using Google.Protobuf;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Net;
using System.Net.NetworkInformation;
using System.Net.Sockets;
using System.Text;
using System.Threading.Tasks;
using System.Timers;
using Tango.Core;
using Tango.Core.ExtensionMethods;
using Tango.Logging;
using Tango.PMR.Discovery;
using Tango.PMR.Integration;
using Tango.Transport.Helpers;
using Tango.Transport.Servers;

namespace Tango.Transport.Discovery
{
    /// <summary>
    /// Represents UDP discovery service broadcasting a discovery message of type <see cref="BasicDiscoveryMessage"/>.
    /// </summary>
    /// <seealso cref="Tango.Transport.Discovery.IDiscoveryService{Tango.PMR.Discovery.BasicDiscoveryMessage}" />
    public class UdpDiscoveryService<DiscoveryMessage> : ExtendedObject, IDiscoveryService<DiscoveryMessage> where DiscoveryMessage : IMessage
    {
        private Timer _timer;
        private TcpServer _tcpValidationServer;

        /// <summary>
        /// Occurs before broadcasting the discovery message and gives a chance to modify the packet message.
        /// </summary>
        public event EventHandler<DiscoveryMessage> BeforeBroadcasting;

        /// <summary>
        /// Gets or sets the current discovery message.
        /// </summary>
        public DiscoveryMessage CurrentDiscoveryMessage { get; set; }

        /// <summary>
        /// Gets or sets the TCP validation information.
        /// </summary>
        public TcpValidationInfo TcpValidationInfo { get; set; }

        /// <summary>
        /// Gets or sets the multi-cast group address when using multi-cast discovery method.
        /// </summary>
        public String MulticastGroupAddress { get; set; }

        /// <summary>
        /// Gets or sets the interval in which the discovery message will be sent.
        /// </summary>
        public TimeSpan Interval { get; set; }

        /// <summary>
        /// Gets a value indicating whether this service has been started.
        /// </summary>
        public bool IsStarted { get; private set; }

        /// <summary>
        /// Gets the UDP port number.
        /// </summary>
        public int Port { get; private set; }

        /// <summary>
        /// Prevents a default instance of the <see cref="UdpDiscoveryService{DiscoveryMessage}"/> class from being created.
        /// </summary>
        private UdpDiscoveryService()
        {
            TcpValidationInfo = new TcpValidationInfo();
            Interval = TimeSpan.FromSeconds(5);
            CurrentDiscoveryMessage = Activator.CreateInstance<DiscoveryMessage>();
        }

        /// <summary>
        /// Initializes a new instance of the <see cref="UdpDiscoveryService{DiscoveryMessage}"/> class.
        /// </summary>
        /// <param name="port">The port.</param>
        public UdpDiscoveryService(int port) : this()
        {
            Port = port;
            _tcpValidationServer = new TcpServer(Port);
            _tcpValidationServer.ClientConnected += (x, e) =>
            {
                try
                {
                    var data = GenericMessageSerializer.Serialize(TcpValidationInfo, GenericMessageProtocol.Bson);
                    e.Socket.GetStream().Write(data, 0, data.Length);
                    e.Socket.Dispose();
                }
                catch (Exception ex)
                {
                    LogManager.Log(ex, "TCP Validation Server Response Error.");
                }
            };
        }

        /// <summary>
        /// Initializes a new instance of the <see cref="UdpDiscoveryService{DiscoveryMessage}"/> class.
        /// </summary>
        /// <param name="port">The port.</param>
        /// <param name="discoveryMessage">The discovery message.</param>
        public UdpDiscoveryService(int port, DiscoveryMessage discoveryMessage) : this(port)
        {
            CurrentDiscoveryMessage = discoveryMessage;
        }

        /// <summary>
        /// Starts the discovery service.
        /// </summary>
        public void Start()
        {
            if (!IsStarted)
            {
                _tcpValidationServer.Start();

                _timer = new Timer();
                _timer.Interval = Interval.TotalMilliseconds;
                _timer.Elapsed += _timer_Elapsed;
                _timer.Enabled = true;
                _timer.Start();

                IsStarted = true;
            }
        }

        /// <summary>
        /// Stops the discovery service.
        /// </summary>
        public void Stop()
        {
            if (IsStarted)
            {
                _tcpValidationServer.Stop();

                //Transmit the discovery packet one more time so clients can tell that we have disconnected.
                BroadcastDiscoveryPacket();
                _timer.Stop();
                IsStarted = false;
            }
        }

        /// <summary>
        /// Handles the Elapsed event of the _timer control.
        /// </summary>
        /// <param name="sender">The source of the event.</param>
        /// <param name="e">The <see cref="ElapsedEventArgs"/> instance containing the event data.</param>
        private void _timer_Elapsed(object sender, ElapsedEventArgs e)
        {
            BroadcastDiscoveryPacket();
        }

        private void BroadcastDiscoveryPacket()
        {
            //Broadcast
            try
            {
                BeforeBroadcasting?.Invoke(this, CurrentDiscoveryMessage);

                UdpClient client = new UdpClient();

                IPEndPoint endPoint = new IPEndPoint(IPAddress.Broadcast, Port);

                byte[] bytes = CurrentDiscoveryMessage.ToByteArray();

                client.EnableBroadcast = true;
                client.Send(bytes, bytes.Length, endPoint);

                client.Close();
            }
            catch (Exception ex)
            {
                LogManager.Log(ex, "Error broadcasting discovery packet.");
            }

            //Multicast
            try
            {
                UdpClient client = new UdpClient(AddressFamily.InterNetwork);

                IPEndPoint endPoint = new IPEndPoint(IPAddress.Parse(MulticastGroupAddress), Port);

                client.JoinMulticastGroup(IPAddress.Parse(MulticastGroupAddress), IPAddress.Parse(IPAddressHelper.GetLocalIpAddress()));

                byte[] bytes = CurrentDiscoveryMessage.ToByteArray();

                client.Client.Ttl = 10;
                client.Send(bytes, bytes.Length, endPoint);

                client.Close();
            }
            catch (Exception ex)
            {
                LogManager.Log(ex, LogCategory.Debug, "Error multicasting discovery packet.");
            }
        }
    }
}