# Source code for can.interface

    # coding: utf-8

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

    from __future__ import absolute_import, print_function

    import sys
    import importlib
    import logging

    import can
    from .bus import BusABC
    from .broadcastmanager import CyclicSendTaskABC, MultiRateCyclicSendTaskABC
    from .util import load_config
    from .interfaces import BACKENDS

    if 'linux' in sys.platform:
        # Deprecated and undocumented access to SocketCAN cyclic tasks
        # Will be removed in version 4.0
        from can.interfaces.socketcan import CyclicSendTask, MultiRateCyclicSendTask

    # Required by "detect_available_configs" for argument interpretation
    if sys.version_info.major > 2:
        basestring = str

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

    def _get_class_for_interface(interface):
        """
        Returns the main bus class for the given interface.

        :raises:
            NotImplementedError if the interface is not known
        :raises:
            ImportError     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("CAN interface '{}' not supported".format(interface))

        # Import the correct interface module
        try:
            module = importlib.import_module(module_name)
        except Exception as e:
            raise ImportError(
                "Cannot import module {} for CAN interface '{}': {}".format(module_name, interface, e)
            )

        # Get the correct class
        try:
            bus_class = getattr(module, class_name)
        except Exception as e:
            raise ImportError(
                "Cannot import class {} from module {} for CAN interface '{}': {}"
                    .format(class_name, module_name, interface, e)
            )

        return bus_class

    class Bus(BusABC):
        """Bus wrapper with configuration loading.

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

        @staticmethod
        def __new__(cls, channel=None, *args, **kwargs):
            """
            Takes the same arguments as :class:`can.BusABC.__init__`.
            Some might have a special meaning, see below.

            :param channel:
                Set to ``None`` to let it be reloved automatically from the default
                configuration. That might fail, see below.

                Expected type is backend dependent.

            :param dict kwargs:
                Should contain an ``interface`` key with a valid interface name. If not,
                it is completed using :meth:`can.util.load_config`.

            :raises: NotImplementedError
                if the ``interface`` isn't recognized

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

            # figure out the rest of the configuration; this might raise an error
            if channel is not None:
                kwargs['channel'] = channel
            if 'context' in kwargs:
                context = kwargs['context']
                del kwargs['context']
            else:
                context = None
            kwargs = load_config(config=kwargs, context=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
            if 'channel' not in kwargs:
                raise ValueError("'channel' argument missing")
            else:
                channel = kwargs['channel']
                del kwargs['channel']

            if channel is None:
                # Use the default channel for the backend
                return cls(*args, **kwargs)
            else:
                return cls(channel, *args, **kwargs)

    def detect_available_configs(interfaces=None):
        """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 with 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.
        :rtype: list[dict]
        :return: an iterable of dicts, each suitable for usage in
                 the constructor of :class:`can.BusABC`.
        """

        # Figure out where to search
        if interfaces is None:
            # use an iterator over the keys so we do not have to copy it
            interfaces = BACKENDS.keys()
        elif isinstance(interfaces, basestring):
            interfaces = [interfaces, ]
        # else it is supposed to be an iterable of strings

        result = []
        for interface in interfaces:

            try:
                bus_class = _get_class_for_interface(interface)
            except ImportError:
                log_autodetect.debug('interface "%s" can not be loaded for detection of available configurations', interface)
                continue

            # get available channels
            try:
                available = list(bus_class._detect_available_configs())
            except NotImplementedError:
                log_autodetect.debug('interface "%s" does not support detection of available configurations', interface)
            else:
                log_autodetect.debug('interface "%s" detected %i available configurations', interface, len(available))

                # add the interface name to the configs if it is not already present
                for config in available:
                    if 'interface' not in config:
                        config['interface'] = interface

                # append to result
                result += available

        return result