# This file is part of Buildbot.  Buildbot 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, version 2.
#
# 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, write to the Free Software Foundation, Inc., 51
# Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
#
# Copyright Buildbot Team Members

from __future__ import annotations

import inspect
from functools import wraps
from typing import TYPE_CHECKING

from twisted.internet import defer
from twisted.internet import reactor
from twisted.python import threadpool

if TYPE_CHECKING:
    from typing import Any
    from typing import Callable
    from typing import Coroutine
    from typing import TypeVar

    from typing_extensions import ParamSpec

    _T = TypeVar('_T')
    _P = ParamSpec('_P')


def async_to_deferred(
    fn: Callable[_P, Coroutine[Any, Any, _T]],
) -> Callable[_P, defer.Deferred[_T]]:
    @wraps(fn)
    def wrapper(*args: _P.args, **kwargs: _P.kwargs) -> defer.Deferred[_T]:
        try:
            return defer.ensureDeferred(fn(*args, **kwargs))
        except Exception as e:
            return defer.fail(e)

    return wrapper


async def any_to_async(value: Coroutine[Any, Any, _T] | defer.Deferred[_T] | _T) -> _T:
    if inspect.isawaitable(value):
        # defer.Deferred is awaitable too
        return await value
    return value


class ThreadPool(threadpool.ThreadPool):
    # This thread pool ensures that it stops on reactor shutdown

    _stop_event = None  # if not None, then pool is running

    def start(self):
        if self._stop_event:
            return

        super().start()
        self._stop_event = reactor.addSystemEventTrigger(
            'during', 'shutdown', self._stop_on_shutdown
        )

    def _stop_on_shutdown(self):
        self._stop_impl(remove_trigger=False)

    def stop(self):
        self._stop_impl(remove_trigger=True)

    def _stop_impl(self, remove_trigger):
        if not self._stop_event:
            return
        super().stop()
        if remove_trigger:
            reactor.removeSystemEventTrigger(self._stop_event)
        self._stop_event = None
