"""Custom argparse actions."""

from __future__ import annotations

import argparse
from typing import Any


class KeyValueAction(argparse.Action):
    """Argparse action that accumulates ``KEY=VALUE`` pairs into a dict.

    Usage::

        parser.add_argument("--config", action=KeyValueAction,
                            default={}, metavar="KEY=VALUE",
                            help="Set a config option (can be repeated)")

    Then ``args.config`` is a ``dict[str, str]``.
    """

    def __call__(
        self,
        parser: argparse.ArgumentParser,
        namespace: argparse.Namespace,
        values: Any,
        option_string: str | None = None,
    ) -> None:
        d = getattr(namespace, self.dest, None) or {}
        if "=" not in values:
            parser.error(f"Invalid format: {values!r} (expected KEY=VALUE)")
        key, _, value = values.partition("=")
        d[key.strip()] = value.strip()
        setattr(namespace, self.dest, d)