# 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.

# [START functions_bearer_token]

import requests

# TODO<developer>: set these values

REGION = "us-central1"

PROJECT_ID = "my-project"

RECEIVING_FUNCTION = "my-function"

# Constants for setting up metadata server request

# See https://cloud.google.com/compute/docs/instances/verifying-instance-identity#request_signature

function_url = f"https://{REGION}-{PROJECT_ID}.cloudfunctions.net/{RECEIVING_FUNCTION}"

metadata_server_url = "http://metadata/computeMetadata/v1/instance/service-accounts/default/identity?audience="

token_full_url = metadata_server_url + function_url

token_headers = {"Metadata-Flavor": "Google"}

def calling_function(request):

# Fetch the token

token_response = requests.get(token_full_url, headers=token_headers)

jwt = token_response.text

# Provide the token in the request to the receiving function

function_headers = {"Authorization": f"bearer {jwt}"}

function_response = requests.get(function_url, headers=function_headers)

return function_response.text

# [END functions_bearer_token]