'use strict'

const forge = require('node-forge')

/**
 * Maps an IPFS hash name to its node-forge equivalent.
 *
 * See https://github.com/multiformats/multihash/blob/master/hashtable.csv
 *
 * @private
 */
const hashName = {
  sha1: 'sha1',
  'sha2-256': 'sha256',
  'sha2-512': 'sha512'
}

/**
 * Computes the Password-Based Key Derivation Function 2.
 *
 * @param {string} password
 * @param {string} salt
 * @param {number} iterations
 * @param {number} keySize (in bytes)
 * @param {string} hash - The hash name ('sha1', 'sha2-512, ...)
 * @returns {string} - A new password
 */
function pbkdf2 (password, salt, iterations, keySize, hash) {
  const hasher = hashName[hash]
  if (!hasher) {
    throw new Error(`Hash '${hash}' is unknown or not supported`)
  }
  const dek = forge.pkcs5.pbkdf2(
    password,
    salt,
    iterations,
    keySize,
    hasher)
  return forge.util.encode64(dek)
}

module.exports = pbkdf2