Dart Base64 encode decode with validation

import 'dart:convert';

String encodeBase64(List<int> bytes) => base64Encode(bytes);

List<int> decodeBase64(String text) {
  final cleaned = text.replaceAll(RegExp(r'\s'), '');
  final padded = cleaned.padRight((cleaned.length + 3) ~/ 4 * 4, '=');
  if (!RegExp(r'^[A-Za-z0-9+/]*={0,2}$').hasMatch(padded)) {
    throw const FormatException('Invalid Base64 characters');
  }
  try {
    return base64Decode(padded);
  } on FormatException {
    throw const FormatException('Invalid Base64 payload or length');
  }
}

String decodeBase64Text(String text) => utf8.decode(decodeBase64(text), allowMalformed: false);