaBrowser.Controller.SyncPlay.GroupStates
         protected void SendGroupStateUpdate(IGroupStateContext context, IGroupPlaybackRequest reason, SessionInfo session, CancellationToken cancellationToken)
         {
             // Notify relevant state change event.
-            var stateUpdate = new GroupStateUpdate()
-            {
-                State = Type,
-                Reason = reason.Type
-            };
+            var stateUpdate = new GroupStateUpdate(Type, reason.Type);
             var update = context.NewSyncPlayGroupUpdate(GroupUpdateType.StateUpdate, stateUpdate);
             context.SendGroupUpdate(session, SyncPlayBroadcastType.AllGroup, update, cancellationToken);
         }
 
         private void UnhandledRequest(IGroupPlaybackRequest request)
         {
-            Logger.LogWarning("HandleRequest: unhandled {0} request for {1} state.", request.Type, Type);
+            Logger.LogWarning("HandleRequest: unhandled {RequestType} request in {StateType} state.", request.Type, Type);
         }
     }
 }
diff --git a/MediaBrowser.Controller/SyncPlay/GroupStates/WaitingGroupState.cs b/MediaBrowser.Controller/SyncPlay/GroupStates/WaitingGroupState.cs
index 78318dd94..e33e711fb 100644
--- a/MediaBrowser.Controller/SyncPlay/GroupStates/WaitingGroupState.cs
+++ b/MediaBrowser.Controller/SyncPlay/GroupStates/WaitingGroupState.cs
@@ -103,7 +103,7 @@ namespace MediaBrowser.Controller.SyncPlay.GroupStates
                     var unpauseRequest = new UnpauseGroupRequest();
                     playingState.HandleRequest(context, Type, unpauseRequest, session, cancellationToken);
 
-                    Logger.LogDebug("SessionLeaving: {0} left the group {1}, notifying others to resume.", session.Id, context.GroupId.ToString());
+                    Logger.LogDebug("SessionLeaving: {SessionId} left group {GroupId}, notifying others to resume.", session.Id, context.GroupId.ToString());
                 }
                 else
                 {
@@ -111,7 +111,7 @@ namespace MediaBrowser.Controller.SyncPlay.GroupStates
                     var pausedState = new PausedGroupState(Logger);
                     context.SetState(pausedState);
 
-                    Logger.LogDebug("SessionLeaving: {0} left the group {1}, returning to previous state.", session.Id, context.GroupId.ToString());
+                    Logger.LogDebug("SessionLeaving: {SessionId} left group {GroupId}, returning to previous state.", session.Id, context.GroupId.ToString());
                 }
             }
         }
@@ -131,7 +131,7 @@ namespace MediaBrowser.Controller.SyncPlay.GroupStates
             var setQueueStatus = context.SetPlayQueue(request.PlayingQueue, request.PlayingItemPosition, request.StartPositionTicks);
             if (!setQueueStatus)
             {
-                Logger.LogError("HandleRequest: {0} in group {1}, unable to set playing queue.", request.Type, context.GroupId.ToString());
+                Logger.LogError("HandleRequest: {RequestType} in group {GroupId}, unable to set playing queue.", request.Type, context.GroupId.ToString());
 
                 // Ignore request and return to previous state.
                 IGroupState newState = prevState switch {
@@ -151,7 +151,7 @@ namespace MediaBrowser.Controller.SyncPlay.GroupStates
             // Reset status of sessions and await for all Ready events.
             context.SetAllBuffering(true);
 
-            Logger.LogDebug("HandleRequest: {0} in group {1}, {2} set a new play queue.", request.Type, context.GroupId.ToString(), session.Id);
+            Logger.LogDebug("HandleRequest: {RequestType} in group {GroupId}, {SessionId} set a new play queue.", request.Type, context.GroupId.ToString(), session.Id);
         }
 
         /// <inheritdoc />
@@ -188,7 +188,7 @@ namespace MediaBrowser.Controller.SyncPlay.GroupStates
 
                 context.SetState(newState);
 
