Conditional Templating in Dialogflow with Custom Payloads and Google Cloud Functions

index.js

'use strict';

const {
  dialogflow
} = require('actions-on-google');
const pug = require('pug');
 
/*
  * Uses Pug.js https://pugjs.org/language/plain-text.html
  * Requires a Dialogflow custom payload like:
  * {
    "custom": {
      "locals": {
        "username": "$username"
      },
      "pug": [
        "if username\n",
        " | Hello $username\n",
        "else\n",
        " | Hello stranger"
      ]
    }
  }
*/
const templateHelper = function(payload){
  var str = payload.custom.pug;
  if(Array.isArray(payload.custom.pug)) {
    str = payload.custom.pug.join("");
  };
  var fn = pug.compile(str);
  var text = fn(payload.custom.locals);

  return text;
}


const templateHandler = (conv) => {
  console.log('Dialogflow Request headers: ' + JSON.stringify(conv.headers));
  console.log('Dialogflow Request body: ' + JSON.stringify(conv.body));
  
  var payload = conv.body.queryResult.fulfillmentMessages[0].payload;
  var text = templateHelper(payload);

  conv.ask(text);
};


const app = dialogflow();

app.intent('[templating] example', templateHandler);

exports.index = app;


/* package.json
{
    "name": "Dialogflow Conditionals",
    "description": "Advanced Google Assistant with Dialogflow",
    "version": "1.0.0",
    "license": "Apache-2.0",
    "author": "Lee Boonstra",
    "engines": {
        "node": "^6.11.5"
    },
    "dependencies": {
        "actions-on-google": "2.1.1",
        "pug": "2.0.3"
    }
} */