from __future__ import annotations
import logging
from typing import TYPE_CHECKING
import pykka
from mopidy import listener
if TYPE_CHECKING:
from typing import Any, Dict, List, Optional, Set, TypeVar, Union
from typing_extensions import Literal
from mopidy.models import Image, Playlist, Ref, SearchResult, Track
# TODO Fix duplication with mopidy.internal.validation.TRACK_FIELDS_WITH_TYPES
TrackField = Literal[
"uri",
"track_name",
"album",
"artist",
"albumartist",
"composer",
"performer",
"track_no",
"genre",
"date",
"comment",
"disc_no",
"musicbrainz_albumid",
"musicbrainz_artistid",
"musicbrainz_trackid",
]
SearchField = Literal[TrackField, "any"]
DistinctField = TrackField
F = TypeVar("F")
QueryValue = Union[str, int]
Query = Dict[F, List[QueryValue]]
Uri = str
UriScheme = str
GstElement = TypeVar("GstElement")
logger = logging.getLogger(__name__)
[docs]
class Backend:
"""Backend API
If the backend has problems during initialization it should raise
:exc:`mopidy.exceptions.BackendError` with a descriptive error message.
This will make Mopidy print the error message and exit so that the user can
fix the issue.
:param config: the entire Mopidy configuration
:type config: dict
:param audio: actor proxy for the audio subsystem
:type audio: :class:`pykka.ActorProxy` for :class:`mopidy.audio.Audio`
"""
#: Actor proxy to an instance of :class:`mopidy.audio.Audio`.
#:
#: Should be passed to the backend constructor as the kwarg ``audio``,
#: which will then set this field.
# TODO(typing) Replace Any with an ActorProxy[Audio] type
audio: Optional[Any] = None
#: The library provider. An instance of
#: :class:`~mopidy.backend.LibraryProvider`, or :class:`None` if
#: the backend doesn't provide a library.
library: Optional[LibraryProvider] = None
#: The playback provider. An instance of
#: :class:`~mopidy.backend.PlaybackProvider`, or :class:`None` if
#: the backend doesn't provide playback.
playback: Optional[PlaybackProvider] = None
#: The playlists provider. An instance of
#: :class:`~mopidy.backend.PlaylistsProvider`, or class:`None` if
#: the backend doesn't provide playlists.
playlists: Optional[PlaylistsProvider] = None
#: List of URI schemes this backend can handle.
uri_schemes: List[UriScheme] = []
# Because the providers is marked as pykka.traversable(), we can't get()
# them from another actor, and need helper methods to check if the
# providers are set or None.
def has_library(self) -> bool:
return self.library is not None
def has_library_browse(self) -> bool:
return (
self.library is not None and self.library.root_directory is not None
)
def has_playback(self) -> bool:
return self.playback is not None
def has_playlists(self) -> bool:
return self.playlists is not None
[docs]
def ping(self) -> bool:
"""Called to check if the actor is still alive."""
return True
[docs]
@pykka.traversable
class LibraryProvider:
"""
:param backend: backend the controller is a part of
:type backend: :class:`mopidy.backend.Backend`
"""
root_directory: Optional[Ref] = None
"""
:class:`mopidy.models.Ref.directory` instance with a URI and name set
representing the root of this library's browse tree. URIs must
use one of the schemes supported by the backend, and name should
be set to a human friendly value.
*MUST be set by any class that implements* :meth:`LibraryProvider.browse`.
"""
def __init__(self, backend: Backend) -> None:
self.backend = backend
[docs]
def browse(self, uri: Uri) -> List[Ref]:
"""
See :meth:`mopidy.core.LibraryController.browse`.
If you implement this method, make sure to also set
:attr:`root_directory`.
*MAY be implemented by subclass.*
"""
return []
[docs]
def get_distinct(
self, field: DistinctField, query: Optional[Query[DistinctField]] = None
) -> Set[str]:
"""
See :meth:`mopidy.core.LibraryController.get_distinct`.
*MAY be implemented by subclass.*
Default implementation will simply return an empty set.
Note that backends should always return an empty set for unexpected
field types.
"""
return set()
[docs]
def get_images(self, uris: List[Uri]) -> Dict[Uri, List[Image]]:
"""
See :meth:`mopidy.core.LibraryController.get_images`.
*MAY be implemented by subclass.*
Default implementation will simply return an empty dictionary.
"""
return {}
[docs]
def lookup(self, uri: Uri) -> Dict[Uri, List[Track]]:
"""
See :meth:`mopidy.core.LibraryController.lookup`.
