"""
Small classes to assist with timezone calculations, LOGGER configuration,
and other common operations.
"""

import datetime
import pytz
import logging


LOGGER = logging.getLogger('QSimLogger')

def parse_date(dt_str):
    """parse strings according to the same format as generated by format_date"""
    if(dt_str == None):
        return None
    parts = dt_str.split(".")
    dt = datetime.datetime.strptime(parts[0], '%Y/%m/%d-%H:%M:%S').replace(microsecond=int(parts[1]+"000"), tzinfo = pytz.utc)
    return dt

def format_date(dt):
    """Format the date into a date with millesecond resolution and string/alphabetical
    sorting that is equivalent to datetime sorting"""
    if(dt == None):
        return None
    dt_str = dt.strftime('%Y/%m/%d-%H:%M:%S') + "." + str(dt.microsecond / 1000)
    return dt_str

def configure_logging(loglevel=logging.DEBUG):
    """configures qsim.util.LOGGER to write a rotating file (10M per file, 5 files) to /var/log/qsim.log"""
    LOGGER.setLevel(loglevel)
    handler = logging.handlers.RotatingFileHandler(
                "/var/log/qsim/{lfn}.log".format(lfn="qsim"),
                maxBytes=10*1024*1024, backupCount=5)
    handler.setFormatter(logging.Formatter(
                "%(asctime)s %(levelname)s %(filename)s %(funcName)s - %(message)s","%Y-%m-%d %H:%M:%S %Z"))
    LOGGER.addHandler(handler)
    LOGGER.info("logging started...")