https://stackoverflow.com/questions/50413387/

// load all the things we need
var LocalStrategy = require('passport-local').Strategy
// var bcrypt = require('bcrypt')
var bcrypt = require('bcryptjs')
// load up the user model
var mysql = require('mysql')
const dbConfig = require('./db')

// expose this function to our app using module.exports
module.exports = function (passport) {

  // =========================================================================
  // passport session setup ==================================================
  // =========================================================================
  // required for persistent login sessions
  // passport needs ability to serialize and unserialize users out of session

  // used to serialize the user for the session
  passport.serializeUser(function (user, done) {
    done(null, user.id);
  });

  // used to deserialize the user
  passport.deserializeUser(function (id, done) {
    const connection = mysql.createConnection(dbConfig)
    connection.connect(function(err) {
      if (err) return done(err)
      connection.query('SELECT * FROM users WHERE id = ?', [id], function (err, results) {
        if (err) return done(err)
        connection.end()
        done(null, results.length === 1 ? results[0] : null);
      });
    })
  });

  passport.use('local-login', new LocalStrategy({
      usernameField : 'username',
      passwordField : 'password',
      passReqToCallback: true // allows us to pass back the entire request to the callback
    },
    function (req, username, password, done) { // callback with username and password from our form
        req.getConnection(function(err, connection) {
          if (err)  {
            console.log('Mysql connection has not been established ', err)
            return done(err);
          }

          connection.query('SELECT * FROM users WHERE username = ?', [username], function(err, results) {
            if (err) {
              console.log('Sql query error ' + err)
              return done(err);
            }

            if(!results || results.length !== 1) {
              console.log('User not found ', username)
              return done(null, false, req.flash('loginMessage', 'Invalid credentials #1'))

            }

            bcrypt.compare(password, results[0].password, function(err, passwordsMatch) {
              if (err || !passwordsMatch) {
                console.log('Password validation error ', err, passwordsMatch)
                return done(null, false, req.flash('loginMessage', 'Invalid credentials'));
              }
              // all is well, return successful user
              return done(null, results[0]);
            })
          });

        });
    }))

}