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MariuszC
445
venv/lib/python3.7/site-packages/mopidy/backend.py
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445
venv/lib/python3.7/site-packages/mopidy/backend.py
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import logging
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import pykka
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from mopidy import listener
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logger = logging.getLogger(__name__)
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class Backend:
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"""Backend API
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If the backend has problems during initialization it should raise
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:exc:`mopidy.exceptions.BackendError` with a descriptive error message.
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This will make Mopidy print the error message and exit so that the user can
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fix the issue.
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:param config: the entire Mopidy configuration
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:type config: dict
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:param audio: actor proxy for the audio subsystem
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:type audio: :class:`pykka.ActorProxy` for :class:`mopidy.audio.Audio`
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"""
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#: Actor proxy to an instance of :class:`mopidy.audio.Audio`.
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#:
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#: Should be passed to the backend constructor as the kwarg ``audio``,
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#: which will then set this field.
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audio = None
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#: The library provider. An instance of
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#: :class:`~mopidy.backend.LibraryProvider`, or :class:`None` if
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#: the backend doesn't provide a library.
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library = None
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#: The playback provider. An instance of
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#: :class:`~mopidy.backend.PlaybackProvider`, or :class:`None` if
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#: the backend doesn't provide playback.
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playback = None
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#: The playlists provider. An instance of
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#: :class:`~mopidy.backend.PlaylistsProvider`, or class:`None` if
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#: the backend doesn't provide playlists.
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playlists = None
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#: List of URI schemes this backend can handle.
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uri_schemes = []
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# Because the providers is marked as pykka.traversable(), we can't get()
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# them from another actor, and need helper methods to check if the
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# providers are set or None.
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def has_library(self):
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return self.library is not None
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def has_library_browse(self):
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return self.has_library() and self.library.root_directory is not None
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def has_playback(self):
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return self.playback is not None
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def has_playlists(self):
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return self.playlists is not None
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def ping(self):
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"""Called to check if the actor is still alive."""
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return True
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@pykka.traversable
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class LibraryProvider:
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"""
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:param backend: backend the controller is a part of
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:type backend: :class:`mopidy.backend.Backend`
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"""
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root_directory = None
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"""
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:class:`mopidy.models.Ref.directory` instance with a URI and name set
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representing the root of this library's browse tree. URIs must
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use one of the schemes supported by the backend, and name should
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be set to a human friendly value.
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*MUST be set by any class that implements* :meth:`LibraryProvider.browse`.
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"""
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def __init__(self, backend):
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self.backend = backend
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def browse(self, uri):
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"""
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See :meth:`mopidy.core.LibraryController.browse`.
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If you implement this method, make sure to also set
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:attr:`root_directory`.
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*MAY be implemented by subclass.*
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"""
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return []
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def get_distinct(self, field, query=None):
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"""
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See :meth:`mopidy.core.LibraryController.get_distinct`.
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*MAY be implemented by subclass.*
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Default implementation will simply return an empty set.
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Note that backends should always return an empty set for unexpected
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field types.
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"""
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return set()
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def get_images(self, uris):
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"""
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See :meth:`mopidy.core.LibraryController.get_images`.
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*MAY be implemented by subclass.*
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Default implementation will simply return an empty dictionary.
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"""
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return {}
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def lookup(self, uri):
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"""
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See :meth:`mopidy.core.LibraryController.lookup`.
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*MUST be implemented by subclass.*
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"""
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raise NotImplementedError
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def refresh(self, uri=None):
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"""
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See :meth:`mopidy.core.LibraryController.refresh`.
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*MAY be implemented by subclass.*
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"""
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pass
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def search(self, query=None, uris=None, exact=False):
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"""
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See :meth:`mopidy.core.LibraryController.search`.
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*MAY be implemented by subclass.*
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.. versionadded:: 1.0
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The ``exact`` param which replaces the old ``find_exact``.
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"""
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pass
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@pykka.traversable
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class PlaybackProvider:
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"""
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:param audio: the audio actor
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:type audio: actor proxy to an instance of :class:`mopidy.audio.Audio`
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:param backend: the backend
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:type backend: :class:`mopidy.backend.Backend`
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"""
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def __init__(self, audio, backend):
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self.audio = audio
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self.backend = backend
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def pause(self):
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"""
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Pause playback.
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*MAY be reimplemented by subclass.*
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:rtype: :class:`True` if successful, else :class:`False`
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"""
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return self.audio.pause_playback().get()
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def play(self):
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"""
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Start playback.
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*MAY be reimplemented by subclass.*
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:rtype: :class:`True` if successful, else :class:`False`
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"""
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return self.audio.start_playback().get()
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def prepare_change(self):
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"""
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Indicate that an URI change is about to happen.
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*MAY be reimplemented by subclass.*
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It is extremely unlikely it makes sense for any backends to override
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this. For most practical purposes it should be considered an internal
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call between backends and core that backend authors should not touch.
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"""
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self.audio.prepare_change().get()
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def translate_uri(self, uri):
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"""
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Convert custom URI scheme to real playable URI.
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*MAY be reimplemented by subclass.*
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This is very likely the *only* thing you need to override as a backend
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author. Typically this is where you convert any Mopidy specific URI
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to a real URI and then return it. If you can't convert the URI just
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return :class:`None`.
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:param uri: the URI to translate
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:type uri: string
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:rtype: string or :class:`None` if the URI could not be translated
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"""
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return uri
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def is_live(self, uri):
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"""
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Decide if the URI should be threated as a live stream or not.
