API reference¶

class Device(PDevice, abc.ABC):
    """Base class for devices.

    Users may subclass from this device and implement their own
    configuration properties and methods.

    Parameters
    ----------
    name : str
        Name of the device. Serves as a unique identifier for the object created from it.
    kwargs : Any, optional
        Additional keyword arguments for device subclasses.
    """

    @abc.abstractmethod
    def __init__(self, name: str, /, **kwargs: Any) -> None:
        self._name = name
        super().__init__(**kwargs)

    @abc.abstractmethod
    def describe_configuration(self) -> dict[str, Descriptor]:
        """Provide a description of the device configuration.

        Subclasses should override this method to provide their own
        configuration description compatible with the Bluesky event model.

        Returns
        -------
        dict[str, Descriptor]
            A dictionary with the description of each field of the device configuration.
        """
        raise NotImplementedError

    @abc.abstractmethod
    def read_configuration(self) -> dict[str, Reading[Any]]:
        """Provide a description of the device configuration.

        Subclasses should override this method to provide their own
        configuration reading compatible with the Bluesky event model.

        Returns
        -------
        dict[str, Reading[Any]]
            A dictionary with the reading of each field of the device configuration.
        """
        raise NotImplementedError

    @property
    def name(self) -> str:
        """The name of the device, serving as a unique identifier."""
        return self._name

    @property
    def parent(self) -> None:
        """Parent of the device. Always returns None for compliance with [`HasParent`]() protocol."""
        return None

@runtime_checkable
class PDevice(HasName, HasParent, Configurable[Any], Protocol):  # pragma: no cover
    """Minimal required protocol for a recognizable device in Redsun."""

@runtime_checkable
class PPresenter(Protocol):  # pragma: no cover
    """Presenter protocol class.

    Attributes
    ----------
    name : str
        Identity key of the presenter.
    devices : Mapping[str, sunflare.device.Device]
        Reference to the devices used in the presenter.

    Notes
    -----
    Access to the virtual container is optional and should be acquired
    by implementing :class:`~sunflare.virtual.IsProvider` or
    :class:`~sunflare.virtual.IsInjectable`.
    """

    name: str
    devices: Mapping[str, Device]

class Presenter(PPresenter, ABC):
    """Presenter base class.

    Parameters
    ----------
    name : str
        Identity key of the presenter. Passed as positional-only argument.
    devices : Mapping[str, sunflare.device.Device]
        Reference to the devices used in the presenter.
    kwargs : Any, optional
        Additional keyword arguments for presenter subclasses.
    """

    @abstractmethod
    def __init__(
        self,
        name: str,
        devices: Mapping[str, Device],
        /,
        **kwargs: Any,
    ) -> None:
        self.name = name
        self.devices = devices
        super().__init__(**kwargs)

class RedSunConfig(TypedDict, total=False):
    """Base configuration schema for Redsun applications."""

    schema_version: Required[float]
    """Plugin schema version."""

    frontend: Required[str]
    """Frontend toolkit identifier (e.g. `"pyqt"`, `"pyside"`)."""

    session: NotRequired[str]
    """Session display name. If not provided, default is `"redsun"`."""

    metadata: NotRequired[dict[str, Any]]
    """Additional session-specific metadata to include in the configuration."""

class VirtualContainer(dic.DynamicContainer, Loggable):
    """Data exchange and dependency injection layer.

    `VirtualContainer` is a [`DynamicContainer`][dependency_injector.containers.DynamicContainer]
    that also acts as a runtime signal bus and data sharing layer for an application.
    """

    _signals = dip.Factory(dict[str, SignalCache])
    _callbacks = dip.Factory(dict[str, CallbackType])
    _config = dip.Singleton(_FrozenConfig)

    @property
    def schema_version(self) -> float:
        """The plugin schema version specified in the configuration."""
        return self._config().schema_version

    @property
    def frontend(self) -> str:
        """The frontend toolkit identifier specified in the configuration."""
        return self._config().frontend

    @property
    def session(self) -> str:
        """The session display name specified in the configuration."""
        return self._config().session

    @property
    def metadata(self) -> dict[str, object]:
        """The session metadata specified in the configuration."""
        return self._config().metadata

    def _set_configuration(self, config: RedSunConfig) -> None:
        """Set the application configuration.

        Private for use by the application layer at build time.

        Parameters
        ----------
        config : RedSunConfig
            The application configuration to set.
        """
        self._config.set_kwargs(
            schema_version=config["schema_version"],
            frontend=config["frontend"],
            session=config.get("session", "redsun"),
            metadata=config.get("metadata", {}),
        )

    def register_signals(
        self, owner: HasName, name: str | None = None, only: Iterable[str] | None = None
    ) -> None:
        """Register the signals of an object in the virtual container.

        Parameters
        ----------
        owner : HasName
            The instance whose class's signals are to be cached.
            Must provide a `name` attribute.
        name : str | None
            An optional name to use as the key for caching the signals.
            If not provided, the `name` of `owner` will be used.
        only : Iterable[str], optional
            A list of signal names to cache. If not provided, all
            signals in the class will be cached automatically by inspecting
            the class attributes.

        Notes
        -----
        This method inspects the attributes of the owner's class to find
        [`psygnal.Signal`][psygnal.Signal] descriptors. For each such descriptor, it
        retrieves the [`psygnal.SignalInstance`][psygnal.SignalInstance] from the owner using
        the descriptor protocol and stores it in the registry.
        """
        owner_class = type(owner)
        if name is not None:
            cache_entry = name
        else:
            cache_entry = owner.name

        if only is None:
            only = [
                name
                for name in dir(owner_class)
                if isinstance(getattr(owner_class, name, None), Signal)
            ]

        batch: dict[str, SignalInstance] = {}
        for name in only:
            signal_descriptor = getattr(owner_class, name, None)
            if isinstance(signal_descriptor, Signal):
                signal_instance = getattr(owner, name)
                batch[name] = signal_instance
        if batch:
            self._signals.add_kwargs(**{cache_entry: batch})

    @staticmethod
    def _validate_callback(callback: object) -> CallbackType:
        """Validate that *callback* is an acceptable ``CallbackType``.

        Parameters
        ----------
        callback :
            The object to validate.

        Returns
        -------
        CallbackType
            The validated callback, unchanged.

        Raises
        ------
        TypeError
            If *callback* is not callable, or if it is a callable but
            its call signature is not compatible with ``(str, Document)``.
        """
        if isinstance(callback, DocumentRouter):
            return callback

        if not callable(callback):
            raise TypeError(
                f"{callback!r} is not callable. "
                "A callback must be a DocumentRouter subclass instance or a "
                "callable accepting (str, Document) arguments."
            )

        try:
            inspect.signature(callback.__call__).bind(None, None)
        except TypeError as e:
            raise TypeError(
                f"{callback!r} is callable but its signature is not compatible "
                "with the expected (str, Document) callback interface."
            ) from e

        return callback

    def register_callbacks(
        self,
        owner: HasName,
        name: str | None = None,
        callback_map: dict[str, CallbackType] | None = None,
    ) -> None:
        """Register one or more document callbacks in the virtual container.

        Accepts any object that is a valid ``CallbackType`` and exposes a
        ``name`` attribute used as the registry key.  Two forms are supported:

        * A [DocumentRouter][event_model.DocumentRouter] subclass instance;
        * Any other object that implements ``__call__(self, name, doc)`` with
          the correct two-parameter signature.

        When *callback_map* is provided the owner itself is not registered;
        instead each entry in the mapping is validated and registered
        independently under its own key, allowing a single owner to expose
        multiple callbacks.

        Parameters
        ----------
        owner : HasName
            The component registering callbacks.  Must expose a ``name``
            attribute.  When *callback_map* is ``None``, *owner* itself is
            registered as the callback.
        name : str | None
            Override for the registry key used when registering *owner*
            directly.  Ignored when *callback_map* is provided.
            Defaults to ``owner.name``.
        callback_map : dict[str, CallbackType] | None
            Optional mapping of registry key to callback object.  When
            supplied, each value is validated and registered under its
            corresponding key; *name* is ignored.

        Raises
        ------
        TypeError
            If a callback is not callable or its signature is incompatible
            with ``(str, Document)``.
        """
        if callback_map is not None:
            for key, callback in callback_map.items():
                self._callbacks.add_kwargs(**{key: self._validate_callback(callback)})
            return

        cache_entry = name if name is not None else owner.name
        self._callbacks.add_kwargs(**{cache_entry: self._validate_callback(owner)})

    @property
    def callbacks(self) -> dict[str, CallbackType]:
        """The currently registered document callbacks."""
        return self._callbacks()

    @property
    def signals(self) -> dict[str, SignalCache]:
        """The currently registered signals."""
        return self._signals()

@runtime_checkable
class HasShutdown(Protocol):  # pragma: no cover
    """Protocol marking your class as capable of shutting down."""

