# Source code for scrapy.utils.reactor

    import asyncio
    import sys
    from asyncio import AbstractEventLoop, AbstractEventLoopPolicy
    from contextlib import suppress
    from typing import Any, Callable, Dict, Optional, Sequence, Type
    from warnings import catch_warnings, filterwarnings, warn

    from twisted.internet import asyncioreactor, error
    from twisted.internet.base import DelayedCall

    from scrapy.exceptions import ScrapyDeprecationWarning
    from scrapy.utils.misc import load_object

    def listen_tcp(portrange, host, factory):
        """Like reactor.listenTCP but tries different ports in a range."""
        from twisted.internet import reactor

        if len(portrange) > 2:
            raise ValueError(f"invalid portrange: {portrange}")
        if not portrange:
            return reactor.listenTCP(0, factory, interface=host)
        if not hasattr(portrange, "__iter__"):
            return reactor.listenTCP(portrange, factory, interface=host)
        if len(portrange) == 1:
            return reactor.listenTCP(portrange[0], factory, interface=host)
        for x in range(portrange[0], portrange[1] + 1):
            try:
                return reactor.listenTCP(x, factory, interface=host)
            except error.CannotListenError:
                if x == portrange[1]:
                    raise

    class CallLaterOnce:
        """Schedule a function to be called in the next reactor loop, but only if
        it hasn't been already scheduled since the last time it ran.
        """

        def __init__(self, func: Callable, *a: Any, **kw: Any):
            self._func: Callable = func
            self._a: Sequence[Any] = a
            self._kw: Dict[str, Any] = kw
            self._call: Optional[DelayedCall] = None

        def schedule(self, delay: float = 0) -> None:
            from twisted.internet import reactor

            if self._call is None:
                self._call = reactor.callLater(delay, self)

        def cancel(self) -> None:
            if self._call:
                self._call.cancel()

        def __call__(self) -> Any:
            self._call = None
            return self._func(*self._a, **self._kw)

    def set_asyncio_event_loop_policy() -> None:
        """The policy functions from asyncio often behave unexpectedly,
        so we restrict their use to the absolutely essential case.
        This should only be used to install the reactor.
        """
        _get_asyncio_event_loop_policy()

    def get_asyncio_event_loop_policy() -> AbstractEventLoopPolicy:
        warn(
            "Call to deprecated function "
            "scrapy.utils.reactor.get_asyncio_event_loop_policy().\n"
            "\n"
            "Please use get_event_loop, new_event_loop and set_event_loop"
            " from asyncio instead, as the corresponding policy methods may lead"
            " to unexpected behaviour.\n"
            "This function is replaced by set_asyncio_event_loop_policy and"
            " is meant to be used only when the reactor is being installed.",
            category=ScrapyDeprecationWarning,
            stacklevel=2,
        )
        return _get_asyncio_event_loop_policy()

    def _get_asyncio_event_loop_policy() -> AbstractEventLoopPolicy:
        policy = asyncio.get_event_loop_policy()
        if (
            sys.version_info >= (3, 8)
            and sys.platform == "win32"
            and not isinstance(policy, asyncio.WindowsSelectorEventLoopPolicy)
        ):
            policy = asyncio.WindowsSelectorEventLoopPolicy()
            asyncio.set_event_loop_policy(policy)
        return policy

    def install_reactor(reactor_path: str, event_loop_path: Optional[str] = None) -> None:
        """Installs the :mod:`~twisted.internet.reactor` with the specified
        import path. Also installs the asyncio event loop with the specified import
        path if the asyncio reactor is enabled"""
        reactor_class = load_object(reactor_path)
        if reactor_class is asyncioreactor.AsyncioSelectorReactor:
            set_asyncio_event_loop_policy()
            with suppress(error.ReactorAlreadyInstalledError):
                event_loop = set_asyncio_event_loop(event_loop_path)
                asyncioreactor.install(eventloop=event_loop)
        else:
            *module, _ = reactor_path.split(".")
            installer_path = module + ["install"]
            installer = load_object(".".join(installer_path))
            with suppress(error.ReactorAlreadyInstalledError):
                installer()

    def _get_asyncio_event_loop() -> AbstractEventLoop:
        return set_asyncio_event_loop(None)

    def set_asyncio_event_loop(event_loop_path: Optional[str]) -> AbstractEventLoop:
        """Sets and returns the event loop with specified import path."""
        if event_loop_path is not None:
            event_loop_class: Type[AbstractEventLoop] = load_object(event_loop_path)
            event_loop = event_loop_class()
            asyncio.set_event_loop(event_loop)
        else:
            try:
                with catch_warnings():
                    # In Python 3.10.9, 3.11.1, 3.12 and 3.13, a DeprecationWarning
                    # is emitted about the lack of a current event loop, because in
                    # Python 3.14 and later `get_event_loop` will raise a
                    # RuntimeError in that event. Because our code is already
                    # prepared for that future behavior, we ignore the deprecation
                    # warning.
                    filterwarnings(
                        "ignore",
                        message="There is no current event loop",
                        category=DeprecationWarning,
                    )
                    event_loop = asyncio.get_event_loop()
            except RuntimeError:
                # `get_event_loop` raises RuntimeError when called with no asyncio
                # event loop yet installed in the following scenarios:
                # - Previsibly on Python 3.14 and later.
                #   https://github.com/python/cpython/issues/100160#issuecomment-1345581902
                event_loop = asyncio.new_event_loop()
                asyncio.set_event_loop(event_loop)
        return event_loop

    def verify_installed_reactor(reactor_path: str) -> None:
        """Raises :exc:`Exception` if the installed
        :mod:`~twisted.internet.reactor` does not match the specified import
        path."""
        from twisted.internet import reactor

        reactor_class = load_object(reactor_path)
        if not reactor.__class__ == reactor_class:
            msg = (
                "The installed reactor "
                f"({reactor.__module__}.{reactor.__class__.__name__}) does not "
                f"match the requested one ({reactor_path})"
            )
            raise Exception(msg)

    def verify_installed_asyncio_event_loop(loop_path: str) -> None:
        from twisted.internet import reactor

        loop_class = load_object(loop_path)
        if isinstance(reactor._asyncioEventloop, loop_class):
            return
        installed = (
            f"{reactor._asyncioEventloop.__class__.__module__}"
            f".{reactor._asyncioEventloop.__class__.__qualname__}"
        )
        specified = f"{loop_class.__module__}.{loop_class.__qualname__}"
        raise Exception(
            "Scrapy found an asyncio Twisted reactor already "
            f"installed, and its event loop class ({installed}) does "
            "not match the one specified in the ASYNCIO_EVENT_LOOP "
            f"setting ({specified})"
        )

    def is_asyncio_reactor_installed() -> bool:
        from twisted.internet import reactor

        return isinstance(reactor, asyncioreactor.AsyncioSelectorReactor)