How can I call req.flash() from inside the mongoose save function? - mongodb

Question

Upon finding duplicate user entries in my database, I want to flash a message to the view using req.flash(). However, the only parameters allowed in the User.save() function are errors and the results of the save. How can I get the request object in there too so that if there is
an error (i.e. duplicate entry), the user is notified?
requires
const express = require('express')
const router = express.Router()
const mongoose = require('mongoose')
const Quote = require('../models/quotes')
const User = require('../models/users')
const ObjectId = mongoose.Types.ObjectId;
const expressValidator = require('express-validator')
const flash = require('express-flash-messages')
const passport = require('passport')
const bcrypt = require('bcrypt')
const saltRounds = 10
get request:
/* route handling for SIGNUP page. */
router.get('/signup', (req, res, next) => {
const flashMessages = res.locals.getMessages()
console.log('flash:', flashMessages)
if (flashMessages.error) {
console.log('flash:', flashMessages)
res.render('signup', {
showErrors: true,
signupErrors: flashMessages.error
})
} else {
console.log('no flash errors detected.')
res.render('signup')
}
})
post request:
/* route handling for submission to SIGNUP page */
// this is all just front end validation, with no relation to the database. I think flash messages use that
router.post('/signup/users', (req, res, next) => {
req.checkBody('username', 'Username field cannot be empty.').notEmpty()
req.checkBody('username', 'Username must be between 4-30 characters long.').len(4, 30)
req.checkBody('email', 'The email you entered is invalid, please try again.').isEmail()
req.checkBody('email', 'Email address must be between 4-100 characters long, please try again.').len(4, 100)
req.checkBody('password', 'Password must be between 8-100 characters long.').len(8, 100)
// req.checkBody('password', 'Password must include one lowercase character, one uppercase character, a number, and a special character.').matches(/^(?=.*\d)(?=.*[a-z])(?=.*[A-Z])(?!.* )(?=.*[^a-zA-Z0-9]).{8,}$/, 'i')
req.checkBody('passwordMatch', 'Password must be between 8-100 characters long.').len(8, 100)
req.checkBody('passwordMatch', 'Passwords do not match, please try again.').equals(req.body.password)
// Additional validation to ensure username is alphanumeric with underscores and dashes
req.checkBody('username', 'Username can only contain letters, numbers, or underscores.').matches(/^[A-Za-z0-9_-]+$/, 'i')
const errors = req.validationErrors()
if(errors || flashMessages.error) {
res.render('signup', {
errors: errors,
showErrors: true,
signupErrors: flashMessages.error
})
} else {
let password = req.body.password
bcrypt.hash(password, saltRounds, (err, hash) => {
user = new User()
user.username = req.body.username
user.email = req.body.email
user.password = hash
// PROBLEM STARTS HERE
user.save((err, result) => {
if(err) {
// add flash message here to let user know something was wrong!
const flashMessages = res.locals.getMessages()
console.log('flash', flashMessages)
console.log("Your error: ", err.message)
if (err.message.indexOf("duplicate key error") > -1) {
req.flash('signupErrors', "Username already in use.")
console.log(req.flash("hi"))
res.redirect('/signup')
console.log("Made it down here.")
} else {
req.flash('signupErrors', "There was a problem with your registration.")
console.log("Made it wayyyyyy down here.")
res.redirect('/signup')
}
// AND ENDS HERE
} else {
User.find({}).sort({ _id:-1 }).limit(1)
.exec((err, newuser) => {
if (err) {
console.log(err)
} else {
// logins user through passport function
req.login(newuser[0], (err) => {
if (err) {
console.log("Login error 1: " + err)
console.log("Login error 2: " + newuser[0])
console.log("Login error 3: " + newuser[0]._id)
} else {
console.log("Login sucess BULK: " + newuser[0])
console.log("Login success ._id: " + newuser[0]._id)
res.redirect('/home')
}
})
}
})
.catch(next)
}
})
})
}
})
/* route handling for submission to LOGIN page */
router.post('/login/users', passport.authenticate('local', {
successRedirect: '/profile',
failureRedirect: '/login',
failureFlash: true
}))