# Copyright 2020 Google LLC
#
# 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 Async HTTP (aiohttp).

NOTE: This async support is experimental and marked internal. This surface may
change in minor releases.
"""

from __future__ import absolute_import

import asyncio
import functools

import aiohttp  # type: ignore
import six
import urllib3  # type: ignore

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

# Timeout can be re-defined depending on async requirement. Currently made 60s more than
# sync timeout.
_DEFAULT_TIMEOUT = 180  # in seconds


class _CombinedResponse(transport.Response):
    """
    In order to more closely resemble the `requests` interface, where a raw
    and deflated content could be accessed at once, this class lazily reads the
    stream in `transport.Response` so both return forms can be used.

    The gzip and deflate transfer-encodings are automatically decoded for you
    because the default parameter for autodecompress into the ClientSession is set
    to False, and therefore we add this class to act as a wrapper for a user to be
    able to access both the raw and decoded response bodies - mirroring the sync
    implementation.
    """

    def __init__(self, response):
        self._response = response
        self._raw_content = None

    def _is_compressed(self):
        headers = self._response.headers
        return "Content-Encoding" in headers and (
            headers["Content-Encoding"] == "gzip"
            or headers["Content-Encoding"] == "deflate"
        )

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

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

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

    async def raw_content(self):
        if self._raw_content is None:
            self._raw_content = await self._response.content.read()
        return self._raw_content

    async def content(self):
        # Load raw_content if necessary
        await self.raw_content()
        if self._is_compressed():
            decoder = urllib3.response.MultiDecoder(
                self._response.headers["Content-Encoding"]
            )
            decompressed = decoder.decompress(self._raw_content)
            return decompressed

        return self._raw_content


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

    @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 asyncio 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.aiohttp_requests

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

        credentials.refresh(request)

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

    .. automethod:: __call__
    """

    def __init__(self, session=None):
        # TODO: Use auto_decompress property for aiohttp 3.7+
        if session is not None and session._auto_decompress:
            raise ValueError(
                "Client sessions with auto_decompress=True are not supported."
            )
        self.session = session

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

        Args:
            url (str): The URL to be requested.
            method (Optional[str]):
                The HTTP method to use for the request. Defaults to 'GET'.
            body (Optional[bytes]):
                The payload or body in HTTP request.
            headers (Optional[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:
            if self.session is None:  # pragma: NO COVER
                self.session = aiohttp.ClientSession(
                    auto_decompress=False
                )  # pragma: NO COVER
            requests._LOGGER.debug("Making request: %s %s", method, url)
            response = await self.session.request(
                method, url, data=body, headers=headers, timeout=timeout, **kwargs
            )
            return _CombinedResponse(response)

        except aiohttp.ClientError as caught_exc:
            new_exc = exceptions.TransportError(caught_exc)
            six.raise_from(new_exc, caught_exc)

        except asyncio.TimeoutError as caught_exc:
            new_exc = exceptions.TransportError(caught_exc)
            six.raise_from(new_exc, caught_exc)


class AuthorizedSession(aiohttp.ClientSession):
    """This is an async implementation of the Authorized Session class. We utilize an
    aiohttp transport instance, and the interface mirrors the google.auth.transport.requests
    Authorized Session class, except for the change in the transport used in the async use case.

    A Requests Session class with credentials.

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

        from google.auth.transport import aiohttp_requests

        async with aiohttp_requests.AuthorizedSession(credentials) as authed_session:
            response = await 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_async.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.
        auth_request (google.auth.transport.aiohttp_requests.Request):
            (Optional) An instance of
            :class:`~google.auth.transport.aiohttp_requests.Request` used when
            refreshing credentials. If not passed,
            an instance of :class:`~google.auth.transport.aiohttp_requests.Request`
            is created.
    """

