import logging
import select
import socket
import struct

from typing import List, Optional, Tuple, Union

log = logging.getLogger(__name__)

import can
from can import BusABC
from can.typechecking import AutoDetectedConfig

from .utils import pack_message, unpack_message, check_msgpack_installed


# see socket.getaddrinfo()
IPv4_ADDRESS_INFO = Tuple[str, int]  # address, port
IPv6_ADDRESS_INFO = Tuple[str, int, int, int]  # address, port, flowinfo, scope_id
IP_ADDRESS_INFO = Union[IPv4_ADDRESS_INFO, IPv6_ADDRESS_INFO]

# Additional constants for the interaction with Unix kernels
SO_TIMESTAMPNS = 35


class UdpMulticastBus(BusABC):
    """A virtual interface for CAN communications between multiple processes using UDP over Multicast IP.

    It supports IPv4 and IPv6, specified via the channel (which really is just a multicast IP address as a
    string). You can also specify the port and the IPv6 *hop limit*/the IPv4 *time to live* (TTL).

    This bus does not support filtering based on message IDs on the kernel level but instead provides it in
    user space (in Python) as a fallback.

    Both default addresses should allow for multi-host CAN networks in a normal local area network (LAN) where
    multicast is enabled.

    .. note::
        The auto-detection of available interfaces (see) is implemented using heuristic that checks if the
        required socket operations are available. It then returns two configurations, one based on
        the :attr:`~UdpMulticastBus.DEFAULT_GROUP_IPv6` address and another one based on
        the :attr:`~UdpMulticastBus.DEFAULT_GROUP_IPv4` address.

    .. warning::
        The parameter `receive_own_messages` is currently unsupported and setting it to `True` will raise an
        exception.

    .. warning::
        This interface does not make guarantees on reliable delivery and message ordering, and also does not
        implement rate limiting or ID arbitration/prioritization under high loads. Please refer to the section
        :ref:`other_virtual_interfaces` for more information on this and a comparison to alternatives.

    :param channel: A multicast IPv4 address (in `224.0.0.0/4`) or an IPv6 address (in `ff00::/8`).
                    This defines which version of IP is used. See
                    `Wikipedia ("Multicast address") <https://en.wikipedia.org/wiki/Multicast_address>`__
                    for more details on the addressing schemes.
                    Defaults to :attr:`~UdpMulticastBus.DEFAULT_GROUP_IPv6`.
    :param port: The IP port to read from and write to.
    :param hop_limit: The hop limit in IPv6 or in IPv4 the time to live (TTL).
    :param receive_own_messages: If transmitted messages should also be received by this bus.
                                 CURRENTLY UNSUPPORTED.
    :param fd:
        If CAN-FD frames should be supported. If set to false, an error will be raised upon sending such a
        frame and such received frames will be ignored.
    :param can_filters: See :meth:`~can.BusABC.set_filters`.

    :raises RuntimeError: If the *msgpack*-dependency is not available. It should be installed on all
                          non Windows platforms via the `setup.py` requirements.
    :raises NotImplementedError: If the `receive_own_messages` is passed as `True`.
    """

    #: An arbitrary IPv6 multicast address with "site-local" scope, i.e. only to be routed within the local
    #: physical network and not beyond it. It should allow for multi-host CAN networks in a normal IPv6 LAN.
    #: This is the default channel and should work with most modern routers if multicast is allowed.
    DEFAULT_GROUP_IPv6 = "ff15:7079:7468:6f6e:6465:6d6f:6d63:6173"

    #: An arbitrary IPv4 multicast address with "administrative" scope, i.e. only to be routed within
    #: administrative organizational boundaries and not beyond it.
    #: It should allow for multi-host CAN networks in a normal IPv4 LAN.
    #: This is provided as a default fallback channel if IPv6 is (still) not supported.
    DEFAULT_GROUP_IPv4 = "239.74.163.2"

    def __init__(
        self,
        channel: str = DEFAULT_GROUP_IPv6,
        port: int = 43113,
        hop_limit: int = 1,
        receive_own_messages: bool = False,
        fd: bool = True,
        **kwargs,
    ) -> None:
        check_msgpack_installed()

        if receive_own_messages:
            raise can.CanInterfaceNotImplementedError(
                "receiving own messages is not yet implemented"
            )

