expandIPv6 static method
Returns the expanded form for ip.
Implementation
static String? expandIPv6(String ip) {
if (!isIPv6(ip)) return null;
final bytes = InternetAddress(ip).rawAddress;
final parts = [for (var b in bytes) b.toRadixString(16).padLeft(2, '0')];
var result = parts.join('');
result = result.replaceAllMapped(RegExp(r'(.{4})'), (m) => '${m[1]}:');
return result.substring(0, result.length - 1);
}