using System;
using System.Collections.Generic;
using System.Linq;
using System.Net.NetworkInformation;
using System.Net.Sockets;
using System.Net;
using System.Text;
using System.Threading.Tasks;



namespace ServerCore;


//=============================================================================================
// 네트워크 관련 각종 지원 함수
//
// author : kangms
// 
//=============================================================================================
public static class NetworkHelper
{
    private static string m_ip_address_ipv4 = string.Empty;

    public static bool parseIPnPort(this string _this, UInt16 defaultPort, out string host, out UInt16 port)
    {
        host = string.Empty;
        port = 0;

        var splitted_value = _this.Split(":");
        if (2 == splitted_value.Length)
        {
            host = splitted_value[0];
            port = Convert.ToUInt16(splitted_value[1].Trim());
        }
        else if (1 == splitted_value.Length)
        {
            host = splitted_value[0];
            port = defaultPort;
        }
        else
        {
            return false;
        }

        return true;
    }

    public static string getEthernetLocalIPv4()
    {
        if(true == m_ip_address_ipv4.isNullOrWhiteSpace())
        {
            m_ip_address_ipv4 = NetworkHelper.getLocalIPAddress(new[] { NetworkInterfaceType.Ethernet }, AddressFamily.InterNetwork);
        }

        return m_ip_address_ipv4;
    }

    public static string getLocalIPAddress(IEnumerable<NetworkInterfaceType> networkTypes, AddressFamily addressFamiltyType)
    {
        string return_address = string.Empty;

        // Get a list of all network interfaces (including Ethernet, Wi-Fi, etc.)
        NetworkInterface[] networkInterfaces = NetworkInterface.GetAllNetworkInterfaces();

        foreach (NetworkInterface network in networkInterfaces)
        {
            // Check if the network type matches the given types
            if (false == networkTypes.Contains(network.NetworkInterfaceType))
                continue;

            // Read the IP configuration for each network
            IPInterfaceProperties properties = network.GetIPProperties();

            // Check if the network interface is up and is not a virtual/pseudo interface
            if (   network.OperationalStatus != OperationalStatus.Up
                || true == network.Description.ToLower().Contains("virtual")
                || true == network.Description.ToLower().Contains("pseudo"))
            {
                continue;
            }

            // Each network interface may have multiple IP addresses
            foreach (IPAddressInformation address in properties.UnicastAddresses)
            {
                if (   address.Address.AddressFamily == addressFamiltyType)
                {
                    if (false == IPAddress.IsLoopback(address.Address))
                    {
                        return_address = address.Address.ToString();
                        break; // Exit after first non-loopback address found
                    }
                }
            }

            if (false == string.IsNullOrEmpty(return_address)) { break; }
        }

        if (string.IsNullOrEmpty(return_address))
        {
            // If no address is found, return appropriate loopback address based on the available version
            if (true == isIPv6Available(networkTypes))
            {
                return_address = "::1";  // Fallback to IPv6 loopback address if no address found
            }
            else
            {
                return_address = "127.0.0.1";  // Fallback to IPv4 loopback address if no address found
            }
        }

        return return_address;
    }

    // Private IP 범위 체크 (네트워크 범위도 아규먼트로 받기)
    public static bool isPrivateIP(string ipAddress, string[] privateRanges)
    {
        if (IPAddress.TryParse(ipAddress, out IPAddress? ip))
        {
            if (ip.AddressFamily == System.Net.Sockets.AddressFamily.InterNetwork)
            {
                // IPv4 처리
                var octets = ip.GetAddressBytes();
                foreach (var range in privateRanges)
                {
                    if(false == range.Contains(":"))
                    {
                        // IPv4 체크
                        if (isInRangeIPv4(octets, range))
                        {
                            return true;
                        }
                    }
                }
            }
            else if (ip.AddressFamily == System.Net.Sockets.AddressFamily.InterNetworkV6)
            {
                // IPv6 처리
                var octets = ip.GetAddressBytes();
                foreach (var range in privateRanges)
                {
                    if (range.Contains(":"))
                    {
                        if (isInRangeIPv6(octets, range))
                        {
                            return true;
                        }
                    }
                }
            }
        }

        return false; // Public IP
    }

    // IPv4 주소가 특정 대역에 포함되는가
    public static bool isInRangeIPv4(byte[] ipAddress, string range)
    {
        var parts = range.Split('/');
        var network = IPAddress.Parse(parts[0]);
        int prefixLength = int.Parse(parts[1]);

        var networkBytes = network.GetAddressBytes();
        int mask = 32 - prefixLength;

        for (int i = 0; i < 4; i++)
        {
            if ((networkBytes[i] & (255 << mask)) != (ipAddress[i] & (255 << mask)))
            {
                return false;
            }
        }

        return true;
    }

    // IPv6 주소가 특정 대역에 포함되는가
    public static bool isInRangeIPv6(byte[] ipAddress, string range)
    {
        var parts = range.Split('/');
        var network = IPAddress.Parse(parts[0]);
        int prefixLength = int.Parse(parts[1]);

        var networkBytes = network.GetAddressBytes();
        int mask = 128 - prefixLength;

        for (int i = 0; i < 16; i++)
        {
            if ((networkBytes[i] & (255 << mask)) != (ipAddress[i] & (255 << mask)))
            {
                return false;
            }
        }

        return true;
    }

    private static bool isIPv6Available(IEnumerable<NetworkInterfaceType> networkTypes)
    {
        // Check if any network interface of the specified types has an IPv6 address
        NetworkInterface[] networkInterfaces = NetworkInterface.GetAllNetworkInterfaces();

        foreach (var network in networkInterfaces)
        {
            // Check if the network type matches the given types
            if (!networkTypes.Contains(network.NetworkInterfaceType))
                continue;

            IPInterfaceProperties properties = network.GetIPProperties();

            // Check if this network interface has any IPv6 address
            foreach (var address in properties.UnicastAddresses)
            {
                if (address.Address.AddressFamily == AddressFamily.InterNetworkV6)
                {
                    return true;  // Found an IPv6 address
                }
            }
        }

        return false;  // No IPv6 address found
    }
}