/**
 * Node.js implementation of platform-specific routines.
 */

"use strict";

var os = require("os");
var crypto = require("crypto");
var promise = typeof Promise === "undefined" ?
              require("es6-promise").Promise :
              Promise;
var bignum = require("bignum");
var assert = require("./util").assert;
var worker = require("./worker");

var createHash = crypto.createHash;

exports.sha512 = function(buf) {
  return createHash("sha512").update(buf).digest();
};

exports.sha256 = function(buf) {
  return createHash("sha256").update(buf).digest();
};

exports.ripemd160 = function(buf) {
  return createHash("ripemd160").update(buf).digest();
};

exports.randomBytes = crypto.randomBytes;

// 2^64.
var B64 = bignum("18446744073709551616");

// NOTE(Kagami): We can't calculate entire target in JavaScript but the
// result can be represented in native number type without losing
// precision (targets mainly much less than 2^53).
exports.getTarget = function(opts) {
  // Calculate it bottom-up, right-to-left.
  var length = bignum(opts.payloadLength)
    // To account for the nonce which we will append later.
    .add(8)
    .add(opts.payloadLengthExtraBytes);
  var denominator = bignum(opts.ttl)
    .mul(length)
    .div(65536)
    .add(length)
    .mul(opts.nonceTrialsPerByte);
  var target = B64.div(denominator).toNumber();
  assert(target <= 9007199254740991, "Unsafe target");
  return target;
};

exports.doPOW = function(opts) {
  var poolSize = opts.poolSize || os.cpus().length;

  // Check all input params prematurely to not let promise executor or
  // worker to fail because of it.
  // 1 - UINT32_MAX
  assert(poolSize > 0, "Pool size is too low");
  assert(poolSize <= 4294967295, "Pool size is too high");
  // 0 - (2^53 - 1)
  assert(typeof opts.target === "number", "Bad target");
  assert(opts.target >= 0, "Target is too low");
  assert(opts.target <= 9007199254740991, "Target is too high");
  assert(Buffer.isBuffer(opts.initialHash), "Bad initial hash");

  // TODO(Kagami): Allow to cancel a POW (see `platform.browser.js`).
  return new promise(function(resolve, reject) {
    worker.powAsync(
      poolSize,
      opts.target,
      opts.initialHash,
      function(err, nonce) {
        if (err) {
          reject(err);
        } else {
          resolve(nonce);
        }
      }
    );
  });
};