"""Logging that goes to a file as well as to stdout.

WHY BOTH

stdout is what `docker compose logs` reads and what Docker's own log
driver captures, so it has to stay. The file is so that every component
in this stack has ONE findable place - ./logs, bind-mounted at /logs -
rather than leaving somebody to work out which compose invocation shows
the thing they are looking for.

Falling back to stdout alone is deliberate. A container run without the
mount, or with the directory not writable, should keep working and say
why once; refusing to start because a log file could not be opened would
be the tail wagging the dog.
"""

from __future__ import annotations

import logging
import os
import sys

FORMAT = "%(asctime)s %(levelname)-7s %(name)s | %(message)s"


def configure(component: str, level: str = "INFO") -> logging.Logger:
    """stdout always; ./logs/<component>.log when the directory is there."""
    handlers: list[logging.Handler] = [logging.StreamHandler(sys.stdout)]
    problem = ""
    log_dir = os.environ.get("OWUITOOLS_LOG_DIR", "/logs")
    if log_dir:
        try:
            os.makedirs(log_dir, exist_ok=True)
            handlers.append(logging.FileHandler(
                os.path.join(log_dir, f"{component}.log"), encoding="utf-8"))
        except OSError as exc:
            problem = f"{log_dir} is not writable ({exc}); logging to stdout only"

    logging.basicConfig(level=getattr(logging, level.upper(), logging.INFO),
                        format=FORMAT, handlers=handlers, force=True)
    logger = logging.getLogger(component)
    if problem:
        logger.warning(problem)
    return logger