var crypto = require('crypto')

/**
 *
 * @param {number} len
 */
var random = (len = 32) => {
  var buf = crypto.randomBytes(len)
  return buf.toString('hex')
}

/**
 *
 * @param {string} str
 */
var sha256 = (str) => {
  return crypto.createHash('sha256').update(str).digest('base64')
}

/**
 *
 * @param {string} str
 */
var genPassHash = (str) => {
  var hash = random(16)
  var pass = sha256(str + hash)
  return `$${hash}$${pass}`
}

/**
 *
 * @param {string} plain
 * @param {string} hash
 */
var comparePass = (plain, hash) => {
  var match = hash.match(/^\$(.+?)\$(.+)$/)
  if (match == null || match.length < 3 || !match[1] || !match[2]) return false
  var pass = sha256(plain + match[1])
  if (pass === match[2]) return true
  return false
}

module.exports = {
  random,
  sha256,
  genPassHash,
  comparePass
}