    def __init__(
        self,
        credentials,
        refresh_status_codes=transport.DEFAULT_REFRESH_STATUS_CODES,
        max_refresh_attempts=transport.DEFAULT_MAX_REFRESH_ATTEMPTS,
        refresh_timeout=None,
        auth_request=None,
        auto_decompress=False,
    ):
        super(AuthorizedSession, self).__init__()
        self.credentials = credentials
        self._refresh_status_codes = refresh_status_codes
        self._max_refresh_attempts = max_refresh_attempts
        self._refresh_timeout = refresh_timeout
        self._is_mtls = False
        self._auth_request = auth_request
        self._auth_request_session = None
        self._loop = asyncio.get_event_loop()
        self._refresh_lock = asyncio.Lock()
        self._auto_decompress = auto_decompress

    async def request(
        self,
        method,
        url,
        data=None,
        headers=None,
        max_allowed_time=None,
        timeout=_DEFAULT_TIMEOUT,
        auto_decompress=False,
        **kwargs,
    ):

        """Implementation of Authorized Session aiohttp request.

        Args:
            method (str):
                The http request method used (e.g. GET, PUT, DELETE)
            url (str):
                The url at which the http request is sent.
            data (Optional[dict]): Dictionary, list of tuples, bytes, or file-like
                object to send in the body of the Request.
            headers (Optional[dict]): Dictionary of HTTP Headers to send with the
                Request.
            timeout (Optional[Union[float, aiohttp.ClientTimeout]]):
                The amount of time in seconds to wait for the server response
                with each individual request. Can also be passed as an
                ``aiohttp.ClientTimeout`` object.
            max_allowed_time (Optional[float]):
                If the method runs longer than this, a ``Timeout`` exception is
                automatically raised. Unlike the ``timeout`` parameter, this
                value applies to the total method execution time, even if
                multiple requests are made under the hood.

                Mind that it is not guaranteed that the timeout error is raised
                at ``max_allowed_time``. It might take longer, for example, if
                an underlying request takes a lot of time, but the request
                itself does not timeout, e.g. if a large file is being
                transmitted. The timout error will be raised after such
                request completes.
        """
        # Headers come in as bytes which isn't expected behavior, the resumable
        # media libraries in some cases expect a str type for the header values,
        # but sometimes the operations return these in bytes types.
        if headers:
            for key in headers.keys():
                if type(headers[key]) is bytes:
                    headers[key] = headers[key].decode("utf-8")

        async with aiohttp.ClientSession(
            auto_decompress=self._auto_decompress
        ) as self._auth_request_session:
            auth_request = Request(self._auth_request_session)
            self._auth_request = auth_request

            # 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 {}

            # Do not apply the timeout unconditionally in order to not override the
            # _auth_request's default timeout.
            auth_request = (
                self._auth_request
                if timeout is None
                else functools.partial(self._auth_request, timeout=timeout)
            )

            remaining_time = max_allowed_time

            with requests.TimeoutGuard(remaining_time, asyncio.TimeoutError) as guard:
                await self.credentials.before_request(
                    auth_request, method, url, request_headers
                )

            with requests.TimeoutGuard(remaining_time, asyncio.TimeoutError) as guard:
                response = await super(AuthorizedSession, self).request(
                    method,
                    url,
                    data=data,
                    headers=request_headers,
                    timeout=timeout,
                    **kwargs,
                )

            remaining_time = guard.remaining_timeout

            if (
                response.status in self._refresh_status_codes
                and _credential_refresh_attempt < self._max_refresh_attempts
            ):

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

                # Do not apply the timeout unconditionally in order to not override the
                # _auth_request's default timeout.
                auth_request = (
                    self._auth_request
                    if timeout is None
                    else functools.partial(self._auth_request, timeout=timeout)
                )

                with requests.TimeoutGuard(
                    remaining_time, asyncio.TimeoutError
                ) as guard:
                    async with self._refresh_lock:
                        await self._loop.run_in_executor(
                            None, self.credentials.refresh, auth_request
                        )

                remaining_time = guard.remaining_timeout

                return await self.request(
                    method,
                    url,
                    data=data,
                    headers=headers,
                    max_allowed_time=remaining_time,
                    timeout=timeout,
                    _credential_refresh_attempt=_credential_refresh_attempt + 1,
                    **kwargs,
                )

        return response
