Remove code duplication

mopidy/core/actor.py

@@ -30,25 +30,44 @@ class Core(pykka.ThreadingActor, AudioListener):
     def __init__(self, audio=None, backends=None):
         super(Core, self).__init__()
 
-        self._backends = backends
+        self.backends = Backends(backends)
 
         self.current_playlist = CurrentPlaylistController(core=self)
 
-        self.library = LibraryController(backends=backends, core=self)
+        self.library = LibraryController(backends=self.backends, core=self)
 
         self.playback = PlaybackController(
-            audio=audio, backends=backends, core=self)
+            audio=audio, backends=self.backends, core=self)
 
         self.stored_playlists = StoredPlaylistsController(
-            backends=backends, core=self)
+            backends=self.backends, core=self)
 
     @property
     def uri_schemes(self):
         """List of URI schemes we can handle"""
-        futures = [backend.uri_schemes for backend in self._backends]
+        futures = [b.uri_schemes for b in self.backends]
         results = pykka.get_all(futures)
         uri_schemes = itertools.chain(*results)
         return sorted(uri_schemes)
 
     def reached_end_of_stream(self):
         self.playback.on_end_of_track()
+
+
+class Backends(object):
+    def __init__(self, backends):
+        self._backends = backends
+
+        uri_schemes_by_backend = {
+            backend: backend.uri_schemes.get()
+            for backend in backends}
+        self.by_uri_scheme = {
+            uri_scheme: backend
+            for backend, uri_schemes in uri_schemes_by_backend.items()
+            for uri_scheme in uri_schemes}
+
+    def __len__(self):
+        return len(self._backends)
+
+    def __getitem__(self, key):
+        return self._backends[key]

mopidy/core/library.py

@@ -11,19 +11,11 @@ class LibraryController(object):
 
     def __init__(self, backends, core):
         self.backends = backends
-        uri_schemes_by_backend = {
-            backend: backend.uri_schemes.get()
-            for backend in backends}
-        self.backends_by_uri_scheme = {
-            uri_scheme: backend
-            for backend, uri_schemes in uri_schemes_by_backend.items()
-            for uri_scheme in uri_schemes}
-
         self.core = core
 
     def _get_backend(self, uri):
         uri_scheme = urlparse.urlparse(uri).scheme
-        return self.backends_by_uri_scheme.get(uri_scheme)
+        return self.backends.by_uri_scheme.get(uri_scheme)
 
     def find_exact(self, **query):
         """

mopidy/core/playback.py

@@ -77,16 +77,7 @@ class PlaybackController(object):
 
     def __init__(self, audio, backends, core):
         self.audio = audio
-
         self.backends = backends
-        uri_schemes_by_backend = {
-            backend: backend.uri_schemes.get()
-            for backend in backends}
-        self.backends_by_uri_scheme = {
-            uri_scheme: backend
-            for backend, uri_schemes in uri_schemes_by_backend.items()
-            for uri_scheme in uri_schemes}
-
         self.core = core
 
         self._state = PlaybackState.STOPPED
@@ -99,7 +90,7 @@ class PlaybackController(object):
             return None
         uri = self.current_cp_track.track.uri
         uri_scheme = urlparse.urlparse(uri).scheme
-        return self.backends_by_uri_scheme[uri_scheme]
+        return self.backends.by_uri_scheme[uri_scheme]
 
     def _get_cpid(self, cp_track):
         if cp_track is None: