// Password hashing using Node's built-in scrypt + a per-hash random salt.
//
// No external dependency (bcrypt would need a native build step). scrypt is
// memory-hard and well suited for interactive logins. Hash format:
//   "<saltHex>:<hashHex>"  (salt is 16 bytes, hash is 64 bytes)

const crypto = require('crypto');

const KEYLEN = 64;

function hash(password) {
  const salt = crypto.randomBytes(16).toString('hex');
  const out = crypto.scryptSync(password, salt, KEYLEN).toString('hex');
  return `${salt}:${out}`;
}

function verify(password, stored) {
  if (typeof stored !== 'string' || !stored.includes(':')) return false;
  const idx = stored.indexOf(':');
  const salt = stored.slice(0, idx);
  const expected = stored.slice(idx + 1);
  if (!salt || !expected) return false;
  let computed;
  try {
    computed = crypto.scryptSync(password, salt, KEYLEN).toString('hex');
  } catch (e) {
    return false;
  }
  if (computed.length !== expected.length) return false;
  // Constant-time compare to avoid timing side channels.
  return crypto.timingSafeEqual(Buffer.from(computed), Buffer.from(expected));
}

module.exports = { hash, verify };