-                Logger.LogDebug("HandleRequest: {0} in group {1}, unable to change current playing item.", request.Type, context.GroupId.ToString());
+                Logger.LogDebug("HandleRequest: {RequestType} in group {GroupId}, unable to change current playing item.", request.Type, context.GroupId.ToString());
             }
         }
 
@@ -214,13 +214,13 @@ namespace MediaBrowser.Controller.SyncPlay.GroupStates
                 // Reset status of sessions and await for all Ready events.
                 context.SetAllBuffering(true);
 
-                Logger.LogDebug("HandleRequest: {0} in group {1}, waiting for all ready events.", request.Type, context.GroupId.ToString());
+                Logger.LogDebug("HandleRequest: {RequestType} in group {GroupId}, waiting for all ready events.", request.Type, context.GroupId.ToString());
             }
             else
             {
                 if (ResumePlaying)
                 {
-                    Logger.LogDebug("HandleRequest: {0} in group {1}, ignoring sessions that are not ready and forcing the playback to start.", request.Type, context.GroupId.ToString());
+                    Logger.LogDebug("HandleRequest: {RequestType} in group {GroupId}, ignoring sessions that are not ready and forcing the playback to start.", request.Type, context.GroupId.ToString());
 
                     // An Unpause request is forcing the playback to start, ignoring sessions that are not ready.
                     context.SetAllBuffering(false);
@@ -326,7 +326,7 @@ namespace MediaBrowser.Controller.SyncPlay.GroupStates
             // Make sure the client is playing the correct item.
             if (!request.PlaylistItemId.Equals(context.PlayQueue.GetPlayingItemPlaylistId(), StringComparison.OrdinalIgnoreCase))
             {
-                Logger.LogDebug("HandleRequest: {0} in group {1}, {2} has wrong playlist item.", request.Type, context.GroupId.ToString(), session.Id);
+                Logger.LogDebug("HandleRequest: {RequestType} in group {GroupId}, {SessionId} has wrong playlist item.", request.Type, context.GroupId.ToString(), session.Id);
 
                 var playQueueUpdate = context.GetPlayQueueUpdate(PlayQueueUpdateReason.SetCurrentItem);
                 var updateSession = context.NewSyncPlayGroupUpdate(GroupUpdateType.PlayQueue, playQueueUpdate);
@@ -400,7 +400,7 @@ namespace MediaBrowser.Controller.SyncPlay.GroupStates
             // Make sure the client is playing the correct item.
             if (!request.PlaylistItemId.Equals(context.PlayQueue.GetPlayingItemPlaylistId(), StringComparison.OrdinalIgnoreCase))
             {
-                Logger.LogDebug("HandleRequest: {0} in group {1}, {2} has wrong playlist item.", request.Type, context.GroupId.ToString(), session.Id);
+                Logger.LogDebug("HandleRequest: {RequestType} in group {GroupId}, {SessionId} has wrong playlist item.", request.Type, context.GroupId.ToString(), session.Id);
 
                 var playQueueUpdate = context.GetPlayQueueUpdate(PlayQueueUpdateReason.SetCurrentItem);
                 var update = context.NewSyncPlayGroupUpdate(GroupUpdateType.PlayQueue, playQueueUpdate);
@@ -420,7 +420,7 @@ namespace MediaBrowser.Controller.SyncPlay.GroupStates
             var timeSyncThresholdTicks = TimeSpan.FromMilliseconds(context.TimeSyncOffset).Ticks;
             if (Math.Abs(elapsedTime.Ticks) > timeSyncThresholdTicks)
             {
-                Logger.LogWarning("HandleRequest: {0} in group {1}, {2} is not time syncing properly. Ignoring elapsed time.", request.Type, context.GroupId.ToString(), session.Id);
+                Logger.LogWarning("HandleRequest: {RequestType} in group {GroupId}, {SessionId} is not time syncing properly. Ignoring elapsed time.", request.Type, context.GroupId.ToString(), session.Id);
 
                 elapsedTime = TimeSpan.Zero;
             }
@@ -436,7 +436,7 @@ namespace MediaBrowser.Controller.SyncPlay.GroupStates
             var delayTicks = context.PositionTicks - clientPosition.Ticks;
             var maxPlaybackOffsetTicks = TimeSpan.FromMilliseconds(context.MaxPlaybackOffset).Ticks;
 
