# 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.

"""OAuth 2.0 async client.

This is a client for interacting with an OAuth 2.0 authorization server's
token endpoint.

For more information about the token endpoint, see
`Section 3.1 of rfc6749`_

.. _Section 3.1 of rfc6749: https://tools.ietf.org/html/rfc6749#section-3.2
"""

import asyncio
import http.client as http_client
import json
import urllib

from google.auth import _exponential_backoff
from google.auth import _helpers
from google.auth import exceptions
from google.auth import jwt
from google.oauth2 import _client as client


async def _token_endpoint_request_no_throw(
    request, token_uri, body, access_token=None, use_json=False, can_retry=True
):
    """Makes a request to the OAuth 2.0 authorization server's token endpoint.
    This function doesn't throw on response errors.

    Args:
        request (google.auth.transport.Request): A callable used to make
            HTTP requests.
        token_uri (str): The OAuth 2.0 authorizations server's token endpoint
            URI.
        body (Mapping[str, str]): The parameters to send in the request body.
        access_token (Optional(str)): The access token needed to make the request.
        use_json (Optional(bool)): Use urlencoded format or json format for the
            content type. The default value is False.
        can_retry (bool): Enable or disable request retry behavior.

    Returns:
        Tuple(bool, Mapping[str, str], Optional[bool]): A boolean indicating
          if the request is successful, a mapping for the JSON-decoded response
          data and in the case of an error a boolean indicating if the error
          is retryable.
    """
    if use_json:
        headers = {"Content-Type": client._JSON_CONTENT_TYPE}
        body = json.dumps(body).encode("utf-8")
    else:
        headers = {"Content-Type": client._URLENCODED_CONTENT_TYPE}
        body = urllib.parse.urlencode(body).encode("utf-8")

    if access_token:
        headers["Authorization"] = "Bearer {}".format(access_token)

    response_data = {}
    retryable_error = False

    retries = _exponential_backoff.ExponentialBackoff()
    for _ in retries:
        response = await request(
            method="POST", url=token_uri, headers=headers, body=body
        )

        # Using data.read() resulted in zlib decompression errors. This may require future investigation.
        response_body1 = await response.content()

        response_body = (
            response_body1.decode("utf-8")
            if hasattr(response_body1, "decode")
            else response_body1
        )

        try:
            response_data = json.loads(response_body)
        except ValueError:
            response_data = response_body

        if response.status == http_client.OK:
            return True, response_data, None

        retryable_error = client._can_retry(
            status_code=response.status, response_data=response_data
        )

        if not can_retry or not retryable_error:
            return False, response_data, retryable_error

    return False, response_data, retryable_error


async def _token_endpoint_request(
    request, token_uri, body, access_token=None, use_json=False, can_retry=True
):
    """Makes a request to the OAuth 2.0 authorization server's token endpoint.

    Args:
        request (google.auth.transport.Request): A callable used to make
            HTTP requests.
        token_uri (str): The OAuth 2.0 authorizations server's token endpoint
            URI.
        body (Mapping[str, str]): The parameters to send in the request body.
        access_token (Optional(str)): The access token needed to make the request.
        use_json (Optional(bool)): Use urlencoded format or json format for the
            content type. The default value is False.
        can_retry (bool): Enable or disable request retry behavior.

    Returns:
        Mapping[str, str]: The JSON-decoded response data.

    Raises:
        google.auth.exceptions.RefreshError: If the token endpoint returned
            an error.
    """

    (
        response_status_ok,
        response_data,
        retryable_error,
    ) = await _token_endpoint_request_no_throw(
        request,
        token_uri,
        body,
        access_token=access_token,
        use_json=use_json,
        can_retry=can_retry,
    )
    if not response_status_ok:
        client._handle_error_response(response_data, retryable_error)
    return response_data


async def jwt_grant(request, token_uri, assertion, can_retry=True):
    """Implements the JWT Profile for OAuth 2.0 Authorization Grants.

    For more details, see `rfc7523 section 4`_.

    Args:
        request (google.auth.transport.Request): A callable used to make
            HTTP requests.
        token_uri (str): The OAuth 2.0 authorizations server's token endpoint
            URI.
        assertion (str): The OAuth 2.0 assertion.
        can_retry (bool): Enable or disable request retry behavior.

    Returns:
        Tuple[str, Optional[datetime], Mapping[str, str]]: The access token,
            expiration, and additional data returned by the token endpoint.

    Raises:
        google.auth.exceptions.RefreshError: If the token endpoint returned
            an error.

