Basic AoG fulfillment to add a donation to a Firestore collection

index.js

'use strict';

const {dialogflow} = require('actions-on-google');
const admin = require('firebase-admin');
const functions = require('firebase-functions');

const app = dialogflow({debug: true});
admin.initializeApp(functions.config().firebase);

const db = admin.firestore();
const settings = {timestampsInSnapshots: true};
db.settings(settings);

app.intent('Donation', (conv, {Category}) => {
    var donationData = {
        donation: Category,
        donationID: conv.id,
        location: "DACHFest",
        user: "netomarin"
    };
	// Add a new document in collection "donations"
    return db.collection("donations").doc(conv.id).set(data).then(() => {
        return conv.close('Thanks! I added your ' + Category + ' to our list.');
    });
});

exports.dialogflowFirebaseFulfillment = functions.https.onRequest(app);