/*
 * Copyright 2011 Future Systems, Inc.
 * 
 * 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 org.krakenapps.confdb.file;

import java.lang.ref.WeakReference;
import java.util.HashSet;
import java.util.Set;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ConcurrentMap;

import org.krakenapps.confdb.ConfigTransactionCache;
import org.krakenapps.confdb.ReferenceKeys;

public class FileConfigTransactionCache implements ConfigTransactionCache {
	private ConcurrentMap<Class<?>, WeakReference<Set<Object>>> cache;

	public FileConfigTransactionCache() {
		this.cache = new ConcurrentHashMap<Class<?>, WeakReference<Set<Object>>>();
	}

	@Override
	public Object get(Class<?> cls, ReferenceKeys keys) {
		Set<Object> l = getCachedObjects(cls);

		for (Object o : l)
			if (keys.eval(o))
				return o;

		return null;
	}

	@Override
	public void put(Class<?> cls, Object obj) {
		Set<Object> l = getCachedObjects(cls);
		l.add(obj);
	}

	@Override
	public void remove(Class<?> cls, Object obj) {
		Set<Object> l = getCachedObjects(cls);
		l.remove(obj);
	}

	private Set<Object> getCachedObjects(Class<?> cls) {
		WeakReference<Set<Object>> ref = cache.get(cls);
		if (ref == null) {
			WeakReference<Set<Object>> old = cache.putIfAbsent(cls, new WeakReference<Set<Object>>(new HashSet<Object>()));
			if (old != null)
				ref = old;
		}

		if (ref != null)
			return ref.get();
		return new HashSet<Object>();
	}

}