curds: Add a way to get parent playlists from the playlist manager

We can figure this out a little easier on the backend side, so let's
handle this there rather than on the UI side

Signed-off-by: Anna Schumaker <Anna@NoWheyCreamery.com>

curds/playlist/manager.py

@@ -73,6 +73,15 @@ class PlaylistManager(dict):
         self["Previous"].add(self.track)
         return self.track
 
+    def parent(self, child):
+        if child in self.values():
+            return self
+        if isinstance(child, genre.GenrePlaylist):
+            parent = self["Genre"]
+        elif isinstance(child, library.LibraryPlaylist):
+            parent = self["Library"]
+        return parent if child in parent else None
+
     def previous(self):
         self.track = self["Previous"].next()
         return self.track

curds/playlist/test_manager.py

@@ -75,6 +75,13 @@ class TestPlaylistManager(unittest.TestCase):
         self.assertEqual(self.playman["Library"].lookup(test_library + "/"), plist)
         self.assertIsNone(self.playman["Library"].lookup("No such library"))
 
+        parent = self.playman.parent(plist)
+        self.assertEqual(parent, self.playman["Library"])
+        parent = self.playman.parent(alist)
+        self.assertEqual(parent, self.playman["Library"])
+        parent = self.playman.parent(self.playman["Library"])
+        self.assertEqual(parent, self.playman)
+
         self.playman.reset()
         self.assertEqual(len(self.playman["Library"]), 0)
 
@@ -93,6 +100,13 @@ class TestPlaylistManager(unittest.TestCase):
         self.assertEqual(plist.icon, "audio-x-generic-symbolic")
         self.assertEqual(len(genreman), 5)
 
+        parent = self.playman.parent(plist)
+        self.assertEqual(parent, genreman)
+        parent = self.playman.parent(genre.GenrePlaylist("Other"))
+        self.assertEqual(parent, None)
+        parent = self.playman.parent(genreman)
+        self.assertEqual(parent, self.playman)
+
         notify.cancel("new-track", genreman.add_track)
         self.playman.reset()
         self.assertEqual(len(genreman), 0)