    @abstractmethod
    def shutdown(self) -> None:
        """Shutdown an object. Performs cleanup operations."""
        ...

@runtime_checkable
class IsInjectable(Protocol):  # pragma: no cover
    """Protocol marking a class as injectable with dependencies from the container."""

    @abstractmethod
    def inject_dependencies(self, container: VirtualContainer) -> None:
        """Inject dependencies from the container."""
        ...

@runtime_checkable
class IsProvider(Protocol):  # pragma: no cover
    """Protocol marking a class as a provider of dependencies."""

    @abstractmethod
    def register_providers(self, container: VirtualContainer) -> None:
        """Register providers in the virtual container."""
        ...

@runtime_checkable
class PView(Protocol):
    """Minimal protocol a view component should implement.

    Attributes
    ----------
    name : str
        Identity key of the view.

    Notes
    -----
    Access to the virtual container is optional and should be acquired
    by implementing :class:`~sunflare.virtual.IsInjectable`.
    """

    name: str

    @property
    @abstractmethod
    def view_position(self) -> ViewPosition:
        """Position of the view component in the main view of the UI."""

class View(PView, ABC):
    """Base view class.

    Parameters
    ----------
    name : str
        Identity key of the view. Passed as positional-only argument.
    kwargs : ``Any``, optional
        Additional keyword arguments for view subclasses.
    """

    @abstractmethod
    def __init__(
        self,
        name: str,
        /,
        **kwargs: Any,
    ) -> None:
        self.name = name
        super().__init__(**kwargs)

    @property
    @abstractmethod
    def view_position(self) -> ViewPosition:
        """Position of the view component in the main view of the UI."""

@unique
class ViewPosition(str, Enum):
    """Supported view positions.

    Used to define the position of a view component in the main view of the UI.

    !!! warning
        These values are based on how Qt manages dock widgets.
        They may change in the future.

    Attributes
    ----------
    CENTER : str
        Center view position.
    LEFT : str
        Left view position.
    RIGHT : str
        Right view position.
    TOP : str
        Top view position.
    BOTTOM : str
        Bottom view position.
    """

    CENTER = "center"
    LEFT = "left"
    RIGHT = "right"
    TOP = "top"
    BOTTOM = "bottom"

class Loggable:
    """Mixin class that adds a logger to a class instance with extra contextual information."""

    @cached_property
    def logger(self) -> _LoggerAdapter:
        """Logger instance with contextual information."""
        return ContextualAdapter(logging.getLogger("redsun"), self)

class Status(PStatus):
    """
    Track the status of a potentially-lengthy action like moving or triggering.

    Parameters
    ----------
    timeout: float, optional
        The amount of time to wait before marking the Status as failed.  If
        ``None`` (default) wait forever. It is strongly encouraged to set a
        finite timeout.  If settle_time below is set, that time is added to the
        effective timeout.
    settle_time: float, optional
        The amount of time to wait between the caller specifying that the
        status has completed to running callbacks. Default is 0.

    Notes
    -----
    Theory of operation:

    This employs two ``threading.Event`` objects, one thread that runs for
    (timeout + settle_time) seconds, and one thread that runs for
    settle_time seconds (if settle_time is nonzero).

    At __init__ time, a *timeout* and *settle_time* are specified. A thread
    is started, on which user callbacks, registered after __init__ time via
    [`add_callback`](), will eventually be run. The thread waits on an
    Event be set or (timeout + settle_time) seconds to pass, whichever
    happens first.

    If (timeout + settle_time) expires and the Event has not
    been set, an internal Exception is set to ``StatusTimeoutError``, and a
    second Event is set, marking the Status as done and failed. The
    callbacks are run.

    If a callback is registered after the Status is done, it will be run
    immediately.

    If the first Event is set before (timeout + settle_time) expires,
    then the second Event is set and no internal Exception is set, marking
    the Status as done and successful. The callbacks are run.

