Google Analytics tracking using Dialogflow API v2 and some REST API

index.js

const ua = require("universal-analytics");
const request = require("request-promise");
const { https } = require("firebase-functions");

function getUserID (obj) {
    if (!obj.source) {
        return "dialogflow";
    } else {
        switch (obj.source) {
            case "twilio":
                return obj.payload.data.From;
            case "facebook":
                return obj.payload.data.sender.id;
            default:
                return "unknown";
        }
    }
}

function trackEvent (uid, category, action, label = null) {  // label is optional
    const visitor = ua("UA-XXXXXXXX-X", uid, { strictCidFormat: false });  // format is not strict
    visitor.event(category, action, label, function (err) {
        if (err) console.error(err);
    })
}

function makeResponse(msg) {
    return JSON.stringify({
        "fulfillmentText": msg
    });
}

function sampleAction(sampleInput, userID, res) {
    request({
        method: "GET",
        uri: `http://sample.api/sampleEndpoint?sampleInput=${sampleInput}`,
        json: true
    })
    .then((json) => {
        if (json.result) {
            trackEvent(userID, "actionSuccess", "sampleAction", `Found.`);
            res.send(makeResponse("I found it!"));
        } else {
            trackEvent(userID, "actionFail", "sampleAction", "Not found.");
            res.send(makeResponse("I couldn't find it!"));
        }
    })
    .catch((err) => {
        console.error(err);
        trackEvent(userID, "actionFail", "sampleAction", "API error.");
        res.send(makeResponse(`I had an issue with the API!`));
    })
}

// 'dialogflowFirebaseFulfillment' is the name of the function that is exported
// cloud functions configuration executes this function and keeps it running as a webhook
exports.dialogflowFirebaseFulfillment = https.onRequest((req, res) => {
    const { action, parameters } = req.body.queryResult;
    const userID = getUserID(req.body.originalDetectIntentRequest);
    switch (action) {
        case "sampleAction":
            trackEvent(userID, "actionRequest", "sampleAction");
            sampleAction(parameters.sampleInput, userID, res);  // 'res' (response) object is passed for executing .send()
            break;
        default:
            res.send(makeResponse([]));  // empty array simply tells console to reply instead
    }
})

package.json

{
  "name": "dialogflowFirebaseFulfillment",
  "description": "This is the default fulfillment for a Dialogflow agents using Cloud Functions for Firebase",
  "version": "0.0.1",
  "private": true,
  "license": "Apache Version 2.0",
  "author": "Google Inc.",
  "engines": {
    "node": "8"
  },
  "scripts": {
    "start": "firebase serve --only functions:dialogflowFirebaseFulfillment",
    "deploy": "firebase deploy --only functions:dialogflowFirebaseFulfillment"
  },
  "dependencies": {
    "actions-on-google": "^2.2.0",
    "firebase-admin": "^5.13.1",
    "firebase-functions": "^2.0.2",
    "request": "^2.88.0",
    "request-promise": "^4.2.2",
    "universal-analytics": "^0.4.20"
  }
}