"""
Interface to socketcand
see https://github.com/linux-can/socketcand

Authors: Marvin Seiler, Gerrit Telkamp

Copyright (C) 2021  DOMOLOGIC GmbH
http://www.domologic.de
"""

import logging
import os
import select
import socket
import time
import traceback
import urllib.parse as urlparselib
import xml.etree.ElementTree as ET
from collections import deque
from typing import List

import can

log = logging.getLogger(__name__)

DEFAULT_SOCKETCAND_DISCOVERY_ADDRESS = ""
DEFAULT_SOCKETCAND_DISCOVERY_PORT = 42000


def detect_beacon(timeout_ms: int = 3100) -> List[can.typechecking.AutoDetectedConfig]:
    """
    Detects socketcand servers

    This is what :meth:`can.detect_available_configs` ends up calling to search
    for available socketcand servers with a default timeout of 3100ms
    (socketcand sends a beacon packet every 3000ms).

    Using this method directly allows for adjusting the timeout. Extending
    the timeout beyond the default time period could be useful if UDP
    packet loss is a concern.

    :param timeout_ms:
        Timeout in milliseconds to wait for socketcand beacon packets

    :return:
        See :meth:`~can.detect_available_configs`
    """
    with socket.socket(socket.AF_INET, socket.SOCK_DGRAM) as sock:
        sock.bind(
            (DEFAULT_SOCKETCAND_DISCOVERY_ADDRESS, DEFAULT_SOCKETCAND_DISCOVERY_PORT)
        )
        log.info(
            "Listening on for socketcand UDP advertisement on %s:%s",
            DEFAULT_SOCKETCAND_DISCOVERY_ADDRESS,
            DEFAULT_SOCKETCAND_DISCOVERY_PORT,
        )

        now = time.time() * 1000
        end_time = now + timeout_ms
        while (time.time() * 1000) < end_time:
            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([sock], [], [], 1)

                if not ready_receive_sockets:
                    log.debug("No advertisement received")
                    continue

                msg = sock.recv(1024).decode("utf-8")
                root = ET.fromstring(msg)
                if root.tag != "CANBeacon":
                    log.debug("Unexpected message received over UDP")
                    continue

                det_devs = []
                det_host = None
                det_port = None
                for child in root:
                    if child.tag == "Bus":
                        bus_name = child.attrib["name"]
                        det_devs.append(bus_name)
                    elif child.tag == "URL":
                        url = urlparselib.urlparse(child.text)
                        det_host = url.hostname
                        det_port = url.port

                if not det_devs:
                    log.debug(
                        "Got advertisement, but no SocketCAN devices advertised by socketcand"
                    )
                    continue

                if (det_host is None) or (det_port is None):
                    det_host = None
                    det_port = None
                    log.debug(
                        "Got advertisement, but no SocketCAN URL advertised by socketcand"
                    )
                    continue

                log.info(f"Found SocketCAN devices: {det_devs}")
                return [
                    {
                        "interface": "socketcand",
                        "host": det_host,
                        "port": det_port,
                        "channel": channel,
                    }
                    for channel in det_devs
                ]

            except ET.ParseError:
                log.debug("Unexpected message received over UDP")
                continue

            except Exception as exc:
                # something bad happened (e.g. the interface went down)
                log.error(f"Failed to detect beacon: {exc}  {traceback.format_exc()}")
                raise OSError(
                    f"Failed to detect beacon: {exc} {traceback.format_exc()}"
                ) from exc

        return []


def convert_ascii_message_to_can_message(ascii_msg: str) -> can.Message:
    if not ascii_msg.startswith("< frame ") or not ascii_msg.endswith(" >"):
        log.warning(f"Could not parse ascii message: {ascii_msg}")
        return None
    else:
        # frame_string = ascii_msg.removeprefix("< frame ").removesuffix(" >")
        frame_string = ascii_msg[8:-2]
        parts = frame_string.split(" ", 3)
        can_id, timestamp = int(parts[0], 16), float(parts[1])
        is_ext = len(parts[0]) != 3

        data = bytearray.fromhex(parts[2])
        can_dlc = len(data)
        can_message = can.Message(
            timestamp=timestamp,
            arbitration_id=can_id,
            data=data,
            dlc=can_dlc,
            is_extended_id=is_ext,
            is_rx=True,
        )
        return can_message


def convert_can_message_to_ascii_message(can_message: can.Message) -> str:
    # Note: socketcan bus adds extended flag, remote_frame_flag & error_flag to id
    # not sure if that is necessary here
    can_id = can_message.arbitration_id
    if can_message.is_extended_id:
        can_id_string = f"{(can_id&0x1FFFFFFF):08X}"
    else:
        can_id_string = f"{(can_id&0x7FF):03X}"
    # Note: seems like we cannot add CANFD_BRS (bitrate_switch) and CANFD_ESI (error_state_indicator) flags
    data = can_message.data
    length = can_message.dlc
    bytes_string = " ".join(f"{x:x}" for x in data[0:length])
    return f"< send {can_id_string} {length:X} {bytes_string} >"


def connect_to_server(s, host, port):
    timeout_ms = 10000
    now = time.time() * 1000
    end_time = now + timeout_ms
    while now < end_time:
        try:
            s.connect((host, port))
            return
        except Exception as e:
            log.warning(f"Failed to connect to server: {type(e)} Message: {e}")
            now = time.time() * 1000
    raise TimeoutError(
        f"connect_to_server: Failed to connect server for {timeout_ms} ms"
    )


class SocketCanDaemonBus(can.BusABC):
    def __init__(self, channel, host, port, tcp_tune=False, can_filters=None, **kwargs):
        """Connects to a CAN bus served by socketcand.

