#!/usr/bin/python
#
#  Copyright (c) 2016, The OpenThread Authors.
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import os
import socket
import sys


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

    WELLKNOWN_NODE_ID = 34

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

    def __init__(self, nodeid):
        self._nodeid = nodeid
        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.WELLKNOWN_NODE_ID) + nodeid

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

    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.bind(self._nodeid_to_address(self._nodeid))

    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 SnifferTransportFactory(object):

    def create_transport(self, nodeid):
        if sys.platform != "win32":
            return SnifferSocketTransport(nodeid)

        else:
            raise NotImplementedError
