"""
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")).replace(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):  
    logger.setLevel(loglevel)
    handler = logging.handlers.RotatingFileHandler("/tmp/{lfn}.log".format(lfn="qsim-log"), 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...")