// Copyright 2018 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';

// [START gae_flex_analytics_track_event]

const express = require('express');

const fetch = require('node-fetch');

const app = express();

app.enable('trust proxy');

// The following environment variable is set by app.yaml when running on App

// Engine, but will need to be set manually when running locally. See README.md.

const {GA_TRACKING_ID} = process.env;

const trackEvent = (category, action, label, value) => {

const data = {

// API Version.

v: '1',

// Tracking ID / Property ID.

tid: GA_TRACKING_ID,

// Anonymous Client Identifier. Ideally, this should be a UUID that

// is associated with particular user, device, or browser instance.

cid: '555',

// Event hit type.

t: 'event',

// Event category.

ec: category,

// Event action.

ea: action,

// Event label.

el: label,

// Event value.

ev: value,

};

return fetch('http://www.google-analytics.com/debug/collect', {

params: data,

});

};

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

// Event value must be numeric.

try {

await trackEvent(

'Example category',

'Example action',

'Example label',

'100'

);

res.status(200).send('Event tracked.').end();

} catch (error) {

// This sample treats an event tracking error as a fatal error. Depending

// on your application's needs, failing to track an event may not be

// considered an error.

next(error);

}

});

const PORT = parseInt(process.env.PORT) || 8080;

app.listen(PORT, () => {

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

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

});

// [END gae_flex_analytics_track_event]

module.exports = app;