src/app_kit/logging_utils.py

from __future__ import annotations

import json
import logging
import sys
from datetime import datetime, timezone


class JsonLineFormatter(logging.Formatter):
    def format(self, record: logging.LogRecord) -> str:
        payload = {
            'ts': datetime.now(timezone.utc).isoformat(),
            'level': record.levelname,
            'logger': record.name,
            'message': record.getMessage(),
        }
        if record.exc_info:
            payload['exception'] = self.formatException(record.exc_info)
        return json.dumps(payload, ensure_ascii=False)


def setup_logging(name: str = 'app_kit', level: int = logging.INFO, stream=None) -> logging.Logger:
    logger = logging.getLogger(name)
    logger.setLevel(level)
    if not any(getattr(h, '_all4_json', False) for h in logger.handlers):
        handler = logging.StreamHandler(stream or sys.stderr)
        handler._all4_json = True  # type: ignore[attr-defined]
        handler.setFormatter(JsonLineFormatter())
        logger.addHandler(handler)
    logger.propagate = False
    return logger