Support caching for cover art images

Signed-off-by: David Sn <divad.nnamtdeis@gmail.com>

mopidy_funkwhale/library.py

@@ -259,11 +259,16 @@ class FunkwhaleLibraryProvider(backend.LibraryProvider):
         logger.debug("Handling get images: %s", uris)
         result = {}
 
-        # TODO Add cache
         for uri in uris:
             track_id = uri.split(":")[-1]
-            payload = self.backend.client.get_track(track_id)
+            cache_key = "funkwhale:images:%s" % track_id
+            from_cache = self.cache.get(cache_key)
 
+            if from_cache:
+                result[uri] = from_cache
+                continue
+
+            payload = self.backend.client.get_track(track_id)
             if not payload["album"]["cover"]:
                 continue
 
@@ -282,6 +287,8 @@ class FunkwhaleLibraryProvider(backend.LibraryProvider):
 
                 result[uri].append(image)
 
+            self.cache.set(cache_key, result[uri])
+
         return result
 
     def search(self, query=None, uris=None, exact=False):