        It implements :meth:`can.BusABC._detect_available_configs` to search for
        available interfaces.

        It will attempt to connect to the server for up to 10s, after which a
        TimeoutError exception will be thrown.

        If the handshake with the socketcand server fails, a CanError exception
        is thrown.

        :param channel:
            The can interface name served by socketcand.
            An example channel would be 'vcan0' or 'can0'.
        :param host:
            The host address of the socketcand server.
        :param port:
            The port of the socketcand server.
        :param tcp_tune:
            This tunes the TCP socket for low latency (TCP_NODELAY, and
            TCP_QUICKACK).
            This option is not available under windows.
        :param can_filters:
            See :meth:`can.BusABC.set_filters`.
        """
        self.__host = host
        self.__port = port

        self.__tcp_tune = tcp_tune
        self.__socket = socket.socket(socket.AF_INET, socket.SOCK_STREAM)

        if self.__tcp_tune:
            if os.name == "nt":
                self.__tcp_tune = False
                log.warning("'tcp_tune' not available in Windows. Setting to False")
            else:
                self.__socket.setsockopt(socket.IPPROTO_TCP, socket.TCP_NODELAY, 1)

        self.__message_buffer = deque()
        self.__receive_buffer = ""  # i know string is not the most efficient here
        self.channel = channel
        self.channel_info = f"socketcand on {channel}@{host}:{port}"
        connect_to_server(self.__socket, self.__host, self.__port)
        self._expect_msg("< hi >")

        log.info(
            f"SocketCanDaemonBus: connected with address {self.__socket.getsockname()}"
        )
        self._tcp_send(f"< open {channel} >")
        self._expect_msg("< ok >")
        self._tcp_send("< rawmode >")
        self._expect_msg("< ok >")
        super().__init__(channel=channel, can_filters=can_filters, **kwargs)

    def _recv_internal(self, timeout):
        if len(self.__message_buffer) != 0:
            can_message = self.__message_buffer.popleft()
            return can_message, False

        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 OSError as exc:
            # something bad happened (e.g. the interface went down)
            log.error(f"Failed to receive: {exc}")
            raise can.CanError(f"Failed to receive: {exc}") from exc

        try:
            if not ready_receive_sockets:
                # socket wasn't readable or timeout occurred
                log.debug("Socket not ready")
                return None, False

            ascii_msg = self.__socket.recv(1024).decode(
                "ascii"
            )  # may contain multiple messages
            if self.__tcp_tune:
                self.__socket.setsockopt(socket.IPPROTO_TCP, socket.TCP_QUICKACK, 1)
            self.__receive_buffer += ascii_msg
            log.debug(f"Received Ascii Message: {ascii_msg}")
            buffer_view = self.__receive_buffer
            chars_processed_successfully = 0
            while True:
                if len(buffer_view) == 0:
                    break

                start = buffer_view.find("<")
                if start == -1:
                    log.warning(
                        f"Bad data: No opening < found => discarding entire buffer '{buffer_view}'"
                    )
                    chars_processed_successfully = len(self.__receive_buffer)
                    break
                end = buffer_view.find(">")
                if end == -1:
                    log.warning("Got incomplete message => waiting for more data")
                    if len(buffer_view) > 200:
                        log.warning(
                            "Incomplete message exceeds 200 chars => Discarding"
                        )
                        chars_processed_successfully = len(self.__receive_buffer)
                    break
                chars_processed_successfully += end + 1
                single_message = buffer_view[start : end + 1]
                parsed_can_message = convert_ascii_message_to_can_message(
                    single_message
                )
                if parsed_can_message is None:
                    log.warning(f"Invalid Frame: {single_message}")
                else:
                    parsed_can_message.channel = self.channel
                    self.__message_buffer.append(parsed_can_message)
                buffer_view = buffer_view[end + 1 :]

            self.__receive_buffer = self.__receive_buffer[chars_processed_successfully:]
            can_message = (
                None
                if len(self.__message_buffer) == 0
                else self.__message_buffer.popleft()
            )
            return can_message, False

        except Exception as exc:
            log.error(f"Failed to receive: {exc}  {traceback.format_exc()}")
            raise can.CanError(
                f"Failed to receive: {exc}  {traceback.format_exc()}"
            ) from exc

    def _tcp_send(self, msg: str):
        log.debug(f"Sending TCP Message: '{msg}'")
        self.__socket.sendall(msg.encode("ascii"))
        if self.__tcp_tune:
            self.__socket.setsockopt(socket.IPPROTO_TCP, socket.TCP_QUICKACK, 1)

    def _expect_msg(self, msg):
        ascii_msg = self.__socket.recv(256).decode("ascii")
        if self.__tcp_tune:
            self.__socket.setsockopt(socket.IPPROTO_TCP, socket.TCP_QUICKACK, 1)
        if not ascii_msg == msg:
            raise can.CanError(f"Expected '{msg}' got: '{ascii_msg}'")

    def send(self, msg, timeout=None):
        """Transmit a message to the CAN bus.

        :param msg: A message object.
        :param timeout: Ignored
        """
        ascii_msg = convert_can_message_to_ascii_message(msg)
        self._tcp_send(ascii_msg)

    def shutdown(self):
        """Stops all active periodic tasks and closes the socket."""
        super().shutdown()
        self.__socket.close()

    @staticmethod
    def _detect_available_configs() -> List[can.typechecking.AutoDetectedConfig]:
        try:
            return detect_beacon()
        except Exception as e:
            log.warning(f"Could not detect socketcand beacon: {e}")
            return []
