using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Net;
using System.Net.NetworkInformation;
using System.Net.Sockets;
using System.Text;
using System.Text.RegularExpressions;
using System.Threading;
using System.Threading.Tasks;
using System.Xml;
using System.Xml.Serialization;

namespace EC.Onvif.RemoteDiscovery
{
	public class Discovery
	{
		#region Discover

		/// <summary>
		/// Discover new onvif devices on the network
		/// </summary>
		/// <param name="timeout">A timeout in seconds to wait for onvif devices</param>
		/// <param name="cancellationToken">A cancellation token</param>
		/// <returns>a list of <see cref="DiscoveryDevice"/></returns>
		/// <remarks>Use the <see cref="Discover(int, Action{DiscoveryDevice}, CancellationToken)"/>
		///  overload (with an action as a parameter) if you want to retrieve devices as they reply.</remarks>
		public async Task<IEnumerable<DiscoveryDevice>> DiscoverByAdapter(IEnumerable<NetworkInterface> adapterList,
				int timeout, CancellationToken cancellationToken = default)
		{
			List<DiscoveryDevice> deviceList = new();
			await Discover(adapterList, d => deviceList.Add(d), timeout, cancellationToken);
			deviceList.Sort((a, b) => CastIp(a.Address).CompareTo(CastIp(b.Address)));
			return deviceList;
		}

		/// <summary>
		/// Discover new onvif devices on the network
		/// </summary>
		/// <param name="timeout">A timeout in seconds to wait for onvif devices</param>
		/// <param name="cancellationToken">A cancellation token</param>
		/// <returns>a list of <see cref="DiscoveryDevice"/></returns>
		/// <remarks>Use the <see cref="Discover(int, Action{DiscoveryDevice}, CancellationToken)"/>
		///  overload (with an action as a parameter) if you want to retrieve devices as they reply.</remarks>
		public async Task<IEnumerable<DiscoveryDevice>> DiscoverAll(int timeout, CancellationToken cancellationToken = default)
		{
			IEnumerable<NetworkInterface> adapterList = OnvifUdpClient.GetVaildNetworkAdapters();
			IEnumerable<DiscoveryDevice> deviceList = await DiscoverByAdapter(adapterList, timeout, cancellationToken);
			return deviceList;
		}

		/// <summary>
		/// Discover new onvif devices on the network passing a callback
		/// to retrieve devices as they reply
		/// </summary>
		/// <param name="onDeviceDiscovered">A method that is called each time a new device replies.</param>
		/// <param name="timeout">A timeout in seconds to wait for onvif devices</param>
		/// <param name="cancellationToken">A cancellation token</param>
		/// <returns>The Task to be awaited</returns>
		private async Task Discover(IEnumerable<NetworkInterface> adapterList, Action<DiscoveryDevice> onDeviceDiscovered,
				int timeout, CancellationToken cancellationToken = default)
		{
			IEnumerable<OnvifUdpClient> clientList = OnvifUdpClient.CreateClientList(adapterList);
			if (!clientList.Any())
			{
				throw new Exception("Missing valid NetworkInterfaces, UdpClients could not be created");
			}
			Task[] discoveries = clientList.Select(client => Discover(client, onDeviceDiscovered, timeout, cancellationToken)).ToArray();
			await Task.WhenAll(discoveries);
		}

		private async Task Discover(OnvifUdpClient client, Action<DiscoveryDevice> onDeviceDiscovered, int timeout, CancellationToken cancellationToken = default)
		{
			Guid messageId = Guid.NewGuid();
			List<UdpReceiveResult> responseList = new();
			CancellationTokenSource cts = new(TimeSpan.FromSeconds(timeout));