-            Logger.LogDebug("HandleRequest: {0} in group {1}, {2} at {3} (delay of {4} seconds).", request.Type, context.GroupId.ToString(), session.Id, clientPosition, TimeSpan.FromTicks(delayTicks).TotalSeconds);
+            Logger.LogDebug("HandleRequest: {RequestType} in group {GroupId}, {SessionId} at {PositionTicks} (delay of {Delay} seconds).", request.Type, context.GroupId.ToString(), session.Id, clientPosition, TimeSpan.FromTicks(delayTicks).TotalSeconds);
 
             if (ResumePlaying)
             {
@@ -454,7 +454,7 @@ namespace MediaBrowser.Controller.SyncPlay.GroupStates
                     // Notify relevant state change event.
                     SendGroupStateUpdate(context, request, session, cancellationToken);
 
-                    Logger.LogWarning("HandleRequest: {0} in group {1}, {2} got lost in time, correcting.", request.Type, context.GroupId.ToString(), session.Id);
+                    Logger.LogWarning("HandleRequest: {RequestType} in group {GroupId}, {SessionId} got lost in time, correcting.", request.Type, context.GroupId.ToString(), session.Id);
                     return;
                 }
 
@@ -468,7 +468,7 @@ namespace MediaBrowser.Controller.SyncPlay.GroupStates
                     command.When = currentTime.AddTicks(delayTicks);
                     context.SendCommand(session, SyncPlayBroadcastType.CurrentSession, command, cancellationToken);
 
-                    Logger.LogInformation("HandleRequest: {0} in group {1}, others still buffering, {2} will pause when ready in {3} seconds.", request.Type, context.GroupId.ToString(), session.Id, TimeSpan.FromTicks(delayTicks).TotalSeconds);
+                    Logger.LogInformation("HandleRequest: {RequestType} in group {GroupId}, others still buffering, {SessionId} will pause when ready in {Delay} seconds.", request.Type, context.GroupId.ToString(), session.Id, TimeSpan.FromTicks(delayTicks).TotalSeconds);
                 }
                 else
                 {
@@ -487,7 +487,7 @@ namespace MediaBrowser.Controller.SyncPlay.GroupStates
 
                         context.SendCommand(session, filter, command, cancellationToken);
 
-                        Logger.LogInformation("HandleRequest: {0} in group {1}, {2} is recovering, notifying others to resume in {3} seconds.", request.Type, context.GroupId.ToString(), session.Id, TimeSpan.FromTicks(delayTicks).TotalSeconds);
+                        Logger.LogInformation("HandleRequest: {RequestType} in group {GroupId}, {SessionId} is recovering, notifying others to resume in {Delay} seconds.", request.Type, context.GroupId.ToString(), session.Id, TimeSpan.FromTicks(delayTicks).TotalSeconds);
                     }
                     else
                     {
@@ -500,7 +500,7 @@ namespace MediaBrowser.Controller.SyncPlay.GroupStates
                         var command = context.NewSyncPlayCommand(SendCommandType.Unpause);
                         context.SendCommand(session, SyncPlayBroadcastType.AllGroup, command, cancellationToken);
 
-                        Logger.LogWarning("HandleRequest: {0} in group {1}, {2} resumed playback but did not update others in time. {3} seconds to recover.", request.Type, context.GroupId.ToString(), session.Id, TimeSpan.FromTicks(delayTicks).TotalSeconds);
+                        Logger.LogWarning("HandleRequest: {RequestType} in group {GroupId}, {SessionId} resumed playback but did not update others in time. {Delay} seconds to recover.", request.Type, context.GroupId.ToString(), session.Id, TimeSpan.FromTicks(delayTicks).TotalSeconds);
                     }
 
