/**
 * @packageDocumentation
 * @module harmony-crypto
 */

/**
 * Uses JS-native CSPRNG to generate a specified number of bytes.
 * @NOTE
 * this method throws if no PRNG is available.
 * @param {Number} bytes bytes number to generate
 * @return {String} ramdom hex string
 */
export const randomBytes = (bytes: number): string => {
  let randBz: number[] | Uint8Array;

  if (typeof window !== 'undefined' && window.crypto && window.crypto.getRandomValues) {
    randBz = window.crypto.getRandomValues(new Uint8Array(bytes));
  } else if (typeof require !== 'undefined') {
    randBz = require('crypto').randomBytes(bytes);
  } else {
    throw new Error('Unable to generate safe random numbers.');
  }

  let randStr = '';
  for (let i = 0; i < bytes; i += 1) {
    randStr += `00${randBz[i].toString(16)}`.slice(-2);
  }

  return randStr;
};