export function urlBase64Decode(str: string): string {
  let output = str.replace(/-/g, '+').replace(/_/g, '/');
  switch (output.length % 4) {
    case 0: {
      break;
    }
    case 2: {
      output += '==';
      break;
    }
    case 3: {
      output += '=';
      break;
    }
    default: {
      throw new Error(`'atob' failed: The string to be decoded is not correctly encoded.`);
    }
  }
  return b64DecodeUnicode(output);
}

function b64decode(str: string): string {
  const chars = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=';
  let output = '';

  str = String(str).replace(/=+$/, '');

  for (
    // initialize result and counters
    // tslint:disable:no-conditional-assignment binary-expression-operand-order
    // tslint:disable-next-line:no-any
    let bc = 0, bs: any, buffer: any, idx = 0;
    // get next character
    (buffer = str.charAt(idx++));
    // character found in table? initialize bit storage and add its ascii value;
    ~buffer &&
    // tslint:disable-next-line: ban-comma-operator
    ((bs = bc % 4 ? bs * 64 + buffer : buffer),
      // and if not first of each 4 characters,
      // convert the first 8 bits to one ascii character
    bc++ % 4)
      ? (output += String.fromCharCode(255 & (bs >> ((-2 * bc) & 6))))
      : 0
  ) {
    // try to find character in table (0-63, not found => -1)
    buffer = chars.indexOf(buffer);
  }
  return output;
}

// https://developer.mozilla.org/en/docs/Web/API/WindowBase64/Base64_encoding_and_decoding#The_Unicode_Problem
function b64DecodeUnicode(str: string) {
  return decodeURIComponent(
    Array.prototype.map
      .call(b64decode(str), (c: string) => {
        return '%' + ('00' + c.charCodeAt(0).toString(16)).slice(-2);
      })
      .join('')
  );
}