//
// Copyright (c) ZeroC, Inc. All rights reserved.
//

namespace IceInternal
{
    using System;
    using System.Collections.Generic;
    using System.ComponentModel;
    using System.Diagnostics;
    using System.Net;
    using System.Net.Sockets;
    using System.Text;

    sealed class UdpTransceiver : Transceiver
    {
        public Socket fd()
        {
            return _fd;
        }

        public int initialize(Buffer readBuffer, Buffer writeBuffer, ref bool hasMoreData)
        {
            if(_state == StateNeedConnect)
            {
                _state = StateConnectPending;
                try
                {
                    if(_sourceAddr != null)
                    {
                        _fd.Bind(_sourceAddr);
                    }
                    _fd.Connect(_addr);
                }
                catch(SocketException ex)
                {
                    if(Network.wouldBlock(ex))
                    {
                        return SocketOperation.Connect;
                    }
                    throw new Ice.ConnectFailedException(ex);
                }
                catch(Exception ex)
                {
                    throw new Ice.ConnectFailedException(ex);
                }
                _state = StateConnected;
            }

            Debug.Assert(_state >= StateConnected);
            return SocketOperation.None;
        }

        public int closing(bool initiator, Ice.LocalException ex)
        {
            //
            // Nothing to do.
            //
            return SocketOperation.None;
        }

        public void close()
        {
            if(_fd != null)
            {
                try
                {
                    _fd.Close();
                }
                catch(System.IO.IOException)
                {
                }
                _fd = null;
            }
        }

        public EndpointI bind()
        {
            if(Network.isMulticast((IPEndPoint)_addr))
            {
                Network.setReuseAddress(_fd, true);
                _mcastAddr = (IPEndPoint)_addr;
                if(AssemblyUtil.isWindows)
                {
                    //
                    // Windows does not allow binding to the mcast address itself
                    // so we bind to INADDR_ANY (0.0.0.0) instead. As a result,
                    // bi-directional connection won't work because the source
                    // address won't the multicast address and the client will
                    // therefore reject the datagram.
                    //
                    if(_addr.AddressFamily == AddressFamily.InterNetwork)
                    {
                        _addr = new IPEndPoint(IPAddress.Any, _port);
                    }
                    else
                    {
                        _addr = new IPEndPoint(IPAddress.IPv6Any, _port);
                    }
                }

                _addr = Network.doBind(_fd, _addr);
                if(_port == 0)
                {
                    _mcastAddr.Port = ((IPEndPoint)_addr).Port;
                }
                Network.setMcastGroup(_fd, _mcastAddr.Address, _mcastInterface);
            }
            else
            {
                 _addr = Network.doBind(_fd, _addr);
            }
            _bound = true;
            _endpoint = _endpoint.endpoint(this);
            return _endpoint;
        }

        public void destroy()
        {
            _readEventArgs.Dispose();
            _writeEventArgs.Dispose();
        }

        public int write(Buffer buf)
        {
            if(!buf.b.hasRemaining())
            {
                return SocketOperation.None;
            }

            Debug.Assert(buf.b.position() == 0);
            Debug.Assert(_fd != null && _state >= StateConnected);

            // The caller is supposed to check the send size before by calling checkSendSize
            Debug.Assert(Math.Min(_maxPacketSize, _sndSize - _udpOverhead) >= buf.size());

            int ret = 0;
            while(true)
            {
                try
                {
                    if(_state == StateConnected)
                    {
                        ret = _fd.Send(buf.b.rawBytes(), 0, buf.size(), SocketFlags.None);
                    }
                    else
                    {
                        if(_peerAddr == null)
                        {
                            throw new Ice.SocketException();
                        }
                        ret = _fd.SendTo(buf.b.rawBytes(), 0, buf.size(), SocketFlags.None, _peerAddr);
                    }
                    break;
                }
                catch(SocketException ex)
                {
                    if(Network.interrupted(ex))
                    {
                        continue;
                    }

                    if(Network.wouldBlock(ex))
                    {
                        return SocketOperation.Write;
                    }

                    if(Network.connectionLost(ex))
                    {
                        throw new Ice.ConnectionLostException(ex);
                    }
                    else
                    {
                        throw new Ice.SocketException(ex);
                    }
                }
                catch(Exception e)
                {
                    throw new Ice.SyscallException(e);
                }
            }