        super().__init__(channel, **kwargs)

        self.is_fd = fd
        self._multicast = GeneralPurposeUdpMulticastBus(channel, port, hop_limit)

    def _recv_internal(self, timeout: Optional[float]):
        result = self._multicast.recv(timeout)
        if not result:
            return None, False

        data, _, timestamp = result
        try:
            can_message = unpack_message(
                data, replace={"timestamp": timestamp}, check=True
            )
        except Exception as exception:
            raise can.CanOperationError(
                "could not unpack received message"
            ) from exception

        if not self.is_fd and can_message.is_fd:
            return None, False

        return can_message, False

    def send(self, msg: can.Message, timeout: Optional[float] = None) -> None:
        if not self.is_fd and msg.is_fd:
            raise can.CanOperationError(
                "cannot send FD message over bus with CAN FD disabled"
            )

        data = pack_message(msg)
        self._multicast.send(data, timeout)

    def fileno(self) -> int:
        """Provides the internally used file descriptor of the socket or `-1` if not available."""
        return self._multicast.fileno()

    def shutdown(self) -> None:
        """Close all sockets and free up any resources.

        Never throws errors and only logs them.
        """
        super().shutdown()
        self._multicast.shutdown()

    @staticmethod
    def _detect_available_configs() -> List[AutoDetectedConfig]:
        if hasattr(socket, "CMSG_SPACE"):
            return [
                {
                    "interface": "udp_multicast",
                    "channel": UdpMulticastBus.DEFAULT_GROUP_IPv6,
                },
                {
                    "interface": "udp_multicast",
                    "channel": UdpMulticastBus.DEFAULT_GROUP_IPv4,
                },
            ]

        # else, this interface cannot be used
        return []


class GeneralPurposeUdpMulticastBus:
    """A general purpose send and receive handler for multicast over IP/UDP.

    However, it raises CAN-specific exceptions for convenience.
    """

    def __init__(
        self, group: str, port: int, hop_limit: int, max_buffer: int = 4096
    ) -> None:
        self.group = group
        self.port = port
        self.hop_limit = hop_limit
        self.max_buffer = max_buffer

        # Look up multicast group address in name server and find out IP version of the first suitable target
        # and then get the address family of it (socket.AF_INET or socket.AF_INET6)
        connection_candidates = socket.getaddrinfo(  # type: ignore
            group, self.port, type=socket.SOCK_DGRAM
        )
        sock = None
        for connection_candidate in connection_candidates:
            address_family: socket.AddressFamily = connection_candidate[0]
            self.ip_version = 4 if address_family == socket.AF_INET else 6
            try:
                sock = self._create_socket(address_family)
            except OSError as error:
                log.info(
                    "could not connect to the multicast IP network of candidate %s; reason: %s",
                    connection_candidates,
                    error,
                )
        if sock is not None:
            self._socket = sock
        else:
            raise can.CanInitializationError(
                "could not connect to a multicast IP network"
            )

        # used in recv()
        self.received_timestamp_struct = "@ll"
        ancillary_data_size = struct.calcsize(self.received_timestamp_struct)
        self.received_ancillary_buffer_size = socket.CMSG_SPACE(ancillary_data_size)

        # used by send()
        self._send_destination = (self.group, self.port)
        self._last_send_timeout: Optional[float] = None

    def _create_socket(self, address_family: socket.AddressFamily) -> socket.socket:
        """Creates a new socket. This might fail and raise an exception!

        :param address_family: whether this is of type `socket.AF_INET` or `socket.AF_INET6`

        :raises can.CanInitializationError:
            if the socket could not be opened or configured correctly; in this case, it is
            guaranteed to be closed/cleaned up
        """
        # create the UDP socket
        # this might already fail but then there is nothing to clean up
        sock = socket.socket(address_family, socket.SOCK_DGRAM)

        # configure the socket
        try:

            # set hop limit / TTL
            ttl_as_binary = struct.pack("@I", self.hop_limit)
            if self.ip_version == 4:
                sock.setsockopt(
                    socket.IPPROTO_IP, socket.IP_MULTICAST_TTL, ttl_as_binary
                )
            else:
                sock.setsockopt(
                    socket.IPPROTO_IPV6, socket.IPV6_MULTICAST_HOPS, ttl_as_binary
                )

