const crypto = require('crypto')

function getOfflineUUID (username) {
  // Hash the UUID
  const md5 = crypto.createHash('md5')
  md5.update('OfflinePlayer:' + username, 'utf-8')
  const hash = md5.digest()

  // From https://github.com/openjdk/jdk/blob/master/src/java.base/share/classes/java/util/UUID.java#L182-L185
  hash[6] &= 0x0f  /* clear version        */
  hash[6] |= 0x30  /* set to version 3     */
  hash[8] &= 0x3f  /* clear variant        */
  hash[8] |= 0x80  /* set to IETF variant  */

  const hex = hash.toString('hex')
  return `${hex.substring(0, 8)}-${hex.substring(8, 12)}-${hex.substring(12, 16)}-${hex.substring(16, 20)}-${hex.substring(20, 32)}`
}

module.exports = getOfflineUUID