Added draft for mopidy backend over websocket

platypush/backend/music/mopidy.py

@@ -0,0 +1,64 @@
+import asyncio
+import time
+
+from platypush.backend import Backend
+from platypush.message.event.music import MusicPlayEvent, MusicPauseEvent, \
+    MusicStopEvent, NewPlayingTrackEvent, PlaylistChangeEvent, VolumeChangeEvent, \
+    PlaybackConsumeModeChangeEvent, PlaybackSingleModeChangeEvent, \
+    PlaybackRepeatModeChangeEvent, PlaybackRandomModeChangeEvent
+
+
+class MusicMopidyBackend(Backend):
+    """
+    This backend listens for events on a Mopidy music server streaming port.
+    Since this backend leverages the Mopidy websocket interface it is only
+    compatible with Mopidy and not with other MPD servers. Please use the
+    :class:`platypush.backend.music.mpd.MusicMpdBackend` for a similar polling
+    solution if you're not running Mopidy or your instance has the websocket
+    interface or web port disabled.
+
+    Triggers:
+
+        * :class:`platypush.message.event.music.MusicPlayEvent` if the playback state changed to play
+        * :class:`platypush.message.event.music.MusicPauseEvent` if the playback state changed to pause
+        * :class:`platypush.message.event.music.MusicStopEvent` if the playback state changed to stop
+        * :class:`platypush.message.event.music.NewPlayingTrackEvent` if a new track is being played
+        * :class:`platypush.message.event.music.PlaylistChangeEvent` if the main playlist has changed
+        * :class:`platypush.message.event.music.VolumeChangeEvent` if the main volume has changed
+
+    Requires:
+        * **websockets** (``pip install websockets``)
+        * Mopidy installed and the HTTP service enabled
+    """
+
+    def __init__(self, server='localhost', port=6680, **kwargs):
+        super().__init__(**kwargs)
+
+        self.server = server
+        self.port = int(port)
+        self.url = 'ws://{}:{}/mopidy/ws'.format(server, port)
+
+    async def poll_events(self):
+        import websockets
+
+        try:
+            while not self.should_stop():
+                async with websockets.connect(self.url) as ws:
+                    msg = await ws.recv()
+                    # TODO handle the message
+        except Exception as e:
+            self.logger.warning('The Mopidy backend raised an exception')
+            self.logger.exception(e)
+            time.sleep(2)  # Wait a bit before retrying
+
+    def run(self):
+        super().run()
+
+        loop = asyncio.new_event_loop()
+        asyncio.set_event_loop(loop)
+
+        while not self.should_stop():
+            loop.run_until_complete(self.poll_events())
+
+
+# vim:sw=4:ts=4:et: