# This file is dual licensed under the terms of the Apache License, Version
# 2.0, and the MIT License.  See the LICENSE file in the root of this
# repository for complete details.

"""
Processors and helpers specific to the :mod:`logging` module from the `Python
standard library <https://docs.python.org/>`_.

See also :doc:`structlog's standard library support <standard-library>`.
"""

from __future__ import annotations

import asyncio
import contextvars
import functools
import logging
import sys

from functools import partial
from typing import Any, Callable, Collection, Iterable, Sequence

from . import _config
from ._base import BoundLoggerBase
from ._frames import _find_first_app_frame_and_name, _format_stack
from ._log_levels import _LEVEL_TO_NAME, _NAME_TO_LEVEL, add_log_level
from .contextvars import merge_contextvars
from .exceptions import DropEvent
from .processors import StackInfoRenderer
from .typing import Context, EventDict, ExcInfo, Processor, WrappedLogger


__all__ = [
    "add_log_level_number",
    "add_log_level",
    "add_logger_name",
    "ExtraAdder",
    "BoundLogger",
    "filter_by_level",
    "get_logger",
    "LoggerFactory",
    "PositionalArgumentsFormatter",
    "ProcessorFormatter",
    "recreate_defaults",
    "render_to_log_kwargs",
]


def recreate_defaults(*, log_level: int | None = logging.NOTSET) -> None:
    """
    Recreate defaults on top of standard library's logging.

    The output looks the same, but goes through `logging`.

    As with vanilla defaults, the backwards-compatibility guarantees don't
    apply to the settings applied here.

    :param log_level: If `None`, don't configure standard library logging **at
        all**.

        Otherwise configure it to log to `sys.stdout` at *log_level*
        (``logging.NOTSET`` being the default).

        If you need more control over `logging`, pass `None` here and configure
        it yourself.

    .. versionadded:: 22.1
    """
    if log_level is not None:
        kw = {}
        # 3.7 doesn't have the force keyword and we don't care enough to
        # re-implement it.
        if sys.version_info >= (3, 8):
            kw = {"force": True}

        logging.basicConfig(
            format="%(message)s",
            stream=sys.stdout,
            level=log_level,
            **kw,  # type: ignore[arg-type]
        )

    _config.reset_defaults()
    _config.configure(
        processors=[
            merge_contextvars,
            add_log_level,
            StackInfoRenderer(),
            _config._BUILTIN_DEFAULT_PROCESSORS[-2],  # TimeStamper
            _config._BUILTIN_DEFAULT_PROCESSORS[-1],  # ConsoleRenderer
        ],
        wrapper_class=BoundLogger,
        logger_factory=LoggerFactory(),
    )


_SENTINEL = object()


class _FixedFindCallerLogger(logging.Logger):
    """
    Change the behavior of `logging.Logger.findCaller` to cope with
    *structlog*'s extra frames.
    """

    def findCaller(
        self, stack_info: bool = False, stacklevel: int = 1
    ) -> tuple[str, int, str, str | None]:
        """
        Finds the first caller frame outside of structlog so that the caller
        info is populated for wrapping stdlib.

        This logger gets set as the default one when using LoggerFactory.
        """
        sinfo: str | None
        f, name = _find_first_app_frame_and_name(["logging"])
        if stack_info:
            sinfo = _format_stack(f)
        else:
            sinfo = None

        return f.f_code.co_filename, f.f_lineno, f.f_code.co_name, sinfo


class BoundLogger(BoundLoggerBase):
    """
    Python Standard Library version of `structlog.BoundLogger`.

    Works exactly like the generic one except that it takes advantage of
    knowing the logging methods in advance.

    Use it like::

        structlog.configure(
            wrapper_class=structlog.stdlib.BoundLogger,
        )

    It also contains a bunch of properties that pass-through to the wrapped
    `logging.Logger` which should make it work as a drop-in replacement.
    """

    _logger: logging.Logger

    def bind(self, **new_values: Any) -> BoundLogger:
        """
        Return a new logger with *new_values* added to the existing ones.
        """
        return super().bind(**new_values)  # type: ignore[return-value]

    def unbind(self, *keys: str) -> BoundLogger:
        """
        Return a new logger with *keys* removed from the context.

        :raises KeyError: If the key is not part of the context.
        """
        return super().unbind(*keys)  # type: ignore[return-value]

    def try_unbind(self, *keys: str) -> BoundLogger:
        """
        Like :meth:`unbind`, but best effort: missing keys are ignored.

        .. versionadded:: 18.2.0
        """
        return super().try_unbind(*keys)  # type: ignore[return-value]

    def new(self, **new_values: Any) -> BoundLogger:
        """
        Clear context and binds *initial_values* using `bind`.

        Only necessary with dict implementations that keep global state like
        those wrapped by `structlog.threadlocal.wrap_dict` when threads
        are re-used.
        """
        return super().new(**new_values)  # type: ignore[return-value]

    def debug(self, event: str | None = None, *args: Any, **kw: Any) -> Any:
        """
        Process event and call `logging.Logger.debug` with the result.
        """
        return self._proxy_to_logger("debug", event, *args, **kw)

    def info(self, event: str | None = None, *args: Any, **kw: Any) -> Any:
        """
        Process event and call `logging.Logger.info` with the result.
        """
        return self._proxy_to_logger("info", event, *args, **kw)

    def warning(self, event: str | None = None, *args: Any, **kw: Any) -> Any:
        """
        Process event and call `logging.Logger.warning` with the result.
        """
        return self._proxy_to_logger("warning", event, *args, **kw)

    warn = warning

    def error(self, event: str | None = None, *args: Any, **kw: Any) -> Any:
        """
        Process event and call `logging.Logger.error` with the result.
        """
        return self._proxy_to_logger("error", event, *args, **kw)

    def critical(self, event: str | None = None, *args: Any, **kw: Any) -> Any:
        """
        Process event and call `logging.Logger.critical` with the result.
        """
        return self._proxy_to_logger("critical", event, *args, **kw)

    def exception(
        self, event: str | None = None, *args: Any, **kw: Any
    ) -> Any:
        """
        Process event and call `logging.Logger.error` with the result,
        after setting ``exc_info`` to `True`.
        """
        kw.setdefault("exc_info", True)

        return self.error(event, *args, **kw)

    def log(
        self, level: int, event: str | None = None, *args: Any, **kw: Any
    ) -> Any:
        """
        Process *event* and call the appropriate logging method depending on
        *level*.
        """
        return self._proxy_to_logger(_LEVEL_TO_NAME[level], event, *args, **kw)

    fatal = critical

    def _proxy_to_logger(
        self,
        method_name: str,
        event: str | None = None,
        *event_args: str,
        **event_kw: Any,
    ) -> Any:
        """
        Propagate a method call to the wrapped logger.

        This is the same as the superclass implementation, except that
        it also preserves positional arguments in the ``event_dict`` so
        that the stdlib's support for format strings can be used.
        """
        if event_args:
            event_kw["positional_args"] = event_args

        return super()._proxy_to_logger(method_name, event=event, **event_kw)

    # Pass-through attributes and methods to mimic the stdlib's logger
    # interface.

    @property
    def name(self) -> str:
        """
        Returns :attr:`logging.Logger.name`
        """
        return self._logger.name

    @property
    def level(self) -> int:
        """
        Returns :attr:`logging.Logger.level`
        """
        return self._logger.level

    @property
    def parent(self) -> Any:
        """
        Returns :attr:`logging.Logger.parent`
        """
        return self._logger.parent

    @property
    def propagate(self) -> bool:
        """
        Returns :attr:`logging.Logger.propagate`
        """
        return self._logger.propagate

    @property
    def handlers(self) -> Any:
        """
        Returns :attr:`logging.Logger.handlers`
        """
        return self._logger.handlers

    @property
    def disabled(self) -> int:
        """
        Returns :attr:`logging.Logger.disabled`
        """
        return self._logger.disabled

    def setLevel(self, level: int) -> None:
        """
        Calls :meth:`logging.Logger.setLevel` with unmodified arguments.
        """
        self._logger.setLevel(level)

    def findCaller(
        self, stack_info: bool = False
    ) -> tuple[str, int, str, str | None]:
        """
        Calls :meth:`logging.Logger.findCaller` with unmodified arguments.
        """
        return self._logger.findCaller(stack_info=stack_info)

    def makeRecord(
        self,
        name: str,
        level: int,
        fn: str,
        lno: int,
        msg: str,
        args: tuple[Any, ...],
        exc_info: ExcInfo,
        func: str | None = None,
        extra: Any = None,
    ) -> logging.LogRecord:
        """
        Calls :meth:`logging.Logger.makeRecord` with unmodified arguments.
        """
        return self._logger.makeRecord(
            name, level, fn, lno, msg, args, exc_info, func=func, extra=extra
        )

    def handle(self, record: logging.LogRecord) -> None:
        """
        Calls :meth:`logging.Logger.handle` with unmodified arguments.
        """
        self._logger.handle(record)

    def addHandler(self, hdlr: logging.Handler) -> None:
        """
        Calls :meth:`logging.Logger.addHandler` with unmodified arguments.
        """
        self._logger.addHandler(hdlr)

    def removeHandler(self, hdlr: logging.Handler) -> None:
        """
        Calls :meth:`logging.Logger.removeHandler` with unmodified arguments.
        """
        self._logger.removeHandler(hdlr)

    def hasHandlers(self) -> bool:
        """
        Calls :meth:`logging.Logger.hasHandlers` with unmodified arguments.

        Exists only in Python 3.
        """
        return self._logger.hasHandlers()

    def callHandlers(self, record: logging.LogRecord) -> None:
        """
        Calls :meth:`logging.Logger.callHandlers` with unmodified arguments.
        """
        self._logger.callHandlers(record)

    def getEffectiveLevel(self) -> int:
        """
        Calls :meth:`logging.Logger.getEffectiveLevel` with unmodified
        arguments.
        """
        return self._logger.getEffectiveLevel()

    def isEnabledFor(self, level: int) -> bool:
        """
        Calls :meth:`logging.Logger.isEnabledFor` with unmodified arguments.
        """
        return self._logger.isEnabledFor(level)

    def getChild(self, suffix: str) -> logging.Logger:
        """
        Calls :meth:`logging.Logger.getChild` with unmodified arguments.
        """
        return self._logger.getChild(suffix)


def get_logger(*args: Any, **initial_values: Any) -> BoundLogger:
    """
    Only calls `structlog.get_logger`, but has the correct type hints.

    .. warning::

       Does **not** check whether -- or ensure that -- you've configured
       *structlog* for standard library :mod:`logging`!

       See :doc:`standard-library` for details.

    .. versionadded:: 20.2.0
    """
    return _config.get_logger(*args, **initial_values)


class AsyncBoundLogger:
    """
    Wraps a `BoundLogger` & exposes its logging methods as ``async`` versions.

    Instead of blocking the program, they are run asynchronously in a thread
    pool executor.

    This means more computational overhead per log call. But it also means that
    the processor chain (e.g. JSON serialization) and I/O won't block your
    whole application.

    Only available for Python 3.7 and later.

    :ivar structlog.stdlib.BoundLogger sync_bl: The wrapped synchronous logger.
       It is useful to be able to log synchronously occasionally.

    .. versionadded:: 20.2.0
    .. versionchanged:: 20.2.0 fix _dispatch_to_sync contextvars usage
    """

    __slots__ = ["sync_bl", "_loop"]

    sync_bl: BoundLogger

    # Blatant lie, we use a property for _context. Need this for Protocol
    # though.
    _context: Context

    _executor = None
    _bound_logger_factory = BoundLogger

    def __init__(
        self,
        logger: logging.Logger,
        processors: Iterable[Processor],
        context: Context,
        *,
        # Only as an optimization for binding!
        _sync_bl: Any = None,  # *vroom vroom* over purity.
        _loop: Any = None,
    ):
        if _sync_bl:
            self.sync_bl = _sync_bl
            self._loop = _loop

            return

        self.sync_bl = self._bound_logger_factory(
            logger=logger, processors=processors, context=context
        )
        self._loop = asyncio.get_running_loop()

    # We have to ignore the type because we've already declared it to ensure
    # we're a BindableLogger.
    # Instances would've been correctly recognized as such, however the class
    # not and we need the class in `structlog.configure()`.
    @property  # type: ignore[no-redef]
    def _context(self) -> Context:
        return self.sync_bl._context

    def bind(self, **new_values: Any) -> AsyncBoundLogger:
        return AsyncBoundLogger(
            # logger, processors and context are within sync_bl. These
            # arguments are ignored if _sync_bl is passed. *vroom vroom* over
            # purity.
            logger=None,  # type: ignore[arg-type]
            processors=(),
            context={},
            _sync_bl=self.sync_bl.bind(**new_values),
            _loop=self._loop,
        )

    def new(self, **new_values: Any) -> AsyncBoundLogger:
        return AsyncBoundLogger(
            # c.f. comment in bind
            logger=None,  # type: ignore[arg-type]
            processors=(),
            context={},
            _sync_bl=self.sync_bl.new(**new_values),
            _loop=self._loop,
        )

    def unbind(self, *keys: str) -> AsyncBoundLogger:
        return AsyncBoundLogger(
            # c.f. comment in bind
            logger=None,  # type: ignore[arg-type]
            processors=(),
            context={},
            _sync_bl=self.sync_bl.unbind(*keys),
            _loop=self._loop,
        )

    def try_unbind(self, *keys: str) -> AsyncBoundLogger:
        return AsyncBoundLogger(
            # c.f. comment in bind
            logger=None,  # type: ignore[arg-type]
            processors=(),
            context={},
            _sync_bl=self.sync_bl.try_unbind(*keys),
            _loop=self._loop,
        )

    async def _dispatch_to_sync(
        self,
        meth: Callable[..., Any],
        event: str,
        args: tuple[Any, ...],
        kw: dict[str, Any],
    ) -> None:
        """
        Merge contextvars and log using the sync logger in a thread pool.
        """
        ctx = contextvars.copy_context()

        await asyncio.get_running_loop().run_in_executor(
            self._executor,
            lambda: ctx.run(lambda: meth(event, *args, **kw)),
        )

    async def debug(self, event: str, *args: Any, **kw: Any) -> None:
        await self._dispatch_to_sync(self.sync_bl.debug, event, args, kw)

    async def info(self, event: str, *args: Any, **kw: Any) -> None:
        await self._dispatch_to_sync(self.sync_bl.info, event, args, kw)

    async def warning(self, event: str, *args: Any, **kw: Any) -> None:
        await self._dispatch_to_sync(self.sync_bl.warning, event, args, kw)

    warn = warning

    async def error(self, event: str, *args: Any, **kw: Any) -> None:
        await self._dispatch_to_sync(self.sync_bl.error, event, args, kw)

    async def critical(self, event: str, *args: Any, **kw: Any) -> None:
        await self._dispatch_to_sync(self.sync_bl.critical, event, args, kw)

    fatal = critical

    async def exception(self, event: str, *args: Any, **kw: Any) -> None:
        # To make `log.exception("foo") work, we have to check if the user
        # passed an explicit exc_info and if not, supply our own.
        ei = kw.pop("exc_info", None)
        if ei is None and kw.get("exception") is None:
            ei = sys.exc_info()

        kw["exc_info"] = ei

        await self._dispatch_to_sync(self.sync_bl.exception, event, args, kw)

    async def log(self, level: Any, event: str, *args: Any, **kw: Any) -> None:
        await self._dispatch_to_sync(
            partial(self.sync_bl.log, level), event, args, kw
        )


class LoggerFactory:
    """
    Build a standard library logger when an *instance* is called.

    Sets a custom logger using :func:`logging.setLoggerClass` so variables in
    log format are expanded properly.

    >>> from structlog import configure
    >>> from structlog.stdlib import LoggerFactory
    >>> configure(logger_factory=LoggerFactory())

    :param ignore_frame_names: When guessing the name of a logger, skip frames
        whose names *start* with one of these.  For example, in pyramid
        applications you'll want to set it to
        ``["venusian", "pyramid.config"]``. This argument is
        called *additional_ignores* in other APIs throughout *structlog*.
    """

    def __init__(self, ignore_frame_names: list[str] | None = None):
        self._ignore = ignore_frame_names
        logging.setLoggerClass(_FixedFindCallerLogger)

    def __call__(self, *args: Any) -> logging.Logger:
        """
        Deduce the caller's module name and create a stdlib logger.

        If an optional argument is passed, it will be used as the logger name
        instead of guesswork.  This optional argument would be passed from the
        :func:`structlog.get_logger` call.  For example
        ``structlog.get_logger("foo")`` would cause this method to be called
        with ``"foo"`` as its first positional argument.

        .. versionchanged:: 0.4.0
            Added support for optional positional arguments.  Using the first
            one for naming the constructed logger.
        """
        if args:
            return logging.getLogger(args[0])

        # We skip all frames that originate from within structlog or one of the
        # configured names.
        _, name = _find_first_app_frame_and_name(self._ignore)

        return logging.getLogger(name)


class PositionalArgumentsFormatter:
    """
    Apply stdlib-like string formatting to the ``event`` key.

    If the ``positional_args`` key in the event dict is set, it must
    contain a tuple that is used for formatting (using the ``%s`` string
    formatting operator) of the value from the ``event`` key.  This works
    in the same way as the stdlib handles arguments to the various log
    methods: if the tuple contains only a single `dict` argument it is
    used for keyword placeholders in the ``event`` string, otherwise it
    will be used for positional placeholders.

    ``positional_args`` is populated by `structlog.stdlib.BoundLogger` or
    can be set manually.

    The *remove_positional_args* flag can be set to `False` to keep the
    ``positional_args`` key in the event dict; by default it will be
    removed from the event dict after formatting a message.
    """

    def __init__(self, remove_positional_args: bool = True) -> None:
        self.remove_positional_args = remove_positional_args

    def __call__(
        self, _: WrappedLogger, __: str, event_dict: EventDict
    ) -> EventDict:
        args = event_dict.get("positional_args")

        # Mimic the formatting behaviour of the stdlib's logging module, which
        # accepts both positional arguments and a single dict argument. The
        # "single dict" check is the same one as the stdlib's logging module
        # performs in LogRecord.__init__().
        if args:
            if len(args) == 1 and isinstance(args[0], dict) and args[0]:
                args = args[0]

            event_dict["event"] %= args

        if self.remove_positional_args and args is not None:
            del event_dict["positional_args"]

        return event_dict


def filter_by_level(
    logger: logging.Logger, method_name: str, event_dict: EventDict
) -> EventDict:
    """
    Check whether logging is configured to accept messages from this log level.

    Should be the first processor if stdlib's filtering by level is used so
    possibly expensive processors like exception formatters are avoided in the
    first place.

    >>> import logging
    >>> from structlog.stdlib import filter_by_level
    >>> logging.basicConfig(level=logging.WARN)
    >>> logger = logging.getLogger()
    >>> filter_by_level(logger, 'warn', {})
    {}
    >>> filter_by_level(logger, 'debug', {})
    Traceback (most recent call last):
    ...
    DropEvent
    """
    if logger.isEnabledFor(_NAME_TO_LEVEL[method_name]):
        return event_dict

    raise DropEvent


def add_log_level_number(
    logger: logging.Logger, method_name: str, event_dict: EventDict
) -> EventDict:
    """
    Add the log level number to the event dict.

    Log level numbers map to the log level names. The Python stdlib uses them
    for filtering logic. This adds the same numbers so users can leverage
    similar filtering. Compare::

       level in ("warning", "error", "critical")
       level_number >= 30

    The mapping of names to numbers is in
    ``structlog.stdlib._log_levels._NAME_TO_LEVEL``.

    .. versionadded:: 18.2.0
    """
    event_dict["level_number"] = _NAME_TO_LEVEL[method_name]

    return event_dict


def add_logger_name(
    logger: logging.Logger, method_name: str, event_dict: EventDict
) -> EventDict:
    """
    Add the logger name to the event dict.
    """
    record = event_dict.get("_record")
    if record is None:
        event_dict["logger"] = logger.name
    else:
        event_dict["logger"] = record.name
    return event_dict


_LOG_RECORD_KEYS = logging.LogRecord(
    "name", 0, "pathname", 0, "msg", tuple(), None
).__dict__.keys()


class ExtraAdder:
    """
    Add extra attributes of `logging.LogRecord` objects to the event
    dictionary.

    This processor can be used for adding data passed in the ``extra``
    parameter of the `logging` module's log methods to the event dictionary.

    :param allow: An optional collection of attributes that, if present in
        `logging.LogRecord` objects, will be copied to event dictionaries.

        If ``allow`` is None all attributes of `logging.LogRecord` objects that
        do not exist on a standard `logging.LogRecord` object will be copied to
        event dictionaries.

