# -*- coding: utf-8 -*-
# vpnlauncher.py
# Copyright (C) 2013 LEAP
#
# 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 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 General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program.  If not, see <http://www.gnu.org/licenses/>.
"""
Platform independant VPN launcher interface.
"""
import getpass
import logging
import os
import stat

from abc import ABCMeta, abstractmethod
from functools import partial

from leap.bitmask.config import flags
from leap.bitmask.config.leapsettings import LeapSettings
from leap.bitmask.config.providerconfig import ProviderConfig
from leap.bitmask.services.eip.eipconfig import EIPConfig, VPNGatewaySelector
from leap.bitmask.util import first
from leap.bitmask.util import get_path_prefix
from leap.common.check import leap_assert, leap_assert_type
from leap.common.files import which

logger = logging.getLogger(__name__)


class VPNLauncherException(Exception):
    pass


class OpenVPNNotFoundException(VPNLauncherException):
    pass


def _has_updown_scripts(path, warn=True):
    """
    Checks the existence of the up/down scripts and its
    exec bit if applicable.

    :param path: the path to be checked
    :type path: str

    :param warn: whether we should log the absence
    :type warn: bool

    :rtype: bool
    """
    is_file = os.path.isfile(path)
    if warn and not is_file:
        logger.error("Could not find up/down script %s. "
                     "Might produce DNS leaks." % (path,))

    # XXX check if applies in win
    is_exe = False
    try:
        is_exe = (stat.S_IXUSR & os.stat(path)[stat.ST_MODE] != 0)
    except OSError as e:
        logger.warn("%s" % (e,))
    if warn and not is_exe:
        logger.error("Up/down script %s is not executable. "
                     "Might produce DNS leaks." % (path,))
    return is_file and is_exe


def _has_other_files(path, warn=True):
    """
    Checks the existence of other important files.

    :param path: the path to be checked
    :type path: str

    :param warn: whether we should log the absence
    :type warn: bool

    :rtype: bool
    """
    is_file = os.path.isfile(path)
    if warn and not is_file:
        logger.warning("Could not find file during checks: %s. " % (
            path,))
    return is_file


class VPNLauncher(object):
    """
    Abstract launcher class
    """
    __metaclass__ = ABCMeta

    UPDOWN_FILES = None
    OTHER_FILES = None

    @classmethod
    @abstractmethod
    def get_vpn_command(kls, eipconfig, providerconfig,
                        socket_host, socket_port, openvpn_verb=1):
        """
        Returns the platform dependant vpn launching command

        Might raise:
            OpenVPNNotFoundException,
            VPNLauncherException.

        :param eipconfig: eip configuration object
        :type eipconfig: EIPConfig
        :param providerconfig: provider specific configuration
        :type providerconfig: ProviderConfig
        :param socket_host: either socket path (unix) or socket IP
        :type socket_host: str
        :param socket_port: either string "unix" if it's a unix socket,
                            or port otherwise
        :type socket_port: str
        :param openvpn_verb: the openvpn verbosity wanted
        :type openvpn_verb: int

        :return: A VPN command ready to be launched.
        :rtype: list
        """
        leap_assert_type(eipconfig, EIPConfig)
        leap_assert_type(providerconfig, ProviderConfig)

        kwargs = {}
        if flags.STANDALONE:
            kwargs['path_extension'] = os.path.join(
                get_path_prefix(), "..", "apps", "eip")

        openvpn_possibilities = which(kls.OPENVPN_BIN, **kwargs)
        if len(openvpn_possibilities) == 0:
            raise OpenVPNNotFoundException()

        openvpn = first(openvpn_possibilities)
        args = []

        args += [
            '--setenv', "LEAPOPENVPN", "1"
        ]

        if openvpn_verb is not None:
            args += ['--verb', '%d' % (openvpn_verb,)]

        gateways = []
        leap_settings = LeapSettings()
        domain = providerconfig.get_domain()
        gateway_conf = leap_settings.get_selected_gateway(domain)

        if gateway_conf == leap_settings.GATEWAY_AUTOMATIC:
            gateway_selector = VPNGatewaySelector(eipconfig)
            gateways = gateway_selector.get_gateways()
        else:
            gateways = [gateway_conf]

        if not gateways:
            logger.error('No gateway was found!')
            raise VPNLauncherException(kls.tr('No gateway was found!'))