*MUST be implemented by subclass.*
"""
raise NotImplementedError
[docs]
def refresh(self, uri: Optional[Uri] = None) -> None:
"""
See :meth:`mopidy.core.LibraryController.refresh`.
*MAY be implemented by subclass.*
"""
pass
[docs]
def search(
self,
query: Query[SearchField],
uris: Optional[List[Uri]] = None,
exact: bool = False,
) -> List[SearchResult]:
"""
See :meth:`mopidy.core.LibraryController.search`.
*MAY be implemented by subclass.*
.. versionadded:: 1.0
The ``exact`` param which replaces the old ``find_exact``.
"""
return []
[docs]
@pykka.traversable
class PlaybackProvider:
"""
:param audio: the audio actor
:type audio: actor proxy to an instance of :class:`mopidy.audio.Audio`
:param backend: the backend
:type backend: :class:`mopidy.backend.Backend`
"""
def __init__(self, audio: Any, backend: Backend) -> None:
# TODO(typing) Replace Any with an ActorProxy[Audio] type
self.audio = audio
self.backend = backend
[docs]
def pause(self) -> bool:
"""
Pause playback.
*MAY be reimplemented by subclass.*
:rtype: :class:`True` if successful, else :class:`False`
"""
return self.audio.pause_playback().get()
[docs]
def play(self) -> bool:
"""
Start playback.
*MAY be reimplemented by subclass.*
:rtype: :class:`True` if successful, else :class:`False`
"""
return self.audio.start_playback().get()
[docs]
def prepare_change(self) -> None:
"""
Indicate that an URI change is about to happen.
*MAY be reimplemented by subclass.*
It is extremely unlikely it makes sense for any backends to override
this. For most practical purposes it should be considered an internal
call between backends and core that backend authors should not touch.
"""
self.audio.prepare_change().get()
[docs]
def translate_uri(self, uri: Uri) -> Optional[Uri]:
"""
Convert custom URI scheme to real playable URI.
*MAY be reimplemented by subclass.*
This is very likely the *only* thing you need to override as a backend
author. Typically this is where you convert any Mopidy specific URI
to a real URI and then return it. If you can't convert the URI just
return :class:`None`.
:param uri: the URI to translate
:type uri: string
:rtype: string or :class:`None` if the URI could not be translated
"""
return uri
[docs]
def is_live(self, uri: Uri) -> bool:
"""
Decide if the URI should be treated as a live stream or not.
*MAY be reimplemented by subclass.*
Playing a source as a live stream disables buffering, which reduces
latency before playback starts, and discards data when paused.
:param uri: the URI
:type uri: string
:rtype: bool
"""
return False
[docs]
def should_download(self, uri: Uri) -> bool:
"""
Attempt progressive download buffering for the URI or not.
*MAY be reimplemented by subclass.*
When streaming a fixed length file, the entire file can be buffered
to improve playback performance.
:param uri: the URI
:type uri: string
:rtype: bool
"""
return False
[docs]
def on_source_setup(self, source: GstElement) -> None:
"""
Called when a new GStreamer source is created, allowing us to configure
the source. This runs in the audio thread so should not block.
*MAY be reimplemented by subclass.*
:param source: the GStreamer source element
:type source: GstElement
.. versionadded:: 3.4
"""
pass
[docs]
def change_track(self, track: Track) -> bool:
"""
Switch to provided track.
*MAY be reimplemented by subclass.*
It is unlikely it makes sense for any backends to override
this. For most practical purposes it should be considered an internal
call between backends and core that backend authors should not touch.
The default implementation will call :meth:`translate_uri` which
is what you want to implement.
:param track: the track to play
:type track: :class:`mopidy.models.Track`
:rtype: :class:`True` if successful, else :class:`False`
"""
uri = self.translate_uri(track.uri)
if uri != track.uri:
logger.debug("Backend translated URI from %s to %s", track.uri, uri)
if not uri:
return False
self.audio.set_source_setup_callback(self.on_source_setup).get()
self.audio.set_uri(
uri,
live_stream=self.is_live(uri),
download=self.should_download(uri),
).get()
return True
[docs]
def resume(self) -> bool:
"""
Resume playback at the same time position playback was paused.
*MAY be reimplemented by subclass.*
:rtype: :class:`True` if successful, else :class:`False`
"""
return self.audio.start_playback().get()
[docs]
def seek(self, time_position: int) -> bool:
"""
Seek to a given time position.
