Add AutoDJ feature. First issue #14 implementation.

Updating to this commit requires human interaction: you must add a
boolean AutoDJ key to the [GENERAL] config section.

airhead/playlist.py

@@ -1,4 +1,5 @@
 import queue
+import random
 from airhead.library import TrackNotFoundError
 
 
@@ -10,10 +11,17 @@ class EmptyPlaylist(Exception):
     pass
 
 
+def random_track(library):
+    track = random.choice(library.query())
+    return track['uuid']
+
+
 class Playlist:
-    def __init__(self, library, notify=lambda: None):
+    def __init__(self, library, notify=lambda: None, auto_dj=False):
         self._library = library
         self._notify = notify
+        self._auto_dj = auto_dj
+
         self._current = None
         self._queue = queue.Queue()
 
@@ -34,8 +42,13 @@ def pop(self):
             item = self._queue.get(block=False)
 
         except queue.Empty as e:
-            self._current = None
-            raise EmptyPlaylist from e
+            if self._auto_dj:
+                track = random_track(self._library)
+                self._current = track
+                return track
+            else:
+                self._current = None
+                raise EmptyPlaylist from e
 
         else:
             self._current = item

conf/airhead.ini.example

@@ -3,6 +3,7 @@ Debug = True
 Address = 127.0.0.1
 Port = 8080
 Library = /tmp/airhead/library
+AutoDJ = False
 Frontend = /tmp/airhead/frontend
 
 [INFO]

web.py

@@ -174,11 +174,13 @@ def broadcaster_shutdown(app):
 app = web.Application()
 
 app['config'] = get_config()
+app['websockets'] = list()
+
 app['library'] = Library(app['config'].get('GENERAL', 'Library'),
                          notify=broadcast_library_update)
-app['playlist'] = Playlist(app['library'], notify=broadcast_playlist_update)
+app['playlist'] = Playlist(app['library'], notify=broadcast_playlist_update,
+                           auto_dj=app['config'].getboolean('GENERAL', 'AutoDj'))
 app['broadcaster'] = Broadcaster(app['config']['ICECAST'], app['playlist'])
-app['websockets'] = list()
 
 app.router.add_route('GET', '/api/info', info)
 app.router.add_route('GET', '/api/library', library_query)