Code that actually works as a bridge between Twilio & Dialogflow on AWS Lambda

lambda.js

// 1. This uses claudiajs & its API Gateway to deploy to lambda & handle api post

// 2. Assumes an existing dialogflow project, google cloud project, and google cloud billing

// 3. Got credentials .json file using steps 1-5 (ONLY) here: 
//      https://cloud.google.com/docs/authentication/getting-started

// 4. Put that json file in a directory called "sekrets' which I added to .gitignore

// 5. Other helpful options for Google authentication are here:
//      https://stackoverflow.com/questions/50355556/how-authenticate-with-gcloud-credentials-an-dialogflow-api

// 6. Requires npm installation of @google-cloud/dialogflow & twilio

// 7. When deployed, appended the word "endpoint" to the lambda URL I gave to Twilio as a POST webhook
//      for incoming SMS messages

// Dialogflow setup
const dialogflow = require('@google-cloud/dialogflow')
const projectId = '<google-cloud-project-id>'
const credentials_file = '/sekrets/<credentials-json-file-name>.json'
const lambda_runtime_directory = '/var/task'
const credentials_file_path = lambda_runtime_directory + credentials_file
const sessionClient = new dialogflow.SessionsClient({
    projectId,
    keyFilename: credentials_file_path,
});

// Twilio setup
const MessagingResponse = require('twilio').twiml.MessagingResponse;

// API builder setup
var ApiBuilder = require('claudia-api-builder');
var api = new ApiBuilder();
module.exports = api;

// code executed for each call to the lambda function
api.post('/endpoint', async function(req, res){
    
    // from Twilio
    const data = req.post
    const text = data.Body;
    const twilio_id = data.From;

    const sessionId = twilio_id;
    const languageCode = 'en-US';
    
    const sessionPath = `projects/${projectId}/agent/sessions/${sessionId}`

    // The text query request.
    const request = {
      session: sessionPath,
      queryInput: {
        text: {
          // The query to send to the dialogflow agent
          text: text,
          // The language used by the client (en-US)
          languageCode: languageCode,
        },
      },
    };

    // Send sent text to Dialogflow and log result
    const responses = await sessionClient.detectIntent(request);
    const result = responses[0].queryResult;
    const sendback = result.fulfillmentText
    
    console.log(`  Query: ${result.queryText}`);
    console.log(`  Response: ${result.fulfillmentText}`);
    if (result.intent) {
      console.log(`  Intent: ${result.intent.displayName}`);
    } else {
      console.log(`  No intent matched.`);
    }

    // Reply to texter via Twilio
    const twiml = new  MessagingResponse()
    const message = twiml.message(sendback)
    return twiml.toString()

    }, {
    // this optional 3rd argument changes the format of the response, for twilio 
    success: { contentType: 'application/xml' },
    error: { contentType: 'application/xml' }
});