                     // Change state.
@@ -511,7 +511,7 @@ namespace MediaBrowser.Controller.SyncPlay.GroupStates
             }
             else
             {
-                // Check that session is really ready, tollerate player imperfections under a certain threshold.
+                // Check that session is really ready, tolerate player imperfections under a certain threshold.
                 if (Math.Abs(context.PositionTicks - requestTicks) > maxPlaybackOffsetTicks)
                 {
                     // Session still not ready.
@@ -523,7 +523,7 @@ namespace MediaBrowser.Controller.SyncPlay.GroupStates
                     // Notify relevant state change event.
                     SendGroupStateUpdate(context, request, session, cancellationToken);
 
-                    Logger.LogWarning("HandleRequest: {0} in group {1}, {2} was seeking to wrong position, correcting.", request.Type, context.GroupId.ToString(), session.Id);
+                    Logger.LogWarning("HandleRequest: {RequestType} in group {GroupId}, {SessionId} is seeking to wrong position, correcting.", request.Type, context.GroupId.ToString(), session.Id);
                     return;
                 }
                 else
@@ -549,7 +549,7 @@ namespace MediaBrowser.Controller.SyncPlay.GroupStates
                         pausedState.HandleRequest(context, Type, request, session, cancellationToken);
                     }
 
-                    Logger.LogDebug("HandleRequest: {0} in group {1}, {2} is ready, returning to previous state.", request.Type, context.GroupId.ToString(), session.Id);
+                    Logger.LogDebug("HandleRequest: {RequestType} in group {GroupId}, {SessionId} is ready, returning to previous state.", request.Type, context.GroupId.ToString(), session.Id);
                 }
             }
         }
@@ -569,7 +569,7 @@ namespace MediaBrowser.Controller.SyncPlay.GroupStates
             // Make sure the client knows the playing item, to avoid duplicate requests.
             if (!request.PlaylistItemId.Equals(context.PlayQueue.GetPlayingItemPlaylistId(), StringComparison.OrdinalIgnoreCase))
             {
-                Logger.LogDebug("HandleRequest: {0} in group {1}, client provided the wrong playlist identifier.", request.Type, context.GroupId.ToString());
+                Logger.LogDebug("HandleRequest: {RequestType} in group {GroupId}, {SessionId} provided the wrong playlist identifier.", request.Type, context.GroupId.ToString(), session.Id);
                 return;
             }
 
@@ -596,7 +596,7 @@ namespace MediaBrowser.Controller.SyncPlay.GroupStates
 
                 context.SetState(newState);
 
-                Logger.LogDebug("HandleRequest: {0} in group {1}, no next track available.", request.Type, context.GroupId.ToString());
+                Logger.LogDebug("HandleRequest: {RequestType} in group {GroupId}, no next track available.", request.Type, context.GroupId.ToString());
             }
         }
 
@@ -615,7 +615,7 @@ namespace MediaBrowser.Controller.SyncPlay.GroupStates
             // Make sure the client knows the playing item, to avoid duplicate requests.
             if (!request.PlaylistItemId.Equals(context.PlayQueue.GetPlayingItemPlaylistId(), StringComparison.OrdinalIgnoreCase))
             {
-                Logger.LogDebug("HandleRequest: {0} in group {1}, client provided the wrong playlist identifier.", request.Type, context.GroupId.ToString());
+                Logger.LogDebug("HandleRequest: {RequestType} in group {GroupId}, {SessionId} provided the wrong playlist identifier.", request.Type, context.GroupId.ToString(), session.Id);
                 return;
             }
 
@@ -642,7 +642,7 @@ namespace MediaBrowser.Controller.SyncPlay.GroupStates
 
                 context.SetState(newState);
 
