// Copyright 2016 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.

'use strict';

const express = require('express');

const bodyParser = require('body-parser');

const {OAuth2Client} = require('google-auth-library');

const path = require('path');

const process = require('process'); // Required for mocking environment variables

// By default, the client will authenticate using the service account file

// specified by the GOOGLE_APPLICATION_CREDENTIALS environment variable and use

// the project specified by the GOOGLE_CLOUD_PROJECT environment variable. See

// https://github.com/GoogleCloudPlatform/google-cloud-node/blob/master/docs/authentication.md

// These environment variables are set automatically on Google App Engine

const {PubSub} = require('@google-cloud/pubsub');

// Instantiate a pubsub client

const authClient = new OAuth2Client();

const pubsub = new PubSub();

const app = express();

app.set('view engine', 'pug');

app.set('views', path.join(__dirname, 'views'));

const formBodyParser = bodyParser.urlencoded({extended: false});

const jsonBodyParser = bodyParser.json();

// List of all messages received by this instance

const messages = [];

const claims = [];

const tokens = [];

// The following environment variables are set by app.yaml when running on GAE,

// but will need to be manually set when running locally.

const {PUBSUB_VERIFICATION_TOKEN} = process.env;

const TOPIC = process.env.PUBSUB_TOPIC;

const topic = pubsub.topic(TOPIC);

// [START gae_flex_pubsub_index]

app.get('/', (req, res) => {

res.render('index', {messages, tokens, claims});

});

app.post('/', formBodyParser, async (req, res, next) => {

if (!req.body.payload) {

res.status(400).send('Missing payload');

return;

}

const data = Buffer.from(req.body.payload);

try {

const messageId = await topic.publish(data);

res.status(200).send(`Message ${messageId} sent.`);

} catch (error) {

next(error);

}

});

// [END gae_flex_pubsub_index]

// [START gae_flex_pubsub_push]

app.post('/pubsub/push', jsonBodyParser, (req, res) => {

if (req.query.token !== PUBSUB_VERIFICATION_TOKEN) {

res.status(400).send();

return;

}

// The message is a unicode string encoded in base64.

const message = Buffer.from(req.body.message.data, 'base64').toString(

'utf-8'

);

messages.push(message);

res.status(200).send();

});

// [END gae_flex_pubsub_push]

// [START gae_flex_pubsub_auth_push]

app.post('/pubsub/authenticated-push', jsonBodyParser, async (req, res) => {

// Verify that the request originates from the application.

if (req.query.token !== PUBSUB_VERIFICATION_TOKEN) {

res.status(400).send('Invalid request');

return;

}

// Verify that the push request originates from Cloud Pub/Sub.

try {

// Get the Cloud Pub/Sub-generated JWT in the "Authorization" header.

const bearer = req.header('Authorization');

const [, token] = bearer.match(/Bearer (.*)/);

tokens.push(token);

// Verify and decode the JWT.

// Note: For high volume push requests, it would save some network

// overhead if you verify the tokens offline by decoding them using

// Google's Public Cert; caching already seen tokens works best when

// a large volume of messages have prompted a single push server to

// handle them, in which case they would all share the same token for

// a limited time window.

const ticket = await authClient.verifyIdToken({

idToken: token,

audience: 'example.com',

});

const claim = ticket.getPayload();

claims.push(claim);

} catch (e) {

res.status(400).send('Invalid token');

return;

}

// The message is a unicode string encoded in base64.

const message = Buffer.from(req.body.message.data, 'base64').toString(

'utf-8'

);

messages.push(message);

res.status(200).send();

});

// [END gae_flex_pubsub_auth_push]

// Start the server

const PORT = process.env.PORT || 8080;

app.listen(PORT, () => {

console.log(`App listening on port ${PORT}`);

console.log('Press Ctrl+C to quit.');

});

module.exports = app;