/*
 * 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.plc4x.java.spi;

import io.netty.channel.ChannelHandler;
import io.netty.channel.ChannelHandlerContext;
import io.netty.handler.codec.MessageToMessageCodec;
import org.apache.commons.lang3.reflect.FieldUtils;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.lang.reflect.Field;

public abstract class PlcMessageToMessageCodec<INBOUND_IN, OUTBOUND_IN>
    extends MessageToMessageCodec<INBOUND_IN, OUTBOUND_IN> {

    private static final Logger logger = LoggerFactory.getLogger(PlcMessageToMessageCodec.class);

    private ChannelHandler prevChannelHandler = null;

    protected PlcMessageToMessageCodec() {
    }

    protected PlcMessageToMessageCodec(Class<? extends INBOUND_IN> inboundMessageType,
                                    Class<? extends OUTBOUND_IN> outboundMessageType) {
        super(inboundMessageType, outboundMessageType);
    }

    protected ChannelHandler getPrevChannelHandler(ChannelHandlerContext ctx) {
        if(prevChannelHandler == null) {
            try {
                Field prevField = FieldUtils.getField(ctx.getClass(), "prev", true);
                if(prevField != null) {
                    ChannelHandlerContext prevContext = (ChannelHandlerContext) prevField.get(ctx);
                    prevChannelHandler = prevContext.handler();
                }
            } catch(Exception e) {
                logger.error("Error accessing field 'prev'", e);
            }
        }
        return prevChannelHandler;
    }

}
