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# Source code for can.interface

    """
    This module contains the base implementation of :class:`can.BusABC` as well
    as a list of all available backends and some implemented
    CyclicSendTasks.
    """

    import concurrent.futures.thread
    import importlib
    import logging
    from collections.abc import Callable, Iterable, Sequence
    from typing import Any, Optional, Union, cast

    from . import util
    from .bus import BusABC
    from .exceptions import CanInterfaceNotImplementedError
    from .interfaces import BACKENDS
    from .typechecking import AutoDetectedConfig, Channel

    log = logging.getLogger("can.interface")
    log_autodetect = log.getChild("detect_available_configs")

    def _get_class_for_interface(interface: str) -> type[BusABC]:
        """
        Returns the main bus class for the given interface.

        :raises:
            NotImplementedError if the interface is not known
        :raises CanInterfaceNotImplementedError:
             if there was a problem while importing the interface or the bus class within that
        """
        # Find the correct backend
        try:
            module_name, class_name = BACKENDS[interface]
        except KeyError:
            raise NotImplementedError(
                f"CAN interface '{interface}' not supported"
            ) from None

        # Import the correct interface module
        try:
            module = importlib.import_module(module_name)
        except Exception as e:
            raise CanInterfaceNotImplementedError(
                f"Cannot import module {module_name} for CAN interface '{interface}': {e}"
            ) from None

        # Get the correct class
        try:
            bus_class = getattr(module, class_name)
        except Exception as e:
            raise CanInterfaceNotImplementedError(
                f"Cannot import class {class_name} from module {module_name} for CAN interface "
                f"'{interface}': {e}"
            ) from None

        return cast("type[BusABC]", bus_class)

    @util.deprecated_args_alias(
        deprecation_start="4.2.0",
        deprecation_end="5.0.0",
        bustype="interface",
        context="config_context",
    )
    def Bus(  # noqa: N802
        channel: Optional[Channel] = None,
        interface: Optional[str] = None,
        config_context: Optional[str] = None,
        ignore_config: bool = False,
        **kwargs: Any,
    ) -> BusABC:
        """Create a new bus instance with configuration loading.

        Instantiates a CAN Bus of the given ``interface``, falls back to reading a
        configuration file from default locations.

        .. note::
            Please note that while the arguments provided to this class take precedence
            over any existing values from configuration, it is possible that other parameters
            from the configuration may be added to the bus instantiation.
            This could potentially have unintended consequences. To prevent this,
            you may use the *ignore_config* parameter to ignore any existing configurations.

        :param channel:
            Channel identification. Expected type is backend dependent.
            Set to ``None`` to let it be resolved automatically from the default
            :ref:`configuration`.

        :param interface:
            See :ref:`interface names` for a list of supported interfaces.
            Set to ``None`` to let it be resolved automatically from the default
            :ref:`configuration`.

        :param config_context:
            Extra 'context', that is passed to config sources.
            This can be used to select a section other than 'default' in the configuration file.

        :param ignore_config:
            If ``True``, only the given arguments will be used for the bus instantiation. Existing
            configuration sources will be ignored.

        :param kwargs:
            ``interface`` specific keyword arguments.

        :raises ~can.exceptions.CanInterfaceNotImplementedError:
            if the ``interface`` isn't recognized or cannot be loaded

        :raises ~can.exceptions.CanInitializationError:
            if the bus cannot be instantiated

        :raises ValueError:
            if the ``channel`` could not be determined
        """

        # figure out the rest of the configuration; this might raise an error
        if interface is not None:
            kwargs["interface"] = interface
        if channel is not None:
            kwargs["channel"] = channel

        if not ignore_config:
            kwargs = util.load_config(config=kwargs, context=config_context)

        # resolve the bus class to use for that interface
        cls = _get_class_for_interface(kwargs["interface"])

        # remove the "interface" key, so it doesn't get passed to the backend
        del kwargs["interface"]

        # make sure the bus can handle this config format
        channel = kwargs.pop("channel", channel)
        if channel is None:
            # Use the default channel for the backend
            bus = cls(**kwargs)
        else:
            bus = cls(channel, **kwargs)

        return bus

    def detect_available_configs(
        interfaces: Union[None, str, Iterable[str]] = None,
        timeout: float = 5.0,
    ) -> Sequence[AutoDetectedConfig]:
        """Detect all configurations/channels that the interfaces could
        currently connect with.

        This might be quite time-consuming.

        Automated configuration detection may not be implemented by
        every interface on every platform. This method will not raise
        an error in that case, but will rather return an empty list
        for that interface.

        :param interfaces: either
            - the name of an interface to be searched in as a string,
            - an iterable of interface names to search in, or
            - `None` to search in all known interfaces.
        :param timeout: maximum number of seconds to wait for all interface
            detection tasks to complete. If exceeded, any pending tasks
            will be cancelled, a warning will be logged, and the method
            will return results gathered so far.
        :rtype: list[dict]
        :return: an iterable of dicts, each suitable for usage in
                 the constructor of :class:`can.BusABC`. Interfaces that
                 timed out will be logged as warnings and excluded.
        """

        # Determine which interfaces to search
        if interfaces is None:
            interfaces = BACKENDS
        elif isinstance(interfaces, str):
            interfaces = (interfaces,)
        # otherwise assume iterable of strings

        # Collect detection callbacks
        callbacks: dict[str, Callable[[], Sequence[AutoDetectedConfig]]] = {}
        for interface_keyword in interfaces:
            try:
                bus_class = _get_class_for_interface(interface_keyword)
                callbacks[interface_keyword] = (
                    bus_class._detect_available_configs  # pylint: disable=protected-access
                )
            except CanInterfaceNotImplementedError:
                log_autodetect.debug(
                    'interface "%s" cannot be loaded for detection of available configurations',
                    interface_keyword,
                )

        result: list[AutoDetectedConfig] = []

        # Use manual executor to allow shutdown without waiting
        executor = concurrent.futures.ThreadPoolExecutor()
        try:
            futures_to_keyword = {
                executor.submit(func): kw for kw, func in callbacks.items()
            }
            done, not_done = concurrent.futures.wait(
                futures_to_keyword,
                timeout=timeout,
                return_when=concurrent.futures.ALL_COMPLETED,
            )
            # Log timed-out tasks
            if not_done:
                log_autodetect.warning(
                    "Timeout (%.2fs) reached for interfaces: %s",
                    timeout,
                    ", ".join(sorted(futures_to_keyword[fut] for fut in not_done)),
                )
            # Process completed futures
            for future in done:
                keyword = futures_to_keyword[future]
                try:
                    available = future.result()
                except NotImplementedError:
                    log_autodetect.debug(
                        'interface "%s" does not support detection of available configurations',
                        keyword,
                    )
                else:
                    log_autodetect.debug(
                        'interface "%s" detected %i available configurations',
                        keyword,
                        len(available),
                    )
                    for config in available:
                        config.setdefault("interface", keyword)
                    result.extend(available)
        finally:
            # shutdown immediately, do not wait for pending threads
            executor.shutdown(wait=False, cancel_futures=True)
        return result