time.py

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# -*- coding: utf-8 -*-
#
# Copyright 2018 Mycroft AI Inc.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#    http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
#
from datetime import datetime
from dateutil.tz import gettz, tzlocal


def default_timezone():
    """ Get the default timezone

    Based on user location settings location.timezone.code or
    the default system value if no setting exists.

    Returns:
        (datetime.tzinfo): Definition of the default timezone
    """
    try:
        # Obtain from user's configurated settings
        #   location.timezone.code (e.g. "America/Chicago")
        #   location.timezone.name (e.g. "Central Standard Time")
        #   location.timezone.offset (e.g. -21600000)
        from mycroft.configuration import Configuration
        config = Configuration.get()
        code = config["location"]["timezone"]["code"]

        return gettz(code)
    except Exception:
        # Just go with system default timezone
        return tzlocal()


def now_utc():
    """ Retrieve the current time in UTC

    Returns:
        (datetime): The current time in Universal Time, aka GMT
    """
    return to_utc(datetime.utcnow())


def now_local(tz=None):
    """ Retrieve the current time

    Args:
        tz (datetime.tzinfo, optional): Timezone, default to user's settings

    Returns:
        (datetime): The current time
    """
    if not tz:
        tz = default_timezone()
    return datetime.now(tz)


def to_utc(dt):
    """ Convert a datetime with timezone info to a UTC datetime

    Args:
        dt (datetime): A datetime (presumably in some local zone)
    Returns:
        (datetime): time converted to UTC
    """
    tzUTC = gettz("UTC")
    if dt.tzinfo:
        return dt.astimezone(tzUTC)
    else:
        return dt.replace(tzinfo=gettz("UTC")).astimezone(tzUTC)


def to_local(dt):
    """ Convert a datetime to the user's local timezone

    Args:
        dt (datetime): A datetime (if no timezone, defaults to UTC)
    Returns:
        (datetime): time converted to the local timezone
    """
    tz = default_timezone()
    if dt.tzinfo:
        return dt.astimezone(tz)
    else:
        return dt.replace(tzinfo=gettz("UTC")).astimezone(tz)


def to_system(dt):
    """ Convert a datetime to the system's local timezone

    Args:
        dt (datetime): A datetime (if no timezone, assumed to be UTC)
    Returns:
        (datetime): time converted to the operation system's timezone
    """
    tz = tzlocal()
    if dt.tzinfo:
        return dt.astimezone(tz)
    else:
        return dt.replace(tzinfo=gettz("UTC")).astimezone(tz)