diligent-next/pages/api/auth/[...nextauth].js

import NextAuth from 'next-auth';
import Credentials from 'next-auth/providers/credentials';

import { connectToDatabase } from '../../../utils/helpers/dbHelpers';
import { verifyPassword } from '../../../utils/helpers/hashPasswordHelpers';

export default NextAuth({
  session: {
    jwt: true,
  },
  providers: [
    Credentials({
      async authorize(credentials) {
        const client = await connectToDatabase();

        const usersCollection = client.db().collection('users');

        const user = await usersCollection.findOne({
          username: credentials.username,
        });

        if (!user) {
          client.close();
          throw new Error('No user found!');
        }

        const isValid = await verifyPassword(
          credentials.password,
          user.password
        );

        if (!isValid) {
          client.close();
          throw new Error('Could not log you in!');
        }

        client.close();
        return { name: user.fullName };
      },
    }),
  ],
});