            Debug.Assert(ret > 0);
            Debug.Assert(ret == buf.b.limit());
            buf.b.position(buf.b.limit());
            return SocketOperation.None;
        }

        public int read(Buffer buf, ref bool hasMoreData)
        {
            if(!buf.b.hasRemaining())
            {
                return SocketOperation.None;
            }

            Debug.Assert(buf.b.position() == 0);
            Debug.Assert(_fd != null);

            int packetSize = Math.Min(_maxPacketSize, _rcvSize - _udpOverhead);
            buf.resize(packetSize, true);
            buf.b.position(0);

            int ret = 0;
            while(true)
            {
                try
                {
                    EndPoint peerAddr = _peerAddr;
                    if(peerAddr == null)
                    {
                        if(_addr.AddressFamily == AddressFamily.InterNetwork)
                        {
                            peerAddr = new IPEndPoint(IPAddress.Any, 0);
                        }
                        else
                        {
                            Debug.Assert(_addr.AddressFamily == AddressFamily.InterNetworkV6);
                            peerAddr = new IPEndPoint(IPAddress.IPv6Any, 0);
                        }
                    }

                    // TODO: Workaround for https://github.com/dotnet/corefx/issues/31182
                    if(_state == StateConnected ||
                       AssemblyUtil.isMacOS && _fd.AddressFamily == AddressFamily.InterNetworkV6 && _fd.DualMode)
                    {
                        ret = _fd.Receive(buf.b.rawBytes(), 0, buf.b.limit(), SocketFlags.None);
                    }
                    else
                    {
                        ret = _fd.ReceiveFrom(buf.b.rawBytes(), 0, buf.b.limit(), SocketFlags.None, ref peerAddr);
                        _peerAddr = (IPEndPoint)peerAddr;
                    }
                    break;
                }
                catch(SocketException e)
                {
                    if(Network.recvTruncated(e))
                    {
                        // The message was truncated and the whole buffer is filled. We ignore
                        // this error here, it will be detected at the connection level when
                        // the Ice message size is checked against the buffer size.
                        ret = buf.size();
                        break;
                    }

                    if(Network.interrupted(e))
                    {
                        continue;
                    }

                    if(Network.wouldBlock(e))
                    {
                        return SocketOperation.Read;
                    }

                    if(Network.connectionLost(e))
                    {
                        throw new Ice.ConnectionLostException();
                    }
                    else
                    {
                        throw new Ice.SocketException(e);
                    }
                }
                catch(Exception e)
                {
                    throw new Ice.SyscallException(e);
                }
            }

            if(ret == 0)
            {
                throw new Ice.ConnectionLostException();
            }

            if(_state == StateNeedConnect)
            {
                Debug.Assert(_incoming);

                //
                // If we must connect, then we connect to the first peer that sends us a packet.
                //
                bool connected = Network.doConnect(_fd, _peerAddr, null);
                Debug.Assert(connected);
                _state = StateConnected; // We're connected now

                if(_instance.traceLevel() >= 1)
                {
                    string s = "connected " + protocol() + " socket\n" + ToString();
                    _instance.logger().trace(_instance.traceCategory(), s);
                }
            }

            buf.resize(ret, true);
            buf.b.position(ret);

            return SocketOperation.None;
        }

        public bool startRead(Buffer buf, AsyncCallback callback, object state)
        {
            Debug.Assert(buf.b.position() == 0);

            int packetSize = Math.Min(_maxPacketSize, _rcvSize - _udpOverhead);
            buf.resize(packetSize, true);
            buf.b.position(0);

