from datetime import timedelta

from dateutil import tz

UTC = tz.UTC


def get_timezone(key):
    if not key:
        raise KeyError("Unknown time zone: %s" % key)

    try:
        rv = tz.gettz(key)
    except Exception:
        rv = None

    if rv is None or not isinstance(rv, (tz.tzutc, tz.tzfile)):
        raise KeyError("Unknown time zone: %s" % key)

    return rv


def get_timezone_file(f, key=None):
    return tz.tzfile(f)


def get_fixed_offset_zone(offset):
    return tz.tzoffset(None, timedelta(minutes=offset))


def is_ambiguous(dt):
    return tz.datetime_ambiguous(dt)


def is_imaginary(dt):
    return not tz.datetime_exists(dt)


enfold = tz.enfold


def get_fold(dt):
    return getattr(dt, "fold", 0)