    There are two methods that directly set the first Event. One,
    [`set_exception`](), sets it directly after setting the internal
    Exception.  The other, [`set_finished`](), starts a
    ``threading.Timer`` that will set it after a delay (the settle_time).
    One of these methods may be called, and at most once. If one is called
    twice or if both are called, ``InvalidState`` is raised. If they are
    called too late to prevent a ``StatusTimeoutError``, they are ignored
    but one call is still allowed. Thus, an external callback, e.g. pyepics,
    may reports success or failure after the Status object has expired, but
    to no effect because the callbacks have already been called and the
    program has moved on.
    """

    def __init__(self, *, timeout: float | None = None, settle_time: float | None = 0):
        super().__init__()
        self._logger = logging.getLogger("redsun")
        self._tname = None
        self._lock = threading.RLock()
        self._event = threading.Event()  # state associated with done-ness
        self._settled_event = threading.Event()
        # "Externally initiated" means set_finished() or set_exception(exc) was
        # called, as opposed to completion via an internal timeout.
        self._externally_initiated_completion_lock = threading.Lock()
        self._externally_initiated_completion = False
        self._callbacks: deque[Callable[[Status], None]] = deque()
        self._exception: BaseException | None = None

        if settle_time is None:
            settle_time = 0.0

        self._settle_time = float(settle_time)

        if timeout is not None:
            timeout = float(timeout)
        self._timeout = timeout

        self._callback_thread = threading.Thread(
            target=self._run_callbacks, daemon=True, name=self._tname
        )
        self._callback_thread.start()

    @property
    def timeout(self) -> float | None:
        """The timeout for this action.

        This is set when the Status is created, and it cannot be changed.
        """
        return self._timeout

    @property
    def settle_time(self) -> float:
        """A delay between when [`set_finished`]() is when the Status is done.

        This is set when the Status is created, and it cannot be changed.
        """
        return self._settle_time

    @property
    def done(self) -> bool:
        """Boolean indicating whether associated operation has completed.

        This is set to True at __init__ time or by calling
        [`set_finished`](), [`set_exception`]().
        Once True, it can never become False.
        """
        return self._event.is_set()

    @property
    def success(self) -> bool:
        """Boolean indicating whether associated operation has completed.

        This is set to True at __init__ time or by calling
        [`set_finished`](), [`set_exception`]()
        . Once True, it can never become False.
        """
        return self.done and self._exception is None

    def _handle_failure(self) -> None:
        """Do something if an exception occurred during the action."""
        # TODO: implement this; maybe ophyd has a good example
        pass

    def _settled(self) -> None:
        """Connect to this this when status has completed and settled."""
        # TODO: implement this; maybe ophyd has a good example
        pass

    def _run_callbacks(self) -> None:
        """Set the Event and run the callbacks."""
        if self.timeout is None:
            timeout = None
        else:
            timeout = self.timeout + self.settle_time
        if not self._settled_event.wait(timeout):
            # We have timed out. It's possible that set_finished() has already
            # been called but we got here before the settle_time timer expired.
            # And it's possible that in this space be between the above
            # statement timing out grabbing the lock just below,
            # set_exception(exc) has been called. Both of these possibilties
            # are accounted for.
            self._logger.warning("%r has timed out", self)
            with self._externally_initiated_completion_lock:
                # Set the exception and mark the Status as done, unless
                # set_exception(exc) was called externally before we grabbed
                # the lock.
                if self._exception is None:
                    exc = StatusTimeoutError(
                        f"Status {self!r} failed to complete in specified timeout."
                    )
                    self._exception = exc
        # Mark this as "settled".
        try:
            self._settled()
        except Exception:
            # No alternative but to log this. We can't supersede set_exception,
            # and we have to continue and run the callbacks.
            self._logger.exception("%r encountered error during _settled()", self)
        # Now we know whether or not we have succeed or failed, either by
        # timeout above or by set_exception(exc), so we can set the Event that
        # will mark this Status as done.
        with self._lock:
            self._event.set()
        if self._exception is not None:
            try:
                self._handle_failure()
            except Exception:
                self._logger.exception(
                    "%r encountered an error during _handle_failure()", self
                )
        # The callbacks have access to self, from which they can distinguish
        # success or failure.
        for cb in self._callbacks:
            try:
                cb(self)
            except Exception:
                self._logger.exception(
                    "An error was raised on a background thread while "
                    "running the callback %r(%r).",
                    cb,
                    self,
                )
        self._callbacks.clear()

    def set_exception(self, exc: BaseException) -> None:
        """Mark as finished but failed with the given Exception.

        This method should generally not be called by the *recipient* of this
        Status object, but only by the object that created and returned it.

