Copyright (c) 2009, 2016 IBM Corporation and others.
This program and the accompanying materials
are made available under the terms of the Eclipse Public License 2.0
which accompanies this distribution, and is available at
https://www.eclipse.org/legal/epl-2.0/
SPDX-License-Identifier: EPL-2.0
Contributors:
    IBM Corporation - initial API and implementation
/*******************************************************************************
 * Copyright (c) 2009, 2016 IBM Corporation and others.
 *
 * This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License 2.0
 * which accompanies this distribution, and is available at
 * https://www.eclipse.org/legal/epl-2.0/
 *
 * SPDX-License-Identifier: EPL-2.0
 * 
 * Contributors:
 *     IBM Corporation - initial API and implementation
 *******************************************************************************/
package org.eclipse.osgi.framework.util;

import java.lang.ref.WeakReference;
import java.util.Map;
import java.util.WeakHashMap;
import org.eclipse.osgi.internal.debug.Debug;

public class ObjectPool {
	//private static String OPTION_DEBUG_OBJECTPOOL_ADDS = Debug.ECLIPSE_OSGI + "/debug/objectPool/adds"; //$NON-NLS-1$
	//private static String OPTION_DEBUG_OBJECTPOOL_DUPS = Debug.ECLIPSE_OSGI + "/debug/objectPool/dups"; //$NON-NLS-1$
	// TODO need to set these
	private static final boolean DEBUG_OBJECTPOOL_ADDS = false;
	private static final boolean DEBUG_OBJECTPOOL_DUPS = false;
	private static Map<Object, WeakReference<Object>> objectCache = new WeakHashMap<>();

	@SuppressWarnings("unchecked")
	public static <T> T intern(T obj) {
		synchronized (objectCache) {
			WeakReference<Object> ref = objectCache.get(obj);
			if (ref != null) {
				Object refValue = ref.get();
				if (refValue != null) {
					obj = (T) refValue;
					if (DEBUG_OBJECTPOOL_DUPS)
						Debug.println("[ObjectPool] Found duplicate object: " + getObjectString(obj)); //$NON-NLS-1$
				}
			} else {
				objectCache.put(obj, new WeakReference<Object>(obj));
				if (DEBUG_OBJECTPOOL_ADDS)
					Debug.println("[ObjectPool] Added unique object to pool: " + getObjectString(obj) + " Pool size: " + objectCache.size()); //$NON-NLS-1$ //$NON-NLS-2$
			}
		}
		return obj;
	}

	private static String getObjectString(Object obj) {
		return "[(" + obj.getClass().getName() + ") " + obj.toString() + "]"; //$NON-NLS-1$ //$NON-NLS-2$ //$NON-NLS-3$
	}
}