import signal
from types import FrameType
from typing import Any, Callable, Dict, Optional, Union

# copy of _HANDLER from typeshed/stdlib/signal.pyi
SignalHandlerT = Union[
    Callable[[int, Optional[FrameType]], Any], int, signal.Handlers, None
]

signal_names: Dict[int, str] = {}
for signame in dir(signal):
    if signame.startswith("SIG") and not signame.startswith("SIG_"):
        signum = getattr(signal, signame)
        if isinstance(signum, int):
            signal_names[signum] = signame


def install_shutdown_handlers(
    function: SignalHandlerT, override_sigint: bool = True
) -> None:
    """Install the given function as a signal handler for all common shutdown
    signals (such as SIGINT, SIGTERM, etc). If override_sigint is ``False`` the
    SIGINT handler won't be install if there is already a handler in place
    (e.g.  Pdb)
    """
    from twisted.internet import reactor

    reactor._handleSignals()
    signal.signal(signal.SIGTERM, function)
    if signal.getsignal(signal.SIGINT) == signal.default_int_handler or override_sigint:
        signal.signal(signal.SIGINT, function)
    # Catch Ctrl-Break in windows
    if hasattr(signal, "SIGBREAK"):
        signal.signal(signal.SIGBREAK, function)