            try
            {
                // TODO: Workaround for https://github.com/dotnet/corefx/issues/31182
                if(_state == StateConnected ||
                   AssemblyUtil.isMacOS && _fd.AddressFamily == AddressFamily.InterNetworkV6 && _fd.DualMode)
                {
                    _readCallback = callback;
                    _readEventArgs.UserToken = state;
                    _readEventArgs.SetBuffer(buf.b.rawBytes(), buf.b.position(), packetSize);
                    return !_fd.ReceiveAsync(_readEventArgs);
                }
                else
                {
                    Debug.Assert(_incoming);
                    _readCallback = callback;
                    _readEventArgs.UserToken = state;
                    _readEventArgs.SetBuffer(buf.b.rawBytes(), 0, buf.b.limit());
                    return !_fd.ReceiveFromAsync(_readEventArgs);
                }
            }
            catch(SocketException ex)
            {
                if(Network.recvTruncated(ex))
                {
                    // Nothing todo
                    return true;
                }
                else
                {
                    if(Network.connectionLost(ex))
                    {
                        throw new Ice.ConnectionLostException(ex);
                    }
                    else
                    {
                        throw new Ice.SocketException(ex);
                    }
                }
            }
        }

        public void finishRead(Buffer buf)
        {
            if(_fd == null)
            {
                return;
            }

            int ret;
            try
            {
                if(_readEventArgs.SocketError != SocketError.Success)
                {
                    throw new SocketException((int)_readEventArgs.SocketError);
                }
                ret = _readEventArgs.BytesTransferred;
                // TODO: Workaround for https://github.com/dotnet/corefx/issues/31182
                if(_state != StateConnected &&
                   !(AssemblyUtil.isMacOS && _fd.AddressFamily == AddressFamily.InterNetworkV6 && _fd.DualMode))
                {
                    _peerAddr = _readEventArgs.RemoteEndPoint;
                }
            }
            catch(SocketException ex)
            {
                if(Network.recvTruncated(ex))
                {
                    // The message was truncated and the whole buffer is filled. We ignore
                    // this error here, it will be detected at the connection level when
                    // the Ice message size is checked against the buffer size.
                    ret = buf.size();
                }
                else
                {
                    if(Network.connectionLost(ex))
                    {
                        throw new Ice.ConnectionLostException(ex);
                    }

                    if(Network.connectionRefused(ex))
                    {
                        throw new Ice.ConnectionRefusedException(ex);
                    }
                    else
                    {
                        throw new Ice.SocketException(ex);
                    }
                }
            }

            if(ret == 0)
            {
                throw new Ice.ConnectionLostException();
            }

            Debug.Assert(ret > 0);

            if(_state == StateNeedConnect)
            {
                Debug.Assert(_incoming);

                //
                // If we must connect, then we connect to the first peer that
                // sends us a packet.
                //
                bool connected = !_fd.ConnectAsync(_readEventArgs);
                Debug.Assert(connected);
                _state = StateConnected; // We're connected now

                if(_instance.traceLevel() >= 1)
                {
                    string s = "connected " + protocol() + " socket\n" + ToString();
                    _instance.logger().trace(_instance.traceCategory(), s);
                }
            }

            buf.resize(ret, true);
            buf.b.position(ret);
        }

        public bool startWrite(Buffer buf, AsyncCallback callback, object state, out bool completed)
        {
            if(!_incoming && _state < StateConnected)
            {
                Debug.Assert(_addr != null);
                completed = false;
                if(_sourceAddr != null)
                {
                    _fd.Bind(_sourceAddr);
                }
                _writeEventArgs.UserToken = state;
                return !_fd.ConnectAsync(_writeEventArgs);
            }

            Debug.Assert(_fd != null);

            // The caller is supposed to check the send size before by calling checkSendSize
            Debug.Assert(Math.Min(_maxPacketSize, _sndSize - _udpOverhead) >= buf.size());

            Debug.Assert(buf.b.position() == 0);

            bool completedSynchronously;
            try
            {
                _writeCallback = callback;

                if(_state == StateConnected)
                {
                    _writeEventArgs.UserToken = state;
                    _writeEventArgs.SetBuffer(buf.b.rawBytes(), 0, buf.b.limit());
                    completedSynchronously = !_fd.SendAsync(_writeEventArgs);
                }
                else
                {
                    if(_peerAddr == null)
                    {
                        throw new Ice.SocketException();
                    }
                    _writeEventArgs.RemoteEndPoint = _peerAddr;
                    _writeEventArgs.UserToken = state;
                    _writeEventArgs.SetBuffer(buf.b.rawBytes(), 0, buf.b.limit());
                    completedSynchronously = !_fd.SendToAsync(_writeEventArgs);
                }
            }
            catch(SocketException ex)
            {
                if(Network.connectionLost(ex))
                {
                    throw new Ice.ConnectionLostException(ex);
                }
                else
                {
                    throw new Ice.SocketException(ex);
                }
            }

