import logging as _logging
from syslog import LOG_ALERT, LOG_CRIT, LOG_ERR, LOG_WARNING, LOG_INFO, LOG_DEBUG
from typing import Union


LevelT = Union[str, int]


def check_level(level: LevelT) -> int:
    """
    Custom implementation of the logging module's _checkLevel(...) function.
    Returns the numeric representation of a log level.

    Args:
        level: Either a string such as 'DEBUG' or 'WARNING' or an integer.

    Returns:
        If an integer is passed, it is returned unchanged;
        if a string is passed, the corresponding numeric log level is returned.

    Raises:
        TypeError if something other than a string or an integer is passed.
        ValueError if the string has no corresponding level in the logging module.
    """
    if isinstance(level, int):
        return level
    if str(level) != level:
        raise TypeError(f"Level not an integer or a valid string: {level}")
    output = getattr(_logging, level)
    if output is None:
        raise ValueError(f"Unknown level: {level}")
    return output


def py_to_sys_lvl(level_num: int) -> int:
    """
    Maps a (numeric) log level as defined in Python stdlib logging module to the syslog module's log levels.
    The output number corresponds to a syslog `PRI` without the enclosing angle brackets.
    Even though there are more levels available to syslog, the `EMERG` (num. 0) and `NOTICE` (num. 5) levels are
    omitted here, i.e. it goes straight from `INFO` (num. 6) to `WARNING` (num. 4) because there is no equivalent
    in the Python logging module to `NOTICE`, and `EMERG` is unnecessary because no Python script should be able to
    cause such severe problems.
    """
    if level_num <= _logging.DEBUG:
        return LOG_DEBUG
    if level_num <= _logging.INFO:
        return LOG_INFO
    if level_num <= _logging.WARNING:
        return LOG_WARNING
    if level_num <= _logging.ERROR:
        return LOG_ERR
    if level_num <= _logging.CRITICAL:
        return LOG_CRIT
    return LOG_ALERT