# vim: tabstop=4 shiftwidth=4 softtabstop=4

# Copyright 2011 OpenStack LLC.
# All Rights Reserved.
#
#    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.

"""
System-level utilities and helper functions.
"""

import datetime
import sys

from openstack.common import exception


TIME_FORMAT = "%Y-%m-%dT%H:%M:%SZ"


def int_from_bool_as_string(subject):
    """
    Interpret a string as a boolean and return either 1 or 0.

    Any string value in:
        ('True', 'true', 'On', 'on', '1')
    is interpreted as a boolean True.

    Useful for JSON-decoded stuff and config file parsing
    """
    return bool_from_string(subject) and 1 or 0


def bool_from_string(subject):
    """
    Interpret a string as a boolean.

    Any string value in:
        ('True', 'true', 'On', 'on', '1')
    is interpreted as a boolean True.

    Useful for JSON-decoded stuff and config file parsing
    """
    if type(subject) == type(bool):
        return subject
    if hasattr(subject, 'startswith'):  # str or unicode...
        if subject.strip().lower() in ('true', 'on', '1'):
            return True
    return False


def import_class(import_str):
    """Returns a class from a string including module and class"""
    mod_str, _sep, class_str = import_str.rpartition('.')
    try:
        __import__(mod_str)
        return getattr(sys.modules[mod_str], class_str)
    except (ImportError, ValueError, AttributeError):
        raise exception.NotFound('Class %s cannot be found' % class_str)


def import_object(import_str):
    """Returns an object including a module or module and class"""
    try:
        __import__(import_str)
        return sys.modules[import_str]
    except ImportError:
        cls = import_class(import_str)
        return cls()


def isotime(at=None):
    if not at:
        at = datetime.datetime.utcnow()
    return at.strftime(TIME_FORMAT)


def parse_isotime(timestr):
    return datetime.datetime.strptime(timestr, TIME_FORMAT)