using System;
using System.Linq;
using System.Net;
using System.Threading;
using System.Threading.Tasks;
using SharpPcap;
using PacketDotNet;

namespace LanDiscovery.Services
{
    public class PassiveDiscoveryResult
    {
        public required IPAddress Ip { get; set; }
        public required string MacAddress { get; set; }
    }

    public class ArpPassiveSniffer
    {
        private ICaptureDevice? _device;
        private Action<PassiveDiscoveryResult>? _onDiscovery;
        private bool _isCapturing;

        public bool IsSupported { get; private set; } = true;
        public string Status { get; private set; } = "Ready";

        public void Start(string nicId, Action<PassiveDiscoveryResult> onDiscovery)
        {
            try
            {
                _onDiscovery = onDiscovery;

                var devices = CaptureDeviceList.Instance;
                if (devices.Count == 0)
                {
                    Status = "No Capture Devices found (Npcap missing?)";
                    IsSupported = false;
                    return;
                }

                _device = null;
                foreach(var dev in devices)
                {
                    if (dev.Name.Contains(nicId) || dev.Description.Contains(nicId))
                    {
                        _device = dev;
                        break;
                    }
                }
                
                if (_device == null) return;

                _device.OnPacketArrival += OnPacketArrival;
                _device.Open(DeviceModes.Promiscuous, 1000);
                _device.Filter = "arp";
                _device.StartCapture();
                _isCapturing = true;
                Status = "Running";
            }
            catch (Exception ex)
            {
                IsSupported = false;
                Status = $"Failed: {ex.Message}";
            }
        }
        
        public void StartByIp(string ipAddress, Action<PassiveDiscoveryResult> onDiscovery)
        {
             try
            {
                _onDiscovery = onDiscovery;
                var devices = CaptureDeviceList.Instance;
                
                foreach(var dev in devices)
                {
                    // Check addresses by casting to LibPcapLiveDevice if possible
                    if (dev is SharpPcap.LibPcap.LibPcapLiveDevice pcapDev)
                    {
                         foreach(var addr in pcapDev.Addresses)
                         {
                             if (addr.Addr != null && addr.Addr.ipAddress != null && addr.Addr.ipAddress.ToString() == ipAddress)
                             {
                                 _device = dev;
                                 goto Found;
                             }
                         }
                    }
                }
                
                Status = $"No Pcap device found for IP {ipAddress}";
                return;

            Found:
                if (_device != null)
                {
                    _device.OnPacketArrival += OnPacketArrival;
                    _device.Open(DeviceModes.Promiscuous | DeviceModes.MaxResponsiveness);
                    _device.Filter = "arp";
                    _device.StartCapture();
                    _isCapturing = true;
                    Status = "Running";
                }

            }
            catch (Exception ex)
            {
                 IsSupported = false;
                 Status = $"Capture Init Failed: {ex.Message}";
            }
        }

        private void OnPacketArrival(object sender, PacketCapture e)
        {
            try 
            {
                var packet = Packet.ParsePacket(e.GetPacket().LinkLayerType, e.GetPacket().Data);
                var arpPacket = packet.Extract<ArpPacket>();

                if (arpPacket != null)
                {
                    var senderIp = arpPacket.SenderProtocolAddress;
                    var senderMac = arpPacket.SenderHardwareAddress;
                    
                    if (senderIp != null && senderMac != null)
                    {
                        _onDiscovery?.Invoke(new PassiveDiscoveryResult
                        {
                            Ip = senderIp,
                            MacAddress = senderMac.ToString()
                        });
                    }
                }
            }
            catch {}
        }

        public void Stop()
        {
            if (_isCapturing && _device != null)
            {
                try { _device.StopCapture(); _device.Close(); } catch {}
                _isCapturing = false;
                Status = "Stopped";
            }
        }
    }
}