        Parameters
        ----------
        exc: BaseException
            The exception that caused the failure.
        """
        # Since we rely on this being raise-able later, check proactively to
        # avoid potentially very confusing failures.
        if not (isinstance(exc, BaseException)):
            # Note that Python allows `raise Exception` or raise Exception()`
            # so we allow a class or an instance here too.
            raise ValueError(f"Expected an Exception, got {exc!r}")

        # Ban certain Timeout subclasses that have special significance. This
        # would probably never come up except due to some rare user error, but
        # if it did it could be very confusing indeed!
        for exc_class in (StatusTimeoutError, WaitTimeoutError):
            if isinstance(exc, exc_class):
                raise ValueError(
                    f"{exc_class} has special significance and cannot be set "
                    "as the exception. Use a plain TimeoutError or some other "
                    "subclass thereof."
                )

        with self._externally_initiated_completion_lock:
            if self._externally_initiated_completion:
                raise InvalidState(
                    "Either set_finished() or set_exception() has "
                    f"already been called on {self!r}"
                )
            self._externally_initiated_completion = True
            if isinstance(self._exception, StatusTimeoutError):
                # We have already timed out.
                return
            self._exception = exc
            self._settled_event.set()

    def set_finished(self) -> None:
        """Mark as finished successfully.

        This method should generally not be called by the *recipient* of this
        Status object, but only by the object that created and returned it.
        """
        with self._externally_initiated_completion_lock:
            if self._externally_initiated_completion:
                raise InvalidState(
                    "Either set_finished() or set_exception() has "
                    f"already been called on {self!r}"
                )
            self._externally_initiated_completion = True
        # Note that in either case, the callbacks themselves are run from the
        # same thread. This just sets an Event, either from this thread (the
        # one calling set_finished) or the thread created below.
        if self.settle_time > 0:
            threading.Timer(self.settle_time, self._settled_event.set).start()
        else:
            self._settled_event.set()

    def exception(self, timeout: float | None = None) -> BaseException | None:
        """Return the exception raised by the action.

        If the action has completed successfully, return ``None``. If it has
        finished in error, return the exception.

        Parameters
        ----------
        timeout: float | None, optional
            If None (default) wait indefinitely until the status finishes.

        Returns
        -------
        Exception:
            The exception raised by the action. If the action has completed
            successfully, return ``None``.

        Raises
        ------
        WaitTimeoutError
            If the status has not completed within ``timeout`` (starting from
            when this method was called, not from the beginning of the action).
        """
        if not self._event.wait(timeout=timeout):
            raise WaitTimeoutError("Status has not completed yet.")
        return self._exception

    def wait(self, timeout: float | None = None) -> None:
        """Block until the action completes.

        When the action has finished succesfully, return ``None``. If the
        action has failed, raise the exception.

        Parameters
        ----------
        timeout: ``float``, optional
            If ``None`` (default) wait indefinitely until the status finishes.

        Raises
        ------
        WaitTimeoutError
            If the status has not completed within ``timeout`` (starting from
            when this method was called, not from the beginning of the action).
        StatusTimeoutError
            If the status has failed because the *timeout* that it was
            initialized with has expired.
        Exception
            This is ``status.exception()``, raised if the status has finished
            with an error.  This may include ``TimeoutError``, which
            indicates that the action itself raised ``TimeoutError``, distinct
            from ``WaitTimeoutError`` above.
        """
        if not self._event.wait(timeout=timeout):
            raise WaitTimeoutError("Status has not completed yet.")
        if self._exception is not None:
            raise self._exception

    @property
    def callbacks(self) -> deque[Callable[[Status], None]]:
        """Callbacks to be run when the status is marked as finished."""
        return self._callbacks

    def add_callback(self, callback: Callable[[Status], None]) -> None:
        """Register a callback to be called once when the Status finishes.

        The callback will be called exactly once. If the Status is finished
        before a callback is added, it will be called immediately. This is
        threadsafe.
        The callback will be called regardless of success of failure. The
        callback has access to this status object, so it can distinguish success
        or failure by inspecting the object.

        Parameters
        ----------
        callback: ``Callable[[Status], None]``
            The callback to be called when the status is marked as finished.

            ```python
            def callback(status: Status) -> None:
                # Do something with the status object
                ...
            ```
        """
        with self._lock:
            if self.done:
                # Call it once and do not hold a reference to it.
                callback(self)
            else:
                # Hold a strong reference to this. In other contexts we tend to
                # hold weak references to callbacks, but this is a single-shot
                # callback, so we will hold a strong reference until we call it,
                # and then clear this cache to drop the reference(s).
                self._callbacks.append(callback)