/*******************************************************************************
 * Copyright (c) 2007, 2010 Association for Decentralized Information Management
 * in Industry THTH ry.
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 *
 * Contributors:
 *     VTT Technical Research Centre of Finland - initial API and implementation
 *******************************************************************************/
package org.simantics.utils.datastructures;

import java.util.concurrent.ConcurrentHashMap;

import org.simantics.utils.datastructures.disposable.AbstractDisposable;

/**
 * This class provides context-local variables. There is a different value for 
 * each context. This class handles disposing of all values if optional
 * disposer is provided.  
 *
 * @param <T>
 */
public class ContextLocal<T> extends AbstractDisposable {
	
	protected ConcurrentHashMap<Object, T> reg = new ConcurrentHashMap<Object, T>();
	
	public static interface Disposer<T> {
		public void dispose(T object);
	}
	
	Disposer<T> disposer;
	
	/**
	 * Creates context-local variable container.
	 */
	public ContextLocal() 
	{		
	}
	
	/**
	 * Create context-local variable container.
	 * Container created with this method takes ownership of its object.
	 * 
	 * @param disposed
	 */
	public ContextLocal(Disposer<T> disposer)
	{
		this.disposer = disposer;
	}
	
	/**
	 * Gets the object associated in the specified context
	 * 
	 * @param context
	 * @return associated Object or <code>null</code> if not found
	 */
	public T get(Object context) {
		return reg.get(context);
	}

	/**
	 * Associates the specified Object with the specified context.
	 * 
	 * @param context
	 * @param monitor
	 */
	public void replace(Object context, T value) {
		T old = value != null ? reg.put(context, value) : reg.remove(context);
		if (old!=null && disposer!=null)
			disposer.dispose(old);
	}
	
	public void remove(Object context) {
		replace(context, null);
	}

	@Override
	protected void doDispose() {
		if (disposer!=null)
			for (T lr : reg.values()) {
				disposer.dispose(lr);
			}
		reg.clear();
	}


}