isURL method

Implementation

bool isURL(
  String? value, {
  List<String?> protocols = const <String?>['http', 'https', 'ftp'],
  bool requireTld = true,
  bool requireProtocol = false,
  bool allowUnderscore = false,
  List<String> hostWhitelist = const <String>[],
  List<String> hostBlacklist = const <String>[],
}) {
  if (value == null ||
      value.isEmpty ||
      value.length > _maxUrlLength ||
      value.startsWith('mailto:')) {
    return false;
  }
  final int port;
  final String? protocol;
  final String? auth;
  final String user;
  final String host;
  final String hostname;
  final String portStr;
  final String path;
  final String query;
  final String hash;

  // check protocol
  List<String> split = value.split('://');
  if (split.length > 1) {
    protocol = shift(split).toLowerCase();
    if (!protocols.contains(protocol)) {
      return false;
    }
  } else if (requireProtocol == true) {
    return false;
  }
  final String str1 = split.join('://');

  // check hash
  split = str1.split('#');
  final String str2 = shift(split);
  hash = split.join('#');
  if (hash.isNotEmpty && RegExp(r'\s').hasMatch(hash)) {
    return false;
  }

  // check query params
  split = str2.split('?');
  final String str3 = shift(split);
  query = split.join('?');
  if (query.isNotEmpty && RegExp(r'\s').hasMatch(query)) {
    return false;
  }

  // check path
  split = str3.split('/');
  final String str4 = shift(split);
  path = split.join('/');
  if (path.isNotEmpty && RegExp(r'\s').hasMatch(path)) {
    return false;
  }

  // check auth type urls
  split = str4.split('@');
  if (split.length > 1) {
    auth = shift(split);
    if (auth?.contains(':') ?? false) {
      user = shift(auth!.split(':'));
      if (!RegExp(r'^\S+$').hasMatch(user)) {
        return false;
      }
      if (!RegExp(r'^\S*$').hasMatch(user)) {
        return false;
      }
    }
  }

  // check hostname
  hostname = split.join('@');
  split = hostname.split(':');
  host = shift(split).toLowerCase();
  if (split.isNotEmpty) {
    portStr = split.join(':');
    try {
      port = int.parse(portStr, radix: 10);
    } catch (e) {
      return false;
    }
    if (!RegExp(r'^[0-9]+$').hasMatch(portStr) || port <= 0 || port > 65535) {
      return false;
    }
  }

  if (!_ipValidator.isIP(host, 0) &&
      !isFQDN(
        host,
        requireTld: requireTld,
        allowUnderscores: allowUnderscore,
      ) &&
      host != 'localhost') {
    return false;
  }

  if (hostWhitelist.isNotEmpty && !hostWhitelist.contains(host)) {
    return false;
  }

  if (hostBlacklist.isNotEmpty && hostBlacklist.contains(host)) {
    return false;
  }

  return true;
}