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*MAY be reimplemented by subclass.*
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Playing a source as a live stream disables buffering, which reduces
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latency before playback starts, and discards data when paused.
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:param uri: the URI
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:type uri: string
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:rtype: bool
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"""
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return False
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def change_track(self, track):
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"""
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Swith to provided track.
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*MAY be reimplemented by subclass.*
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It is unlikely it makes sense for any backends to override
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this. For most practical purposes it should be considered an internal
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call between backends and core that backend authors should not touch.
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The default implementation will call :meth:`translate_uri` which
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is what you want to implement.
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:param track: the track to play
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:type track: :class:`mopidy.models.Track`
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:rtype: :class:`True` if successful, else :class:`False`
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"""
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uri = self.translate_uri(track.uri)
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if uri != track.uri:
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logger.debug("Backend translated URI from %s to %s", track.uri, uri)
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if not uri:
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return False
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self.audio.set_uri(uri, live_stream=self.is_live(uri)).get()
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return True
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def resume(self):
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"""
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Resume playback at the same time position playback was paused.
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*MAY be reimplemented by subclass.*
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:rtype: :class:`True` if successful, else :class:`False`
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"""
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return self.audio.start_playback().get()
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def seek(self, time_position):
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"""
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Seek to a given time position.
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*MAY be reimplemented by subclass.*
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:param time_position: time position in milliseconds
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:type time_position: int
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:rtype: :class:`True` if successful, else :class:`False`
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"""
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return self.audio.set_position(time_position).get()
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def stop(self):
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"""
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Stop playback.
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*MAY be reimplemented by subclass.*
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Should not be used for tracking if tracks have been played or when we
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are done playing them.
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:rtype: :class:`True` if successful, else :class:`False`
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"""
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return self.audio.stop_playback().get()
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def get_time_position(self):
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"""
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Get the current time position in milliseconds.
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*MAY be reimplemented by subclass.*
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:rtype: int
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"""
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return self.audio.get_position().get()
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@pykka.traversable
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class PlaylistsProvider:
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"""
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A playlist provider exposes a collection of playlists, methods to
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create/change/delete playlists in this collection, and lookup of any
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playlist the backend knows about.
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:param backend: backend the controller is a part of
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:type backend: :class:`mopidy.backend.Backend` instance
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"""
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def __init__(self, backend):
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self.backend = backend
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def as_list(self):
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"""
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Get a list of the currently available playlists.
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Returns a list of :class:`~mopidy.models.Ref` objects referring to the
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playlists. In other words, no information about the playlists' content
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is given.
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:rtype: list of :class:`mopidy.models.Ref`
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.. versionadded:: 1.0
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"""
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raise NotImplementedError
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def get_items(self, uri):
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"""
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Get the items in a playlist specified by ``uri``.
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Returns a list of :class:`~mopidy.models.Ref` objects referring to the
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playlist's items.
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If a playlist with the given ``uri`` doesn't exist, it returns
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:class:`None`.
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:rtype: list of :class:`mopidy.models.Ref`, or :class:`None`
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.. versionadded:: 1.0
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"""
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raise NotImplementedError
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def create(self, name):
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"""
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Create a new empty playlist with the given name.
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Returns a new playlist with the given name and an URI, or :class:`None`
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on failure.
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*MUST be implemented by subclass.*
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:param name: name of the new playlist
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:type name: string
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:rtype: :class:`mopidy.models.Playlist` or :class:`None`
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"""
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raise NotImplementedError
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def delete(self, uri):
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"""
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Delete playlist identified by the URI.
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Returns :class:`True` if deleted, :class:`False` otherwise.
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*MUST be implemented by subclass.*
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:param uri: URI of the playlist to delete
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:type uri: string
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:rtype: :class:`bool`
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.. versionchanged:: 2.2
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Return type defined.
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"""
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raise NotImplementedError
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def lookup(self, uri):
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"""
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Lookup playlist with given URI in both the set of playlists and in any
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other playlist source.
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Returns the playlists or :class:`None` if not found.
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*MUST be implemented by subclass.*
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:param uri: playlist URI
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:type uri: string
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:rtype: :class:`mopidy.models.Playlist` or :class:`None`
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"""
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raise NotImplementedError
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def refresh(self):
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"""
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Refresh the playlists in :attr:`playlists`.
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*MUST be implemented by subclass.*
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"""
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raise NotImplementedError
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def save(self, playlist):
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"""
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Save the given playlist.
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The playlist must have an ``uri`` attribute set. To create a new
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playlist with an URI, use :meth:`create`.
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Returns the saved playlist or :class:`None` on failure.
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*MUST be implemented by subclass.*
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:param playlist: the playlist to save
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:type playlist: :class:`mopidy.models.Playlist`
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:rtype: :class:`mopidy.models.Playlist` or :class:`None`
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"""
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raise NotImplementedError
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class BackendListener(listener.Listener):
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"""
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Marker interface for recipients of events sent by the backend actors.
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Any Pykka actor that mixes in this class will receive calls to the methods
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defined here when the corresponding events happen in a backend actor. This
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interface is used both for looking up what actors to notify of the events,
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and for providing default implementations for those listeners that are not
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interested in all events.
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Normally, only the Core actor should mix in this class.
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"""
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@staticmethod
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def send(event, **kwargs):
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"""Helper to allow calling of backend listener events"""
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listener.send(BackendListener, event, **kwargs)
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def playlists_loaded(self):
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"""
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Called when playlists are loaded or refreshed.
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*MAY* be implemented by actor.
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"""
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pass
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