# Copyright 2023 VyOS maintainers and contributors <maintainers@vyos.io>
#
# This library is free software; you can redistribute it and/or
# modify it under the terms of the GNU Lesser General Public
# License as published by the Free Software Foundation; either
# version 2.1 of the License, or (at your option) any later version.
#
# This library 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
# Lesser General Public License for more details.
#
# You should have received a copy of the GNU Lesser General Public
# License along with this library.  If not, see <http://www.gnu.org/licenses/>.

from subprocess import run


def sysctl_read(name: str) -> str:
    """Read and return current value of sysctl() option

    Args:
        name (str): sysctl key name

    Returns:
        str: sysctl key value
    """
    tmp = run(['sysctl', '-nb', name], capture_output=True)
    return tmp.stdout.decode()


def sysctl_write(name: str, value: str | int) -> bool:
    """Change value via sysctl()

    Args:
        name (str): sysctl key name
        value (str | int): sysctl key value

    Returns:
        bool: True if changed, False otherwise
    """
    # convert other types to string before comparison
    if not isinstance(value, str):
        value = str(value)
    # do not change anything if a value is already configured
    if sysctl_read(name) == value:
        return True
    # return False if sysctl call failed
    if run(['sysctl', '-wq', f'{name}={value}']).returncode != 0:
        return False
    # compare old and new values
    # sysctl may apply value, but its actual value will be
    # different from requested
    if sysctl_read(name) == value:
        return True
    # False in other cases
    return False


def sysctl_apply(sysctl_dict: dict[str, str], revert: bool = True) -> bool:
    """Apply sysctl values.

    Args:
        sysctl_dict (dict[str, str]): dictionary with sysctl keys with values
        revert (bool, optional): Revert to original values if new were not 
        applied. Defaults to True.

    Returns:
        bool: True if all params configured properly, False in other cases
    """
    # get current values
    sysctl_original: dict[str, str] = {}
    for key_name in sysctl_dict.keys():
        sysctl_original[key_name] = sysctl_read(key_name)
    # apply new values and revert in case one of them was not applied
    for key_name, value in sysctl_dict.items():
        if not sysctl_write(key_name, value):
            if revert:
                sysctl_apply(sysctl_original, revert=False)
            return False
    # everything applied
    return True