app.js

// This script is the main app script that powers Princeton Courses. It runs immediately when the app launches

// Greet the world!
console.log('Launching Princeton Courses.')

// Load Node.js components
const path = require('path')

// Load external dependencies
let mongoose = require('mongoose')
let express = require('express')
let session = require('cookie-session')

// Make Mongoose use native promises
mongoose.Promise = global.Promise

// Initialise Express, which makes the server work
let app = express()

// Initialise bodyParser, which parses the data out of web requests
app.use(express.urlencoded({ extended: true }))
app.use(express.json())

// Load internal modules
let config = require('./controllers/config')
let auth = require('./controllers/authentication.js')
let api = require('./controllers/api.js')

// Connect to the database
require('./controllers/database.js')

// Configure the app to save a cookie
app.use(session({
  secret: config.sessionSecret,
  maxAge: 24 * 60 * 60 * 1000 * 365 // 365 days
}))

// Attempt to load the currently logged-in user
app.use('*', auth.loadUser)

// Pre-compose the variables that will be sent to the page to render
app.use('*', function (req, res, next) {
  res.locals.renderLocals = {}
  if (res.locals.user) {
    res.locals.renderLocals.netid = res.locals.user._id
  }
  if (process.env.NODE_ENV) {
    res.locals.renderLocals.environment = process.env.NODE_ENV
  }
  if (process.env.HEROKU_RELEASE_VERSION) {
    res.locals.renderLocals.release = process.env.HEROKU_RELEASE_VERSION
  } else {
    res.locals.renderLocals.release = 'v0'
  }
  next()
})

// Attach routers (these are modules that contain a distinct set of routes)
app.use('/auth', auth.router)
app.use('/api', api.router)

// Route a request for the homepage
app.get('/', function (req, res) {
  // Check whether the user sending this request is authenticated
  if (!auth.userIsAuthenticated(req)) {
    // The user in unauthenticated. Display a splash page.
    res.render('pages/splash', res.locals.renderLocals)
  } else {
    // The user has authenticated. Display the app
    res.render('pages/app', res.locals.renderLocals)
  }
})

const crawlerRegex = new RegExp('(facebookexternalhit|twitterbot|facebot)')

const Course = require('./models/course.js')
// Route a request for a page inside the app
app.get('/course/:id', express.urlencoded({extended: true}), function (req, res) {
  // Check whether the user sending this request is authenticated
  if (!auth.userIsAuthenticated(req)) {
    // Dislay a simple page with crawler markup for Facebook, Twitter, and iMessage crawlers
    if (crawlerRegex.test(req.get('User-Agent'))) {
      return Course.findById(req.params.id).then(course => {
        if (!course) {
          return res.redirect('/auth/login?redirect=' + req.originalUrl)
        }
        return res.render('pages/crawlerCourse', {course})
      })
    }

    // Redirect to the login URL
    return res.redirect('/auth/login?redirect=' + req.originalUrl)
  } else {
    // The user has authenticated. Display the app
    return res.render('pages/app', res.locals.renderLocals)
  }
})

// Route a request for the about page
app.get('/about', function (req, res) {
  res.render('pages/about', res.locals.renderLocals)
})

// Route a request for the main app page
app.get('/app', function (req, res) {
  res.render('pages/app', res.locals.renderLocals)
})

// Route a request for the main app page
app.get('/privacy', function (req, res) {
  res.render('pages/privacy', res.locals.renderLocals)
})

// Map any files in the /public folder to the root of our domain
// For example, if there is a file at /public/cat.jpg of this app,
// it can be accessed on the web at [APP DOMAIN NAME]/cat.jpg
app.use(express.static(path.join(__dirname, '/public')))

app.get('*', function (req, res) {
  res.sendStatus(404)
})

// Configure the EJS templating system (http://www.embeddedjs.com)
app.set('view engine', 'ejs')

const cluster = require('cluster')
if (cluster.isMaster) {
  const os = require('os')
  const workers = process.env.WEB_CONCURRENCY || os.cpus().length || 1

  console.log(`Forking for ${workers} workers`)
  for (let i = 0; i < workers; i++) {
    cluster.fork()
  }
} else {
  // Start listening for requests
  app.listen(config.port, function () {
    console.log('Listening for reqs on port %d.', config.port)
  })
}