-                Logger.LogDebug("HandleRequest: {0} in group {1}, no previous track available.", request.Type, context.GroupId.ToString());
+                Logger.LogDebug("HandleRequest: {RequestType} in group {GroupId}, no previous track available.", request.Type, context.GroupId.ToString());
             }
         }
 
@@ -653,7 +653,7 @@ namespace MediaBrowser.Controller.SyncPlay.GroupStates
 
             if (!context.IsBuffering())
             {
-                Logger.LogDebug("HandleRequest: {0} in group {1}, returning to previous state.", request.Type, context.GroupId.ToString());
+                Logger.LogDebug("HandleRequest: {RequestType} in group {GroupId}, returning to previous state.", request.Type, context.GroupId.ToString());
 
                 if (ResumePlaying)
                 {
diff --git a/MediaBrowser.Controller/SyncPlay/IGroupStateContext.cs b/MediaBrowser.Controller/SyncPlay/IGroupStateContext.cs
index 3609be36b..13f1b2316 100644
--- a/MediaBrowser.Controller/SyncPlay/IGroupStateContext.cs
+++ b/MediaBrowser.Controller/SyncPlay/IGroupStateContext.cs
@@ -151,7 +151,7 @@ namespace MediaBrowser.Controller.SyncPlay
         /// <param name="playingItemPosition">The playing item position in the play queue.</param>
         /// <param name="startPositionTicks">The start position ticks.</param>
         /// <returns><c>true</c> if the play queue has been changed; <c>false</c> if something went wrong.</returns>
-        bool SetPlayQueue(IEnumerable<Guid> playQueue, int playingItemPosition, long startPositionTicks);
+        bool SetPlayQueue(IReadOnlyList<Guid> playQueue, int playingItemPosition, long startPositionTicks);
 
         /// <summary>
         /// Sets the playing item.
@@ -165,7 +165,7 @@ namespace MediaBrowser.Controller.SyncPlay
         /// </summary>
         /// <param name="playlistItemIds">The items to remove.</param>
         /// <returns><c>true</c> if playing item got removed; <c>false</c> otherwise.</returns>
-        bool RemoveFromPlayQueue(IEnumerable<string> playlistItemIds);
+        bool RemoveFromPlayQueue(IReadOnlyList<string> playlistItemIds);
 
         /// <summary>
         /// Moves an item in the play queue.
@@ -181,7 +181,7 @@ namespace MediaBrowser.Controller.SyncPlay
         /// <param name="newItems">The new items to add to the play queue.</param>
         /// <param name="mode">The mode with which the items will be added.</param>
         /// <returns><c>true</c> if the play queue has been changed; <c>false</c> if something went wrong.</returns>
-        bool AddToPlayQueue(IEnumerable<Guid> newItems, GroupQueueMode mode);
+        bool AddToPlayQueue(IReadOnlyList<Guid> newItems, GroupQueueMode mode);
 
