"""Shared logging for James components.

Usage:
    from james.lib.log import get_logger
    log = get_logger("watcher")
    log.info("started", interval=30)
    log.error("redis connect failed", exc_info=True)

Output is JSON-lines to stderr (captured by systemd journal).
Set JAMES_LOG_LEVEL to DEBUG/INFO/WARNING/ERROR (default: INFO).
"""

import json
import logging
import os
import sys
import time
from typing import Any


class JsonFormatter(logging.Formatter):
    """Formats log records as single-line JSON for easy parsing."""

    def format(self, record: logging.LogRecord) -> str:
        entry: dict[str, Any] = {
            "ts": time.strftime("%Y-%m-%dT%H:%M:%S%z", time.localtime(record.created)),
            "level": record.levelname.lower(),
            "component": record.name,
            "msg": record.getMessage(),
        }
        # Merge extra fields passed via log.info("msg", extra={"k": "v"})
        # or via the convenience wrapper below.
        extras = getattr(record, "_extra_fields", None)
        if extras:
            entry.update(extras)
        if record.exc_info and record.exc_info[1] is not None:
            entry["error"] = str(record.exc_info[1])
            entry["error_type"] = type(record.exc_info[1]).__name__
        return json.dumps(entry, default=str)


class JamesLogger(logging.Logger):
    """Logger subclass that accepts keyword args as structured fields."""

    def _log(self, level, msg, args, exc_info=None, extra=None, stack_info=False, stacklevel=1, **kwargs):
        if extra is None:
            extra = {}
        extra["_extra_fields"] = kwargs
        super()._log(level, msg, args, exc_info=exc_info, extra=extra, stack_info=stack_info, stacklevel=stacklevel + 1)


def get_logger(component: str) -> JamesLogger:
    """Return a named JSON logger for a James component."""
    logging.setLoggerClass(JamesLogger)
    logger = logging.getLogger(f"james.{component}")
    if not logger.handlers:
        handler = logging.StreamHandler(sys.stderr)
        handler.setFormatter(JsonFormatter())
        logger.addHandler(handler)
        level = os.environ.get("JAMES_LOG_LEVEL", "INFO").upper()
        logger.setLevel(getattr(logging, level, logging.INFO))
    return logger  # type: ignore[return-value]