# 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)'


try: # pragma: no cover
  import simplejson
except ImportError: # pragma: no cover
  try:
    # Try to import from django, should work on App Engine
    from django.utils import simplejson
  except ImportError:
    # Should work for Python2.6 and higher.
    import json as 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 = obj.keys()[0]
  if client_type not in 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)