/*
 *
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 *
 */
package org.apache.qpid.server.protocol.v0_10;

import static org.apache.qpid.server.transport.util.Functions.str;
import static org.apache.qpid.server.protocol.v0_10.ServerInputHandler.State.*;

import java.util.ArrayList;
import java.util.List;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import org.apache.qpid.server.bytebuffer.QpidByteBuffer;
import org.apache.qpid.server.protocol.v0_10.transport.ProtocolError;
import org.apache.qpid.server.protocol.v0_10.transport.ProtocolHeader;
import org.apache.qpid.server.protocol.v0_10.transport.SegmentType;


public class ServerInputHandler implements FrameSizeObserver
{
    private static final Logger LOGGER = LoggerFactory.getLogger(ServerInputHandler.class);
    private static final QpidByteBuffer EMPTY_BYTE_BUFFER = QpidByteBuffer.allocateDirect(0);

    private int _maxFrameSize = Constant.MIN_MAX_FRAME_SIZE;


    public enum State
    {
        PROTO_HDR,
        FRAME_HDR,
        ERROR;
    }
    private final ServerAssembler _serverAssembler;

    private State _state = PROTO_HDR;

    private byte flags;
    private SegmentType type;
    private byte track;
    private int channel;


    public ServerInputHandler(ServerAssembler serverAssembler)
    {
        _serverAssembler = serverAssembler;
        _state = PROTO_HDR;
    }

    @Override
    public void setMaxFrameSize(final int maxFrameSize)
    {
        _maxFrameSize = maxFrameSize;
    }

    private void error(String fmt, Object ... args)
    {
        _serverAssembler.error(new ProtocolError(ServerFrame.L1, fmt, args));
    }

    public void received(QpidByteBuffer buf)
    {
        int position = buf.position();

        List<ServerFrame> frames = new ArrayList<>();

        while(buf.hasRemaining() && _state != ERROR)
        {
            buf.mark();
            switch (_state) {
                case PROTO_HDR:
                    if(buf.remaining() < 8)
                    {
                        break;
                    }
                    if (buf.get() != 'A' ||
                        buf.get() != 'M' ||
                        buf.get() != 'Q' ||
                        buf.get() != 'P')
                    {
                        buf.reset();
                        error("bad protocol header: %s", str(buf));
                        _state = ERROR;
                    }
                    else
                    {
                        byte protoClass = buf.get();
                        byte instance = buf.get();
                        byte major = buf.get();
                        byte minor = buf.get();

                        _serverAssembler.init(new ProtocolHeader(protoClass, instance, major, minor));
                        _state = FRAME_HDR;
                    }
                    break;
                case FRAME_HDR:
                    if(buf.remaining() < ServerFrame.HEADER_SIZE)
                    {
                        buf.reset();
                    }
                    else
                    {
                        flags = buf.get();
                        type = SegmentType.get(buf.get());
                        int size = (0xFFFF & buf.getShort());

                        size -= ServerFrame.HEADER_SIZE;
                        if (size < 0 || size > (_maxFrameSize - ServerFrame.HEADER_SIZE))
                        {
                            error("bad frame size: %d", size);
                            _state = ERROR;
                        }
                        else
                        {
                            buf.get(); // skip unused byte
                            byte b = buf.get();
                            if ((b & 0xF0) != 0)
                            {
                                error("non-zero reserved bits in upper nibble of " +
                                      "frame header byte 5: '%x'", b);
                                _state = ERROR;
                            }
                            else
                            {
                                track = (byte) (b & 0xF);

                                channel = (0xFFFF & buf.getShort());
                                buf.position(buf.position() + 4);
                                if (size == 0)
                                {
                                    ServerFrame frame = new ServerFrame(flags, type, track, channel, EMPTY_BYTE_BUFFER.duplicate());
                                    frames.add(frame);

                                }
                                else if (buf.remaining() < size)
                                {
                                    buf.reset();
                                }
                                else
                                {
                                    final QpidByteBuffer body = buf.slice();
                                    body.limit(size);
                                    ServerFrame frame = new ServerFrame(flags, type, track, channel, body);
                                    frames.add(frame);
                                    buf.position(buf.position() + size);
                                }
                            }
                        }
                    }
                    break;
                default:
                    throw new IllegalStateException();
            }

            int newPosition = buf.position();
            if(position == newPosition)
            {
                break;
            }
            else
            {
                position = newPosition;
            }
        }

        _serverAssembler.received(frames);
    }

    public void exception(Throwable t)
    {
        _serverAssembler.exception(t);
    }

    public void closed()
    {
        _serverAssembler.closed();
    }

}