passport.js

const LocalStrategy = require("passport-local").Strategy;
const mongoose = require("mongoose");
const User = require("../models/User");

module.exports = function (passport) {
  passport.use(
    new LocalStrategy({ usernameField: "email" }, async (email, password, done) => {
      try {
        const user = await User.findOne({ email: email.toLowerCase() });
        if (!user) {
          return done(null, false, { msg: `Email ${email} not found.` });
        }
        if (!user.password) {
          return done(null, false, {
            msg:
              "Your account was registered using a sign-in provider. To enable password login, sign in using a provider, and then set a password under your user profile.",
          });
        }
        user.comparePassword(password, (err, isMatch) => {
          if (err) {
            return done(err);
          }
          if (isMatch) {
            return done(null, user);
          }
          return done(null, false, { msg: "Invalid email or password." });
        });
      } catch (err) {
        return done(err);
      }
    })
  );

  passport.serializeUser((user, done) => {
    done(null, user.id);
  });

  passport.deserializeUser(async (id, done) => {
    try {
      const user = await User.findById(id);
      done(null, user);
    } catch (err) {
      done(err, null);
    }
  });
};