# util/concurrency.py
# Copyright (C) 2005-2022 the SQLAlchemy authors and contributors
# <see AUTHORS file>
#
# This module is part of SQLAlchemy and is released under
# the MIT License: https://www.opensource.org/licenses/mit-license.php

import asyncio  # noqa

have_greenlet = False
greenlet_error = None
try:
    import greenlet  # type: ignore # noqa F401
except ImportError as e:
    greenlet_error = str(e)
    pass
else:
    have_greenlet = True
    from ._concurrency_py3k import await_only as await_only
    from ._concurrency_py3k import await_fallback as await_fallback
    from ._concurrency_py3k import greenlet_spawn as greenlet_spawn
    from ._concurrency_py3k import is_exit_exception as is_exit_exception
    from ._concurrency_py3k import AsyncAdaptedLock as AsyncAdaptedLock
    from ._concurrency_py3k import (
        _util_async_run as _util_async_run,
    )  # noqa F401
    from ._concurrency_py3k import (
        _util_async_run_coroutine_function as _util_async_run_coroutine_function,  # noqa F401, E501
    )

if not have_greenlet:

    def _not_implemented():
        # this conditional is to prevent pylance from considering
        # greenlet_spawn() etc as "no return" and dimming out code below it
        if have_greenlet:
            return None

        raise ValueError(
            "the greenlet library is required to use this function."
            " %s" % greenlet_error
            if greenlet_error
            else ""
        )

    def is_exit_exception(e):  # noqa F811
        return not isinstance(e, Exception)

    def await_only(thing):  # type: ignore # noqa F811
        _not_implemented()

    def await_fallback(thing):  # type: ignore # noqa F81
        return thing

    def greenlet_spawn(fn, *args, **kw):  # type: ignore # noqa F81
        _not_implemented()

    def AsyncAdaptedLock(*args, **kw):  # type: ignore # noqa F81
        _not_implemented()

    def _util_async_run(fn, *arg, **kw):  # type: ignore # noqa F81
        return fn(*arg, **kw)

    def _util_async_run_coroutine_function(fn, *arg, **kw):  # type: ignore # noqa F81
        _not_implemented()