*MAY be reimplemented by subclass.*
:param time_position: time position in milliseconds
:type time_position: int
:rtype: :class:`True` if successful, else :class:`False`
"""
return self.audio.set_position(time_position).get()
[docs]
def stop(self) -> bool:
"""
Stop playback.
*MAY be reimplemented by subclass.*
Should not be used for tracking if tracks have been played or when we
are done playing them.
:rtype: :class:`True` if successful, else :class:`False`
"""
return self.audio.stop_playback().get()
[docs]
def get_time_position(self) -> int:
"""
Get the current time position in milliseconds.
*MAY be reimplemented by subclass.*
:rtype: int
"""
return self.audio.get_position().get()
[docs]
@pykka.traversable
class PlaylistsProvider:
"""
A playlist provider exposes a collection of playlists, methods to
create/change/delete playlists in this collection, and lookup of any
playlist the backend knows about.
:param backend: backend the controller is a part of
:type backend: :class:`mopidy.backend.Backend` instance
"""
def __init__(self, backend: Backend) -> None:
self.backend = backend
[docs]
def as_list(self) -> List[Ref]:
"""
Get a list of the currently available playlists.
Returns a list of :class:`~mopidy.models.Ref` objects referring to the
playlists. In other words, no information about the playlists' content
is given.
:rtype: list of :class:`mopidy.models.Ref`
.. versionadded:: 1.0
"""
raise NotImplementedError
[docs]
def get_items(self, uri: Uri) -> Optional[List[Ref]]:
"""
Get the items in a playlist specified by ``uri``.
Returns a list of :class:`~mopidy.models.Ref` objects referring to the
playlist's items.
If a playlist with the given ``uri`` doesn't exist, it returns
:class:`None`.
:rtype: list of :class:`mopidy.models.Ref`, or :class:`None`
.. versionadded:: 1.0
"""
raise NotImplementedError
[docs]
def create(self, name: str) -> Optional[Playlist]:
"""
Create a new empty playlist with the given name.
Returns a new playlist with the given name and an URI, or :class:`None`
on failure.
*MUST be implemented by subclass.*
:param name: name of the new playlist
:type name: string
:rtype: :class:`mopidy.models.Playlist` or :class:`None`
"""
raise NotImplementedError
[docs]
def delete(self, uri: Uri) -> bool:
"""
Delete playlist identified by the URI.
Returns :class:`True` if deleted, :class:`False` otherwise.
*MUST be implemented by subclass.*
:param uri: URI of the playlist to delete
:type uri: string
:rtype: :class:`bool`
.. versionchanged:: 2.2
Return type defined.
"""
raise NotImplementedError
[docs]
def lookup(self, uri: Uri) -> Optional[Playlist]:
"""
Lookup playlist with given URI in both the set of playlists and in any
other playlist source.
Returns the playlists or :class:`None` if not found.
*MUST be implemented by subclass.*
:param uri: playlist URI
:type uri: string
:rtype: :class:`mopidy.models.Playlist` or :class:`None`
"""
raise NotImplementedError
[docs]
def refresh(self) -> None:
"""
Refresh the playlists in :attr:`playlists`.
*MUST be implemented by subclass.*
"""
raise NotImplementedError
[docs]
def save(self, playlist: Playlist) -> Optional[Playlist]:
"""
Save the given playlist.
The playlist must have an ``uri`` attribute set. To create a new
playlist with an URI, use :meth:`create`.
Returns the saved playlist or :class:`None` on failure.
*MUST be implemented by subclass.*
:param playlist: the playlist to save
:type playlist: :class:`mopidy.models.Playlist`
:rtype: :class:`mopidy.models.Playlist` or :class:`None`
"""
raise NotImplementedError
[docs]
class BackendListener(listener.Listener):
"""
Marker interface for recipients of events sent by the backend actors.
Any Pykka actor that mixes in this class will receive calls to the methods
defined here when the corresponding events happen in a backend actor. This
interface is used both for looking up what actors to notify of the events,
and for providing default implementations for those listeners that are not
interested in all events.
Normally, only the Core actor should mix in this class.
"""
[docs]
@staticmethod
def send(event: str, **kwargs: Any) -> None:
"""Helper to allow calling of backend listener events"""
listener.send(BackendListener, event, **kwargs)
[docs]
def playlists_loaded(self) -> None:
"""
Called when playlists are loaded or refreshed.
*MAY* be implemented by actor.
"""
pass