        logger.debug("Using gateways ips: {0}".format(', '.join(gateways)))

        for gw in gateways:
            args += ['--remote', gw, '1194', 'udp']

        args += [
            '--client',
            '--dev', 'tun',
            ##############################################################
            # persist-tun makes ping-restart fail because it leaves a
            # broken routing table
            ##############################################################
            # '--persist-tun',
            '--persist-key',
            '--tls-client',
            '--remote-cert-tls',
            'server'
        ]

        openvpn_configuration = eipconfig.get_openvpn_configuration()
        for key, value in openvpn_configuration.items():
            args += ['--%s' % (key,), value]

        user = getpass.getuser()

        ##############################################################
        # The down-root plugin fails in some situations, so we don't
        # drop privs for the time being
        ##############################################################
        # args += [
        #     '--user', user,
        #     '--group', grp.getgrgid(os.getgroups()[-1]).gr_name
        # ]

        if socket_port == "unix":  # that's always the case for linux
            args += [
                '--management-client-user', user
            ]

        args += [
            '--management-signal',
            '--management', socket_host, socket_port,
            '--script-security', '2'
        ]

        if _has_updown_scripts(kls.UP_SCRIPT):
            args += [
                '--up', '\"%s\"' % (kls.UP_SCRIPT,),
            ]

        if _has_updown_scripts(kls.DOWN_SCRIPT):
            args += [
                '--down', '\"%s\"' % (kls.DOWN_SCRIPT,)
            ]

        ###########################################################
        # For the time being we are disabling the usage of the
        # down-root plugin, because it doesn't quite work as
        # expected (i.e. it doesn't run route -del as root
        # when finishing, so it fails to properly
        # restart/quit)
        ###########################################################
        # if _has_updown_scripts(kls.OPENVPN_DOWN_PLUGIN):
        #     args += [
        #         '--plugin', kls.OPENVPN_DOWN_ROOT,
        #         '\'%s\'' % kls.DOWN_SCRIPT  # for OSX
        #         '\'script_type=down %s\'' % kls.DOWN_SCRIPT  # for Linux
        #     ]

        args += [
            '--cert', eipconfig.get_client_cert_path(providerconfig),
            '--key', eipconfig.get_client_cert_path(providerconfig),
            '--ca', providerconfig.get_ca_cert_path()
        ]

        command_and_args = [openvpn] + args
        logger.debug("Running VPN with command:")
        logger.debug(" ".join(command_and_args))

        return command_and_args

    @classmethod
    def get_vpn_env(kls):
        """
        Returns a dictionary with the custom env for the platform.
        This is mainly used for setting LD_LIBRARY_PATH to the correct
        path when distributing a standalone client

        :rtype: dict
        """
        return {}

    @classmethod
    def missing_updown_scripts(kls):
        """
        Returns what updown scripts are missing.

        :rtype: list
        """
        leap_assert(kls.UPDOWN_FILES is not None,
                    "Need to define UPDOWN_FILES for this particular "
                    "launcher before calling this method")
        file_exist = partial(_has_updown_scripts, warn=False)
        zipped = zip(kls.UPDOWN_FILES, map(file_exist, kls.UPDOWN_FILES))
        missing = filter(lambda (path, exists): exists is False, zipped)
        return [path for path, exists in missing]

    @classmethod
    def missing_other_files(kls):
        """
        Returns what other important files are missing during startup.
        Same as missing_updown_scripts but does not check for exec bit.

        :rtype: list
        """
        leap_assert(kls.OTHER_FILES is not None,
                    "Need to define OTHER_FILES for this particular "
                    "auncher before calling this method")
        file_exist = partial(_has_other_files, warn=False)
        zipped = zip(kls.OTHER_FILES, map(file_exist, kls.OTHER_FILES))
        missing = filter(lambda (path, exists): exists is False, zipped)
        return [path for path, exists in missing]