using System.Net;
using System.Net.NetworkInformation;
using System.Runtime.InteropServices;

namespace NWService
{
    public class NetworkService
    {
        [DllImport("iphlpapi.dll", ExactSpelling = true)]
        private static extern int SendARP(int dstIp, int srcIp, byte[] mac, ref int macLen);

        public static PingReply Ping(IPAddress iPAddress)
        {
            using (Ping ping = new Ping())
            {
                PingReply reply = ping.Send(iPAddress);
                return reply;
            }
        }

        public static List<PingReply> SearchByPing(IPAddress targetIPv4)
        {
            int workThreadsMin;
            int ioThreadsMin;

            ThreadPool.GetMinThreads(out workThreadsMin, out ioThreadsMin);
            ThreadPool.SetMinThreads(260, ioThreadsMin);

            List<PingReply> avaIPs = new List<PingReply>();
            List<Task> allTasks = new List<Task>();

            for (int i = 1 ; i <= 254 ; i++)
            {
                int hostPart = i;
                allTasks.Add(Task.Run(() => {
                    List<string> separateIP = targetIPv4.ToString().Split('.').ToList();
                    separateIP.RemoveAt(3);
                    separateIP.Add(hostPart.ToString());
                    string networkPart = string.Join(".", separateIP);
                    PingReply reply = Ping(IPAddress.Parse(networkPart));
                    if (reply != null && reply.Status == IPStatus.Success)
                    {
                        avaIPs.Add(reply);
                    }
                }));
            }

            Task t = Task.WhenAll(allTasks);
            try
            {
                t.Wait();
            }
            catch(Exception error)
            {
                Console.WriteLine(error);
            }

            return avaIPs;
        }

        public static List<DeviceInfo> SearchARP(IPAddress targetIPv4)
        {
            int workThreadsMin;
            int ioThreadsMin;

            ThreadPool.GetMinThreads(out workThreadsMin, out ioThreadsMin);
            ThreadPool.SetMinThreads(260, ioThreadsMin);

            List<DeviceInfo> avaIPs = new List<DeviceInfo>();

            List<Task> allTasks = new List<Task>();
            for (int i = 1 ; i <= 254; i++)
            {
                int hostPart = i;
                allTasks.Add(Task.Run(() => {
                    List<string> separateIP = targetIPv4.ToString().Split('.').ToList();
                    separateIP.RemoveAt(3);
                    separateIP.Add(hostPart.ToString());
                    string networkPart = string.Join(".", separateIP);

                    int IPBytes = BitConverter.ToInt32(IPAddress.Parse(networkPart).GetAddressBytes(), 0);
                    byte[] macAddressPointer = new byte[6];
                    int physicalAddressLength = macAddressPointer.Length;

                    // ARP
                    int ret = SendARP(IPBytes, 0, macAddressPointer, ref physicalAddressLength);
                    if (ret == 0)
                    {
                        DeviceInfo info = new DeviceInfo(IPAddress.Parse(networkPart), macAddressPointer);
                        avaIPs.Add(info);
                    }
                }));
            }

            Task t = Task.WhenAll(allTasks);
            try
            {
                t.Wait();
            }
            catch(Exception error)
            {
                Console.WriteLine(error);
            }

            return avaIPs;
        }

        public static IEnumerable<IPAddress> GetLocalIPv4()
        {
            List<IPAddress> list = new List<IPAddress>();
            NetworkInterface[] nics = NetworkInterface.GetAllNetworkInterfaces();
            foreach (NetworkInterface nic in nics)
            {
                if (nic.OperationalStatus == OperationalStatus.Up
                && nic.NetworkInterfaceType != NetworkInterfaceType.Loopback
                && nic.NetworkInterfaceType != NetworkInterfaceType.Tunnel)
                {
                    UnicastIPAddressInformationCollection unicast = nic.GetIPProperties().UnicastAddresses;
                    foreach (UnicastIPAddressInformation ip in unicast)
                    {
                        if (ip.Address.AddressFamily == System.Net.Sockets.AddressFamily.InterNetwork)
                        {
                            list.Add(ip.Address);
                        }
                    }
                }
            }
            return list;
        }
    }
}