Dialogflow - Save to Firebase Database

dialogflow_save_to_firebase_database.js

const functions = require('firebase-functions');
const admin = require('firebase-admin');
const {WebhookClient} = require('dialogflow-fulfillment');

admin.initializeApp({
    credential: admin.credential.applicationDefault(),
    databaseURL: 'ws://DATABASE_UNIQUE_ID.firebaseio.com/' 
});

exports.dialogflowFirebaseFulfillment = functions.https.onRequest((request, response) => {
  const agent = new WebhookClient({request, response});   
  
  function saveHandler(agent){
      const value = agent.parameters.PARAMETER_NAME;
      return admin.database().ref(DATABASE_REFERENCE).set({
      	KEY: value
      });
  }
  
  function fetchHandler(agent){
     return admin.database().ref(DATABASE_REFERENCE).once("value").then((snapshot) => {
        const value = snapshot.child("KEY").val();
        if(value !== null){
          agent.add(`The value from DB is ${value}`);
        }
      });
  }
  
  let intentMap = new Map();
  intentMap.set('SaveToDB', saveHandler);
  intentMap.set('FetchFromDB', fetchHandler);
  agent.handleRequest(intentMap);
});