Dialogflow express.js backend for two intents. One fetches next event from barcamp app, the other reacts to opnions.

index.js

// See https://github.com/dialogflow/dialogflow-fulfillment-nodejs
// for Dialogflow fulfillment library docs, samples, and to report issues
'use strict';

const {WebhookClient} = require('dialogflow-fulfillment');
const {Card, Text, Suggestion} = require('dialogflow-fulfillment');
const cache = require('memory-cache');
const https = require('https');
const express = require('express');

const PORT = process.env.PORT || 5000;
const HOUR = 60 * 60 * 1000;

process.env.DEBUG = 'dialogflow:debug'; // enables lib debugging statements

function toTime(dateStr) {
    return new Date(dateStr).getTime();
}

function getNextEvents(events) {
    const now = new Date().getTime();
    let counter = 0;

    return events.filter((event) => {
        const eventStart = toTime(event.time.start);

        if (counter < 8 && eventStart > now && eventStart < now + 24 * HOUR) {
            counter += 1;

            return true;
        }

        return false;
    });
}

function getEvents() {
    let events = cache.get('events');

    if (events !== null) {
        return JSON.parse(events);
    }

    return new Promise((resolve, reject) => {
        https.get('https://lineupr.com/api/organizers/mobilecamp/events/2019/data', function (resp) {
            let data = '';

            // A chunk of data has been recieved.
            resp.on('data', (chunk) => {
                data += chunk;
            });

            // The whole response has been received. Print out the result.
            resp.on('end', () => {
                const parsedData = JSON.parse(data);
                events = parsedData.items;

                cache.put('events', JSON.stringify(events), 5000);

                resolve(events);
            });
        }).on("error", (err) => {
            reject(err);
        });
    });
}

const processWebhook = function( request, response ) {
    const agent = new WebhookClient({ request, response }); // TODO mock on local

    console.log('Dialogflow Request headers: ' + JSON.stringify(request.headers));
    console.log('Dialogflow Request body: ' + JSON.stringify(request.body));

    function fallback(agent) {
        agent.add(`Orsch wer bleede!`);
        agent.add(`Das habsch nu ni verstandn. Was meesnte?`);
    }

    function nextEvents(agent) {
        return getEvents().then((events) => {
            const soonEvents = getNextEvents(events);

            if (!soonEvents || soonEvents.length === 0) {
                agent.add("Leider keine Events in nächster Zeit gefunden.");

                return;
            }

            const responseMsg = soonEvents.map((ev) => {
                return `${ev.name} Start: ${new Date(ev.time.start).toLocaleTimeString('de-DE')}`;
            }).join(' # ');

            agent.add(new Text({
                text: responseMsg
            }));
        }).catch((err) => {
            agent.add("Fehler beim abrufen der Events :( " + err.message);
        });
    }

    function opinionResponse(agent) {
        const opinion = agent.parameters['opinion'];
        let textMsg = '';

        switch(opinion) {
            case 'schlecht':
                textMsg = 'Na dann geh doch zu Netto!';

                break;
            case 'super':
                textMsg = 'Das sehe ich auch so!';

                break;
            case 'gut':
                textMsg = 'Das Mobile Camp ist immer so gut wie seine Teilnehmer!';

                break;
            default:
                textMsg = `"${opinion}" verstehe ich nicht. Kannst du das nochmal anders formulieren?`;
        }

        agent.add(new Text({
            text: textMsg
        }));
    }

    // Run the proper function handler based on the matched Dialogflow intent name
    let intentMap = new Map();

    intentMap.set('Nächste Events', nextEvents);
    intentMap.set('Gruesse-NAME-Frage-Meinung-antwort', opinionResponse);
    intentMap.set('Default Fallback Intent', fallback);

    agent.handleRequest(intentMap);
};


const app = express();
app.use( express.json() );

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

app.post('/', (req, res) => processWebhook(req, res));

app.listen(PORT, () => console.log(`Listening on ${ PORT }`));