# -*- coding: utf-8 -*-
# ----------------------------------------------------------------------------
# Copyright (C) 2013-2018 British Crown (Met Office) & Contributors.
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU Lesser General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU Lesser General Public License for more details.
#
# You should have received a copy of the GNU Lesser General Public License
# along with this program.  If not, see <http://www.gnu.org/licenses/>.
# ----------------------------------------------------------------------------

"""This provides utilities for extracting the local time zone."""

import time
import math


class TimeZoneFormatMode(object):
    normal = "normal"
    reduced = "reduced"
    extended = "extended"


def get_local_time_zone():
    """Return the current local UTC offset in hours and minutes."""
    utc_offset_seconds = -time.timezone
    if time.localtime().tm_isdst == 1 and time.daylight:
        utc_offset_seconds = -time.altzone
    utc_offset_minutes = (utc_offset_seconds // 60) % 60
    utc_offset_hours = math.floor(utc_offset_seconds / float(3600)) if \
        utc_offset_seconds > 0 else math.ceil(utc_offset_seconds / float(3600))
    return int(utc_offset_hours), utc_offset_minutes


def get_local_time_zone_format(tz_fmt_mode=TimeZoneFormatMode.normal):
    """Return a string denoting the current local UTC offset.

    :param tz_fmt_mode:
    :type tz_fmt_mode: TimeZoneFormat:
    """
    utc_offset_hours, utc_offset_minutes = get_local_time_zone()
    if utc_offset_hours == 0 and utc_offset_minutes == 0:
        return "Z"
    reduced_timezone_template = "%s%02d"
    timezone_template = "%s%02d%02d"
    if tz_fmt_mode == TimeZoneFormatMode.extended:
        timezone_template = "%s%02d:%02d"
    sign = "-" if (utc_offset_hours < 0 or utc_offset_minutes < 0) else "+"
    if tz_fmt_mode == TimeZoneFormatMode.reduced and utc_offset_minutes == 0:
        return reduced_timezone_template % (sign, abs(utc_offset_hours))
    return timezone_template % (
        sign, abs(utc_offset_hours), abs(utc_offset_minutes))
