"use strict";

// var b64Alphabet = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=';

function toCharCode(ch) {
  return ch.charCodeAt(0);
}

function isValidB64Char(charCode) {
  return charCode >= toCharCode('A') && charCode <= toCharCode('Z')
      || charCode >= toCharCode('a') && charCode <= toCharCode('z')
      || charCode >= toCharCode('0') && charCode <= toCharCode('9')
      || charCode === toCharCode('+')
      || charCode === toCharCode('/')
      || charCode === toCharCode('=');
}

function atob(str) {
  for (var idx in str)
    if (!isValidB64Char(str.charCodeAt(idx)))
      throw new Error('Invalid character ' + str.charAt(idx) + ' in base64 String');
  return Buffer.from(str, 'base64').toString('binary');
}

module.exports = atob.atob = atob;