import datetime

DATETIME_UNITS = {
    'second': datetime.timedelta(seconds=1),
    'seconds': datetime.timedelta(seconds=1),
    'minute': datetime.timedelta(minutes=1),
    'minutes': datetime.timedelta(minutes=1),
    'hour': datetime.timedelta(hours=1),
    'hours': datetime.timedelta(hours=1),
    'day': datetime.timedelta(days=1),
    'days': datetime.timedelta(days=1),
    'week': datetime.timedelta(days=7),
    'weeks': datetime.timedelta(days=7),
    'month': datetime.timedelta(days=30),
    'months': datetime.timedelta(days=30),
    'year': datetime.timedelta(days=365),
    'years': datetime.timedelta(days=365),
}

FORMAT_DATE_HEADER = '%a, %d %b %Y %H:%M:%S GMT'


def parse_duration(text: str) -> datetime.timedelta:
    (num, unit) = text.split(' ')
    num = int(num)
    unit = DATETIME_UNITS[unit]
    return unit * num


def response_datetime(response) -> datetime.datetime:
    return datetime.datetime.strptime(response.headers['Date'], FORMAT_DATE_HEADER)