"""
Centralized Cloud Logging setup.
Uses CloudLoggingHandler (background thread) so logging does not add latency
"""

import logging
from typing import Optional, Dict, Literal

import google.cloud.logging
from google.cloud.logging.handlers import CloudLoggingHandler

from .config import get_config


_eval_log: logging.Logger | None = None


def _get_logger() -> logging.Logger:
    """Get or create the singleton evaluation logger."""
    global _eval_log
    if _eval_log is not None:
        return _eval_log

    cfg = get_config()
    logger = logging.getLogger(cfg.log_name)
    if any(isinstance(h, CloudLoggingHandler) for h in logger.handlers):
        _eval_log = logger
        return logger

    if cfg.cloud_logging_enabled:
        try:
            client = google.cloud.logging.Client(project=cfg.project_id)
            handler = CloudLoggingHandler(client, name=cfg.log_name)  # async transport
            logger.addHandler(handler)
            logger.setLevel(getattr(logging, cfg.log_level.upper()))
        except Exception as e:
            # Fallback to console if Cloud Logging is unavailable (local dev)
            logging.basicConfig(level=getattr(logging, cfg.log_level.upper()))
            logger = logging.getLogger(cfg.log_name)
            logger.warning("Cloud Logging setup failed; using console. Error: %s", e)
    else:
        logging.basicConfig(level=getattr(logging, cfg.log_level.upper()))
        logger = logging.getLogger(cfg.log_name)

    _eval_log = logger
    return logger


def log_structured_entry(message: str, severity: Literal["INFO", "WARNING", "ERROR"], custom_log: Optional[Dict] = None) -> None:
    """
    Emit a JSON-structured log row.

    Args:
        message: Short label for the row (e.g., "Final agent turn").
        severity: "INFO" | "WARNING" | "ERROR"
        custom_log: A dict with your structured payload.
    """
    level = getattr(logging, severity.upper(), logging.INFO)
    logger = _get_logger()
    logger.log(level, message, extra={"json_fields": {"message": message, "custom": custom_log or {}}})