            completed = true;
            return completedSynchronously;
        }

        public void finishWrite(Buffer buf)
        {
            if(_fd == null)
            {
                buf.b.position(buf.size()); // Assume all the data was sent for at-most-once semantics.
                _writeEventArgs = null;
                return;
            }

            if(!_incoming && _state < StateConnected)
            {
                if(_writeEventArgs.SocketError != SocketError.Success)
                {
                    SocketException ex = new SocketException((int)_writeEventArgs.SocketError);
                    if(Network.connectionRefused(ex))
                    {
                        throw new Ice.ConnectionRefusedException(ex);
                    }
                    else
                    {
                        throw new Ice.ConnectFailedException(ex);
                    }
                }
                return;
            }

            int ret;
            try
            {
                if(_writeEventArgs.SocketError != SocketError.Success)
                {
                    throw new SocketException((int)_writeEventArgs.SocketError);
                }
                ret = _writeEventArgs.BytesTransferred;
            }
            catch(SocketException ex)
            {
                if(Network.connectionLost(ex))
                {
                    throw new Ice.ConnectionLostException(ex);
                }
                else
                {
                    throw new Ice.SocketException(ex);
                }
            }

            if(ret == 0)
            {
                throw new Ice.ConnectionLostException();
            }

            Debug.Assert(ret > 0);
            Debug.Assert(ret == buf.b.limit());
            buf.b.position(buf.b.position() + ret);
        }

        public string protocol()
        {
            return _instance.protocol();
        }

        public Ice.ConnectionInfo getInfo()
        {
            Ice.UDPConnectionInfo info = new Ice.UDPConnectionInfo();
            if(_fd != null)
            {
                EndPoint localEndpoint = Network.getLocalAddress(_fd);
                info.localAddress = Network.endpointAddressToString(localEndpoint);
                info.localPort = Network.endpointPort(localEndpoint);
                if(_state == StateNotConnected)
                {
                    if(_peerAddr != null)
                    {
                        info.remoteAddress = Network.endpointAddressToString(_peerAddr);
                        info.remotePort = Network.endpointPort(_peerAddr);
                    }
                }
                else
                {
                    EndPoint remoteEndpoint = Network.getRemoteAddress(_fd);
                    if(remoteEndpoint != null)
                    {
                        info.remoteAddress = Network.endpointAddressToString(remoteEndpoint);
                        info.remotePort = Network.endpointPort(remoteEndpoint);
                    }
                }
                info.rcvSize = Network.getRecvBufferSize(_fd);
                info.sndSize = Network.getSendBufferSize(_fd);
            }

            if(_mcastAddr != null)
            {
                info.mcastAddress = Network.endpointAddressToString(_mcastAddr);
                info.mcastPort = Network.endpointPort(_mcastAddr);
            }
            return info;
        }

        public void checkSendSize(Buffer buf)
        {
            //
            // The maximum packetSize is either the maximum allowable UDP packet size, or
            // the UDP send buffer size (which ever is smaller).
            //
            int packetSize = Math.Min(_maxPacketSize, _sndSize - _udpOverhead);
            if(packetSize < buf.size())
            {
                throw new Ice.DatagramLimitException();
            }
        }

        public void setBufferSize(int rcvSize, int sndSize)
        {
            setBufSize(rcvSize, sndSize);
        }

        public override string ToString()
        {
            if(_fd == null)
            {
                return "<closed>";
            }

            string s;
            if(_incoming && !_bound)
            {
                s = "local address = " + Network.addrToString(_addr);
            }
            else if(_state == StateNotConnected)
            {
                s = "local address = " + Network.localAddrToString(Network.getLocalAddress(_fd));
                if(_peerAddr != null)
                {
                    s += "\nremote address = " + Network.addrToString(_peerAddr);
                }
            }
            else
            {
                s = Network.fdToString(_fd);
            }

