logger.py

"""Centralized logging configuration for the book downloader application."""

import logging
import sys
from logging.handlers import RotatingFileHandler
from config import FLASK_DEBUG

def setup_logger(name: str, log_file: str = "") -> logging.Logger:
    """Set up and configure a logger instance.
    
    Args:
        name: The name of the logger instance
        log_file: Optional path to log file. If None, logs only to stdout/stderr
        
    Returns:
        logging.Logger: Configured logger instance
    """
    logger = logging.getLogger(name)
    logger.setLevel(logging.INFO)
    
    formatter = logging.Formatter(
        '%(asctime)s - %(name)s - %(levelname)s - %(message)s'
    )

    # Console handler for Docker output
    console_handler = logging.StreamHandler(sys.stdout)
    console_handler.setFormatter(formatter)
    if FLASK_DEBUG:
        console_handler.setLevel(logging.DEBUG)
    else:
        console_handler.setLevel(logging.INFO)
    console_handler.addFilter(lambda record: record.levelno < logging.ERROR)  # Only allow logs below ERROR
    logger.addHandler(console_handler)
    
    # Error handler for stderr
    error_handler = logging.StreamHandler(sys.stderr)
    error_handler.setLevel(logging.ERROR)
    error_handler.setFormatter(formatter)
    logger.addHandler(error_handler)
    
    # File handler if log file is specified
    if log_file.strip() != "":
        file_handler = RotatingFileHandler(
            log_file.strip(),
            maxBytes=10485760,  # 10MB
            backupCount=5
        )
        file_handler.setFormatter(formatter)
        logger.addHandler(file_handler)
    
    return logger