auth.js

import NextAuth from "next-auth";
import GoogleProvider from "next-auth/providers/google";
import CredentialsProvider from "next-auth/providers/credentials";
import { MongoDBAdapter } from "@auth/mongodb-adapter";
import { clientPromise } from "./lib/mongodb";
import User from "./models/User";
import bcrypt from "bcryptjs";
import dbConnect from "./lib/mongodb";
import { authConfig } from "./auth.config";
import { sendWelcomeEmail } from "./lib/mailer";

export const { handlers, auth, signIn, signOut } = NextAuth({
  ...authConfig,
  adapter: MongoDBAdapter(clientPromise),
  providers: [
    GoogleProvider({
      clientId: process.env.AUTH_GOOGLE_ID,
      clientSecret: process.env.AUTH_GOOGLE_SECRET,
    }),
    CredentialsProvider({
      name: "Credentials",
      credentials: {
        email: { label: "Email", type: "email" },
        password: { label: "Password", type: "password" }
      },
      async authorize(credentials) {
        await dbConnect();
        if (!credentials?.email || !credentials?.password) return null;
        
        const user = await User.findOne({ email: credentials.email });
        if (!user || !user.password) return null;

        const passwordsMatch = await bcrypt.compare(credentials.password, user.password);
        if (passwordsMatch) return user;
        
        return null;
      }
    })
  ],
  events: {
    // Fires once when a brand-new user is created (Google OAuth first sign-in)
    async createUser({ user }) {
      try {
        if (user.email) {
          await sendWelcomeEmail({ to: user.email, name: user.name ?? 'Traveller' });
        }
      } catch (err) {
        console.error('Welcome email failed:', err.message);
      }
    },
  },
});