/**
 * 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.activemq.memory;

import java.util.concurrent.atomic.AtomicLong;
import org.apache.activemq.usage.MemoryUsage;

/**
 * Simple CacheFilter that increases/decreases usage on a UsageManager as
 * objects are added/removed from the Cache.
 * 
 * @version $Revision$
 */
public class UsageManagerCacheFilter extends CacheFilter {

    private final AtomicLong totalUsage = new AtomicLong(0);
    private final MemoryUsage usage;

    public UsageManagerCacheFilter(Cache next, MemoryUsage um) {
        super(next);
        this.usage = um;
    }

    public Object put(Object key, Object value) {
        long usageValue = getUsageOfAddedObject(value);
        Object rc = super.put(key, value);
        if (rc != null) {
            usageValue -= getUsageOfRemovedObject(rc);
        }
        totalUsage.addAndGet(usageValue);
        usage.increaseUsage(usageValue);
        return rc;
    }

    public Object remove(Object key) {
        Object rc = super.remove(key);
        if (rc != null) {
            long usageValue = getUsageOfRemovedObject(rc);
            totalUsage.addAndGet(-usageValue);
            usage.decreaseUsage(usageValue);
        }
        return rc;
    }

    protected long getUsageOfAddedObject(Object value) {
        return 1;
    }

    protected long getUsageOfRemovedObject(Object value) {
        return 1;
    }

    public void close() {
        usage.decreaseUsage(totalUsage.get());
    }
}
