var hashjs = require('hash.js');
var sha512 = require('sha512');

var Hash = module.exports;

Hash.sha256 = function(buf) {
  if (!Buffer.isBuffer(buf))
    throw new Error('sha256 hash must be of a buffer');
  var hash = (new hashjs.sha256()).update(buf).digest();
  return new Buffer(hash);
};

Hash.sha256.blocksize = 512;

Hash.sha256sha256 = function(buf) {
  try {
    return Hash.sha256(Hash.sha256(buf));
  } catch (e) {
    throw new Error('sha256sha256 hash must be of a buffer');
  }
};

Hash.ripemd160 = function(buf) {
  if (!Buffer.isBuffer(buf))
    throw new Error('ripemd160 hash must be of a buffer');
  var hash = (new hashjs.ripemd160()).update(buf).digest();
  return new Buffer(hash);
};

Hash.sha256ripemd160 = function(buf) {
  try {
    return Hash.ripemd160(Hash.sha256(buf));
  } catch (e) {
    throw new Error('sha256ripemd160 hash must be of a buffer');
  }
};

Hash.sha512 = function(buf) {
  if (!Buffer.isBuffer(buf))
    throw new Error('sha512 hash must be of a buffer');
  var hash = sha512(buf);
  return new Buffer(hash);
};

Hash.sha512.blocksize = 1024;

Hash.hmac = function(hashf, data, key) {
  if (!Buffer.isBuffer(data) || !Buffer.isBuffer(key))
    throw new Error('data and key must be buffers');

  //http://en.wikipedia.org/wiki/Hash-based_message_authentication_code
  //http://tools.ietf.org/html/rfc4868#section-2
  if (!hashf.blocksize)
    throw new Error('Blocksize for hash function unknown');

  var blocksize = hashf.blocksize/8;
  
  if (key.length > blocksize)
    key = hashf(key);
  else if (key < blocksize) {
    var fill = new Buffer(blocksize);
    fill.fill(0);
    key.copy(fill);
    key = fill;
  }

  var o_key = new Buffer(blocksize);
  o_key.fill(0x5c);

  var i_key = new Buffer(blocksize);
  i_key.fill(0x36);

  var o_key_pad = new Buffer(blocksize);
  var i_key_pad = new Buffer(blocksize);
  for (var i = 0; i < blocksize; i++) {
    o_key_pad[i] = o_key[i] ^ key[i];
    i_key_pad[i] = i_key[i] ^ key[i];
  }

  return hashf(Buffer.concat([o_key_pad, hashf(Buffer.concat([i_key_pad, data]))]));
};

Hash.sha256hmac = function(data, key) {
  return Hash.hmac(Hash.sha256, data, key);
};

Hash.sha512hmac = function(data, key) {
  return Hash.hmac(Hash.sha512, data, key);
};