Create a Track proxy for spotify (Fixes #72)

mopidy/backends/spotify/library.py

@@ -5,21 +5,54 @@ from spotify import Link, SpotifyError
 
 from mopidy.backends.base import BaseLibraryProvider
 from mopidy.backends.spotify.translator import SpotifyTranslator
-from mopidy.models import Playlist
+from mopidy.models import Track, Playlist
 
 logger = logging.getLogger('mopidy.backends.spotify.library')
 
+
+class SpotifyTrack(Track):
+    def __init__(self, uri):
+        self._spotify_track = Link.from_string(uri).as_track()
+        self._unloaded_track = Track(uri=uri, name=u'[loading...]')
+        self._track = None
+
+    @property
+    def _proxy(self):
+        if self._track:
+            return self._track
+        elif self._spotify_track.is_loaded():
+            self._track = SpotifyTranslator.to_mopidy_track(self._spotify_track)
+            return self._track
+        else:
+            return self._unloaded_track
+
+    def __getattribute__(self, name):
+        if name.startswith('_'):
+            return super(SpotifyTrack, self).__getattribute__(name)
+        return self._proxy.__getattribute__(name)
+
+    def __repr__(self):
+        return self._proxy.__repr__()
+
+    def __hash__(self):  # hash on just uri for consistency?
+        return hash(self._proxy.uri)
+
+    def __eq__(self, other): # compare on just uri for consistency?
+        if not isinstance(other, Track):
+            return False
+        return self._proxy.uri == other.uri
+
+    def copy(self, **values): # is it okay to return a plain track?
+        return self._proxy.copy(**values)
+
+
 class SpotifyLibraryProvider(BaseLibraryProvider):
     def find_exact(self, **query):
         return self.search(**query)
 
     def lookup(self, uri):
         try:
-            spotify_track = Link.from_string(uri).as_track()
-            # TODO Block until metadata_updated callback is called. Before that
-            # the track will be unloaded, unless it's already in the stored
-            # playlists.
-            return SpotifyTranslator.to_mopidy_track(spotify_track)
+            return SpotifyTrack(uri)
         except SpotifyError as e:
             logger.debug(u'Failed to lookup "%s": %s', uri, e)
             return None