/*
 * 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.log4j.rewrite;

import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;

import org.apache.log4j.Logger;
import org.apache.log4j.spi.LoggingEvent;

/**
 * This policy rewrites events where the message of the original event implementes java.util.Map. All other events are
 * passed through unmodified. If the map contains a "message" entry, the value will be used as the message for the
 * rewritten event. The rewritten event will have a property set that is the combination of the original property set
 * and the other members of the message map. If both the original property set and the message map contain the same
 * entry, the value from the message map will overwrite the original property set.
 * <p>
 * The combination of the RewriteAppender and this policy performs the same actions as the MapFilter from log4j 1.3.
 */
public class MapRewritePolicy implements RewritePolicy {
    /**
     * {@inheritDoc}
     */
    public LoggingEvent rewrite(final LoggingEvent source) {
        Object msg = source.getMessage();
        if (msg instanceof Map) {
            Map props = new HashMap(source.getProperties());
            Map eventProps = (Map) msg;
            //
            // if the map sent in the logging request
            // has "message" entry, use that as the message body
            // otherwise, use the entire map.
            //
            Object newMsg = eventProps.get("message");
            if (newMsg == null) {
                newMsg = msg;
            }

            for (Iterator iter = eventProps.entrySet().iterator(); iter.hasNext(); ) {
                Map.Entry entry = (Map.Entry) iter.next();
                if (!("message".equals(entry.getKey()))) {
                    props.put(entry.getKey(), entry.getValue());
                }
            }

            return new LoggingEvent(source.getFQNOfLoggerClass(),
                    source.getLogger() != null ? source.getLogger() : Logger.getLogger(source.getLoggerName()),
                    source.getTimeStamp(), source.getLevel(), newMsg, source.getThreadName(),
                    source.getThrowableInformation(), source.getNDC(), source.getLocationInformation(), props);
        } else {
            return source;
        }

    }
}
