buzz-sheet/lib/auth/server.ts

import "server-only";

import { betterAuth } from "better-auth";
import { drizzleAdapter } from "better-auth/adapters/drizzle";
import { nextCookies } from "better-auth/next-js";
import { headers } from "next/headers";

import { getDb } from "@/db";
import {
  accounts,
  sessions,
  users,
  verifications,
} from "@/db/schema";

import {
  isAllowedAdminRegistration,
  isAuthorizedAdmin,
  isConfiguredAdminEmail,
  type SessionUserLike,
} from "./authorization";

function required(name: string): string {
  const value = process.env[name];
  if (!value) throw new Error(`${name} is required for authentication.`);
  return value;
}

function createAuth() {
  const adminEmail = required("ADMIN_EMAIL");

  return betterAuth({
    appName: "Buzz Sheet",
    database: drizzleAdapter(getDb(), {
      provider: "pg",
      schema: {
        user: users,
        session: sessions,
        account: accounts,
        verification: verifications,
      },
      transaction: true,
    }),
    baseURL: required("BETTER_AUTH_URL"),
    secret: required("BETTER_AUTH_SECRET"),
    emailAndPassword: {
      enabled: true,
      minPasswordLength: 8,
      maxPasswordLength: 128,
    },
    user: {
      validateUserInfo: async ({ user, source }) => {
        if (
          !isAllowedAdminRegistration(
            user.email,
            source.method,
            adminEmail,
          )
        ) {
          return {
            error: "ADMIN_REGISTRATION_FORBIDDEN",
            errorDescription:
              "Registration is limited to the configured administrator.",
          };
        }
      },
    },
    databaseHooks: {
      user: {
        create: {
          before: async (user) => {
            if (!isConfiguredAdminEmail(user.email, adminEmail)) return false;
            return { data: { emailVerified: true } };
          },
        },
      },
    },
    plugins: [nextCookies()],
  });
}

type AuthInstance = ReturnType<typeof createAuth>;
let authInstance: AuthInstance | undefined;

export function getAuth(): AuthInstance {
  if (!authInstance) authInstance = createAuth();
  return authInstance;
}

export interface AdminSession {
  user: SessionUserLike;
  session: { id: string };
}

export async function getAdminSession(): Promise<AdminSession | null> {
  if (process.env.BUZZ_DEMO_MODE === "true") {
    return {
      user: {
        id: "demo-admin",
        email: "[email protected]",
        emailVerified: true,
        name: "Demo Admin",
      },
      session: { id: "demo-session" },
    };
  }

  const session = await getAuth().api.getSession({ headers: await headers() });
  if (
    !session?.session ||
    !isAuthorizedAdmin(session.user, process.env.ADMIN_EMAIL)
  ) {
    return null;
  }
  return {
    user: session.user,
    session: { id: session.session.id },
  };
}

export class AdminAuthorizationError extends Error {
  constructor() {
    super("Admin authorization required.");
    this.name = "AdminAuthorizationError";
  }
}

export async function requireAdmin(): Promise<AdminSession> {
  const session = await getAdminSession();
  if (!session) throw new AdminAuthorizationError();
  return session;
}