Replace redundant BaseFrontend class with list of requirements for frontend implementations

docs/api/frontends.rst

@@ -2,22 +2,26 @@
 Frontend API
 ************
 
-A frontend may do whatever it wants to, including creating threads, opening TCP
-ports and exposing Mopidy for a type of clients.
-
-Frontends got one main limitation: they are restricted to passing messages
-through the ``core_queue`` for all communication with the rest of Mopidy. Thus,
-the frontend API is very small and reveals little of what a frontend may do.
-
-.. warning::
-
-    A stable frontend API is not available yet, as we've only implemented a
-    couple of frontend modules.
-
-.. automodule:: mopidy.frontends.base
-    :synopsis: Base class for frontends
-    :members:
+The following requirements applies to any frontend implementation:
 
+- A frontend MAY do mostly whatever it wants to, including creating threads,
+  opening TCP ports and exposing Mopidy for a group of clients.
+- A frontend MUST implement at least one `Pykka
+  <http://jodal.github.com/pykka/>`_ actor, called the "main actor" from here
+  on.
+- It MAY use additional actors to implement whatever it does, and using actors
+  in frontend implementations is encouraged.
+- The frontend is activated by including its main actor in the
+  :attr:`mopidy.settings.FRONTENDS` setting.
+- The main actor MUST be able to start and stop the frontend when the main
+  actor is started and stopped.
+- The frontend MAY require additional settings to be set for it to
+  work.
+- Such settings MUST be documented.
+- The main actor MUST stop itself if the defined settings are not adequate for
+  the frontend to work properly.
+- Any actor which is part of the frontend MAY implement any listener interface
+  from :mod:`mopidy.listeners` to receive notification of the specified events.
 
 Frontend implementations
 ========================

mopidy/frontends/base.py

@@ -1,5 +0,0 @@
-class BaseFrontend(object):
-    """
-    Base class for frontends.
-    """
-    pass

mopidy/frontends/lastfm.py

@@ -10,7 +10,6 @@ except ImportError as import_error:
 from pykka.actor import ThreadingActor
 
 from mopidy import settings, SettingsError
-from mopidy.frontends.base import BaseFrontend
 from mopidy.listeners import BackendListener
 
 logger = logging.getLogger('mopidy.frontends.lastfm')
@@ -18,7 +17,7 @@ logger = logging.getLogger('mopidy.frontends.lastfm')
 API_KEY = '2236babefa8ebb3d93ea467560d00d04'
 API_SECRET = '94d9a09c0cd5be955c4afaeaffcaefcd'
 
-class LastfmFrontend(ThreadingActor, BaseFrontend, BackendListener):
+class LastfmFrontend(ThreadingActor, BackendListener):
     """
     Frontend which scrobbles the music you play to your `Last.fm
     <http://www.last.fm>`_ profile.

mopidy/frontends/mpd/__init__.py

@@ -3,13 +3,12 @@ import logging
 
 from pykka.actor import ThreadingActor
 
-from mopidy.frontends.base import BaseFrontend
 from mopidy.frontends.mpd.server import MpdServer
 from mopidy.utils.process import BaseThread
 
 logger = logging.getLogger('mopidy.frontends.mpd')
 
-class MpdFrontend(ThreadingActor, BaseFrontend):
+class MpdFrontend(ThreadingActor):
     """
     The MPD frontend.