"""
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 cfg


def _setup_logger() -> logging.Logger:
    """Create or return the singleton evaluation logger."""
    logger = logging.getLogger(cfg.log_name)
    if any(isinstance(h, CloudLoggingHandler) for h in logger.handlers):
        return logger

    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)

    return logger


_eval_log = _setup_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)
    _eval_log.log(level, message, extra={"json_fields": {"message": message, "custom": custom_log or {}}})