#!/usr/bin/env python
# -*- coding: utf-8 -*-

# This file is part of Beremiz, a Integrated Development Environment for
# programming IEC 61131-3 automates supporting plcopen standard and CanFestival.
#
# Copyright (C) 2019: Edouard TISSERANT
#
# See COPYING file for copyrights details.
#
# This program is free software; you can redistribute it and/or
# modify it under the terms of the GNU General Public License
# as published by the Free Software Foundation; either version 2
# of the License, or (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program; if not, write to the Free Software
# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.


"""
The TLS-PSK adapter that handles SSL connections instead of regular sockets,
but using Pre Shared Keys instead of Certificates
"""

from __future__ import absolute_import
from __future__ import print_function

import socket
import re
import ssl
import Pyro
from Pyro.core import PyroURI
from Pyro.protocol import _connect_socket, TCPConnection, PYROAdapter
from Pyro.errors import ConnectionDeniedError, ProtocolError
from Pyro.util import Log

try:
    import sslpsk
except ImportError as e:
    print(str(e))
    sslpsk = None


class PYROPSKAdapter(PYROAdapter):
    """
    This is essentialy the same as in Pyro/protocol.py
    only raw_sock wrapping into sock through sslpsk.wrap_socket was added
    Pyro unfortunately doesn't allow cleaner customization
    """

    def bindToURI(self, URI):
        with self.lock:   # only 1 thread at a time can bind the URI
            try:
                self.URI = URI

                # This are the statements that differ from Pyro/protocol.py
                raw_sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
                _connect_socket(raw_sock, URI.address, URI.port, self.timeout)
                sock = sslpsk.wrap_socket(
                    raw_sock, psk=Pyro.config.PYROPSK, server_side=False,
                    ciphers="PSK-AES256-CBC-SHA",  # available in openssl 1.0.2
                    ssl_version=ssl.PROTOCOL_TLSv1)
                # all the rest is the same as in Pyro/protocol.py

                conn = TCPConnection(sock, sock.getpeername())
                # receive the authentication challenge string, and use that to build the actual identification string.
                try:
                    authChallenge = self.recvAuthChallenge(conn)
                except ProtocolError as x:
                    # check if we were denied
                    if hasattr(x, "partialMsg") and x.partialMsg[:len(self.denyMSG)] == self.denyMSG:
                        raise ConnectionDeniedError(Pyro.constants.deniedReasons[int(x.partialMsg[-1])])
                    else:
                        raise
                # reply with our ident token, generated from the ident passphrase and the challenge
                msg = self._sendConnect(sock, self.newConnValidator.createAuthToken(self.ident, authChallenge, conn.addr, self.URI, None))
                if msg == self.acceptMSG:
                    self.conn = conn
                    self.conn.connected = 1
                    Log.msg('PYROAdapter', 'connected to', str(URI))
                    if URI.protocol == 'PYROLOCPSK':
                        self.resolvePYROLOC_URI("PYROPSK")  # updates self.URI
                elif msg[:len(self.denyMSG)] == self.denyMSG:
                    try:
                        raise ConnectionDeniedError(Pyro.constants.deniedReasons[int(msg[-1])])
                    except (KeyError, ValueError):
                        raise ConnectionDeniedError('invalid response')
            except socket.error:
                Log.msg('PYROAdapter', 'connection failed to URI', str(URI))
                raise ProtocolError('connection failed')


_getProtocolAdapter = Pyro.protocol.getProtocolAdapter


def getProtocolAdapter(protocol):
    if protocol in ('PYROPSK', 'PYROLOCPSK'):
        return PYROPSKAdapter()
    return _getProtocolAdapter(protocol)


_processStringURI = Pyro.core.processStringURI


def processStringURI(URI):
    x = re.match(r'(?P<protocol>PYROLOCPSK)://(?P<hostname>[^\s:]+):?(?P<port>\d+)?/(?P<name>\S*)', URI)
    if x:
        protocol = x.group('protocol')
        hostname = x.group('hostname')
        port = x.group('port')
        if port:
            port = int(port)
        else:
            port = 0
        name = x.group('name')
        return PyroURI(hostname, name, port, protocol)
    return _processStringURI(URI)


def setupPSKAdapter():
    """
    Add PyroAdapter to the list of available in
    Pyro adapters and handle new supported protocols

    This function should be called after
    reimport of Pyro module to enable PYROS:// again.
    """
    if sslpsk is not None:
        Pyro.protocol.getProtocolAdapter = getProtocolAdapter
        Pyro.core.processStringURI = processStringURI
    else:
        raise Exception("sslpsk python module unavailable")