Add pref utilities

lib/utils/validators.dart

@@ -3,7 +3,16 @@ final _urlRegex = RegExp(
   r"^(?:(?:(?:https?|ftp):)?\/\/)(?:\S+(?::\S*)?@)?(?:(?!(?:10|127)(?:\.\d{1,3}){3})(?!(?:169\.254|192\.168)(?:\.\d{1,3}){2})(?!172\.(?:1[6-9]|2\d|3[0-1])(?:\.\d{1,3}){2})(?:[1-9]\d?|1\d\d|2[01]\d|22[0-3])(?:\.(?:1?\d{1,2}|2[0-4]\d|25[0-5])){2}(?:\.(?:[1-9]\d?|1\d\d|2[0-4]\d|25[0-4]))|(?:(?:[a-z0-9\u00a1-\uffff][a-z0-9\u00a1-\uffff_-]{0,62})?[a-z0-9\u00a1-\uffff]\.)+(?:[a-z\u00a1-\uffff]{2,}\.?))(?::\d{2,5})?(?:[/?#]\S*)?$",
 );
 
+/// https://stackoverflow.com/a/12968117
+final _portRegex = RegExp(
+  r"^([1-9][0-9]{0,3}|[1-5][0-9]{4}|6[0-4][0-9]{3}|65[0-4][0-9]{2}|655[0-2][0-9]|6553[0-5])$",
+);
+
 /// https://stackoverflow.com/questions/3809401/what-is-a-good-regular-expression-to-match-a-url/3809435#3809435
 bool isUrl(String input) {
   return _urlRegex.hasMatch(input.trim().toLowerCase());
 }
+
+bool isPort(String input) {
+  return _portRegex.hasMatch(input);
+}