var CryptoJS = require('./core');
require('./sha1');
require('./hmac');

(function() {
  // Shortcuts
  var C = CryptoJS;
  var C_lib = C.lib;
  var Base = C_lib.Base;
  var WordArray = C_lib.WordArray;
  var C_algo = C.algo;
  var MD5 = C_algo.MD5;

  /**
   * This key derivation function is meant to conform with EVP_BytesToKey.
   * www.openssl.org/docs/crypto/EVP_BytesToKey.html
   */
  var EvpKDF = C_algo.EvpKDF = Base.extend({
    /**
     * Configuration options.
     *
     * @property {number} keySize The key size in words to generate. Default: 4 (128 bits)
     * @property {Hasher} hasher The hash algorithm to use. Default: MD5
     * @property {number} iterations The number of iterations to perform. Default: 1
     */
    cfg: Base.extend({
      keySize: 128 / 32,
      hasher: MD5,
      iterations: 1
    }),

    /**
     * Initializes a newly created key derivation function.
     *
     * @param {Object} cfg (Optional) The configuration options to use for the derivation.
     *
     * @example
     *
     *     var kdf = CryptoJS.algo.EvpKDF.create();
     *     var kdf = CryptoJS.algo.EvpKDF.create({ keySize: 8 });
     *     var kdf = CryptoJS.algo.EvpKDF.create({ keySize: 8, iterations: 1000 });
     */
    init: function(cfg) {
      this.cfg = this.cfg.extend(cfg);
    },

    /**
     * Derives a key from a password.
     *
     * @param {WordArray|string} password The password.
     * @param {WordArray|string} salt A salt.
     *
     * @return {WordArray} The derived key.
     *
     * @example
     *
     *     var key = kdf.compute(password, salt);
     */
    compute: function(password, salt) {
      // Shortcut
      var cfg = this.cfg;

      // Init hasher
      var hasher = cfg.hasher.create();

      // Initial values
      var derivedKey = WordArray.create();

      // Shortcuts
      var derivedKeyWords = derivedKey.words;
      var keySize = cfg.keySize;
      var iterations = cfg.iterations;

      // Generate key
      while (derivedKeyWords.length < keySize) {
        if (block) {
          hasher.update(block);
        }
        var block = hasher.update(password).finalize(salt);
        hasher.reset();

        // Iterations
        for (var i = 1; i < iterations; i++) {
          block = hasher.finalize(block);
          hasher.reset();
        }

        derivedKey.concat(block);
      }
      derivedKey.sigBytes = keySize * 4;

      return derivedKey;
    }
  });

  /**
   * Derives a key from a password.
   *
   * @param {WordArray|string} password The password.
   * @param {WordArray|string} salt A salt.
   * @param {Object} cfg (Optional) The configuration options to use for this computation.
   *
   * @return {WordArray} The derived key.
   *
   * @static
   *
   * @example
   *
   *     var key = CryptoJS.EvpKDF(password, salt);
   *     var key = CryptoJS.EvpKDF(password, salt, { keySize: 8 });
   *     var key = CryptoJS.EvpKDF(password, salt, { keySize: 8, iterations: 1000 });
   */
  C.EvpKDF = function(password, salt, cfg) {
    return EvpKDF.create(cfg).compute(password, salt);
  };
}());

module.exports = CryptoJS.EvpKDF;