import { NextAuthOptions } from "next-auth";
import CredentialsProvider from "next-auth/providers/credentials";
import { prisma } from "@/lib/prisma";
import bcrypt from "bcryptjs";

const SINGLE_USER_MODE = process.env.NEXT_PUBLIC_SINGLE_USER_MODE === "true";
const ALLOWED_EMAIL = process.env.SINGLE_USER_EMAIL || "admin@tinker.local";
const SINGLE_USER_PASSWORD = process.env.SINGLE_USER_PASSWORD || "tinker123!";

export const authOptions: NextAuthOptions = {
  providers: [
    CredentialsProvider({
      name: "credentials",
      credentials: {
        email: { label: "Email", type: "email" },
        password: { label: "Password", type: "password" },
      },
      async authorize(credentials) {
        if (!credentials?.email || !credentials?.password) {
          throw new Error("Email and password are required");
        }

        // --- Single-User Mode: bypass DB, use env vars ---
        if (SINGLE_USER_MODE) {
          if (credentials.email !== ALLOWED_EMAIL) {
            throw new Error("Access denied: this instance is limited to a single user.");
          }
          // Create user in DB if not exists (first-login seeding)
          let user = await prisma.user.findUnique({
            where: { email: ALLOWED_EMAIL },
          });
          if (!user) {
            const hashedPassword = await bcrypt.hash(SINGLE_USER_PASSWORD, 10);
            user = await prisma.user.create({
              data: {
                email: ALLOWED_EMAIL,
                name: "Tinker Admin",
                password: hashedPassword,
              },
            });
          }
          return {
            id: user.id,
            name: user.name,
            email: user.email,
            image: user.image,
          };
        }

        // --- Normal multi-user mode ---
        const user = await prisma.user.findUnique({
          where: { email: credentials.email },
        });

        if (!user) {
          throw new Error("No user found with this email");
        }

        if (!user.password) {
          throw new Error("This account does not have a password set.");
        }

        const isPasswordValid = await bcrypt.compare(
          credentials.password,
          user.password
        );

        if (!isPasswordValid) {
          throw new Error("Invalid password");
        }

        return {
          id: user.id,
          name: user.name,
          email: user.email,
          image: user.image,
        };
      },
    }),
  ],
  session: {
    strategy: "jwt",
    maxAge: 30 * 24 * 60 * 60,
  },
  pages: {
    signIn: "/login",
    error: "/login",
  },
  callbacks: {
    async jwt({ token, user }) {
      if (user) {
        token.id = user.id;
      }
      return token;
    },
    async session({ session, token }) {
      if (session.user) {
        session.user.id = token.id as string;
      }
      return session;
    },
  },
  secret: process.env.NEXTAUTH_SECRET,
};