// scrypt password hashing for the standalone fallback UI (design §9/§10.2). Format:
// `scrypt$<saltB64url>$<hashB64url>`. Verification is constant-time. Only used by the standalone
// server; the console-hosted path has no password of its own.

import { randomBytes, scryptSync, timingSafeEqual } from "node:crypto";

const KEYLEN = 32;

/** Hash a password for storage in `config.ui.passwordHash`. */
export const hashPassword = (password: string): string => {
	const salt = randomBytes(16);
	const hash = scryptSync(password, salt, KEYLEN);
	return `scrypt$${salt.toString("base64url")}$${hash.toString("base64url")}`;
};

/** Constant-time verify a password against a stored `scrypt$...` hash. */
export const verifyPassword = (password: string, stored: string): boolean => {
	const parts = stored.split("$");
	if (parts.length !== 3 || parts[0] !== "scrypt" || !parts[1] || !parts[2])
		return false;
	const salt = Buffer.from(parts[1], "base64url");
	const expected = Buffer.from(parts[2], "base64url");
	let actual: Buffer;
	try {
		actual = scryptSync(password, salt, expected.length);
	} catch {
		return false;
	}
	return actual.length === expected.length && timingSafeEqual(actual, expected);
};