const crypto = require('crypto')

const PREFIX = 'scrypt$'

function hash(plain) {
  const salt = crypto.randomBytes(16).toString('hex')
  const digest = crypto.scryptSync(String(plain), salt, 32).toString('hex')
  return `${PREFIX}${salt}$${digest}`
}

function isHashed(stored) {
  return typeof stored === 'string' && stored.startsWith(PREFIX)
}

function verify(plain, stored) {
  if (!isHashed(stored)) return false
  const parts = stored.split('$')
  const expected = Buffer.from(parts[2], 'hex')
  const actual = crypto.scryptSync(String(plain), parts[1], expected.length)
  return crypto.timingSafeEqual(expected, actual)
}

module.exports = { hash, verify, isHashed }