import {
  WordArray,
  Hasher,
} from './core';

// Initialization and round constants tables
const H = [];
const K = [];

// Compute constants
const isPrime = (n) => {
  const sqrtN = Math.sqrt(n);
  for (let factor = 2; factor <= sqrtN; factor += 1) {
    if (!(n % factor)) {
      return false;
    }
  }

  return true;
};

const getFractionalBits = n => ((n - (n | 0)) * 0x100000000) | 0;

let n = 2;
let nPrime = 0;
while (nPrime < 64) {
  if (isPrime(n)) {
    if (nPrime < 8) {
      H[nPrime] = getFractionalBits(n ** (1 / 2));
    }
    K[nPrime] = getFractionalBits(n ** (1 / 3));

    nPrime += 1;
  }

  n += 1;
}

// Reusable object
const W = [];

/**
 * SHA-256 hash algorithm.
 */
export class SHA256Algo extends Hasher {
  _doReset() {
    this._hash = new WordArray(H.slice(0));
  }

  _doProcessBlock(M, offset) {
    // Shortcut
    const _H = this._hash.words;

    // Working variables
    let a = _H[0];
    let b = _H[1];
    let c = _H[2];
    let d = _H[3];
    let e = _H[4];
    let f = _H[5];
    let g = _H[6];
    let h = _H[7];

    // Computation
    for (let i = 0; i < 64; i += 1) {
      if (i < 16) {
        W[i] = M[offset + i] | 0;
      } else {
        const gamma0x = W[i - 15];
        const gamma0 = ((gamma0x << 25) | (gamma0x >>> 7))
          ^ ((gamma0x << 14) | (gamma0x >>> 18))
          ^ (gamma0x >>> 3);

        const gamma1x = W[i - 2];
        const gamma1 = ((gamma1x << 15) | (gamma1x >>> 17))
          ^ ((gamma1x << 13) | (gamma1x >>> 19))
          ^ (gamma1x >>> 10);

        W[i] = gamma0 + W[i - 7] + gamma1 + W[i - 16];
      }

      const ch = (e & f) ^ (~e & g);
      const maj = (a & b) ^ (a & c) ^ (b & c);

      const sigma0 = ((a << 30) | (a >>> 2)) ^ ((a << 19) | (a >>> 13)) ^ ((a << 10) | (a >>> 22));
      const sigma1 = ((e << 26) | (e >>> 6)) ^ ((e << 21) | (e >>> 11)) ^ ((e << 7) | (e >>> 25));

      const t1 = h + sigma1 + ch + K[i] + W[i];
      const t2 = sigma0 + maj;

      h = g;
      g = f;
      f = e;
      e = (d + t1) | 0;
      d = c;
      c = b;
      b = a;
      a = (t1 + t2) | 0;
    }

    // Intermediate hash value
    _H[0] = (_H[0] + a) | 0;
    _H[1] = (_H[1] + b) | 0;
    _H[2] = (_H[2] + c) | 0;
    _H[3] = (_H[3] + d) | 0;
    _H[4] = (_H[4] + e) | 0;
    _H[5] = (_H[5] + f) | 0;
    _H[6] = (_H[6] + g) | 0;
    _H[7] = (_H[7] + h) | 0;
  }

  _doFinalize() {
    // Shortcuts
    const data = this._data;
    const dataWords = data.words;

    const nBitsTotal = this._nDataBytes * 8;
    const nBitsLeft = data.sigBytes * 8;

    // Add padding
    dataWords[nBitsLeft >>> 5] |= 0x80 << (24 - (nBitsLeft % 32));
    dataWords[(((nBitsLeft + 64) >>> 9) << 4) + 14] = Math.floor(nBitsTotal / 0x100000000);
    dataWords[(((nBitsLeft + 64) >>> 9) << 4) + 15] = nBitsTotal;
    data.sigBytes = dataWords.length * 4;

    // Hash final blocks
    this._process();

    // Return final computed hash
    return this._hash;
  }

  clone() {
    const clone = super.clone.call(this);
    clone._hash = this._hash.clone();

    return clone;
  }
}

/**
 * Shortcut function to the hasher's object interface.
 *
 * @param {WordArray|string} message The message to hash.
 *
 * @return {WordArray} The hash.
 *
 * @static
 *
 * @example
 *
 *     var hash = CryptoJS.SHA256('message');
 *     var hash = CryptoJS.SHA256(wordArray);
 */
export const SHA256 = Hasher._createHelper(SHA256Algo);

/**
 * Shortcut function to the HMAC's object interface.
 *
 * @param {WordArray|string} message The message to hash.
 * @param {WordArray|string} key The secret key.
 *
 * @return {WordArray} The HMAC.
 *
 * @static
 *
 * @example
 *
 *     var hmac = CryptoJS.HmacSHA256(message, key);
 */
export const HmacSHA256 = Hasher._createHmacHelper(SHA256Algo);