index.js

'use strict';

const PAGE_ACCESS_TOKEN = process.env.PAGE_ACCESS_TOKEN;

// Imports dependencies and set up http server
const
    fetch = require('node-fetch'),
    request = require('request'),
    express = require('express'),
    body_parser = require('body-parser'),
    app = express().use(body_parser.json()); // creates express http server

// Sets server port and logs message on success
app.listen(process.env.PORT || 1337, () => console.log('webhook is listening'));

// Accepts POST requests at /webhook endpoint
app.post('/webhook', (req, res) => {

  // Parse the request body from the POST
  let body = req.body;

  // Check the webhook event is from a Page subscription
  if (body.object === 'page') {

    body.entry.forEach(function(entry) {

      // Gets the body of the webhook event
      let webhook_event = entry.messaging[0];
      console.log(webhook_event);


      // Get the sender PSID
      let sender_psid = webhook_event.sender.id;
      console.log('Sender PSID: ' + sender_psid);

      // Check if the event is a message or postback and
      // pass the event to the appropriate handler function
      if (webhook_event.message) {
        handleMessage(sender_psid, webhook_event.message);
      } else if (webhook_event.postback) {
        handlePostback(sender_psid, webhook_event.postback);
      }

    });

    // Return a '200 OK' response to all events
    res.status(200).send('EVENT_RECEIVED');

  } else {
    // Return a '404 Not Found' if event is not from a page subscription
    res.sendStatus(404);
  }

});

// Accepts GET requests at the /webhook endpoint
app.get('/webhook', (req, res) => {

  /** UPDATE YOUR VERIFY TOKEN **/
  const VERIFY_TOKEN = process.env.VERIFICATION_TOKEN;

  // Parse params from the webhook verification request
  let mode = req.query['hub.mode'];
  let token = req.query['hub.verify_token'];
  let challenge = req.query['hub.challenge'];

  // Check if a token and mode were sent
  if (mode && token) {

    // Check the mode and token sent are correct
    if (mode === 'subscribe' && token === VERIFY_TOKEN) {

      // Respond with 200 OK and challenge token from the request
      console.log('WEBHOOK_VERIFIED');
      res.status(200).send(challenge);

    } else {
      // Responds with '403 Forbidden' if verify tokens do not match
      res.sendStatus(403);
    }
  }
});

// Handles messages events
async function handleMessage(sender_psid, received_message) {
  let response = await getDefaultResponse();

  // Checks if the message contains text
  if (received_message.text) {
    // Create the payload for a basic text message, which
    // will be added to the body of our request to the Send API

    const list = await callChatbotApi(response, 0);

    // Send the response message
    callSendAPI(sender_psid, list);

  } else if (received_message.attachments) {
    // Get the URL of the message attachment
    // let attachment_url = received_message.attachments[0].payload.url;
  }

}

// Handles messaging_postbacks events
async function handlePostback(sender_psid, received_postback) {
  let response = await getDefaultResponse();

  // Get the payload for the postback
  let payload = received_postback.payload;

  const list = await callChatbotApi(response, payload);

  // Send the message to acknowledge the postback
  callSendAPI(sender_psid, list);
}

// Sends response messages via the Send API
function callSendAPI(sender_psid, response) {
  // Construct the message body
  let request_body = {
    "recipient": {
      "id": sender_psid
    },
    "message": response
  };


  // Send the HTTP request to the Messenger Platform
  request({
    "uri": "https://graph.facebook.com/v2.6/me/messages",
    "qs": { "access_token": PAGE_ACCESS_TOKEN },
    "method": "POST",
    "json": request_body
  }, (err, res, body) => {
    if (!err) {
      console.log(request_body.message);
      console.log(request_body.message.attachment.payload);
      console.log(request_body.message.attachment.payload.elements);
      console.log('message sent!')
    } else {
      console.error("Unable to send message:" + err);
    }
  });
}

function getDefaultResponse() {
  return {
    "attachment": {
      "type": "template",
      "payload": {
        "template_type": "list",
        "top_element_style": "large",
        "sharable": true,
        "buttons": [],
        "elements": [
          {
            "title": "Olá, bem-vindo à experiência Real2U.",
            "subtitle": "Escolha um dos aplicativos abaixo.",
            "image_url": "https://www.real2u.com.br/img/index-logo-real2u@2x.png",
            "default_action": {
              "type": "web_url",
              "url": "https://www.real2u.com.br/",
              "messenger_extensions": false,
              "webview_height_ratio": "tall"
            }
          },
        ]
      }
    }
  }
}

function callChatbotApi(response, start) {
  let requestURL = 'https://script.google.com/a/real2u.com.br/macros/s/AKfycbwe0PFwralZXBn5wNdSyIbmArWnzbKcIC6gVv-u/exec';

  return new Promise((resolve, reject) => {
    fetch(requestURL)
        .then(res => res.json())
        .then(json => {
          let added = 0;
          let counter = start;
          while (added < 3) {
            // noinspection JSUnfilteredForInLoop
            if (json[counter] && json[counter].title && json[counter].subtitle && json[counter].image_url && json[counter].url){
              // noinspection JSUnfilteredForInLoop
              response.attachment.payload.elements.push({
                "title": json[counter].title,
                "subtitle": json[counter].subtitle,
                "image_url": json[counter].image_url,
                "default_action": {
                  "type": "web_url",
                  "url": json[counter].url,
                  "messenger_extensions": false,
                  "webview_height_ratio": "tall"
                }
              });
              counter++;
              added++;
            } else {
              counter = 0;
            }
          }
          response.attachment.payload.buttons.push({
            "type": "postback",
            "title": "VIEW MORE",
            "payload": counter
          });
          resolve(response)
        })
  })
}