using System;
using System.Data;
using System.Data.SqlClient;
using Microsoft.SqlServer.Server;
using System.Net;
using System.Collections.Generic;
using System.Text;
using System.Data.SqlTypes;
using System.Numerics;

namespace SqlCustomFunctions
{
  public static class IPFunctions
  {
    [Microsoft.SqlServer.Server.SqlFunction()]
    static public byte[] ipIPV6toBIN16(SqlString IP)
    {
      BigInteger rv = new BigInteger();
      try
      {
        IPAddress ipAddress = null;//IPAddress.TryParse(IPV6Address, out _);

        if (IPAddress.TryParse(IP.ToString(), out ipAddress) && ipAddress.AddressFamily == System.Net.Sockets.AddressFamily.InterNetworkV6)
        {
          byte[] addressBytes = ipAddress.GetAddressBytes();

          // flip big-endian(network order) to little-endian
          if (BitConverter.IsLittleEndian)
            Array.Reverse(addressBytes);

          rv = new BigInteger(addressBytes);
        }
      }
      catch //(Exception ex)
      {
        rv = 0;
      }
      return rv.ToByteArray();
    }

    [Microsoft.SqlServer.Server.SqlFunction()]
    static public SqlString ipBIN16toIPV6(byte[] IP)
    {
      SqlString rv = string.Empty;
      try
      {
        byte[] paddedBytes = new byte[16];
        if (IP.Length > 16)
        {
          // Truncate to 16 bytes (take the most significant bytes for IPv6)
          Array.Copy(IP, IP.Length - 16, paddedBytes, 0, 16);
        }
        else if (IP.Length < 16)
        {
          // Pad with leading zeros (for smaller numbers)
          Array.Copy(IP, 0, paddedBytes, 16 - IP.Length, IP.Length);
        }
        else
        {
          Array.Copy(IP, paddedBytes, 16);
        }

        // flip big-endian(network order) to little-endian
        if (BitConverter.IsLittleEndian)
          Array.Reverse(paddedBytes);

        IPAddress ipAddress = new IPAddress(paddedBytes);
        rv = ipAddress.ToString();
      }
      catch //(Exception ex)
      {
        rv = string.Empty;
      }
      return rv;
    }

    [Microsoft.SqlServer.Server.SqlFunction()]
    static public byte[] ipIPV4toBIN4(SqlString IP)
    {
      var rv = new byte[] { 0, 0, 0, 0 };

      try
      {
        IPAddress ipAddress = null;

        if (IPAddress.TryParse(IP.ToString(), out ipAddress) && ipAddress.AddressFamily == System.Net.Sockets.AddressFamily.InterNetwork)
        {
          byte[] addressBytes = ipAddress.GetAddressBytes();

          // flip big-endian(network order) to little-endian
          // -- Can't do this, because it would break legacy code! --
          //if (BitConverter.IsLittleEndian)
          //  Array.Reverse(addressBytes);

          rv = addressBytes; //BitConverter.ToUInt32(addressBytes, 0);
        }
      }
      catch //(Exception)
      {
        rv = new byte[] { 0, 0, 0, 0 };
      }

      return rv;
    }
    [Microsoft.SqlServer.Server.SqlFunction()]
    static public SqlString ipBIN4toIPV4(byte[] IP)
    {
      SqlString rv = string.Empty;
      try
      {
        byte[] paddedBytes = new byte[4];
        if (IP.Length > 4)
        {
          // Truncate to 16 bytes (take the most significant bytes for IPv6)
          Array.Copy(IP, IP.Length - 4, paddedBytes, 0, 4);
        }
        else if (IP.Length < 4)
        {
          // Pad with leading zeros (for smaller numbers)
          Array.Copy(IP, 0, paddedBytes, 4 - IP.Length, IP.Length);
        }
        else
        {
          Array.Copy(IP, paddedBytes, 4);
        }

        // flip big-endian(network order) to little-endian
        // -- Can't do this, because it would break legacy code! --
        //if (BitConverter.IsLittleEndian)
        //  Array.Reverse(paddedBytes);

        IPAddress ipAddress = new IPAddress(paddedBytes);
        rv = ipAddress.ToString();
      }
      catch //(Exception ex)
      {
        rv = string.Empty;
      }
      return rv;
    }
  }
}