# Copyright 2014 Google Inc. 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.
"""Thread-local resource stack.

This module is not part of the public API surface of `gcloud`.
"""

import calendar
import datetime
import json
import os
import re
import socket
import sys
from threading import local as Local

from google.protobuf import timestamp_pb2
try:
    from google.appengine.api import app_identity
except ImportError:
    app_identity = None
import six
from six.moves.http_client import HTTPConnection
from six.moves import configparser

from gcloud.environment_vars import PROJECT
from gcloud.environment_vars import CREDENTIALS


_NOW = datetime.datetime.utcnow  # To be replaced by tests.
_RFC3339_MICROS = '%Y-%m-%dT%H:%M:%S.%fZ'
_RFC3339_NO_FRACTION = '%Y-%m-%dT%H:%M:%S'
# datetime.strptime cannot handle nanosecond precision:  parse w/ regex
_RFC3339_NANOS = re.compile(r"""
    (?P<no_fraction>
        \d{4}-\d{2}-\d{2}T\d{2}:\d{2}:\d{2}  # YYYY-MM-DDTHH:MM:SS
    )
    \.                                       # decimal point
    (?P<nanos>\d{1,9})                       # nanoseconds, maybe truncated
    Z                                        # Zulu
""", re.VERBOSE)
DEFAULT_CONFIGURATION_PATH = '~/.config/gcloud/configurations/config_default'


class _LocalStack(Local):
    """Manage a thread-local LIFO stack of resources.

    Intended for use in :class:`gcloud.datastore.batch.Batch.__enter__`,
    :class:`gcloud.storage.batch.Batch.__enter__`, etc.
    """
    def __init__(self):
        super(_LocalStack, self).__init__()
        self._stack = []

    def __iter__(self):
        """Iterate the stack in LIFO order.
        """
        return iter(reversed(self._stack))

    def push(self, resource):
        """Push a resource onto our stack.
        """
        self._stack.append(resource)

    def pop(self):
        """Pop a resource from our stack.

        :rtype: object
        :returns: the top-most resource, after removing it.
        :raises IndexError: if the stack is empty.
        """
        return self._stack.pop()

    @property
    def top(self):
        """Get the top-most resource

        :rtype: object
        :returns: the top-most item, or None if the stack is empty.
        """
        if len(self._stack) > 0:
            return self._stack[-1]


class _UTC(datetime.tzinfo):
    """Basic UTC implementation.

    Implementing a small surface area to avoid depending on ``pytz``.
    """

    _dst = datetime.timedelta(0)
    _tzname = 'UTC'
    _utcoffset = _dst

    def dst(self, dt):  # pylint: disable=unused-argument
        """Daylight savings time offset."""
        return self._dst

    def fromutc(self, dt):
        """Convert a timestamp from (naive) UTC to this timezone."""
        if dt.tzinfo is None:
            return dt.replace(tzinfo=self)
        return super(_UTC, self).fromutc(dt)

    def tzname(self, dt):  # pylint: disable=unused-argument
        """Get the name of this timezone."""
        return self._tzname

    def utcoffset(self, dt):  # pylint: disable=unused-argument
        """UTC offset of this timezone."""
        return self._utcoffset