import logging
import json
from logging.handlers import RotatingFileHandler
from pathlib import Path
from datetime import datetime

class JsonFormatter(logging.Formatter):
    """
    Custom JSON log formatter for structured logging.
    """
    def format(self, record: logging.LogRecord) -> str:
        log_object = {
            "timestamp": datetime.utcfromtimestamp(record.created).strftime("%Y-%m-%dT%H:%M:%SZ"),
            "level": record.levelname,
            "message": record.getMessage(),
            "module": record.module,
            "funcName": record.funcName,
            "line": record.lineno,
        }

        # Include any extra fields added via logger.info("msg", extra={...})
        if hasattr(record, "extra") and isinstance(record.extra, dict):
            log_object.update(record.extra)

        # Include exception info if present
        if record.exc_info:
            log_object["exception"] = self.formatException(record.exc_info)

        return json.dumps(log_object, ensure_ascii=False)

def setup_logger(log_folder: Path, log_file_name: str = "rolling_rename.log", level=logging.INFO) -> logging.Logger:
    """
    Sets up a logger that prints to console and writes to a rotating JSON log file.
    """
    log_folder.mkdir(parents=True, exist_ok=True)
    log_file = log_folder / log_file_name

    logger = logging.getLogger("rolling_rename")
    logger.setLevel(level)
    logger.propagate = False  # Prevent double logging

    # Formatters
    text_formatter = logging.Formatter(
        "%(asctime)s [%(levelname)s] %(message)s (%(module)s:%(lineno)d)",
        datefmt="%Y-%m-%d %H:%M:%S"
    )
    json_formatter = JsonFormatter()

    # Console handler (human-readable)
    console_handler = logging.StreamHandler()
    console_handler.setFormatter(text_formatter)
    console_handler.setLevel(level)

    # File handler (JSON logs)
    file_handler = RotatingFileHandler(log_file, maxBytes=5 * 1024 * 1024, backupCount=3, encoding="utf-8")
    file_handler.setFormatter(json_formatter)
    file_handler.setLevel(level)

    # Add handlers only once
    if not logger.handlers:
        logger.addHandler(console_handler)
        logger.addHandler(file_handler)

    return logger