using System.Net;
using System.Net.Sockets;

namespace MoShiro.Protocol;

/// <summary>哪些地址算「公网上能拨进来的地址」：Agent 上报本机地址和面板自动识别共用同一套判断。</summary>
public static class PublicAddress
{
    public static bool IsPublicIpv4(IPAddress address)
    {
        if (address.AddressFamily != AddressFamily.InterNetwork)
        {
            return false;
        }

        byte[] b = address.GetAddressBytes();
        return !(b[0] is 0 or 10 or 127 or >= 224
            || (b[0] == 100 && b[1] is >= 64 and <= 127)
            || (b[0] == 169 && b[1] == 254)
            || (b[0] == 172 && b[1] is >= 16 and <= 31)
            || (b[0] == 192 && b[1] == 168)
            || (b[0] == 192 && b[1] == 0 && b[2] is 0 or 2)
            || (b[0] == 198 && b[1] is 18 or 19)
            || (b[0] == 198 && b[1] == 51 && b[2] == 100)
            || (b[0] == 203 && b[1] == 0 && b[2] == 113));
    }

    public static bool IsGlobalIpv6(IPAddress address)
    {
        if (address.AddressFamily != AddressFamily.InterNetworkV6 || address.IsIPv4MappedToIPv6)
        {
            return false;
        }

        byte[] b = address.GetAddressBytes();
        if ((b[0] & 0xE0) != 0x20)
        {
            return false;
        }

        // 2001:db8::/32 文档、2002::/16 6to4、2001::/32 Teredo
        return !((b[0] == 0x20 && b[1] == 0x01 && b[2] == 0x0d && b[3] == 0xb8)
            || (b[0] == 0x20 && b[1] == 0x02)
            || (b[0] == 0x20 && b[1] == 0x01 && b[2] == 0 && b[3] == 0));
    }
}