# Copyright 2016 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.

"""Transport adapter for Requests."""

from __future__ import absolute_import

import functools
import logging

try:
    import requests
except ImportError as caught_exc:  # pragma: NO COVER
    import six
    six.raise_from(
        ImportError(
            'The requests library is not installed, please install the '
            'requests package to use the requests transport.'
        ),
        caught_exc,
    )
import requests.adapters  # pylint: disable=ungrouped-imports
import requests.exceptions  # pylint: disable=ungrouped-imports
import six  # pylint: disable=ungrouped-imports

from google.auth import exceptions
from google.auth import transport

_LOGGER = logging.getLogger(__name__)


class _Response(transport.Response):
    """Requests transport response adapter.

    Args:
        response (requests.Response): The raw Requests response.
    """
    def __init__(self, response):
        self._response = response

    @property
    def status(self):
        return self._response.status_code

    @property
    def headers(self):
        return self._response.headers

    @property
    def data(self):
        return self._response.content


class Request(transport.Request):
    """Requests request adapter.

    This class is used internally for making requests using various transports
    in a consistent way. If you use :class:`AuthorizedSession` you do not need
    to construct or use this class directly.

    This class can be useful if you want to manually refresh a
    :class:`~google.auth.credentials.Credentials` instance::

        import google.auth.transport.requests
        import requests

        request = google.auth.transport.requests.Request()

        credentials.refresh(request)

    Args:
        session (requests.Session): An instance :class:`requests.Session` used
            to make HTTP requests. If not specified, a session will be created.

    .. automethod:: __call__
    """
    def __init__(self, session=None):
        if not session:
            session = requests.Session()

        self.session = session

    def __call__(self, url, method='GET', body=None, headers=None,
                 timeout=None, **kwargs):
        """Make an HTTP request using requests.

        Args:
            url (str): The URI to be requested.
            method (str): The HTTP method to use for the request. Defaults
                to 'GET'.
            body (bytes): The payload / body in HTTP request.
            headers (Mapping[str, str]): Request headers.
            timeout (Optional[int]): The number of seconds to wait for a
                response from the server. If not specified or if None, the
                requests default timeout will be used.
            kwargs: Additional arguments passed through to the underlying
                requests :meth:`~requests.Session.request` method.

        Returns:
            google.auth.transport.Response: The HTTP response.

        Raises:
            google.auth.exceptions.TransportError: If any exception occurred.
        """
        try:
            _LOGGER.debug('Making request: %s %s', method, url)
            response = self.session.request(
                method, url, data=body, headers=headers, timeout=timeout,
                **kwargs)
            return _Response(response)
        except requests.exceptions.RequestException as caught_exc:
            new_exc = exceptions.TransportError(caught_exc)
            six.raise_from(new_exc, caught_exc)


class AuthorizedSession(requests.Session):
    """A Requests Session class with credentials.

    This class is used to perform requests to API endpoints that require
    authorization::

        from google.auth.transport.requests import AuthorizedSession

        authed_session = AuthorizedSession(credentials)

        response = authed_session.request(
            'GET', 'https://www.googleapis.com/storage/v1/b')

    The underlying :meth:`request` implementation handles adding the
    credentials' headers to the request and refreshing credentials as needed.

    Args:
        credentials (google.auth.credentials.Credentials): The credentials to
            add to the request.
        refresh_status_codes (Sequence[int]): Which HTTP status codes indicate
            that credentials should be refreshed and the request should be
            retried.
        max_refresh_attempts (int): The maximum number of times to attempt to
            refresh the credentials and retry the request.
        refresh_timeout (Optional[int]): The timeout value in seconds for
            credential refresh HTTP requests.
        kwargs: Additional arguments passed to the :class:`requests.Session`
            constructor.
    """
    def __init__(self, credentials,
                 refresh_status_codes=transport.DEFAULT_REFRESH_STATUS_CODES,
                 max_refresh_attempts=transport.DEFAULT_MAX_REFRESH_ATTEMPTS,
                 refresh_timeout=None,
                 **kwargs):
        super(AuthorizedSession, self).__init__(**kwargs)
        self.credentials = credentials
        self._refresh_status_codes = refresh_status_codes
        self._max_refresh_attempts = max_refresh_attempts
        self._refresh_timeout = refresh_timeout

        auth_request_session = requests.Session()

        # Using an adapter to make HTTP requests robust to network errors.
        # This adapter retrys HTTP requests when network errors occur
        # and the requests seems safely retryable.
        retry_adapter = requests.adapters.HTTPAdapter(max_retries=3)
        auth_request_session.mount("https://", retry_adapter)

        # Request instance used by internal methods (for example,
        # credentials.refresh).
        # Do not pass `self` as the session here, as it can lead to infinite
        # recursion.
        self._auth_request = Request(auth_request_session)

    def request(self, method, url, data=None, headers=None, **kwargs):
        """Implementation of Requests' request."""
        # pylint: disable=arguments-differ
        # Requests has a ton of arguments to request, but only two
        # (method, url) are required. We pass through all of the other
        # arguments to super, so no need to exhaustively list them here.

        # Use a kwarg for this instead of an attribute to maintain
        # thread-safety.
        _credential_refresh_attempt = kwargs.pop(
            '_credential_refresh_attempt', 0)

        # Make a copy of the headers. They will be modified by the credentials
        # and we want to pass the original headers if we recurse.
        request_headers = headers.copy() if headers is not None else {}

        self.credentials.before_request(
            self._auth_request, method, url, request_headers)

        response = super(AuthorizedSession, self).request(
            method, url, data=data, headers=request_headers, **kwargs)

        # If the response indicated that the credentials needed to be
        # refreshed, then refresh the credentials and re-attempt the
        # request.
        # A stored token may expire between the time it is retrieved and
        # the time the request is made, so we may need to try twice.
        if (response.status_code in self._refresh_status_codes
                and _credential_refresh_attempt < self._max_refresh_attempts):

            _LOGGER.info(
                'Refreshing credentials due to a %s response. Attempt %s/%s.',
                response.status_code, _credential_refresh_attempt + 1,
                self._max_refresh_attempts)

            auth_request_with_timeout = functools.partial(
                self._auth_request, timeout=self._refresh_timeout)
            self.credentials.refresh(auth_request_with_timeout)

            # Recurse. Pass in the original headers, not our modified set.
            return self.request(
                method, url, data=data, headers=headers,
                _credential_refresh_attempt=_credential_refresh_attempt + 1,
                **kwargs)

        return response