Express app that subscribes to SNS and displays notifications

sns-express-example.js

var express = require('express')
var app = express()
var request = require('request')
var bodyParser = require('body-parser')

// Middleware to convert SNS request message body from plain text to JSON
var convertToJson = function (req, res, next) {
  if (req.headers['x-amz-sns-message-type']) {
    req.headers['content-type'] = 'application/json;charset=UTF-8';
  }
  next()
}

app.use(convertToJson)

// Middleware to parse the converted SNS request message body in JSON format
app.use(bodyParser.urlencoded({ extended: true }))
app.use(bodyParser.json())

// Use an array to keep track of notifications. Ideally use a database to persist notifications instead.
var notifications = []

app.get('/', function (req, res) {
  if(notifications.length > 0)
  {
    res.send(JSON.stringify(notifications))
  }
  else {
    res.send("hello world")
  }
})

app.post('/sns', function (req, res) {
  // Handle subscription request
  if(req.headers['x-amz-sns-message-type'] == "SubscriptionConfirmation") {
    var subscribeUrl = req.body.SubscribeURL
    request(subscribeUrl, function (err, response, body) {
      if(err) console.log(err)
    })
  }

  // Handle notification request
  if(req.headers['x-amz-sns-message-type'] == "Notification") {
    notifications.push({"subject": req.body.Subject, "msg": req.body.Message})
  }
})

var port = 80

app.listen(port, function () {
  console.log("SNS example app running on port " + port)
})