import urlparse

class OAuthConfig(object):
  def __init__(self, config, key_name):
    self.key_name = key_name
    self.config = config.get(key_name) or {}

  def service_name(self):
    raise NotImplementedError

  def token_endpoint(self):
    raise NotImplementedError

  def user_endpoint(self):
    raise NotImplementedError

  def login_endpoint(self):
    raise NotImplementedError

  def validate_client_id_and_secret(self, http_client):
    raise NotImplementedError

  def client_id(self):
    return self.config.get('CLIENT_ID')

  def client_secret(self):
    return self.config.get('CLIENT_SECRET')

  def _get_url(self, endpoint, *args):
    for arg in args:
      endpoint = urlparse.urljoin(endpoint, arg)

    return endpoint


class GithubOAuthConfig(OAuthConfig):
  def __init__(self, config, key_name):
    super(GithubOAuthConfig, self).__init__(config, key_name)

  def service_name(self):
    return 'GitHub'

  def _endpoint(self):
    endpoint = self.config.get('GITHUB_ENDPOINT', 'https://github.com')
    if not endpoint.endswith('/'):
      endpoint = endpoint + '/'
    return endpoint

  def authorize_endpoint(self):
    return self._get_url(self._endpoint(), '/login/oauth/authorize')  + '?'

  def token_endpoint(self):
    return self._get_url(self._endpoint(), '/login/oauth/access_token')

  def _api_endpoint(self):
    return self.config.get('API_ENDPOINT', self._get_url(self._endpoint(), '/api/v3/'))

  def api_endpoint(self):
    return self._api_endpoint()[0:-1]

  def user_endpoint(self):
    api_endpoint = self._api_endpoint()
    return self._get_url(api_endpoint, 'user')

  def email_endpoint(self):
    api_endpoint = self._api_endpoint()
    return self._get_url(api_endpoint, 'user/emails')

  def validate_client_id_and_secret(self, http_client):
    # First: Verify that the github endpoint is actually Github by checking for the
    # X-GitHub-Request-Id here.
    api_endpoint = self._api_endpoint()
    result = http_client.get(api_endpoint, auth=(self.client_id(), self.client_secret()), timeout=5)
    if not 'X-GitHub-Request-Id' in result.headers:
      raise Exception('Endpoint is not a Github (Enterprise) installation')

    # Next: Verify the client ID and secret.
    # Note: The following code is a hack until such time as Github officially adds an API endpoint
    # for verifying a {client_id, client_secret} pair. That being said, this hack was given to us
    # *by a Github Engineer*, so I think it is okay for the time being :)
    #
    # TODO(jschorr): Replace with the real API call once added.
    #
    # Hitting the endpoint applications/{client_id}/tokens/foo will result in the following
    # behavior IF the client_id is given as the HTTP username and the client_secret as the HTTP
    # password:
    #   - If the {client_id, client_secret} pair is invalid in some way, we get a 401 error.
    #   - If the pair is valid, then we get a 404 because the 'foo' token does not exists.
    validate_endpoint = self._get_url(api_endpoint, 'applications/%s/tokens/foo' % self.client_id())
    result = http_client.get(validate_endpoint, auth=(self.client_id(), self.client_secret()),
                                                timeout=5)
    return result.status_code == 404

  def get_public_config(self):
    return  {
      'CLIENT_ID': self.client_id(),
      'AUTHORIZE_ENDPOINT': self.authorize_endpoint(),
      'GITHUB_ENDPOINT': self._endpoint()
    }



class GoogleOAuthConfig(OAuthConfig):
  def __init__(self, config, key_name):
    super(GoogleOAuthConfig, self).__init__(config, key_name)

  def service_name(self):
    return 'Google'

  def authorize_endpoint(self):
    return 'https://accounts.google.com/o/oauth2/auth?response_type=code&'

  def token_endpoint(self):
    return 'https://accounts.google.com/o/oauth2/token'

  def user_endpoint(self):
    return 'https://www.googleapis.com/oauth2/v1/userinfo'

  def validate_client_id_and_secret(self, http_client):
    # To verify the Google client ID and secret, we hit the
    # https://www.googleapis.com/oauth2/v3/token endpoint with an invalid request. If the client
    # ID or secret are invalid, we get returned a 403 Unauthorized. Otherwise, we get returned
    # another response code.
    url = 'https://www.googleapis.com/oauth2/v3/token'
    data = {
      'code': 'fakecode',
      'client_id': self.client_id(),
      'client_secret': self.client_secret(),
      'grant_type': 'authorization_code',
      'redirect_uri': 'http://example.com'
    }

    result = http_client.post(url, data=data, timeout=5)
    return result.status_code != 401

  def get_public_config(self):
    return  {
      'CLIENT_ID': self.client_id(),
      'AUTHORIZE_ENDPOINT': self.authorize_endpoint()
    }