import os
import sys
import datetime
import logging


def date_uid():
    """Generate a unique id based on date.

    Returns:
        str: Return uid string, e.g. '20171122171307111552'.

    """
    return str(datetime.datetime.now()).replace('-', '') \
        .replace(' ', '').replace(':', '').replace('.', '')


def get_logger(checkpoint_path=None):
    """
    Get the root logger
    :param checkpoint_path: only specify this when the first time call it
    :return: the root logger
    """
    if checkpoint_path:
        logger = logging.getLogger()
        formatter = logging.Formatter('%(asctime)s %(levelname)s %(message)s')
        stream_hdlr = logging.StreamHandler(sys.stdout)
        log_filename = date_uid()
        file_hdlr = logging.FileHandler(os.path.join(checkpoint_path, log_filename + '.log'))
        stream_hdlr.setFormatter(formatter)
        file_hdlr.setFormatter(formatter)
        logger.addHandler(stream_hdlr)
        logger.addHandler(file_hdlr)
        logger.setLevel(logging.INFO)
    else:
        logger = logging.getLogger()
    return logger