            # Allow multiple programs to access that address + port
            sock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)

            # set how to receive timestamps
            sock.setsockopt(socket.SOL_SOCKET, SO_TIMESTAMPNS, 1)

            # Bind it to the port (on any interface)
            sock.bind(("", self.port))

            # Join the multicast group
            group_as_binary = socket.inet_pton(address_family, self.group)
            if self.ip_version == 4:
                request = group_as_binary + struct.pack("@I", socket.INADDR_ANY)
                sock.setsockopt(socket.IPPROTO_IP, socket.IP_ADD_MEMBERSHIP, request)
            else:
                request = group_as_binary + struct.pack("@I", 0)
                sock.setsockopt(socket.IPPROTO_IPV6, socket.IPV6_JOIN_GROUP, request)

            return sock

        except OSError as error:
            # clean up the incompletely configured but opened socket
            try:
                sock.close()
            except OSError as close_error:
                # ignore but log any failures in here
                log.warning("Could not close partly configured socket: %s", close_error)

            # still raise the error
            raise can.CanInitializationError(
                "could not create or configure socket"
            ) from error

    def send(self, data: bytes, timeout: Optional[float] = None) -> None:
        """Send data to all group members. This call blocks.

        :param timeout: the timeout in seconds after which an Exception is raised is sending has failed
        :param data: the data to be sent
        :raises OSError: if an error occurred while writing to the underlying socket
        :raises socket.timeout: if the timeout ran out before sending was completed (this is a subclass of
                                *OSError*)
        """
        if timeout != self._last_send_timeout:
            self._last_send_timeout = timeout
            # this applies to all blocking calls on the socket, but sending is the only one that is blocking
            self._socket.settimeout(timeout)

        bytes_sent = self._socket.sendto(data, self._send_destination)
        if bytes_sent < len(data):
            raise socket.timeout()

    def recv(
        self, timeout: Optional[float] = None
    ) -> Optional[Tuple[bytes, IP_ADDRESS_INFO, float]]:
        """
        Receive up to **max_buffer** bytes.

        :param timeout: the timeout in seconds after which `None` is returned if no data arrived
        :returns: `None` on timeout, or a 3-tuple comprised of:
            - received data,
            - the sender of the data, and
            - a timestamp in seconds
        """
        # get all sockets that are ready (can be a list with a single value
        # being self.socket or an empty list if self.socket is not ready)
        try:
            # get all sockets that are ready (can be a list with a single value
            # being self.socket or an empty list if self.socket is not ready)
            ready_receive_sockets, _, _ = select.select([self._socket], [], [], timeout)
        except socket.error as exc:
            # something bad (not a timeout) happened (e.g. the interface went down)
            raise can.CanOperationError(
                f"Failed to wait for IP/UDP socket: {exc}"
            ) from exc

        if ready_receive_sockets:  # not empty
            # fetch data & source address
            (
                raw_message_data,
                ancillary_data,
                _,  # flags
                sender_address,
            ) = self._socket.recvmsg(
                self.max_buffer, self.received_ancillary_buffer_size
            )

            # fetch timestamp; this is configured in in _create_socket()
            assert len(ancillary_data) == 1, "only requested a single extra field"
            cmsg_level, cmsg_type, cmsg_data = ancillary_data[0]
            assert (
                cmsg_level == socket.SOL_SOCKET and cmsg_type == SO_TIMESTAMPNS
            ), "received control message type that was not requested"
            # see https://man7.org/linux/man-pages/man3/timespec.3.html -> struct timespec for details
            seconds, nanoseconds = struct.unpack(
                self.received_timestamp_struct, cmsg_data
            )
            if nanoseconds >= 1e9:
                raise can.CanError(
                    f"Timestamp nanoseconds field was out of range: {nanoseconds} not less than 1e9"
                )
            timestamp = seconds + nanoseconds * 1.0e-9

            return raw_message_data, sender_address, timestamp

        # socket wasn't readable or timeout occurred
        return None

    def fileno(self) -> int:
        """Provides the internally used file descriptor of the socket or `-1` if not available."""
        return self._socket.fileno()

    def shutdown(self) -> None:
        """Close all sockets and free up any resources.

        Never throws errors and only logs them.
        """
        try:
            self._socket.close()
        except OSError as exception:
            log.error("could not close IP socket: %s", exception)
