Mini Shell

import logging
import signal
import sys
from typing import Union, Iterable, Callable

from ..modules.processor import RequestProcessor

logger = logging.getLogger('tools')


def log_on_receive(signum: int, frame) -> None:
    """
    Signal handler to log received signal
    """
    logger.info('Received sig: %i (%s)', signum, signum)


def sigterm_received(signum: int, frame) -> None:
    """
    Signal handler to dump collected statistics
    """
    logger.info('Received sig: %i', signum)
    RequestProcessor().dump_collected_stats_to_file()
    logger.info('Dumped successfully after %i signal, exiting...', signum)
    sys.exit(0)


def register_a_signal(signum: int, sighandler: Callable) -> None:
    """
    Register given sighandler for given signum
    """
    try:
        signal.signal(signum, sighandler)
        logger.info('Registered %s', signum)
    except (OSError, ValueError) as e:
        logger.info('Skipped %s because of %s', signum, e)


def register_sigterm():
    """
    Register a dump handler for SIGTERM signal
    """
    register_a_signal(signal.SIGTERM, sigterm_received)


def register_signals(signals: Union[int, Iterable] = None,
                     handler: Callable = log_on_receive) -> None:
    """
    Register given handler for given signal or range of signals
    If no signals given, add given handler for all available signals
    """
    if signals is None:
        # register all available signals
        for sig in signal.Signals:
            register_a_signal(sig, handler)
    else:
        if isinstance(signals, int):
            # register single signal
            register_a_signal(signals, handler)
        else:
            # register range of signals
            for sig in signals:
                register_a_signal(sig, handler)