#!/usr/bin/env python3
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import ctypes
import os
import socket


class SnifferTransport(object):
    """ Interface for transport that allows eavesdrop other nodes. """

    def open(self):
        """ Open transport.

        Raises:
            RuntimeError: when transport is already opened or when transport opening failed.
        """
        raise NotImplementedError

    def close(self):
        """ Close transport.

        Raises:
            RuntimeError: when transport is already closed.
        """
        raise NotImplementedError

    @property
    def is_opened(self):
        """ Check if transport is opened.

        Returns:
            bool: True if the transport is opened, False in otherwise
        """
        raise NotImplementedError

    def send(self, data, nodeid):
        """ Send data to the node with nodeid.

        Args:
            data (bytearray): outcoming data.
            nodeid (int): node id

        Returns:
            int: number of sent bytes
        """
        raise NotImplementedError

    def recv(self, bufsize):
        """ Receive data sent by other node.

        Args:
            bufsize (int): size of buffer for incoming data.

        Returns:
            A tuple contains data and node id.

            For example:
            (bytearray([0x00, 0x01...], 1)
        """
        raise NotImplementedError


class SnifferSocketTransport(SnifferTransport):
    """ Socket based implementation of sniffer transport. """

    BASE_PORT = 9000

    MAX_NETWORK_SIZE = 33

    PORT_OFFSET = int(os.getenv('PORT_OFFSET', "0"))

    RADIO_GROUP = '224.0.0.116'

    def __init__(self):
        self._socket = None

    def __del__(self):
        if not self.is_opened:
            return

        self.close()

    def _nodeid_to_address(self, nodeid, ip_address=''):
        return (
            ip_address,
            self.BASE_PORT + (self.PORT_OFFSET * (self.MAX_NETWORK_SIZE + 1)) + nodeid,
        )

    def _address_to_nodeid(self, address):
        _, port = address
        return (port - self.BASE_PORT - (self.PORT_OFFSET * (self.MAX_NETWORK_SIZE + 1)))

    def open(self):
        if self.is_opened:
            raise RuntimeError("Transport is already opened.")

        self._socket = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)

        if not self.is_opened:
            raise RuntimeError("Transport opening failed.")

        self._socket.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
        self._socket.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEPORT, 1)
        self._socket.setsockopt(socket.SOL_SOCKET, socket.SO_RCVBUF, 2 * 1024 * 1024)
        self._socket.setsockopt(socket.SOL_SOCKET, socket.SO_SNDBUF, 2 * 1024 * 1024)
        self._socket.setsockopt(socket.IPPROTO_IP, socket.IP_ADD_MEMBERSHIP,
                                socket.inet_aton(self.RADIO_GROUP) + socket.inet_aton('127.0.0.1'))
        self._socket.bind(self._nodeid_to_address(0))

    def close(self):
        if not self.is_opened:
            raise RuntimeError("Transport is closed.")

        self._socket.close()
        self._socket = None

    @property
    def is_opened(self):
        return bool(self._socket is not None)

    def send(self, data, nodeid):
        address = self._nodeid_to_address(nodeid)

        return self._socket.sendto(data, address)

    def recv(self, bufsize):
        data, address = self._socket.recvfrom(bufsize)

        nodeid = self._address_to_nodeid(address)

        return bytearray(data), nodeid


class MacFrame(ctypes.Structure):
    _fields_ = [
        ("buffer", ctypes.c_ubyte * 128),
        ("length", ctypes.c_ubyte),
        ("nodeid", ctypes.c_uint),
    ]


class SnifferTransportFactory(object):

    def create_transport(self):
        return SnifferSocketTransport()