			try
			{
				await OnvifUdpClient.SendProbe(client, messageId);
				while (true)
				{
					if (client.IsClosed) { return; }
					if (cts.IsCancellationRequested || cancellationToken.IsCancellationRequested) { break; }
					try
					{
						UdpReceiveResult response = await client.ReceiveAsync().WithCancellation(cancellationToken).WithCancellation(cts.Token);
						if (responseList.Exists(resp => resp.RemoteEndPoint.Address.Equals(response.RemoteEndPoint.Address))) { continue; }
						responseList.Add(response);
						DiscoveryDevice discoveredDevice = ProcessResponse(response, messageId);
						if (discoveredDevice != null)
						{
							await Task.Run(() => onDeviceDiscovered(discoveredDevice), cancellationToken);
						}
					}
					catch (OperationCanceledException)
					{
						// Either the user canceled the action or the timeout has fired
					}
					catch (Exception)
					{
						// we catch all exceptions !
						// Something might be bad in the response of a camera when call ReceiveAsync (BeginReceive in socket) fail
					}
				}
			}
			finally
			{
				client.Close();
			}
		}

		#endregion Discover

		#region Discover Helper

		private DiscoveryDevice ProcessResponse(UdpReceiveResult response, Guid messageId)
		{
			if (response.Buffer == null) { return null; }
			string strResponse = Encoding.UTF8.GetString(response.Buffer);
			XmlProbeReponse xmlResponse = DeserializeResponse(strResponse);
			if (xmlResponse.Header.RelatesTo.Contains(messageId.ToString())
				&& xmlResponse.Body.ProbeMatches.Any()
				&& !string.IsNullOrEmpty(xmlResponse.Body.ProbeMatches[0].Scopes))
			{
				return CreateDevice(xmlResponse.Body.ProbeMatches[0], response.RemoteEndPoint);
			}
			return null;
		}

		private XmlProbeReponse DeserializeResponse(string xml)
		{
			XmlSerializer serializer = new(typeof(XmlProbeReponse));
			XmlReaderSettings settings = new();
			using StringReader textReader = new(xml);
			using XmlReader xmlReader = XmlReader.Create(textReader, settings);
			return (XmlProbeReponse)serializer.Deserialize(xmlReader);
		}

		private DiscoveryDevice CreateDevice(ProbeMatch probeMatch, IPEndPoint remoteEndpoint)
		{
			string scopes = probeMatch.Scopes;
			DiscoveryDevice discoveryDevice = new();
			discoveryDevice.Address = remoteEndpoint.Address.ToString();
			discoveryDevice.Model = Regex.Match(scopes, "(?<=hardware/).*?(?= )")?.Value;
			discoveryDevice.Mfr = ParseMfrFromScopes(scopes);
			discoveryDevice.XAdresses = ConvertToList(probeMatch.XAddrs);
			discoveryDevice.Types = ConvertToList(probeMatch.Types);
			return discoveryDevice;
		}

		private string ParseMfrFromScopes(string scopes)
		{
			string name = Regex.Match(scopes, "(?<=name/).*?(?= )")?.Value;
			if (!string.IsNullOrEmpty(name)) { return name; }
			string mfr = Regex.Match(scopes, "(?<=mfr/).*?(?= )")?.Value;
			if (!string.IsNullOrEmpty(mfr)) { return mfr; }
			return string.Empty;
		}

		private List<string> ConvertToList(string spacedListString)
		{
			string[] strings = spacedListString.Split(null);
			List<string> list = new();
			strings.ToList().ForEach(str => list.Add(str.Trim()));
			return list;
		}

		private long CastIp(string ip)
		{
			byte[] addressBytes = IPAddress.Parse(ip).GetAddressBytes();
			if (addressBytes.Length != 4)
			{
				return 0;
				throw new ArgumentException("Must be an IPv4 address");
			}
			uint networkOrder = BitConverter.ToUInt32(addressBytes, 0);
			return networkOrder;
			//byte[] addressBytes = address.GetAddressBytes();
			//int networkOrder = BitConverter.ToInt32(addressBytes, 0);
			//return (uint)IPAddress.NetworkToHostOrder(networkOrder);
		}

		#endregion Discover Helper
	}
}