            if(_mcastAddr != null)
            {
                s += "\nmulticast address = " + Network.addrToString(_mcastAddr);
            }
            return s;
        }

        public string toDetailedString()
        {
            StringBuilder s = new StringBuilder(ToString());
            List<string> intfs;
            if(_mcastAddr == null)
            {
                intfs = Network.getHostsForEndpointExpand(Network.endpointAddressToString(_addr),
                                                          _instance.protocolSupport(), true);
            }
            else
            {
                intfs = Network.getInterfacesForMulticast(_mcastInterface,
                                                          Network.getProtocolSupport(_mcastAddr.Address));
            }
            if(intfs.Count != 0)
            {
                s.Append("\nlocal interfaces = ");
                s.Append(string.Join(", ", intfs.ToArray()));
            }
            return s.ToString();
        }

        public int effectivePort()
        {
            return Network.endpointPort(_addr);
        }

        //
        // Only for use by UdpConnector.
        //
        internal UdpTransceiver(ProtocolInstance instance, EndPoint addr, EndPoint sourceAddr, string mcastInterface,
                                int mcastTtl)
        {
            _instance = instance;
            _addr = addr;
            _sourceAddr = sourceAddr;

            _readEventArgs = new SocketAsyncEventArgs();
            _readEventArgs.RemoteEndPoint = _addr;
            _readEventArgs.Completed += new EventHandler<SocketAsyncEventArgs>(ioCompleted);

            _writeEventArgs = new SocketAsyncEventArgs();
            _writeEventArgs.RemoteEndPoint = _addr;
            _writeEventArgs.Completed += new EventHandler<SocketAsyncEventArgs>(ioCompleted);

            _mcastInterface = mcastInterface;
            _state = StateNeedConnect;
            _incoming = false;

            try
            {
                _fd = Network.createSocket(true, _addr.AddressFamily);
                setBufSize(-1, -1);
                Network.setBlock(_fd, false);
                if(Network.isMulticast((IPEndPoint)_addr))
                {
                    if(_mcastInterface.Length > 0)
                    {
                        Network.setMcastInterface(_fd, _mcastInterface, _addr.AddressFamily);
                    }
                    if(mcastTtl != -1)
                    {
                        Network.setMcastTtl(_fd, mcastTtl, _addr.AddressFamily);
                    }
                }
            }
            catch(Ice.LocalException)
            {
                _fd = null;
                throw;
            }
        }

        //
        // Only for use by UdpEndpoint.
        //
        internal UdpTransceiver(UdpEndpointI endpoint, ProtocolInstance instance, string host, int port,
                                string mcastInterface, bool connect)
        {
            _endpoint = endpoint;
            _instance = instance;
            _state = connect ? StateNeedConnect : StateNotConnected;
            _mcastInterface = mcastInterface;
            _incoming = true;
            _port = port;

            try
            {
                _addr = Network.getAddressForServer(host, port, instance.protocolSupport(), instance.preferIPv6());

                _readEventArgs = new SocketAsyncEventArgs();
                _readEventArgs.RemoteEndPoint = _addr;
                _readEventArgs.Completed += new EventHandler<SocketAsyncEventArgs>(ioCompleted);

                _writeEventArgs = new SocketAsyncEventArgs();
                _writeEventArgs.RemoteEndPoint = _addr;
                _writeEventArgs.Completed += new EventHandler<SocketAsyncEventArgs>(ioCompleted);

                _fd = Network.createServerSocket(true, _addr.AddressFamily, instance.protocolSupport());
                setBufSize(-1, -1);
                Network.setBlock(_fd, false);
            }
            catch(Ice.LocalException)
            {
                if(_readEventArgs != null)
                {
                    _readEventArgs.Dispose();
                }
                if(_writeEventArgs != null)
                {
                    _writeEventArgs.Dispose();
                }
                _fd = null;
                throw;
            }
        }

        private void setBufSize(int rcvSize, int sndSize)
        {
            Debug.Assert(_fd != null);

            for (int i = 0; i < 2; ++i)
            {
                bool isSnd;
                string direction;
                string prop;
                int dfltSize;
                int sizeRequested;
                if(i == 0)
                {
                    isSnd = false;
                    direction = "receive";
                    prop = "Ice.UDP.RcvSize";
                    dfltSize = Network.getRecvBufferSize(_fd);
                    sizeRequested = rcvSize;
                    _rcvSize = dfltSize;
                }
                else
                {
                    isSnd = true;
                    direction = "send";
                    prop = "Ice.UDP.SndSize";
                    dfltSize = Network.getSendBufferSize(_fd);
                    sizeRequested = sndSize;
                    _sndSize = dfltSize;
                }