    .. _rfc7523 section 4: https://tools.ietf.org/html/rfc7523#section-4
    """
    body = {"assertion": assertion, "grant_type": client._JWT_GRANT_TYPE}

    response_data = await _token_endpoint_request(
        request, token_uri, body, can_retry=can_retry
    )

    try:
        access_token = response_data["access_token"]
    except KeyError as caught_exc:
        new_exc = exceptions.RefreshError(
            "No access token in response.", response_data, retryable=False
        )
        raise new_exc from caught_exc

    expiry = client._parse_expiry(response_data)

    return access_token, expiry, response_data


async def id_token_jwt_grant(request, token_uri, assertion, can_retry=True):
    """Implements the JWT Profile for OAuth 2.0 Authorization Grants, but
    requests an OpenID Connect ID Token instead of an access token.

    This is a variant on the standard JWT Profile that is currently unique
    to Google. This was added for the benefit of authenticating to services
    that require ID Tokens instead of access tokens or JWT bearer tokens.

    Args:
        request (google.auth.transport.Request): A callable used to make
            HTTP requests.
        token_uri (str): The OAuth 2.0 authorization server's token endpoint
            URI.
        assertion (str): JWT token signed by a service account. The token's
            payload must include a ``target_audience`` claim.
        can_retry (bool): Enable or disable request retry behavior.

    Returns:
        Tuple[str, Optional[datetime], Mapping[str, str]]:
            The (encoded) Open ID Connect ID Token, expiration, and additional
            data returned by the endpoint.

    Raises:
        google.auth.exceptions.RefreshError: If the token endpoint returned
            an error.
    """
    body = {"assertion": assertion, "grant_type": client._JWT_GRANT_TYPE}

    response_data = await _token_endpoint_request(
        request, token_uri, body, can_retry=can_retry
    )

    try:
        id_token = response_data["id_token"]
    except KeyError as caught_exc:
        new_exc = exceptions.RefreshError(
            "No ID token in response.", response_data, retryable=False
        )
        raise new_exc from caught_exc

    payload = jwt.decode(id_token, verify=False)
    expiry = _helpers.utcfromtimestamp(payload["exp"])

    return id_token, expiry, response_data


async def refresh_grant(
    request,
    token_uri,
    refresh_token,
    client_id,
    client_secret,
    scopes=None,
    rapt_token=None,
    can_retry=True,
):
    """Implements the OAuth 2.0 refresh token grant.

    For more details, see `rfc678 section 6`_.

    Args:
        request (google.auth.transport.Request): A callable used to make
            HTTP requests.
        token_uri (str): The OAuth 2.0 authorizations server's token endpoint
            URI.
        refresh_token (str): The refresh token to use to get a new access
            token.
        client_id (str): The OAuth 2.0 application's client ID.
        client_secret (str): The Oauth 2.0 appliaction's client secret.
        scopes (Optional(Sequence[str])): Scopes to request. If present, all
            scopes must be authorized for the refresh token. Useful if refresh
            token has a wild card scope (e.g.
            'https://www.googleapis.com/auth/any-api').
        rapt_token (Optional(str)): The reauth Proof Token.
        can_retry (bool): Enable or disable request retry behavior.

    Returns:
        Tuple[str, Optional[str], Optional[datetime], Mapping[str, str]]: The
            access token, new or current refresh token, expiration, and additional data
            returned by the token endpoint.

    Raises:
        google.auth.exceptions.RefreshError: If the token endpoint returned
            an error.

    .. _rfc6748 section 6: https://tools.ietf.org/html/rfc6749#section-6
    """
    body = {
        "grant_type": client._REFRESH_GRANT_TYPE,
        "client_id": client_id,
        "client_secret": client_secret,
        "refresh_token": refresh_token,
    }
    if scopes:
        body["scope"] = " ".join(scopes)
    if rapt_token:
        body["rapt"] = rapt_token

    response_data = await _token_endpoint_request(
        request, token_uri, body, can_retry=can_retry
    )
    return client._handle_refresh_grant_response(response_data, refresh_token)


async def _lookup_regional_access_boundary(request, url, headers=None, fail_fast=False):
    """Implements the global lookup of a credential Regional Access Boundary.
    For the lookup, we send a request to the global lookup endpoint and then
    parse the response. Service account credentials, workload identity
    pools and workforce pools implementation may have Regional Access Boundaries configured.
    Args:
        request (google.auth.aio.transport.Request): A callable used to make
            HTTP requests. The returned response must support `await response.read()`
            (standard async transport) or `await response.content()` (legacy/custom transport).
        url (str): The Regional Access Boundary lookup url.
        headers (Optional[Mapping[str, str]]): The headers for the request.
        fail_fast (bool): Whether the lookup should fail fast (uses a short timeout and no retries).
    Returns:
        Optional[Mapping[str,list|str]]: A dictionary containing
            "locations" as a list of allowed locations as strings and
            "encodedLocations" as a hex string.
            e.g:
            {
                "locations": [
                    "us-central1", "us-east1", "europe-west1", "asia-east1"
                ],
                "encodedLocations": "0xA30"
            }
    """
    response_data = await _lookup_regional_access_boundary_request(
        request, url, headers=headers, fail_fast=fail_fast
    )
    if response_data is None:
        # Error was already logged by _lookup_regional_access_boundary_request
        return None

