# This file is part of Tryton.  The COPYRIGHT file at the top level of
# this repository contains the full copyright notices and license terms.
import logging
import os

try:
    import zoneinfo
    ZoneInfo = zoneinfo.ZoneInfo
    ZoneInfoNotFoundError = zoneinfo.ZoneInfoNotFoundError
except ImportError:
    zoneinfo = None
    import pytz
    from dateutil.tz import gettz as ZoneInfo

    class ZoneInfoNotFoundError(KeyError):
        pass

__all__ = ['SERVER', 'UTC', 'get_tzinfo', 'available_timezones']
logger = logging.getLogger(__name__)
_ALL_ZONES = None


def available_timezones():
    global _ALL_ZONES

    if not _ALL_ZONES:
        if zoneinfo:
            _ALL_ZONES = zoneinfo.available_timezones()
        else:
            _ALL_ZONES = set(pytz.all_timezones)
    return set(_ALL_ZONES)


def get_tzinfo(zoneid):
    try:
        zi = ZoneInfo(zoneid)
        if not zi:
            raise ZoneInfoNotFoundError
    except ZoneInfoNotFoundError:
        logger.warning("Timezone %s not found falling back to UTC", zoneid)
        zi = UTC
    return zi


UTC = ZoneInfo('UTC')
SERVER = get_tzinfo(os.environ['TRYTOND_TZ'])