RegExp _email = RegExp(
    r"^((([a-z]|\d|[!#\$%&'*\+\-\/=\?\^_`{\|}~]|[\u00A0-\uD7FF\uF900-\uFDCF\uFDF0-\uFFEF])+(\.([a-z]|\d|[!#\$%&'\*\+\-\/=\?\^_`{\|}~]|[\u00A0-\uD7FF\uF900-\uFDCF\uFDF0-\uFFEF])+)*)|((\x22)((((\x20|\x09)*(\x0d\x0a))?(\x20|\x09)+)?(([\x01-\x08\x0b\x0c\x0e-\x1f\x7f]|\x21|[\x23-\x5b]|[\x5d-\x7e]|[\u00A0-\uD7FF\uF900-\uFDCF\uFDF0-\uFFEF])|(\\([\x01-\x09\x0b\x0c\x0d-\x7f]|[\u00A0-\uD7FF\uF900-\uFDCF\uFDF0-\uFFEF]))))*(((\x20|\x09)*(\x0d\x0a))?(\x20|\x09)+)?(\x22)))@((([a-z]|\d|[\u00A0-\uD7FF\uF900-\uFDCF\uFDF0-\uFFEF])|(([a-z]|\d|[\u00A0-\uD7FF\uF900-\uFDCF\uFDF0-\uFFEF])([a-z]|\d|-|\.|_|~|[\u00A0-\uD7FF\uF900-\uFDCF\uFDF0-\uFFEF])*([a-z]|\d|[\u00A0-\uD7FF\uF900-\uFDCF\uFDF0-\uFFEF])))\.)+(([a-z]|[\u00A0-\uD7FF\uF900-\uFDCF\uFDF0-\uFFEF])|(([a-z]|[\u00A0-\uD7FF\uF900-\uFDCF\uFDF0-\uFFEF])([a-z]|\d|-|\.|_|~|[\u00A0-\uD7FF\uF900-\uFDCF\uFDF0-\uFFEF])*([a-z]|[\u00A0-\uD7FF\uF900-\uFDCF\uFDF0-\uFFEF])))$");

RegExp _phoneNumber = RegExp(r'^(84|0[3|5|7|8|9])+([0-9]{8})\b$');

RegExp _ipv4Maybe = RegExp(r'^(\d?\d?\d)\.(\d?\d?\d)\.(\d?\d?\d)\.(\d?\d?\d)$');
RegExp _ipv6 = RegExp(r'^::|^::1|^([a-fA-F0-9]{1,4}::?){1,7}([a-fA-F0-9]{1,4})$');

RegExp _creditCard = RegExp(
    r'^(?:4[0-9]{12}(?:[0-9]{3})?|5[1-5][0-9]{14}|6(?:011|5[0-9][0-9])[0-9]{12}|3[47][0-9]{13}|3(?:0[0-5]|[68][0-9])[0-9]{11}|(?:2131|1800|35\d{3})\d{11})$');

/// check if the string [str] is an email
bool isEmail(String str) {
  return _email.hasMatch(str.toLowerCase());
}

bool isPhoneNumber(String str) {
  return _phoneNumber.hasMatch(str.toLowerCase());
}

T? shift<T>(List<T> l) {
  if (l.isNotEmpty) {
    // ignore: always_specify_types
    final first = l.first;
    l.removeAt(0);
    return first;
  }
  return null;
}

/// check if the string [str] is a URL
///
/// * [protocols] sets the list of allowed protocols
/// * [requireTld] sets if TLD is required
/// * [requireProtocol] is a `bool` that sets if protocol is required for validation
/// * [allowUnderscore] sets if underscores are allowed
/// * [hostWhitelist] sets the list of allowed hosts
/// * [hostBlacklist] sets the list of disallowed hosts
bool isURL(String? str,
    {List<String?> protocols = const ['http', 'https', 'ftp'],
    bool requireTld = true,
    bool requireProtocol = false,
    bool allowUnderscore = false,
    List<String> hostWhitelist = const [],
    List<String> hostBlacklist = const []}) {
  if (str == null || str.isEmpty || str.length > 2083 || str.startsWith('mailto:')) {
    return false;
  }
  int port;
  String? protocol, auth, user;
  String host, hostname, portStr, path, query, hash;

  // check protocol
  var split = str.split('://');
  if (split.length > 1) {
    protocol = shift(split);
    if (!protocols.contains(protocol)) {
      return false;
    }
  } else if (requireProtocol == true) {
    return false;
  }
  str = split.join('://');

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

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

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

  // check auth type urls
  split = str!.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)!;
  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 (!isIP(host, null) &&
      !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;
}

/// check if the string [str] is IP [version] 4 or 6
///
/// * [version] is a String or an `int`.
bool isIP(String? str, int? version) {
  if (version == null) {
    return isIP(str, 4) || isIP(str, 6);
  } else if (version == 4) {
    if (!_ipv4Maybe.hasMatch(str!)) {
      return false;
    }
    var parts = str.split('.');
    parts.sort((a, b) => int.parse(a) - int.parse(b));
    return int.parse(parts[3]) <= 255;
  }
  return version == 6 && _ipv6.hasMatch(str!);
}

/// check if the string [str] is a fully qualified domain name (e.g. domain.com).
///
/// * [requireTld] sets if TLD is required
/// * [allowUnderscore] sets if underscores are allowed
bool isFQDN(String str, {bool requireTld = true, bool allowUnderscores = false}) {
  var parts = str.split('.');
  if (requireTld) {
    var tld = parts.removeLast();
    if (parts.isEmpty || !RegExp(r'^[a-z]{2,}$').hasMatch(tld)) {
      return false;
    }
  }

  for (var 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;
}

/// check if the string is a credit card
bool isCreditCard(String str) {
  var sanitized = str.replaceAll(RegExp(r'[^0-9]+'), '');
  if (!_creditCard.hasMatch(sanitized)) {
    return false;
  }

  // Luhn algorithm
  var sum = 0;
  String digit;
  var shouldDouble = false;

  for (var i = sanitized.length - 1; i >= 0; i--) {
    digit = sanitized.substring(i, (i + 1));
    var tmpNum = int.parse(digit);

    if (shouldDouble == true) {
      tmpNum *= 2;
      if (tmpNum >= 10) {
        sum += ((tmpNum % 10) + 1);
      } else {
        sum += tmpNum;
      }
    } else {
      sum += tmpNum;
    }
    shouldDouble = !shouldDouble;
  }

  return (sum % 10 == 0);
}

/// check if the string is a date
bool isDate(String str) {
  try {
    DateTime.parse(str);
    return true;
  } catch (e) {
    return false;
  }
}