Avoid rate limit by reducing requests to track stream endpoint.

Combine the request for finding if stream is playable with the
request for the actual stream URI. This should help with mopidy#99.

mopidy_soundcloud/soundcloud.py

@@ -30,6 +30,10 @@ def readable_url(uri):
                   ''.join(c for c in safe_uri if c in valid_chars)).strip()
 
 
+def streamble_url(url, client_id):
+    return '%s?client_id=%s' % (url, client_id)
+
+
 class cache(object):
     # TODO: merge this to util library
 
@@ -244,12 +248,12 @@ def parse_track(self, data, remote_url=False):
             track_kwargs[b'date'] = data['date']
 
         if remote_url:
-            if not self.can_be_streamed(data['stream_url']):
+            track_kwargs[b'uri'] = self.get_streamble_url(data['stream_url'])
+            if track_kwargs[b'uri'] is None:
                 logger.info(
                     "'%s' can't be streamed from SoundCloud" % data.get(
                         'title'))
                 return None
-            track_kwargs[b'uri'] = self.get_streamble_url(data['stream_url'])
         else:
             track_kwargs[b'uri'] = 'soundcloud:song/%s.%s' % (
                 readable_url(data.get('title')), data.get('id')
@@ -276,12 +280,12 @@ def parse_track(self, data, remote_url=False):
         return track
 
     @cache()
-    def can_be_streamed(self, url):
-        req = self.http_client.head(self.get_streamble_url(url))
-        return req.status_code == 302
-
     def get_streamble_url(self, url):
-        return '%s?client_id=%s' % (url, self.CLIENT_ID)
+        req = self.http_client.head(streamble_url(url, self.CLIENT_ID))
+        if req.status_code == 302:
+            return req.headers.get('Location', None)
+        elif req.status_code == 429:
+            logger.info('SoundCloud daily rate limit exceeded')
 
     def resolve_tracks(self, track_ids):
         """Resolve tracks concurrently emulating browser

tests/test_api.py

@@ -108,6 +108,14 @@ def test_resolves_stream_track(self):
         self.assertIsInstance(track, Track)
         self.assertEquals(
             track.uri,
-            'https://api.soundcloud.com/tracks/'
-            '13158665/stream?client_id=93e33e327fd8a9b77becd179652272e2'
+            'https://cf-media.sndcdn.com/fxguEjG4ax6B.128.mp3?Policy=eyJTdGF0ZW'
+            '1lbnQiOlt7IlJlc291cmNlIjoiKjovL2NmLW1lZGlhLnNuZGNkbi5jb20vZnhndUVq'
+            'RzRheDZCLjEyOC5tcDMiLCJDb25kaXRpb24iOnsiRGF0ZUxlc3NUaGFuIjp7IkFXUz'
+            'pFcG9jaFRpbWUiOjE0Nzc2MDA1NTd9fX1dfQ__&Signature=u9bxAkZOtTTF1VqTm'
+            'LGmw3ENrqbiSTFK-sMvZL-ZsQK85DOepHh5MfPA4MNooszUy~PZqiVyBn4YnElhWyb'
+            '~4B7kS6y0VZ6t-qF78CfTMOimemafpqfWJ8nYXczhM9pUpAwiS--lkNjGks4Qxi-FZ'
+            'JDBPG99gAIU0eVW78CADcpuOKLugGpzHl6gRPN2Z4zZ9dVujZ5MlG2OWnPuNiBcE~w'
+            'UFwcOxt9N6ePTff-wMFQR2PGpEK6wc6bWuB4WFNBkE0bmEke4cOQjWHa5FwYEidZN5'
+            'rvv5lVT1r07zzifnADEipwMaZ2-QYdqzOYaM4jymFDhl7DklaU24PY5C5mH0A__&Ke'
+            'y-Pair-Id=APKAJAGZ7VMH2PFPW6UQ'
         )