// /**
//  * File: MyClass.cs
//  * Author: haraldwolff
//  *
//  * This file and it's content is copyrighted by the Author and / or copyright holder.
//  * Any use wihtout proper permission is illegal and may lead to legal actions.
//  *
//  *
//  **/
using System;
using System.Collections.Generic;
using ln.snmp.types;
using System.Net.Sockets;
using System.Net;
using System.Threading;
using ln.snmp.asn1;
using ln.logging;
using ln.snmp.endpoint;

namespace ln.snmp
{
    public class SNMPEngine : IDisposable
    {
        public static bool DEBUG = false;

        private static SNMPEngine __default = null;
        public static SNMPEngine DefaultEngine
        {
            get
            {
                if (__default == null)
                    __default = new SNMPEngine();
                return __default;
            }
            set => __default = value;
        }



        public UdpClient LocalEndpoint { get; private set; }
        public int Timeout { get; set; } = 750;

        private Dictionary<int, SnmpMessage> queuedRequests = new Dictionary<int, SnmpMessage>();
        private bool shutdown = false;
        private Thread ReceiverThread { get; set; }

        private Dictionary<IPEndPoint, SnmpEndpoint> currentEndpoints = new Dictionary<IPEndPoint, SnmpEndpoint>();


        private int nextMessageID = (int)DateTimeOffset.Now.ToUnixTimeSeconds();
        public int NextMessageID => nextMessageID++;

        public SNMPEngine()
        {
            LocalEndpoint = new UdpClient();
            ReceiverThread = new Thread(Receiver);
            ReceiverThread.IsBackground = true;
            ReceiverThread.Start();
        }
        public SNMPEngine(IPEndPoint localEndpoint)
        {
            LocalEndpoint = new UdpClient(localEndpoint);
            ReceiverThread = new Thread(Receiver);
            ReceiverThread.IsBackground = true;
            ReceiverThread.Start();
        }

        public void Close()
        {
            shutdown = true;
            LocalEndpoint.Close();
            ReceiverThread.Interrupt();
        }

        private void Receiver()
        {
            while (!shutdown)
            {
                try
                {
                    IPEndPoint remoteEndpoint = new IPEndPoint(IPAddress.Any, 0);
                    byte[] datagram = LocalEndpoint.Receive(ref remoteEndpoint);

                    if (DEBUG)
                        Logging.Log(LogLevel.DEBUGDETAIL,"SNMPClient: Received:   {0}", BitConverter.ToString(datagram));

                    ASN1Value asn = new ASN1Value(datagram);
                    SnmpMessage snmpMessage = asn;

                    if (currentEndpoints.ContainsKey(remoteEndpoint))
                    {
                        SnmpEndpoint snmpEndpoint = currentEndpoints[remoteEndpoint];
                        snmpEndpoint.Received(snmpMessage);
                    }
                    else
                    {
                        Logging.Log(LogLevel.WARNING, "SnmpEngine.Receiver(): Received message from unknown endpoint ({0})",remoteEndpoint);
                    }

                }
                catch (SocketException)
                {
                }
                catch (Exception e)
                {
                    Logging.Log(e);
                }
            }
        }

        public void SendMessage(IPEndPoint remoteEndpoint,SnmpMessage message)
        {
            ASN1Value snmpMessage = message;
            byte[] snmpMessageBytes = snmpMessage.AsByteArray;

            lock (LocalEndpoint)
            {
                LocalEndpoint.Send(snmpMessageBytes, snmpMessageBytes.Length, remoteEndpoint);
            }
        }

        //public SnmpMessage SNMPRequest(IPEndPoint remoteEndpoint,SnmpMessage snmpMessage,int timeout)
        //{
        //    lock (queuedRequests)
        //    {
        //        ASN1Value snmpRequest = snmpMessage;
        //        byte[] snmpRequestBytes = snmpRequest.AsByteArray;

        //        queuedRequests.Add(snmpMessage.MessageID, snmpMessage);

        //        Logging.Log(LogLevel.DEBUG,"SNMPClient: Send:              {0}", BitConverter.ToString(snmpRequestBytes));
        //        Logging.Log(LogLevel.DEBUG,"sent snmpMessage with MessageID {0} ( 0x{0:x8} )",snmpMessage.MessageID);
        //        snmpMessage.Dump();

        //        LocalEndpoint.Send(snmpRequestBytes, snmpRequestBytes.Length, remoteEndpoint);

        //        lock (snmpMessage)
        //        {
        //            Monitor.Exit(queuedRequests);
        //            bool success = Monitor.Wait(snmpMessage, timeout);
        //            Monitor.Enter(queuedRequests);

        //            if (!success)
        //            {
        //                queuedRequests.Remove(snmpMessage.MessageID);
        //                throw new TimeoutException();
        //            }
        //        }

        //        SnmpMessage responseMessage = queuedRequests[snmpMessage.MessageID];
        //        queuedRequests.Remove(snmpMessage.MessageID);

        //        return responseMessage;
        //    }
        //}

        public void RegisterEndpoint(SnmpEndpoint intf)
        {
            lock (currentEndpoints)
            {
                if (currentEndpoints.ContainsKey(intf.RemoteEndpoint))
                {
                    currentEndpoints[intf.RemoteEndpoint].Close();
                }
                currentEndpoints.Add(intf.RemoteEndpoint,intf);
            }
        }
        public void UnregisterEndpoint(SnmpEndpoint intf)
        {
            lock (currentEndpoints)
            {
                currentEndpoints.Remove(intf.RemoteEndpoint);
            }
        }



        public void Dispose()
        {
            if (ReceiverThread != null)
            {
                if (ReceiverThread.IsAlive)
                {
                    Close();
                    if (!ReceiverThread.Join(250))
                    {
                        ReceiverThread.Abort();
                    }
                }
                ReceiverThread = null;
            }
        }

    }
}