         /// <summary>
         /// Restarts current item in play queue.
diff --git a/MediaBrowser.Controller/SyncPlay/ISyncPlayManager.cs b/MediaBrowser.Controller/SyncPlay/ISyncPlayManager.cs
index 65146d4ae..a98001682 100644
--- a/MediaBrowser.Controller/SyncPlay/ISyncPlayManager.cs
+++ b/MediaBrowser.Controller/SyncPlay/ISyncPlayManager.cs
@@ -49,21 +49,5 @@ namespace MediaBrowser.Controller.SyncPlay
         /// <param name="request">The request.</param>
         /// <param name="cancellationToken">The cancellation token.</param>
         void HandleRequest(SessionInfo session, IGroupPlaybackRequest request, CancellationToken cancellationToken);
-
-        /// <summary>
-        /// Maps a session to a group.
-        /// </summary>
-        /// <param name="session">The session.</param>
-        /// <param name="group">The group.</param>
-        /// <exception cref="InvalidOperationException">Thrown when the user is in another group already.</exception>
-        void AddSessionToGroup(SessionInfo session, IGroupController group);
-
-        /// <summary>
-        /// Unmaps a session from a group.
-        /// </summary>
-        /// <param name="session">The session.</param>
-        /// <param name="group">The group.</param>
-        /// <exception cref="InvalidOperationException">Thrown when the user is not found in the specified group.</exception>
-        void RemoveSessionFromGroup(SessionInfo session, IGroupController group);
     }
 }
diff --git a/MediaBrowser.Controller/SyncPlay/PlaybackRequests/PlayGroupRequest.cs b/MediaBrowser.Controller/SyncPlay/PlaybackRequests/PlayGroupRequest.cs
index 306c161ed..7d27f6151 100644
--- a/MediaBrowser.Controller/SyncPlay/PlaybackRequests/PlayGroupRequest.cs
+++ b/MediaBrowser.Controller/SyncPlay/PlaybackRequests/PlayGroupRequest.cs
@@ -19,9 +19,7 @@ namespace MediaBrowser.Controller.SyncPlay.PlaybackRequests
         /// <param name="startPositionTicks">The start position ticks.</param>
         public PlayGroupRequest(Guid[] playingQueue, int playingItemPosition, long startPositionTicks)
         {
-            var list = new List<Guid>();
-            list.AddRange(playingQueue);
-            PlayingQueue = list;
+            PlayingQueue = playingQueue ?? Array.Empty<Guid>();
             PlayingItemPosition = playingItemPosition;
             StartPositionTicks = startPositionTicks;
         }
diff --git a/MediaBrowser.Controller/SyncPlay/PlaybackRequests/QueueGroupRequest.cs b/MediaBrowser.Controller/SyncPlay/PlaybackRequests/QueueGroupRequest.cs
index 9580b5315..106daecc8 100644
--- a/MediaBrowser.Controller/SyncPlay/PlaybackRequests/QueueGroupRequest.cs
+++ b/MediaBrowser.Controller/SyncPlay/PlaybackRequests/QueueGroupRequest.cs
@@ -18,9 +18,7 @@ namespace MediaBrowser.Controller.SyncPlay.PlaybackRequests
         /// <param name="mode">The enqueue mode.</param>
         public QueueGroupRequest(Guid[] items, GroupQueueMode mode)
         {
-            var list = new List<Guid>();
-            list.AddRange(items);
-            ItemIds = list;
+            ItemIds = items ?? Array.Empty<Guid>();
             Mode = mode;
         }
 
diff --git a/MediaBrowser.Controller/SyncPlay/PlaybackRequests/RemoveFromPlaylistGroupRequest.cs b/MediaBrowser.Controller/SyncPlay/PlaybackRequests/RemoveFromPlaylistGroupRequest.cs
index 21c602846..1e892d819 100644
--- a/MediaBrowser.Controller/SyncPlay/PlaybackRequests/RemoveFromPlaylistGroupRequest.cs
+++ b/MediaBrowser.Controller/SyncPlay/PlaybackRequests/RemoveFromPlaylistGroupRequest.cs
@@ -1,3 +1,4 @@
+using System;
 using System.Collections.Generic;
 using System.Threading;
 using MediaBrowser.Controller.Session;
@@ -16,9 +17,7 @@ namespace MediaBrowser.Controller.SyncPlay.PlaybackRequests
         /// <param name="items">The playlist ids of the items to remove.</param>
         public RemoveFromPlaylistGroupRequest(string[] items)
         {
-            var list = new List<string>();
-            list.AddRange(items);
-            PlaylistItemIds = list;
+            PlaylistItemIds = items ?? Array.Empty<string>();
         }
 
