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/*
 * Copyright 2015-2017 GenerallyCloud.com
 *  
 * Licensed 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 com.generallycloud.baseio.concurrent;

import java.util.ArrayList;
import java.util.List;
import java.util.Map;
import java.util.concurrent.locks.ReentrantLock;

/**
 * 仅适用于：

 * MULTIPLE => PUT 

 * MULTIPLE => REMOVE 

 * SINGLE => FOREACH 

 * SINGLE => SIZE
 * @param 
 * @param 
 */
public class ReentrantMap {

	private Map		snapshot	;
	private List		modifList	= new ArrayList();
	private ReentrantLock	loack	= new ReentrantLock();
	private boolean		modifid	= false;
	
	public ReentrantMap(Map snapshot) {
		this.snapshot = snapshot;
	}

	public Map takeSnapshot() {
		if (modifid) {
			ReentrantLock lock = this.loack;

			lock.lock();

			Map snapshot = this.snapshot;
			
			List modifList = this.modifList;

			for (Event e : modifList) {

				if (e.isAdd) {
					snapshot.put(e.key, e.value);
				} else {
					snapshot.remove(e.key);
				}
			}

			modifList.clear();

			this.modifid = false;

			lock.unlock();
		}
		
		return snapshot;
	}
	
	private boolean modif(K key, V value,boolean isAdd){
		ReentrantLock lock = this.loack;
		lock.lock();
		Event event = new Event();
		event.key = key;
		event.value = value;
		event.isAdd = isAdd;
		this.modifList.add(event);
		this.modifid = true;
		lock.unlock();
		return true;
	}

	public boolean put(K key, V value) {
		return modif(key, value, true);
	}

	public void remove(K key) {
		modif(key, null, false);
	}

	public ReentrantLock getReentrantLock() {
		return loack;
	}

	public int size() {
		return takeSnapshot().size();
	}
	
	public void clear(){
		ReentrantLock lock = this.loack;
		lock.lock();
		this.modifList.clear();
		this.modifid = false;
		this.snapshot.clear();
		lock.unlock();
	}
	
	public boolean isEmpty(){
		return size() == 0;
	}

	class Event {
		K		key;
		V		value;
		boolean	isAdd;
	}

}