                //
                // Get property for buffer size if size not passed in.
                //
                if(sizeRequested == -1)
                {
                    sizeRequested = _instance.properties().getPropertyAsIntWithDefault(prop, dfltSize);
                }
                //
                // Check for sanity.
                //
                if(sizeRequested < (_udpOverhead + Protocol.headerSize))
                {
                    _instance.logger().warning("Invalid " + prop + " value of " + sizeRequested + " adjusted to " +
                                               dfltSize);
                    sizeRequested = dfltSize;
                }

                if(sizeRequested != dfltSize)
                {
                    //
                    // Try to set the buffer size. The kernel will silently adjust
                    // the size to an acceptable value. Then read the size back to
                    // get the size that was actually set.
                    //
                    int sizeSet;
                    if(i == 0)
                    {
                        Network.setRecvBufferSize(_fd, sizeRequested);
                        _rcvSize = Network.getRecvBufferSize(_fd);
                        sizeSet = _rcvSize;
                    }
                    else
                    {
                        Network.setSendBufferSize(_fd, sizeRequested);
                        _sndSize = Network.getSendBufferSize(_fd);
                        sizeSet = _sndSize;
                    }

                    //
                    // Warn if the size that was set is less than the requested size
                    // and we have not already warned
                    //
                    if(sizeSet < sizeRequested)
                    {
                        BufSizeWarnInfo winfo = _instance.getBufSizeWarn(Ice.UDPEndpointType.value);
                        if((isSnd && (!winfo.sndWarn || winfo.sndSize != sizeRequested)) ||
                           (!isSnd && (!winfo.rcvWarn || winfo.rcvSize != sizeRequested)))
                        {
                            _instance.logger().warning("UDP " + direction + " buffer size: requested size of " +
                                                       sizeRequested + " adjusted to " + sizeSet);

                            if(isSnd)
                            {
                                _instance.setSndBufSizeWarn(Ice.UDPEndpointType.value, sizeRequested);
                            }
                            else
                            {
                                _instance.setRcvBufSizeWarn(Ice.UDPEndpointType.value, sizeRequested);
                            }
                        }
                    }
                }
            }
        }

        internal void ioCompleted(object sender, SocketAsyncEventArgs e)
        {
            switch (e.LastOperation)
            {
            case SocketAsyncOperation.Receive:
            case SocketAsyncOperation.ReceiveFrom:
                _readCallback(e.UserToken);
                break;
            case SocketAsyncOperation.Send:
            case SocketAsyncOperation.Connect:
                _writeCallback(e.UserToken);
                break;
            default:
                throw new ArgumentException("The last operation completed on the socket was not a receive or send");
            }
        }

        private UdpEndpointI _endpoint;
        private ProtocolInstance _instance;
        private int _state;
        private bool _incoming;
        private int _rcvSize;
        private int _sndSize;
        private Socket _fd;
        private EndPoint _addr;
        private EndPoint _sourceAddr;
        private IPEndPoint _mcastAddr = null;
        private EndPoint _peerAddr = null;
        private string _mcastInterface = null;

        private int _port = 0;
        private bool _bound = false;

        private SocketAsyncEventArgs _writeEventArgs;
        private SocketAsyncEventArgs _readEventArgs;

        AsyncCallback _writeCallback;
        AsyncCallback _readCallback;

        private const int StateNeedConnect = 0;
        private const int StateConnectPending = 1;
        private const int StateConnected = 2;
        private const int StateNotConnected = 3;

        //
        // The maximum IP datagram size is 65535. Subtract 20 bytes for the IP header and 8 bytes for the UDP header
        // to get the maximum payload.
        //
        private const int _udpOverhead = 20 + 8;
        private const int _maxPacketSize = 65535 - _udpOverhead;
    }
}