app.js

'use strict';

const 
  bodyParser = require('body-parser'),
  config = require('config'),
  crypto = require('crypto'),
  express = require('express'),
  https = require('https'),  
  request = require('request');

var app = express();
app.set('port', process.env.PORT || 5000);
app.set('view engine', 'ejs');
app.use(bodyParser.json({ verify: verifyRequestSignature }));
app.use(express.static('public'));


const APP_SECRET = (process.env.MESSENGER_APP_SECRET) ? 
  process.env.MESSENGER_APP_SECRET :
  config.get('appSecret');

// Arbitrary value used to validate a webhook
const VALIDATION_TOKEN = (process.env.MESSENGER_VALIDATION_TOKEN) ?
  (process.env.MESSENGER_VALIDATION_TOKEN) :
  config.get('validationToken');
  
// Generate a page access token for your page from the App Dashboard
const PAGE_ACCESS_TOKEN = (process.env.MESSENGER_PAGE_ACCESS_TOKEN) ?
  (process.env.MESSENGER_PAGE_ACCESS_TOKEN) :
  config.get('pageAccessToken');  

app.get("/",function(req,res){
  
      console.log("home page");
      res.send("Messenger Bot test!!");  
});

app.get('/webhook', function(req, res) {
  if (req.query['hub.mode'] === 'subscribe' &&
      req.query['hub.verify_token'] === VALIDATION_TOKEN) {
    console.log("Validating webhook");
    res.status(200).send(req.query['hub.challenge']);
  } else {
    console.error("Failed validation. Make sure the validation tokens match.");
    res.sendStatus(403);          
  }  
});


function verifyRequestSignature(req, res, buf) {
  var signature = req.headers["x-hub-signature"];

  if (!signature) {
    // For testing, let's log an error. In production, you should throw an 
    // error.
    console.error("Couldn't validate the signature.");
  } else {
    var elements = signature.split('=');
    var method = elements[0];
    var signatureHash = elements[1];

    var expectedHash = crypto.createHmac('sha1', APP_SECRET)
                        .update(buf)
                        .digest('hex');

    if (signatureHash != expectedHash) {
      throw new Error("Couldn't validate the request signature.");
    }
  }
}


app.post('/webhook', function (req, res) {
  var data = req.body;

  // Make sure this is a page subscription
  if (data.object === 'page') {

    // Iterate over each entry - there may be multiple if batched
    data.entry.forEach(function(entry) {
      var pageID = entry.id;
      var timeOfEvent = entry.time;

      // Iterate over each messaging event
      entry.messaging.forEach(function(event) {
        if (event.message) {
          receivedMessage(event);
        } else {
          console.log("Webhook received unknown event: ", event);
        }
      });
    });

    // Assume all went well.
    //
    // You must send back a 200, within 20 seconds, to let us know
    // you've successfully received the callback. Otherwise, the request
    // will time out and we will keep trying to resend.
    res.sendStatus(200);
  }
});
  
function receivedMessage(event) {
  var senderID = event.sender.id;
  var recipientID = event.recipient.id;
  var timeOfMessage = event.timestamp;
  var message = event.message;

  console.log("Received message for user %d and page %d at %d with message:", 
    senderID, recipientID, timeOfMessage);
  console.log(JSON.stringify(message));

  var messageId = message.mid;

  var messageText = message.text;
  var messageAttachments = message.attachments;

  if (messageText) {
    
    switch (messageText) {
      case 'hi':
        messageText = "Hi " + "Gopinath!!";
        break;
      case 'how are you?':
        messageText = "I'm fine thank you! How about you? And how things going?";
        break;
      case 'type'  :
        messageText = "List here is type of insurance... 1) Auto Insurance 2) Life Insurance type the number to know more";
        break;
      case '1':
        messageText = "We will get your information on Auto Insurance.";
        break;
      case '2':
        messageText = "We will get your information on Life Insurance.";
        break;
      default:
        // code
    }

    // If we receive a text message, check to see if it matches a keyword
    // and send back the example. Otherwise, just echo the text we received.
    switch (messageText) {
      case 'generic':
        sendGenericMessage(senderID);
        break;
      default:
        sendTextMessage(senderID, messageText);
    }
  } else if (messageAttachments) {
    sendTextMessage(senderID, "Message with attachment received");
  }
}

function sendGenericMessage(recipientId, messageText) {
  // To be expanded in later sections
}

function sendTextMessage(recipientId, messageText) {
  var messageData = {
    recipient: {
      id: recipientId
    },
    message: {
      text: messageText
    }
  };

  callSendAPI(messageData);
}



function callSendAPI(messageData) {
  request({
    uri: 'https://graph.facebook.com/v2.6/me/messages',
    qs: { access_token: PAGE_ACCESS_TOKEN },
    method: 'POST',
    json: messageData

  }, function (error, response, body) {
    if (!error && response.statusCode == 200) {
      var recipientId = body.recipient_id;
      var messageId = body.message_id;

      console.log("Successfully sent generic message with id %s to recipient %s", 
        messageId, recipientId);
    } else {
      console.error("Unable to send message.");
      console.error(response);
      console.error(error);
    }
  });  
}





app.listen(app.get('port'), function() {
  console.log('Node app is running on port', app.get('port'));
});

module.exports = app;