    .. versionadded:: 21.5.0
    """

    __slots__ = ["_copier"]

    def __init__(self, allow: Collection[str] | None = None) -> None:
        self._copier: Callable[[EventDict, logging.LogRecord], None]
        if allow is not None:
            # The contents of allow is copied to a new list so that changes to
            # the list passed into the constructor does not change the
            # behaviour of this processor.
            self._copier = functools.partial(self._copy_allowed, [*allow])
        else:
            self._copier = self._copy_all

    def __call__(
        self, logger: logging.Logger, name: str, event_dict: EventDict
    ) -> EventDict:
        record: logging.LogRecord | None = event_dict.get("_record")
        if record is not None:
            self._copier(event_dict, record)
        return event_dict

    @classmethod
    def _copy_all(
        cls, event_dict: EventDict, record: logging.LogRecord
    ) -> None:
        for key, value in record.__dict__.items():
            if key not in _LOG_RECORD_KEYS:
                event_dict[key] = value

    @classmethod
    def _copy_allowed(
        cls,
        allow: Collection[str],
        event_dict: EventDict,
        record: logging.LogRecord,
    ) -> None:
        for key in allow:
            if key in record.__dict__:
                event_dict[key] = record.__dict__[key]


def render_to_log_kwargs(
    _: logging.Logger, __: str, event_dict: EventDict
) -> EventDict:
    """
    Render ``event_dict`` into keyword arguments for `logging.log`.

    The ``event`` field is translated into ``msg`` and the rest of the
    *event_dict* is added as ``extra``.

    This allows you to defer formatting to `logging`.

    .. versionadded:: 17.1.0
    .. versionchanged:: 22.1.0 ``exc_info``, ``stack_info``, and ``stackLevel``
       are passed as proper kwargs and not put into ``extra``.
    """
    return {
        "msg": event_dict.pop("event"),
        "extra": event_dict,
        **{
            kw: event_dict.pop(kw)
            for kw in ("exc_info", "stack_info", "stackLevel")
            if kw in event_dict
        },
    }


class ProcessorFormatter(logging.Formatter):
    r"""
    Call *structlog* processors on `logging.LogRecord`\s.

    This is an implementation of a `logging.Formatter` that can be used to
    format log entries from both *structlog* and `logging`.

    Its static method `wrap_for_formatter` must be the final processor in
    *structlog*'s processor chain.

    Please refer to :ref:`processor-formatter` for examples.

    :param foreign_pre_chain:
        If not `None`, it is used as a processor chain that is applied to
        **non**-*structlog* log entries before the event dictionary is passed
        to *processors*. (default: `None`)
    :param processors:
        A chain of *structlog* processors that is used to process **all** log
        entries. The last one must render to a `str` which then gets passed on
        to `logging` for output.

        Compared to *structlog*'s regular processor chains, there's a few
        differences:

        - The event dictionary contains two additional keys:

          #. ``_record``: a `logging.LogRecord` that either was created using
             `logging` APIs, **or** is a wrapped *structlog* log entry
             created by `wrap_for_formatter`.
          #. ``_from_structlog``: a `bool` that indicates whether or not
             ``_record`` was created by a *structlog* logger.

          Since you most likely don't want ``_record`` and
          ``_from_structlog`` in your log files,  we've added
          the static method `remove_processors_meta` to ``ProcessorFormatter``
          that you can add just before your renderer.

        - Since this is a `logging` *formatter*, raising `structlog.DropEvent`
          will crash your application.

    :param keep_exc_info: ``exc_info`` on `logging.LogRecord`\ s is
        added to the ``event_dict`` and removed afterwards. Set this to
        ``True`` to keep it on the `logging.LogRecord`. (default: False)
    :param keep_stack_info: Same as *keep_exc_info* except for ``stack_info``.
        (default: False)
    :param logger: Logger which we want to push through the *structlog*
        processor chain. This parameter is necessary for some of the
        processors like `filter_by_level`. (default: None)
    :param pass_foreign_args: If True, pass a foreign log record's
        ``args`` attribute to the ``event_dict`` under ``positional_args`` key.
        (default: False)
    :param processor:
        A single *structlog* processor used for rendering the event
        dictionary before passing it off to `logging`. Must return a `str`.
        The event dictionary does **not** contain ``_record`` and
        ``_from_structlog``.

        This parameter exists for historic reasons. Please consider using
        *processors* instead.

    :raises TypeError: If both or neither *processor* and *processors* are
        passed.

