Playlist View: Support undoing and redoing Drag and Drop operations within the playlist

Playlist/DNDArrayController.h

@@ -28,5 +28,8 @@ extern NSString *iTunesDropType;
 // utility methods
 -(void)moveObjectsInArrangedObjectsFromIndexes:(NSIndexSet *)indexSet
                                        toIndex:(NSUInteger)insertIndex;
+// This is needed to undo the above
+- (void)moveObjectsFromIndex:(NSUInteger)fromIndex
+     toArrangedObjectIndexes:(NSIndexSet *)indexSet;
 
 @end

Playlist/DNDArrayController.m

@@ -119,5 +119,28 @@ NSString *iTunesDropType = @"com.apple.tv.metadata";
     }
 }
 
+- (void)moveObjectsFromIndex:(NSUInteger)fromIndex
+     toArrangedObjectIndexes:(NSIndexSet *)indexSet {
+    NSArray *objects = [self arrangedObjects];
+    NSUInteger index = [indexSet firstIndex];
+
+    NSUInteger itemIndex = 0;
+    id object;
+    
+    NSArray *itemsSet = [objects objectsAtIndexes:[NSIndexSet indexSetWithIndexesInRange:NSMakeRange(fromIndex, [indexSet count])]];
+    
+    for (NSUInteger i = 0; i < [itemsSet count]; i++) {
+        [self removeObjectAtArrangedObjectIndex:fromIndex];
+    }
+
+    while (NSNotFound != index) {
+        object = itemsSet[itemIndex++];
+
+        [self insertObject:object atArrangedObjectIndex:index];
+
+        index = [indexSet indexGreaterThanIndex:index];
+    }
+}
+
 
 @end

Playlist/PlaylistController.m

@@ -363,8 +363,28 @@ static inline void dispatch_sync_reentrant(dispatch_queue_t queue, dispatch_bloc
     if ([self shuffle] != ShuffleOff) [self resetShuffleList];
 }
 
+// This action is only needed to revert the one that follows it
+- (void)moveObjectsFromIndex:(NSUInteger)fromIndex
+     toArrangedObjectIndexes:(NSIndexSet *)indexSet {
+    [[[self undoManager] prepareWithInvocationTarget:self]
+     moveObjectsInArrangedObjectsFromIndexes:indexSet toIndex:fromIndex];
+    NSString *actionName =
+            [NSString stringWithFormat:@"Reordering %lu entries", (unsigned long) [indexSet count]];
+    [[self undoManager] setActionName:actionName];
+
+    [super moveObjectsFromIndex:fromIndex toArrangedObjectIndexes:indexSet];
+
+    [playbackController playlistDidChange:self];
+}
+
 - (void)moveObjectsInArrangedObjectsFromIndexes:(NSIndexSet *)indexSet
                                         toIndex:(NSUInteger)insertIndex {
+    [[[self undoManager] prepareWithInvocationTarget:self]
+        moveObjectsFromIndex:insertIndex toArrangedObjectIndexes:indexSet];
+    NSString *actionName =
+            [NSString stringWithFormat:@"Reordering %lu entries", (unsigned long) [indexSet count]];
+    [[self undoManager] setActionName:actionName];
+
     [super moveObjectsInArrangedObjectsFromIndexes:indexSet toIndex:insertIndex];
 
 #if 0 // syncPlaylistEntries is already called for rearrangement