    if not isinstance(response_data, dict) or "encodedLocations" not in response_data:
        client._LOGGER.error(
            "Regional Access Boundary response malformed: missing 'encodedLocations' key in %s",
            response_data,
        )
        return None
    return response_data


async def _lookup_regional_access_boundary_request(
    request, url, can_retry=True, headers=None, fail_fast=False
):
    """Makes a request to the Regional Access Boundary lookup endpoint.

    Args:
        request (google.auth.aio.transport.Request): A callable used to make
            HTTP requests. The returned response must support `await response.read()`
            (standard async transport) or `await response.content()` (legacy/custom transport).
        url (str): The Regional Access Boundary lookup url.
        can_retry (bool): Enable or disable request retry behavior. Defaults to true.
        headers (Optional[Mapping[str, str]]): The headers for the request.
        fail_fast (bool): Whether the lookup should fail fast (uses a short timeout and no retries).

    Returns:
        Optional[Mapping[str, str]]: The JSON-decoded response data on success, or None on failure.
    """
    (
        response_status_ok,
        response_data,
        retryable_error,
    ) = await _lookup_regional_access_boundary_request_no_throw(
        request, url, can_retry=can_retry, headers=headers, fail_fast=fail_fast
    )
    if not response_status_ok:
        client._LOGGER.debug(
            "Regional Access Boundary HTTP request failed after retries: response_data=%s, retryable_error=%s",
            response_data,
            retryable_error,
        )
        return None
    return response_data


async def _lookup_regional_access_boundary_request_no_throw(
    request, url, can_retry=True, headers=None, fail_fast=False
):
    """Makes a request to the Regional Access Boundary lookup endpoint. This
        function doesn't throw on response errors.

    Args:
        request (google.auth.aio.transport.Request): A callable used to make
            HTTP requests. The returned response must support `await response.read()`
            (standard async transport) or `await response.content()` (legacy/custom transport).
        url (str): The Regional Access Boundary lookup url.
        can_retry (bool): Enable or disable request retry behavior. Defaults to true.
        headers (Optional[Mapping[str, str]]): The headers for the request.
        fail_fast (bool): Whether the lookup should fail fast (uses a short timeout and no retries).

    Returns:
        Tuple(bool, Mapping[str, str], Optional[bool]): A boolean indicating
          if the request is successful, a mapping for the JSON-decoded response
          data and in the case of an error a boolean indicating if the error
          is retryable.
    """

    response_data = {}
    retryable_error = False

    timeout = (
        client._BLOCKING_REGIONAL_ACCESS_BOUNDARY_LOOKUP_TIMEOUT if fail_fast else None
    )
    total_attempts = 1 if fail_fast else 6
    retries = _exponential_backoff.AsyncExponentialBackoff(
        total_attempts=total_attempts
    )

    async for _ in retries:
        try:
            if timeout:
                response = await asyncio.wait_for(
                    request(method="GET", url=url, headers=headers, timeout=timeout),
                    timeout=timeout,
                )
            else:
                response = await request(method="GET", url=url, headers=headers)

            # Supports both modern google.auth.aio (exposing read()) and legacy transports (exposing content())
            if hasattr(response, "read"):
                response_bytes = await response.read()
            else:
                response_bytes = await response.content()
        except (asyncio.TimeoutError, exceptions.TransportError):
            retryable_error = True
            if not can_retry:
                return False, {}, retryable_error
            continue
        except Exception:
            # Catch raw transport/socket exceptions raised during body streaming.
            return False, {}, False

        try:
            response_body = (
                response_bytes.decode("utf-8")
                if hasattr(response_bytes, "decode")
                else response_bytes
            )
            response_data = json.loads(response_body)
        except (UnicodeDecodeError, ValueError):
            # Keep types safe and allow status-code checks below to determine retryability
            response_data = {}

        status_code = (
            response.status_code
            if hasattr(response, "status_code")
            else response.status
        )

        if status_code == http_client.OK:
            return True, response_data, None

        retryable_error = client._can_retry(
            status_code=status_code, response_data=response_data
        )
        if status_code == http_client.BAD_GATEWAY:
            retryable_error = True

        if not can_retry or not retryable_error:
            return False, response_data, retryable_error

    return False, response_data, retryable_error
