/*
* Copyright (c) Contributors, http://opensimulator.org/
* See CONTRIBUTORS.TXT for a full list of copyright holders.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
*     * Redistributions of source code must retain the above copyright
*       notice, this list of conditions and the following disclaimer.
*     * Redistributions in binary form must reproduce the above copyright
*       notice, this list of conditions and the following disclaimer in the
*       documentation and/or other materials provided with the distribution.
*     * Neither the name of the OpenSim Project nor the
*       names of its contributors may be used to endorse or promote products
*       derived from this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE DEVELOPERS ``AS IS AND ANY
* EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
* WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
* DISCLAIMED. IN NO EVENT SHALL THE CONTRIBUTORS BE LIABLE FOR ANY
* DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
* (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
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* ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
* SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
* 
*/
using System;
using System.Collections.Generic;
using System.Net;
using System.Net.Sockets;
using libsecondlife.Packets;
using OpenSim.Framework;
using OpenSim.Framework.Communications.Cache;
using OpenSim.Framework.Console;

namespace OpenSim.Region.ClientStack
{
    public class UDPServer : ClientStackNetworkHandler
    {
        protected Dictionary<EndPoint, uint> clientCircuits = new Dictionary<EndPoint, uint>();
        public Socket Server;
        protected IPEndPoint ServerIncoming;
        protected byte[] RecvBuffer = new byte[4096];
        protected byte[] ZeroBuffer = new byte[8192];
        protected IPEndPoint ipeSender;
        protected EndPoint epSender;
        protected AsyncCallback ReceivedData;
        protected PacketServer m_packetServer;

        protected int listenPort;
        protected IScene m_localScene;
        protected AssetCache m_assetCache;
        protected LogBase m_log;
        protected AgentCircuitManager m_authenticateSessionsClass;

        public PacketServer PacketServer
        {
            get { return m_packetServer; }
            set { m_packetServer = value; }
        }

        public IScene LocalScene
        {
            set
            {
                m_localScene = value;
                m_packetServer.LocalScene = m_localScene;
            }
        }

        public UDPServer()
        {
        }

        public UDPServer(int port, AssetCache assetCache, LogBase console, AgentCircuitManager authenticateClass)
        {
            listenPort = port;
            m_assetCache = assetCache;
            m_log = console;
            m_authenticateSessionsClass = authenticateClass;
            CreatePacketServer();
        }

        protected virtual void CreatePacketServer()
        {
            PacketServer packetServer = new PacketServer(this);
        }

        protected virtual void OnReceivedData(IAsyncResult result)
        {
            ipeSender = new IPEndPoint(IPAddress.Parse("0.0.0.0"), 0);
            epSender = (EndPoint) ipeSender;
            Packet packet = null;

            int numBytes;

            try
            {
                numBytes = Server.EndReceiveFrom(result, ref epSender);
            }
            catch (SocketException e)
            {
                // TODO : Actually only handle those states that we have control over, re-throw everything else,
                // TODO: implement cases as we encounter them.
                switch (e.SocketErrorCode)
                {
                    case SocketError.AlreadyInProgress:
                    case SocketError.NetworkReset:
                    default:
                        Console.WriteLine("Remote host Closed connection");
                        CloseEndPoint(epSender);
                        break;
                }

                return;
            }

            int packetEnd = numBytes - 1;

            packet = Packet.BuildPacket(RecvBuffer, ref packetEnd, ZeroBuffer);

            // do we already have a circuit for this endpoint
            uint circuit;
            if (clientCircuits.TryGetValue(epSender, out circuit))
            {
                //if so then send packet to the packetserver
                m_packetServer.InPacket(circuit, packet);
            }
            else if (packet.Type == PacketType.UseCircuitCode)
            {
                // new client
                AddNewClient(packet);
            }
            else
            {
                // invalid client
                m_log.Warn("client", "Got a packet from an invalid client - " + epSender.ToString());
            }

            Server.BeginReceiveFrom(RecvBuffer, 0, RecvBuffer.Length, SocketFlags.None, ref epSender, ReceivedData, null);
        }

        private void CloseEndPoint(EndPoint sender)
        {
            uint circuit;
            if (clientCircuits.TryGetValue(sender, out circuit))
            {
                m_packetServer.CloseCircuit(circuit);
            }
        }

        protected virtual void AddNewClient(Packet packet)
        {
            UseCircuitCodePacket useCircuit = (UseCircuitCodePacket) packet;
            clientCircuits.Add(epSender, useCircuit.CircuitCode.Code);

            PacketServer.AddNewClient(epSender, useCircuit, m_assetCache, m_authenticateSessionsClass);
        }

        public void ServerListener()
        {
            m_log.Verbose("SERVER", "Opening UDP socket on " + listenPort);

            ServerIncoming = new IPEndPoint(IPAddress.Parse("0.0.0.0"), listenPort);
            Server = new Socket(AddressFamily.InterNetwork, SocketType.Dgram, ProtocolType.Udp);
            Server.Bind(ServerIncoming);

            m_log.Verbose("SERVER", "UDP socket bound, getting ready to listen");

            ipeSender = new IPEndPoint(IPAddress.Parse("0.0.0.0"), 0);
            epSender = (EndPoint) ipeSender;
            ReceivedData = new AsyncCallback(OnReceivedData);
            Server.BeginReceiveFrom(RecvBuffer, 0, RecvBuffer.Length, SocketFlags.None, ref epSender, ReceivedData, null);

            m_log.Status("SERVER", "Listening...");
        }

        public virtual void RegisterPacketServer(PacketServer server)
        {
            m_packetServer = server;
        }

        public virtual void SendPacketTo(byte[] buffer, int size, SocketFlags flags, uint circuitcode)
            //EndPoint packetSender)
        {
            // find the endpoint for this circuit
            EndPoint sendto = null;
            foreach (KeyValuePair<EndPoint, uint> p in clientCircuits)
            {
                if (p.Value == circuitcode)
                {
                    sendto = p.Key;
                    break;
                }
            }
            if (sendto != null)
            {
                //we found the endpoint so send the packet to it
                Server.SendTo(buffer, size, flags, sendto);
            }
        }

        public virtual void RemoveClientCircuit(uint circuitcode)
        {
            foreach (KeyValuePair<EndPoint, uint> p in clientCircuits)
            {
                if (p.Value == circuitcode)
                {
                    clientCircuits.Remove(p.Key);
                    break;
                }
            }
        }
    }
}