"""Stdlib logging setup — one stream handler on stdout, human or JSON.

Workers used to print() everything; that gives no levels, no timestamps, and nothing
Loki can parse. Default is a compact human format for local runs; set LOG_JSON=1 in the
container so Grafana Alloy -> Loki gets structured fields (ts, level, logger, msg) plus
any `extra=` keys a call site attaches.
"""

import json
import logging
import sys

# logging.LogRecord built-ins we don't want to echo into a JSON line as "extra" fields.
_RESERVED = set(
    logging.makeLogRecord({}).__dict__
) | {"message", "asctime", "taskName"}


class _JsonFormatter(logging.Formatter):
    def format(self, record: logging.LogRecord) -> str:
        payload = {
            "ts": self.formatTime(record, "%Y-%m-%dT%H:%M:%S%z"),
            "level": record.levelname,
            "logger": record.name,
            "msg": record.getMessage(),
        }
        for key, value in record.__dict__.items():
            if key not in _RESERVED and not key.startswith("_"):
                payload[key] = value
        if record.exc_info:
            payload["exc"] = self.formatException(record.exc_info)
        return json.dumps(payload, default=str)


def configure(level: str = "INFO", json_logs: bool = False) -> None:
    """Install a single stdout handler on the root logger (idempotent)."""
    handler = logging.StreamHandler(sys.stdout)
    if json_logs:
        handler.setFormatter(_JsonFormatter())
    else:
        handler.setFormatter(
            logging.Formatter("%(asctime)s %(levelname)-5s %(name)s | %(message)s", "%H:%M:%S")
        )
    root = logging.getLogger()
    root.handlers.clear()
    root.addHandler(handler)
    root.setLevel(level)