/*!
 * scrypt.js - scrypt for bcoin
 * Copyright (c) 2016, Christopher Jeffrey (MIT License).
 * https://github.com/bcoin-org/bcoin
 *
 * Ported from:
 * https://github.com/Tarsnap/scrypt/blob/master/lib/crypto/crypto_scrypt-ref.c
 *
 * Copyright 2009 Colin Percival
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

'use strict';

var backend = require('./backend');
var native = require('../utils/native').binding;
var U32Array = typeof Uint32Array === 'function' ? Uint32Array : Array;

/**
 * Javascript scrypt implementation. Scrypt is
 * used in bip38. BCoin doesn't support bip38
 * yet, but here it is, just in case.
 * @param {Buffer} passwd
 * @param {Buffer} salt
 * @param {Number} N
 * @param {Number} r
 * @param {Number} p
 * @param {Number} len
 * @returns {Buffer}
 */

function scrypt(passwd, salt, N, r, p, len) {
  var i, B, V, XY;

  if (r * p >= (1 << 30))
    throw new Error('EFBIG');

  if ((N & (N - 1)) !== 0 || N === 0)
    throw new Error('EINVAL');

  if (N > 0xffffffff)
    throw new Error('EINVAL');

  XY = new Buffer(256 * r);
  V = new Buffer(128 * r * N);

  B = backend.pbkdf2(passwd, salt, 1, p * 128 * r, 'sha256');

  for (i = 0; i < p; i++)
    smix(B, i * 128 * r, r, N, V, XY);

  return backend.pbkdf2(passwd, B, 1, len, 'sha256');
}

if (native)
  scrypt = native.scrypt;

function salsa20_8(B) {
  var B32 = new U32Array(16);
  var x = new U32Array(16);
  var i;

  for (i = 0; i < 16; i++)
    B32[i] = B.readUInt32LE(i * 4, true);

  for (i = 0; i < 16; i++)
    x[i] = B32[i];

  for (i = 0; i < 8; i += 2) {
    x[4] ^= R(x[0] + x[12], 7);
    x[8] ^= R(x[4] + x[0], 9);
    x[12] ^= R(x[8] + x[4], 13);
    x[0] ^= R(x[12] + x[8], 18);

    x[9] ^= R(x[5] + x[1], 7);
    x[13] ^= R(x[9] + x[5], 9);
    x[1] ^= R(x[13] + x[9], 13);
    x[5] ^= R(x[1] + x[13], 18);

    x[14] ^= R(x[10] + x[6], 7);
    x[2] ^= R(x[14] + x[10], 9);
    x[6] ^= R(x[2] + x[14], 13);
    x[10] ^= R(x[6] + x[2], 18);

    x[3] ^= R(x[15] + x[11], 7);
    x[7] ^= R(x[3] + x[15], 9);
    x[11] ^= R(x[7] + x[3], 13);
    x[15] ^= R(x[11] + x[7], 18);

    x[1] ^= R(x[0] + x[3], 7);
    x[2] ^= R(x[1] + x[0], 9);
    x[3] ^= R(x[2] + x[1], 13);
    x[0] ^= R(x[3] + x[2], 18);

    x[6] ^= R(x[5] + x[4], 7);
    x[7] ^= R(x[6] + x[5], 9);
    x[4] ^= R(x[7] + x[6], 13);
    x[5] ^= R(x[4] + x[7], 18);

    x[11] ^= R(x[10] + x[9], 7);
    x[8] ^= R(x[11] + x[10], 9);
    x[9] ^= R(x[8] + x[11], 13);
    x[10] ^= R(x[9] + x[8], 18);

    x[12] ^= R(x[15] + x[14], 7);
    x[13] ^= R(x[12] + x[15], 9);
    x[14] ^= R(x[13] + x[12], 13);
    x[15] ^= R(x[14] + x[13], 18);
  }

  for (i = 0; i < 16; i++)
    B32[i] += x[i];

  for (i = 0; i < 16; i++)
    B.writeUInt32LE(B32[i], 4 * i, true);
}

function R(a, b) {
  return (a << b) | (a >>> (32 - b));
}

function blockmix_salsa8(B, Y, Yo, r) {
  var X = new Buffer(64);
  var i;

  blkcpy(X, B, 0, (2 * r - 1) * 64, 64);

  for (i = 0; i < 2 * r; i++) {
    blkxor(X, B, 0, i * 64, 64);
    salsa20_8(X);
    blkcpy(Y, X, Yo + i * 64, 0, 64);
  }

  for (i = 0; i < r; i++)
    blkcpy(B, Y, i * 64, Yo + (i * 2) * 64, 64);

  for (i = 0; i < r; i++)
    blkcpy(B, Y, (i + r) * 64, Yo + (i * 2 + 1) * 64, 64);
}

function integerify(B, r) {
  return B.readUInt32LE((2 * r - 1) * 64, true);
}

function smix(B, Bo, r, N, V, XY) {
  var X = XY;
  var Y = XY;
  var i;
  var j;

  blkcpy(X, B, 0, Bo, 128 * r);

  for (i = 0; i < N; i++) {
    blkcpy(V, X, i * (128 * r), 0, 128 * r);
    blockmix_salsa8(X, Y, 128 * r, r);
  }

  for (i = 0; i < N; i++) {
    j = integerify(X, r) & (N - 1);
    blkxor(X, V, 0, j * (128 * r), 128 * r);
    blockmix_salsa8(X, Y, 128 * r, r);
  }

  blkcpy(B, X, Bo, 0, 128 * r);
}

function blkcpy(dest, src, s1, s2, len) {
  src.copy(dest, s1, s2, s2 + len);
}

function blkxor(dest, src, s1, s2, len) {
  for (var i = 0; i < len; i++)
    dest[s1 + i] ^= src[s2 + i];
}

/*
 * Expose
 */

module.exports = scrypt;