"""Centralised logging configuration."""

from __future__ import annotations

import logging
import sys
from typing import Optional

_CONFIGURED = False
_DEFAULT_FORMAT = "%(asctime)s | %(levelname)-7s | %(name)s | %(message)s"


def setup_logging(level: str | int = "INFO", *, fmt: Optional[str] = None) -> None:
    """Configure the root logger once for the whole application."""
    global _CONFIGURED
    if isinstance(level, str):
        level = logging.getLevelName(level.upper())

    handler = logging.StreamHandler(stream=sys.stderr)
    handler.setFormatter(logging.Formatter(fmt or _DEFAULT_FORMAT))

    root = logging.getLogger()
    root.setLevel(level)
    # Avoid duplicate handlers on repeated calls (e.g. in tests).
    for existing in list(root.handlers):
        root.removeHandler(existing)
    root.addHandler(handler)
    _CONFIGURED = True


def get_logger(name: str) -> logging.Logger:
    """Return a module logger, ensuring logging has been configured."""
    if not _CONFIGURED:
        setup_logging()
    return logging.getLogger(name)