/**
 * Parse byte `size` string.
 *
 * @param {String} size
 * @return {Number}
 * @api public
 */

module.exports = function(size) {
  if ('number' == typeof size) return convert(size);
  var parts = size.match(/^(\d+(?:\.\d+)?) *(kb|mb|gb|tb)$/)
    , n = parseFloat(parts[1])
    , type = parts[2];

  var map = {
      kb: 1 << 10
    , mb: 1 << 20
    , gb: 1 << 30
    , tb: ((1 << 30) * 1024)
  };

  return map[type] * n;
};

/**
 * convert bytes into string.
 *
 * @param {Number} b - bytes to convert
 * @return {String}
 * @api public
 */

function convert (b) {
  var tb = ((1 << 30) * 1024), gb = 1 << 30, mb = 1 << 20, kb = 1 << 10, abs = Math.abs(b);
  if (abs >= tb) return (Math.round(b / tb * 100) / 100) + 'tb';
  if (abs >= gb) return (Math.round(b / gb * 100) / 100) + 'gb';
  if (abs >= mb) return (Math.round(b / mb * 100) / 100) + 'mb';
  if (abs >= kb) return (Math.round(b / kb * 100) / 100) + 'kb';
  return b + 'b';
}