# 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.

"""Caching utility for the discovery document."""

from __future__ import absolute_import

import logging
import os

LOGGER = logging.getLogger(__name__)

DISCOVERY_DOC_MAX_AGE = 60 * 60 * 24  # 1 day
DISCOVERY_DOC_DIR = os.path.join(
    os.path.dirname(os.path.realpath(__file__)), "documents"
)


def autodetect():
    """Detects an appropriate cache module and returns it.

    Returns:
      googleapiclient.discovery_cache.base.Cache, a cache object which
      is auto detected, or None if no cache object is available.
    """
    if "APPENGINE_RUNTIME" in os.environ:
        try:
            from . import appengine_memcache

            return appengine_memcache.cache
        except Exception:
            pass
    try:
        from . import file_cache

        return file_cache.cache
    except Exception:
        LOGGER.info(
            "file_cache is only supported with oauth2client<4.0.0", exc_info=False
        )
        return None


def get_static_doc(serviceName, version):
    """Retrieves the discovery document from the directory defined in
    DISCOVERY_DOC_DIR corresponding to the serviceName and version provided.

    Args:
        serviceName: string, name of the service.
        version: string, the version of the service.

    Returns:
        A string containing the contents of the JSON discovery document,
        otherwise None if the JSON discovery document was not found.
    """

    content = None
    doc_name = "{}.{}.json".format(serviceName, version)

    try:
        with open(os.path.join(DISCOVERY_DOC_DIR, doc_name), "r") as f:
            content = f.read()
    except FileNotFoundError:
        # File does not exist. Nothing to do here.
        pass

    return content
