# Copyright (C) 2011 Google 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.

"""Utilities for reading OAuth 2.0 client secret files.

A client_secrets.json file contains all the information needed to interact with
an OAuth 2.0 protected service.
"""

__author__ = "jcgregorio@google.com (Joe Gregorio)"


from vendor.oauth2client.anyjson import simplejson

# Properties that make a client_secrets.json file valid.
TYPE_WEB = "web"
TYPE_INSTALLED = "installed"

VALID_CLIENT = {
    TYPE_WEB: {
        "required": ["client_id", "client_secret", "redirect_uris", "auth_uri", "token_uri"],
        "string": ["client_id", "client_secret"],
    },
    TYPE_INSTALLED: {
        "required": ["client_id", "client_secret", "redirect_uris", "auth_uri", "token_uri"],
        "string": ["client_id", "client_secret"],
    },
}


class Error(Exception):
    """Base error for this module."""

    pass


class InvalidClientSecretsError(Error):
    """Format of ClientSecrets file is invalid."""

    pass


def _validate_clientsecrets(obj):
    if obj is None or len(obj) != 1:
        raise InvalidClientSecretsError("Invalid file format.")
    client_type = list(obj.keys())[0]
    if client_type not in list(VALID_CLIENT.keys()):
        raise InvalidClientSecretsError("Unknown client type: %s." % client_type)
    client_info = obj[client_type]
    for prop_name in VALID_CLIENT[client_type]["required"]:
        if prop_name not in client_info:
            raise InvalidClientSecretsError(
                'Missing property "%s" in a client type of "%s".' % (prop_name, client_type)
            )
    for prop_name in VALID_CLIENT[client_type]["string"]:
        if client_info[prop_name].startswith("[["):
            raise InvalidClientSecretsError('Property "%s" is not configured.' % prop_name)
    return client_type, client_info


def load(fp):
    obj = simplejson.load(fp)
    return _validate_clientsecrets(obj)


def loads(s):
    obj = simplejson.loads(s)
    return _validate_clientsecrets(obj)


def _loadfile(filename):
    try:
        fp = file(filename, "r")
        try:
            obj = simplejson.load(fp)
        finally:
            fp.close()
    except IOError:
        raise InvalidClientSecretsError('File not found: "%s"' % filename)
    return _validate_clientsecrets(obj)


def loadfile(filename, cache=None):
    """Loading of client_secrets JSON file, optionally backed by a cache.

    Typical cache storage would be App Engine memcache service,
    but you can pass in any other cache client that implements
    these methods:
      - get(key, namespace=ns)
      - set(key, value, namespace=ns)

    Usage:
      # without caching
      client_type, client_info = loadfile('secrets.json')
      # using App Engine memcache service
      from google.appengine.api import memcache
      client_type, client_info = loadfile('secrets.json', cache=memcache)

    Args:
      filename: string, Path to a client_secrets.json file on a filesystem.
      cache: An optional cache service client that implements get() and set()
        methods. If not specified, the file is always being loaded from
        a filesystem.

    Raises:
      InvalidClientSecretsError: In case of a validation error or some
        I/O failure. Can happen only on cache miss.

    Returns:
      (client_type, client_info) tuple, as _loadfile() normally would.
      JSON contents is validated only during first load. Cache hits are not
      validated.
    """
    _SECRET_NAMESPACE = "oauth2client:secrets#ns"

    if not cache:
        return _loadfile(filename)

    obj = cache.get(filename, namespace=_SECRET_NAMESPACE)
    if obj is None:
        client_type, client_info = _loadfile(filename)
        obj = {client_type: client_info}
        cache.set(filename, obj, namespace=_SECRET_NAMESPACE)

    return next(iter(list(obj.items())))