from core.Constants import Constants
from core.Errors import CommandNotFoundError, PolicyInstatementError, PolicyRevocationError, PolicyAssignmentError
from core.models.BasePolicy import BasePolicy
import os
import pwd
import shutil
import subprocess


class PrivilegePolicy(BasePolicy):

    def preview(self):

        username = self.__determine_username()
        return self.__generate(username)

    def instate(self):
        pass

    def revoke(self):

        if shutil.which('pkexec') is None:
            raise CommandNotFoundError('pkexec')

        process = subprocess.Popen(('pkexec', 'rm', Constants.HV_PRIVILEGE_POLICY_PATH))
        completed_successfully = not bool(os.waitpid(process.pid, 0)[1] >> 8)

        if not completed_successfully:
            raise PolicyRevocationError('The privilege policy could not be revoked.')

    def is_suggestible(self):
        return self.__is_compatible()

    def is_instated(self):
        return os.path.exists(Constants.HV_PRIVILEGE_POLICY_PATH)

    @staticmethod
    def __determine_username():

        try:
            password_database_entry = pwd.getpwuid(os.geteuid())
        except (OSError, KeyError):
            raise PolicyAssignmentError('The privilege policy could not be assigned to the current user.')

        if password_database_entry.pw_uid == 0:
            raise PolicyAssignmentError('The privilege policy could not be assigned to the current user.')

        return password_database_entry.pw_name

    @staticmethod
    def __generate(username: str):

        return '\n'.join((
            f'{username} ALL=(root) NOPASSWD: /usr/bin/wg-quick ^up {Constants.HV_SYSTEM_PROFILE_CONFIG_PATH}/[0-9]+/wg.conf$',
        ))

    @staticmethod
    def __is_compatible():
        return False