#!/usr/bin/env python2
# -*- coding: utf-8 -*-

# SAT plugin for NAT port mapping
# Copyright (C) 2009-2016 Jérôme Poisson (goffi@goffi.org)

# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU Affero General Public License as published by
# the Free Software Foundation, either version 3 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 Affero General Public License for more details.

# You should have received a copy of the GNU Affero General Public License
# along with this program.  If not, see <http://www.gnu.org/licenses/>.

from sat.core.i18n import _
from sat.core.constants import Const as C
from sat.core.log import getLogger
log = getLogger(__name__)
from sat.core import exceptions
from twisted.internet import threads
from twisted.internet import defer
from twisted.python import failure
import threading

try:
    import miniupnpc
except ImportError:
    raise exceptions.MissingModule(u"Missing module MiniUPnPc, please download/install it (and its Python binding) at http://miniupnp.free.fr/ (or use pip install miniupnpc)")


PLUGIN_INFO = {
    "name": "NAT port mapping",
    "import_name": "NAT-PORT",
    "type": C.PLUG_TYPE_MISC,
    "main": "NatPort",
    "handler": "no",
    "description": _("""Automatic NAT port mapping using UPnP"""),
}

STARTING_PORT = 6000 # starting point to automatically find a port
DEFAULT_DESC = u'SaT port mapping' # we don't use "à" here as some bugged NAT don't manage charset correctly


class MappingError(Exception):
    pass


class NatPort(object):
    # TODO: refresh data if a new connection is detected (see plugin_misc_ip)

    def __init__(self, host):
        log.info(_("plugin NAT Port initialization"))
        self.host = host
        self._external_ip = None
        self._initialised = defer.Deferred()
        self._upnp = miniupnpc.UPnP() # will be None if no device is available
        self._upnp.discoverdelay=200
        self._mutex = threading.Lock() # used to protect access to self._upnp
        self._starting_port_cache = None # used to cache the first available port
        self._to_unmap = [] # list of tuples (ext_port, protocol) of ports to unmap on unload
        discover_d = threads.deferToThread(self._discover)
        discover_d.chainDeferred(self._initialised)
        self._initialised.addErrback(self._init_failed)

    def unload(self):
        if self._to_unmap:
            log.info(u"Cleaning mapped ports")
            return threads.deferToThread(self._unmapPortsBlocking)

    def _init_failed(self, failure_):
        e = failure_.trap(exceptions.NotFound, exceptions.FeatureNotFound)
        if e == exceptions.FeatureNotFound:
            log.info(u"UPnP-IGD seems to be not activated on the device")
        else:
            log.info(u"UPnP-IGD not available")
        self._upnp = None

    def _discover(self):
        devices = self._upnp.discover()
        if devices:
            log.info(u"{nb} UPnP-IGD device(s) found".format(nb=devices))
        else:
            log.info(u"Can't find UPnP-IGD device on the local network")
            raise failure.Failure(exceptions.NotFound())
        self._upnp.selectigd()
        try:
            self._external_ip = self._upnp.externalipaddress()
        except Exception:
            raise failure.Failure(exceptions.FeatureNotFound())

    def getIP(self, local=False):
        """Return IP address found with UPnP-IGD

        @param local(bool): True to get external IP address, False to get local network one
        @return (None, str): found IP address, or None of something got wrong
        """
        def getIP(dummy):
            if self._upnp is None:
                return None
            # lanaddr can be the empty string if not found,
            # we need to return None in this case
            return (self._upnp.lanaddr or None) if local else self._external_ip
        return self._initialised.addCallback(getIP)

    def _unmapPortsBlocking(self):
        """Unmap ports mapped in this session"""
        self._mutex.acquire()
        try:
            for port, protocol in self._to_unmap:
                log.info(u"Unmapping port {}".format(port))
                unmapping = self._upnp.deleteportmapping(
                    # the last parameter is remoteHost, we don't use it
                    port, protocol, '')

                if not unmapping:
                    log.error(u"Can't unmap port {port} ({protocol})".format(
                        port=port, protocol=protocol))
            del self._to_unmap[:]
        finally:
            self._mutex.release()

    def _mapPortBlocking(self, int_port, ext_port, protocol, desc):
        """Internal blocking method to map port

        @param int_port(int): internal port to use
        @param ext_port(int): external port to use, or None to find one automatically
        @param protocol(str): 'TCP' or 'UDP'
        @param desc(str): description of the mapping
        @param return(int, None): external port used in case of success, otherwise None
        """
        # we use mutex to avoid race condition if 2 threads
        # try to acquire a port at the same time
        self._mutex.acquire()
        try:
            if ext_port is None:
                # find a free port
                starting_port = self._starting_port_cache
                ext_port = STARTING_PORT if starting_port is None else starting_port
                ret = self._upnp.getspecificportmapping(ext_port, protocol)
                while ret != None and ext_port < 65536:
                        ext_port += 1
                        ret = self._upnp.getspecificportmapping(ext_port, protocol)
                if starting_port is None:
                    # XXX: we cache the first successfuly found external port
                    #      to avoid testing again the first series the next time
                    self._starting_port_cache = ext_port

            mapping = self._upnp.addportmapping(
                # the last parameter is remoteHost, we don't use it
                ext_port, protocol, self._upnp.lanaddr, int_port, desc, '')

            if not mapping:
                raise MappingError
            else:
                self._to_unmap.append((ext_port, protocol))
        finally:
            self._mutex.release()

        return ext_port

    def mapPort(self, int_port, ext_port=None, protocol='TCP', desc=DEFAULT_DESC):
        """Add a port mapping

        @param int_port(int): internal port to use
        @param ext_port(int,None): external port to use, or None to find one automatically
        @param protocol(str): 'TCP' or 'UDP'
        @param desc(unicode): description of the mapping
            Some UPnP IGD devices have broken encoding. It's probably a good idea to avoid non-ascii chars here
        @return (D(int, None)): external port used in case of success, otherwise None
        """
        if self._upnp is None:
            return defer.succeed(None)
        def mappingCb(ext_port):
            log.info(u"{protocol} mapping from {int_port} to {ext_port} successful".format(
                protocol = protocol,
                int_port = int_port,
                ext_port = ext_port,
                ))
            return ext_port
        def mappingEb(failure):
            failure.trap(MappingError)
            log.warning(u"Can't map internal {int_port}".format(int_port=int_port))
        d = threads.deferToThread(self._mapPortBlocking, int_port, ext_port, protocol, desc)
        d.addCallbacks(mappingCb, mappingEb)
        return d