Flutter/Dart - Username Validation - Checking for bad words - flutter

Question

In the code below, we have a method which is called whenever the user clicks on the 'Sign Up' button (on our Authentication screen). Currently this method has two different conditions, if it doesn't pass these conditions, the user won't be able to sign up.
We'd also like to add one more condition here. We have an array of strings that shouldn't be accepted as usernames (bad words). But if the bad word is used in combination with other letters or numbers, it should also not be accepted.
Example of a "bad word": Charlie
That means Charlie shouldn't be accepted as a username but there's also potential for millions of other combinations, examples: Charlieee, Charlie124342, Charlie6648, 213charlie, ch1chaRliE32, etc. etc.
So would there be any simple method to check whether the username entered contains any of the bad words listed in an array, regardless of whether its used in combination with other characters or not?
Future<String?> usernameValidator({required String? username}) async {
// Validates username complexity
bool isUsernameComplex(String? text) {
final String _text = (text ?? "");
String? p = r"^(?=(.*[ #$!%*?&=_+/#^.~`]))";
RegExp regExp = RegExp(p);
return regExp.hasMatch(_text);
}
final String _text = (username ?? "");
// Complexity check
if (isUsernameComplex(_text)) {
return "Username can only contain letters and numbers.";
}
// Length check
else if (_text.length < 3 || _text.length > 16) {
return "Username must be between 3-16 characters long.";
}
return null;
}

Answer 1

see if this helps:
List<String> badwords = [
'charlie',
'another_badword',
];
List<String> input = [
'Charlieee',
'Charlie124342',
'Charlie6648',
'213charlie',
'ch1chaRliE32',
'spaghetti',
];
input.forEach((text) {
final bwIndex = badwords.indexWhere(
(badword) => text.toLowerCase().contains(badword),
);
if (bwIndex != -1) {
print('$text is bad word, similar to ${badwords[bwIndex]}');
} else {
print('$text is not a bad word');
}
});