    .. versionadded:: 17.1.0
    .. versionadded:: 17.2.0 *keep_exc_info* and *keep_stack_info*
    .. versionadded:: 19.2.0 *logger*
    .. versionadded:: 19.2.0 *pass_foreign_args*
    .. versionadded:: 21.3.0 *processors*
    .. deprecated:: 21.3.0
       *processor* (singular) in favor of *processors* (plural). Removal is not
       planned.
    """

    def __init__(
        self,
        processor: Processor | None = None,
        processors: Sequence[Processor] | None = (),
        foreign_pre_chain: Sequence[Processor] | None = None,
        keep_exc_info: bool = False,
        keep_stack_info: bool = False,
        logger: logging.Logger | None = None,
        pass_foreign_args: bool = False,
        *args: Any,
        **kwargs: Any,
    ) -> None:
        fmt = kwargs.pop("fmt", "%(message)s")
        super().__init__(*args, fmt=fmt, **kwargs)  # type: ignore[misc]

        if processor and processors:
            raise TypeError(
                "The `processor` and `processors` arguments are mutually "
                "exclusive."
            )

        self.processors: Sequence[Processor]
        if processor is not None:
            self.processors = (self.remove_processors_meta, processor)
        elif processors:
            self.processors = processors
        else:
            raise TypeError(
                "Either `processor` or `processors` must be passed."
            )

        self.foreign_pre_chain = foreign_pre_chain
        self.keep_exc_info = keep_exc_info
        self.keep_stack_info = keep_stack_info
        self.logger = logger
        self.pass_foreign_args = pass_foreign_args

    def format(self, record: logging.LogRecord) -> str:
        """
        Extract *structlog*'s `event_dict` from ``record.msg`` and format it.

        *record* has been patched by `wrap_for_formatter` first though, so the
         type isn't quite right.
        """
        # Make a shallow copy of the record to let other handlers/formatters
        # process the original one
        record = logging.makeLogRecord(record.__dict__)

        logger = getattr(record, "_logger", _SENTINEL)
        meth_name = getattr(record, "_name", _SENTINEL)

        if logger is not _SENTINEL and meth_name is not _SENTINEL:
            # Both attached by wrap_for_formatter
            if self.logger is not None:
                logger = self.logger
            meth_name = record._name  # type: ignore[attr-defined]

            # We need to copy because it's possible that the same record gets
            # processed by multiple logging formatters.  LogRecord.getMessage
            # would transform our dict into a str.
            ed = record.msg.copy()  # type: ignore[attr-defined]
            ed["_record"] = record
            ed["_from_structlog"] = True
        else:
            logger = self.logger
            meth_name = record.levelname.lower()
            ed = {
                "event": record.getMessage(),
                "_record": record,
                "_from_structlog": False,
            }

            if self.pass_foreign_args:
                ed["positional_args"] = record.args

            record.args = ()

            # Add stack-related attributes to event_dict and unset them
            # on the record copy so that the base implementation wouldn't
            # append stacktraces to the output.
            if record.exc_info:
                ed["exc_info"] = record.exc_info
            if record.stack_info:
                ed["stack_info"] = record.stack_info

            if not self.keep_exc_info:
                record.exc_text = None
                record.exc_info = None
            if not self.keep_stack_info:
                record.stack_info = None

            # Non-structlog allows to run through a chain to prepare it for the
            # final processor (e.g. adding timestamps and log levels).
            for proc in self.foreign_pre_chain or ():
                ed = proc(logger, meth_name, ed)

        for p in self.processors:
            ed = p(logger, meth_name, ed)

        record.msg = ed

        return super().format(record)

    @staticmethod
    def wrap_for_formatter(
        logger: logging.Logger, name: str, event_dict: EventDict
    ) -> tuple[tuple[EventDict], dict[str, dict[str, Any]]]:
        """
        Wrap *logger*, *name*, and *event_dict*.

        The result is later unpacked by `ProcessorFormatter` when
        formatting log entries.

        Use this static method as the renderer (i.e. final processor) if you
        want to use `ProcessorFormatter` in your `logging` configuration.
        """
        return (event_dict,), {"extra": {"_logger": logger, "_name": name}}

    @staticmethod
    def remove_processors_meta(
        _: WrappedLogger, __: str, event_dict: EventDict
    ) -> EventDict:
        """
        Remove ``_record`` and ``_from_structlog`` from *event_dict*.

        These keys are added to the event dictionary, before
        `ProcessorFormatter`'s *processors* are run.

        .. versionadded:: 21.3.0
        """
        del event_dict["_record"]
        del event_dict["_from_structlog"]

        return event_dict
