import {
  Base,
  WordArray,
} from './core.js';
import { MD5Algo } from './md5.js';

/**
 * This key derivation function is meant to conform with EVP_BytesToKey.
 * www.openssl.org/docs/crypto/EVP_BytesToKey.html
 */
export class EvpKDFAlgo extends Base {
  /**
   * Initializes a newly created key derivation function.
   *
   * @param {Object} cfg (Optional) The configuration options to use for the derivation.
   *
   * @example
   *
   *     const kdf = CryptoJS.algo.EvpKDF.create();
   *     const kdf = CryptoJS.algo.EvpKDF.create({ keySize: 8 });
   *     const kdf = CryptoJS.algo.EvpKDF.create({ keySize: 8, iterations: 1000 });
   */
  constructor(cfg) {
    super();

    /**
     * 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
     */
    this.cfg = Object.assign(
      new Base(),
      {
        keySize: 128 / 32,
        hasher: MD5Algo,
        iterations: 1,
      },
      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
   *
   *     const key = kdf.compute(password, salt);
   */
  compute(password, salt) {
    let block;

    // Shortcut
    const { cfg } = this;

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

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

    // Shortcuts
    const derivedKeyWords = derivedKey.words;
    const { keySize, iterations } = cfg;

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

      // Iterations
      for (let i = 1; i < iterations; i += 1) {
        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 });
 */
export const EvpKDF = (password, salt, cfg) => EvpKDFAlgo.create(cfg).compute(password, salt);