server.js

/* This allows us to use the environment
 variable throughout our package */
require('dotenv').config()

// We define Express
const express = require('express')

// We define our app
const app = express()

// Trust the proxy to read the X-Forwarded-For header
app.set('trust proxy', 1)

/* We import the 'path' module to provide utilities 
for working with file and directory paths */
const path = require('node:path')

// We import our logger middleware
const { logger } = require('./middleware/logger')

// We import our errorHandler middleware
const errorHandler = require('./middleware/errorHandler')

// We import the cookie-parser 3rd party Express middleware
const cookieParser = require('cookie-parser')

// We import the Cross-Origin Resource Sharing middleware
const cors = require('cors')

// Setting the CORS options
const corsOptions = require('./config/corsOptions')

// Database connection
const connectDB = require('./config/dbConnection')

/* We call the Mongoose library that helps with data modeling,
 schema enforcement, and model validation for MongoDB */
const mongoose = require('mongoose')

// We import our logEvents middleware
const { logEvents } = require('./middleware/logger')

// We define the constant for the port
const PORT = process.env.PORT || 3500

// We log in the console our Node environment variable
console.log(process.env.NODE_ENV)

// We call the DB connection function
connectDB();

// 'logger' middleware to track requests
app.use(logger)

// CORS
app.use(cors(corsOptions))

// Built in middleware in Express to parse incoming requests with JSON
app.use(express.json())

/* 3rd party Express middleware to handle the 
cookies sent from the client to the server */
app.use(cookieParser())

// We provide our app the route to look for static files
app.use('/', express.static(path.join(__dirname, 'public')))

// We require the root of our router
app.use('/', require('./routes/root'))
// We require the auth route
app.use('/auth', require('./routes/authRoutes'))
// We require the users rout
app.use('/users', require('./routes/userRoutes'))
// We require the notes rout
app.use('/notes', require('./routes/noteRoutes'))

// Redirection to 'error' page
app.all('*', (req, res)=> {
  res.status(404)
  if(req.accepts('html')) {
    // HTML response
    res.sendFile(path.join(__dirname, 'views', '404.html'))
  } else if(req.accepts('json')) {
    // JSON response
    res.json({ message: '404 - Not found' })
  } else {
    // Plain text response
    res.type('txt').send('404 - Not found')
  }
})

// 'errorHandler' custom middleware to handle the errors
app.use(errorHandler)

/* We wrap our app listen event inside a 
listener for the mongoose connection */
mongoose.connection.once('open', ()=> {
  console.log('>Connected to MongoDB')
  // We order our app to start listening
  app.listen(PORT, ()=> console.log(`Server running on port ${PORT}...`))
})

// Listener of MongoDB errors
mongoose.connection.on('error', error => {
  console.error(error)
  logEvents(`${error.no}: ${error.code}\t${error.syscall}\t${error.hostname}`,
  'mongoErrorLog.log'
  )
})