Example of a Firebase Cloud Function integrating with DialogFlow

index.js

const functions = require('firebase-functions');
const cors = require('cors')({ origin: true });
const uuid = require('uuid');

// https://cloud.google.com/dialogflow/es/docs/reference/libraries/nodejs
// https://googleapis.dev/nodejs/dialogflow/latest/index.html
const dialogflow = require('@google-cloud/dialogflow');

// The ID of the GCP project where your Dialogflow agent is deployed
const PROJECT_ID = 'your-project-id';

exports.talkToDialogFlowAgent = functions.https.onRequest(async (req, res) => {
  return cors(req, res, async () => {
    functions.logger.info('Query data:', JSON.stringify(req.query));
    const sessionId = uuid.v4();

    // https://github.com/googleapis/gax-nodejs/blob/master/client-libraries.md#creating-the-client-instance
    // https://cloud.google.com/docs/authentication/production#create_service_account
    const options = {
      keyFilename: './service-account.json', 
    };
    const sessionClient = new dialogflow.SessionsClient(options);
    const sessionPath = sessionClient.projectAgentSessionPath(PROJECT_ID, sessionId);

    const queryText = req.query.text;
    const request = {
      session: sessionPath,
      queryInput: {
        text: {
          // The query to send to the Dialogflow agent
          text: queryText,
          languageCode: 'en-US',
        },
      },
    };

    // Send request and log result
    console.log('Sending query:', queryText);
    const responses = await sessionClient.detectIntent(request);
    console.log('Detected intent');
    const result = responses[0].queryResult;
    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.');
    }

    // Respond with the fullfillment text
    const fulfillmentText = result.fulfillmentText;
    console.log('Returning fulfillmentText:', fulfillmentText);
    res.status(200).json({
      result: {
        fulfillment: {
          speech: fulfillmentText,
        },
      },
    });
  });
});