server.js

var express = require('express')
var app = express()
require('dotenv').config()
var request = require('request');
const fetch = require('node-fetch');
const GIPHY_URL = `http://api.giphy.com/v1/gifs/random?api_key=dc6zaTOxFJmzC&tag=`;
const MEME_URL = `http://belikebill.azurewebsites.net/billgen-API.php?default=1&name=`
const apiCall = "http://api.duckduckgo.com/?q="
const apicall2 = "&format=json"

app.get('/', function (req, res) {
  res.send()
})
var bodyParser = require('body-parser')

var app = express()

// parse application/x-www-form-urlencoded
app.use(bodyParser.urlencoded({ extended: false }))

// parse application/json
app.use(bodyParser.json())
const server = app.listen(8080, () => {
  console.log('Express server listening on port 8080');
});

app.get('/webhook', function(req, res) {
  if (req.query['hub.mode'] === 'subscribe' &&
      req.query['hub.verify_token'] === process.env.verify_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);          
  }  
});

app.post('/webhook', function (req, res) {
  var data = req.body;
    // console.log(req.body)
    // console.log(res)
  // 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) {
  // Putting a stub for now, we'll expand it in the following steps
  console.log("Message data: ", event.message);
}

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;
//   console.log(messageText)
  var messageAttachments = message.attachments;

  if (messageText) {

    // 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) {

  
}

function sendTextMessage(recipientId, messageText) {
    var gif = messageText.slice(0,3).toLowerCase();
    var word = messageText.slice(0,4).toLowerCase();
    var search_word = messageText.slice(0,6).toLowerCase();
    var search_this = messageText.slice(7,messageText.length);
    var search = messageText.slice(5,messageText.length);
    var query = messageText.slice(3,messageText.length)
    if(gif == 'gif'){
          fetch(GIPHY_URL + query)
          .then(res => res.json())
          .then(json => {
              img_url = ''
              img_url = json.data.image_url
            });
             if(img_url){ 
                 var messageData = {
                      recipient: {
                        id: recipientId
                      },
                      //  "sender_action":"typing_on",
                      "message":{
                          "attachment":{
                            "type":"image",
                            "payload":{
                              "url":img_url
                                
                            }
                          }
                        }
                    };          
            callSendAPI(messageData);
           }
    }else if(word == 'meme'){
        var img_URL = MEME_URL + search
          if(img_URL){ 
             var messageData = {
                  recipient: {
                    id: recipientId
                  },
                  //  "sender_action":"typing_on",
                  "message":{
                      "attachment":{
                        "type":"image",
                        "payload":{
                          "url":img_URL
                            
                        }
                      }
                    }
                  };
              callSendAPI(messageData);
            }
     }else if(search_word == 'search'){
          var api = apiCall + search_this + apicall2
            fetch(api)
            .then(res => res.json())
            .then(json => {
             Text = ''
             Text = json.AbstractText || json.RelatedTopics[0].Text
              var messageData = {
                 recipient: {
                   id: recipientId
                 },
                 message: {
                   text: Text
                 }
              };
          callSendAPI(messageData);
       })
    }else{
        var messageData = {
           recipient: {
             id: recipientId
           },
           message: {
             text: 'Yo! This is BaE. Try *GIF funny*, *MEME dhrubesh* or *SEARCH Pink Floyd*. Play around by changing the latter words.'
           }
        };
    callSendAPI(messageData);
    }
  
}

function callSendAPI(messageData) {
  request({
    uri: 'https://graph.facebook.com/v2.6/me/messages',
    qs: { access_token: process.env.page_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);
    }
  });  
}