pingerino/Utilities/ValidationHelper.cs

using System;
using System.Net;
using System.Text.RegularExpressions;

namespace Pingerino.Utilities
{
    public static class ValidationHelper
    {
        private static readonly Regex IpAddressRegex = new Regex(
            @"^(?:(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.){3}(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)$",
            RegexOptions.Compiled);

        private static readonly Regex HostnameRegex = new Regex(
            @"^(?:[a-zA-Z0-9](?:[a-zA-Z0-9-]{0,61}[a-zA-Z0-9])?\.)*[a-zA-Z0-9](?:[a-zA-Z0-9-]{0,61}[a-zA-Z0-9])?$",
            RegexOptions.Compiled);

        public static bool IsValidIpAddress(string ipAddress)
        {
            if (string.IsNullOrWhiteSpace(ipAddress))
                return false;

            return IPAddress.TryParse(ipAddress, out _) || IpAddressRegex.IsMatch(ipAddress);
        }

        public static bool IsValidHostname(string hostname)
        {
            if (string.IsNullOrWhiteSpace(hostname))
                return false;

            if (hostname.Length > 253)
                return false;

            return HostnameRegex.IsMatch(hostname);
        }

        public static bool IsValidIpAddressOrHostname(string address)
        {
            return IsValidIpAddress(address) || IsValidHostname(address);
        }

        public static bool IsValidPingInterval(string intervalText, out int interval)
        {
            interval = 0;
            
            if (string.IsNullOrWhiteSpace(intervalText))
                return false;

            if (!int.TryParse(intervalText, out interval))
                return false;

            return interval >= 100 && interval <= 60000; // 100ms to 60 seconds
        }

        public static bool IsValidPingInterval(int interval)
        {
            return interval >= 100 && interval <= 60000;
        }

        public static string SanitizeInput(string input)
        {
            if (string.IsNullOrEmpty(input))
                return string.Empty;

            return input.Trim();
        }

        public static string GetValidationErrorMessage(string fieldName, string value)
        {
            if (string.IsNullOrWhiteSpace(value))
                return $"{fieldName} cannot be empty.";

            switch (fieldName.ToLower())
            {
                case "ip address":
                case "ipaddress":
                    if (!IsValidIpAddressOrHostname(value))
                        return "Please enter a valid IP address or hostname.";
                    break;

                case "interval":
                case "ping interval":
                    if (!IsValidPingInterval(value, out _))
                        return "Ping interval must be between 100 and 60000 milliseconds.";
                    break;
            }

            return null;
        }
    }
}