/*
 * Copyright 2014 Anton Tananaev (anton.tananaev@gmail.com)
 *
 * Licensed 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.traccar.protocol;

import org.jboss.netty.buffer.ChannelBuffer;
import org.jboss.netty.channel.Channel;
import org.jboss.netty.channel.ChannelHandlerContext;
import org.jboss.netty.handler.codec.frame.FrameDecoder;

public class OrionFrameDecoder extends FrameDecoder {
    
    private static final int TYPE_USERLOG = 0;
    private static final int TYPE_SYSLOG = 3;

    @Override
    protected Object decode(
            ChannelHandlerContext ctx,
            Channel channel,
            ChannelBuffer buf) throws Exception {
        
        int length = 6;
        
        if (buf.readableBytes() >= length) {
        
            int type = buf.getUnsignedByte(buf.readerIndex() + 2) & 0x0f;
            
            if (type == TYPE_USERLOG) {
                if (buf.readableBytes() >= length + 5) {
                
                    int index = buf.readerIndex() + 3;
                    int count = buf.getUnsignedByte(index) & 0x0f;
                    index += 5;
                    length += 5;

                    for (int i = 0; i < count; i++) {
                        if (buf.readableBytes() < length) {
                            return null;
                        }
                        int logLength = buf.getUnsignedByte(index + 1);
                        index += logLength;
                        length += logLength;
                    }
                
                    if (buf.readableBytes() >= length) {
                        return buf.readBytes(length);
                    }
                }
            } else if (type == TYPE_SYSLOG) {
                if (buf.readableBytes() >= length + 12) {
                    length += buf.getUnsignedShort(buf.readerIndex() + 8);
                    if (buf.readableBytes() >= length) {
                        return buf.readBytes(length);
                    }
                }
            }
        }

        return null;
    }

}