isFQDN function
check if the string str
is a fully qualified
domain name (e.g. domain.com).
requireTld
sets if TLD is requiredallowUnderscores
sets if underscores are allowed
Implementation
bool isFQDN(String str,
{bool requireTld = true, bool allowUnderscores = false}) {
final parts = str.split('.');
if (requireTld) {
final tld = parts.removeLast();
if (parts.isEmpty || !RegExp(r'^[a-z]{2,}$').hasMatch(tld)) {
return false;
}
}
for (final part in parts) {
if (allowUnderscores) {
if (part.contains('__')) {
return false;
}
}
if (!RegExp(r'^[a-z\\u00a1-\\uffff0-9-]+$').hasMatch(part)) {
return false;
}
if (part[0] == '-' ||
part[part.length - 1] == '-' ||
part.contains('---')) {
return false;
}
}
return true;
}