         /// <summary>
diff --git a/MediaBrowser.Controller/SyncPlay/Queue/PlayQueueManager.cs b/MediaBrowser.Controller/SyncPlay/Queue/PlayQueueManager.cs
index 2d1d1533b..73457f447 100644
--- a/MediaBrowser.Controller/SyncPlay/Queue/PlayQueueManager.cs
+++ b/MediaBrowser.Controller/SyncPlay/Queue/PlayQueueManager.cs
@@ -94,7 +94,7 @@ namespace MediaBrowser.Controller.SyncPlay.Queue
         /// Sets a new playlist. Playing item is reset.
         /// </summary>
         /// <param name="items">The new items of the playlist.</param>
-        public void SetPlaylist(IEnumerable<Guid> items)
+        public void SetPlaylist(IReadOnlyList<Guid> items)
         {
             SortedPlaylist.Clear();
             ShuffledPlaylist.Clear();
@@ -114,7 +114,7 @@ namespace MediaBrowser.Controller.SyncPlay.Queue
         /// Appends new items to the playlist. The specified order is mantained.
         /// </summary>
         /// <param name="items">The items to add to the playlist.</param>
-        public void Queue(IEnumerable<Guid> items)
+        public void Queue(IReadOnlyList<Guid> items)
         {
             var newItems = CreateQueueItemsFromArray(items);
 
@@ -209,7 +209,7 @@ namespace MediaBrowser.Controller.SyncPlay.Queue
         /// Adds new items to the playlist right after the playing item. The specified order is mantained.
         /// </summary>
         /// <param name="items">The items to add to the playlist.</param>
-        public void QueueNext(IEnumerable<Guid> items)
+        public void QueueNext(IReadOnlyList<Guid> items)
         {
             var newItems = CreateQueueItemsFromArray(items);
 
@@ -312,13 +312,12 @@ namespace MediaBrowser.Controller.SyncPlay.Queue
         /// </summary>
         /// <param name="playlistItemIds">The items to remove.</param>
         /// <returns><c>true</c> if playing item got removed; <c>false</c> otherwise.</returns>
-        public bool RemoveFromPlaylist(IEnumerable<string> playlistItemIds)
+        public bool RemoveFromPlaylist(IReadOnlyList<string> playlistItemIds)
         {
             var playingItem = GetPlayingItem();
-            var playlistItemIdsList = playlistItemIds.ToList();
 
-            SortedPlaylist.RemoveAll(item => playlistItemIdsList.Contains(item.PlaylistItemId));
-            ShuffledPlaylist.RemoveAll(item => playlistItemIdsList.Contains(item.PlaylistItemId));
+            SortedPlaylist.RemoveAll(item => playlistItemIds.Contains(item.PlaylistItemId));
+            ShuffledPlaylist.RemoveAll(item => playlistItemIds.Contains(item.PlaylistItemId));
 
             LastChange = DateTime.UtcNow;
 
@@ -369,8 +368,7 @@ namespace MediaBrowser.Controller.SyncPlay.Queue
 
             var queueItem = playlist[oldIndex];
             playlist.RemoveAt(oldIndex);
-            newIndex = Math.Min(newIndex, playlist.Count);
-            newIndex = Math.Max(newIndex, 0);
+            newIndex = Math.Clamp(newIndex, 0, playlist.Count);
             playlist.Insert(newIndex, queueItem);
 
             LastChange = DateTime.UtcNow;
@@ -489,7 +487,7 @@ namespace MediaBrowser.Controller.SyncPlay.Queue
                 }
                 else
                 {
-                    PlayingItemIndex--;
+                    PlayingItemIndex = SortedPlaylist.Count - 1;
                     return false;
                 }
             }
@@ -519,7 +517,7 @@ namespace MediaBrowser.Controller.SyncPlay.Queue
                 }
                 else
                 {
-                    PlayingItemIndex++;
+                    PlayingItemIndex = 0;
                     return false;
                 }
             }
@@ -558,7 +556,7 @@ namespace MediaBrowser.Controller.SyncPlay.Queue
         /// Creates a list from the array of items. Each item is given an unique playlist identifier.
         /// </summary>
         /// <returns>The list of queue items.</returns>
-        private List<QueueItem> CreateQueueItemsFromArray(IEnumerable<Guid> items)
+        private List<QueueItem> CreateQueueItemsFromArray(IReadOnlyList<Guid> items)
         {
             var list = new List<QueueItem>();
             foreach (var item in items)