Mini Shell

"""
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 <https://www.gnu.org/licenses/>.

Copyright © 2019 Cloud Linux Software Inc.

This software is also available under ImunifyAV commercial license,
see <https://www.imunify360.com/legal/eula>
"""
import re
from typing import Optional

from defence360agent.utils import atomic_rewrite


class KWConfig:
    """
    Basic class for working with key-value configuration files
    Subclasses must define SEARCH_PATTERN and WRITE_PATTERN
    attributes
    """
    SEARCH_PATTERN = DEFAULT_FILENAME = WRITE_PATTERN = ''
    ALLOW_EMPTY_CONFIG = True

    def __init__(self, name, filename=None):
        assert self.SEARCH_PATTERN

        self._pattern = re.compile(self.SEARCH_PATTERN.format(name),
                                   re.MULTILINE)
        self._filename = filename or self.DEFAULT_FILENAME
        self._name = name

    def set(self, value) -> Optional[str]:
        assert self.WRITE_PATTERN

        with open(self._filename) as f:
            content = f.read()

        old_value = self._parse(content)
        if old_value is None:
            # If no variable found, just add to the bottom
            content += '\n' + self.WRITE_PATTERN.format(
                self._name, value) + '\n'
        else:
            content = self._pattern.sub(
                self.WRITE_PATTERN.format(self._name, value), content)

        atomic_rewrite(self._filename, content,
                       allow_empty_content=self.ALLOW_EMPTY_CONFIG)
        return old_value

    def get(self) -> Optional[str]:
        with open(self._filename) as f:
            content = f.read()
        return self._parse(content)

    def _parse(self, content) -> Optional[str]:
        match = self._pattern.search(content)
        return match and match.group(1)