# -*- coding: utf-8 -*-
# privilege_policies.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/>.
"""
Helpers to determine if the needed policies for privilege escalation
are operative under this client run.
"""
import logging
import os
import platform

from abc import ABCMeta, abstractmethod

from leap.bitmask.config import flags

logger = logging.getLogger(__name__)


def is_missing_policy_permissions():
    """
    Returns True if we do not have implemented a policy checker for this
    platform, or if the policy checker exists but it cannot find the
    appropriate policy mechanisms in place.

    :rtype: bool
    """
    _system = platform.system()
    platform_checker = _system + "PolicyChecker"
    policy_checker = globals().get(platform_checker, None)
    if not policy_checker:
        # it is true that we miss permission to escalate
        # privileges without asking for password each time.
        logger.debug("we could not find a policy checker implementation "
                     "for %s" % (_system,))
        return True
    return policy_checker().is_missing_policy_permissions()


class PolicyChecker:
    """
    Abstract PolicyChecker class
    """

    __metaclass__ = ABCMeta

    @abstractmethod
    def is_missing_policy_permissions(self):
        """
        Returns True if we could not find any policy mechanisms that
        are defined to be in used for this particular platform.

        :rtype: bool
        """
        return True


class LinuxPolicyChecker(PolicyChecker):
    """
    PolicyChecker for Linux
    """
    LINUX_POLKIT_FILE = ("/usr/share/polkit-1/actions/"
                         "se.leap.bitmask.policy")
    LINUX_POLKIT_FILE_BUNDLE = ("/usr/share/polkit-1/actions/"
                                "se.leap.bitmask.bundle.policy")

    @classmethod
    def get_polkit_path(self):
        """
        Returns the polkit file path.

        :rtype: str
        """
        return (self.LINUX_POLKIT_FILE_BUNDLE if flags.STANDALONE
                else self.LINUX_POLKIT_FILE)

    def is_missing_policy_permissions(self):
    # FIXME this name is quite confusing, it does not have anything to do with
    # file permissions.
        """
        Returns True if we could not find the appropriate policykit file
        in place

        :rtype: bool
        """
        path = self.get_polkit_path()
        return not os.path.isfile(path)