/**

 *    Copyright 2009-2018 the original author or authors.

 *

 *    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.apache.ibatis.cache.decorators;

import java.util.Deque;

import java.util.LinkedList;

import java.util.concurrent.locks.ReadWriteLock;

import org.apache.ibatis.cache.Cache;

/**

 * FIFO (first in, first out) cache decorator

 *

 * @author Clinton Begin

 */

public class FifoCache implements Cache {

  private final Cache delegate;

  private final Deque<Object> keyList;

  private int size;

  public FifoCache(Cache delegate) {

    this.delegate = delegate;

    this.keyList = new LinkedList<>();

    this.size = 1024;

  }

  @Override

  public String getId() {

    return delegate.getId();

  }

  @Override

  public int getSize() {

    return delegate.getSize();

  }

  public void setSize(int size) {

    this.size = size;

  }

  @Override

  public void putObject(Object key, Object value) {

    cycleKeyList(key);

    delegate.putObject(key, value);

  }

  @Override

  public Object getObject(Object key) {

    return delegate.getObject(key);

  }

  @Override

  public Object removeObject(Object key) {

    return delegate.removeObject(key);

  }

  @Override

  public void clear() {

    delegate.clear();

    keyList.clear();

  }

  @Override

  public ReadWriteLock getReadWriteLock() {

    return null;

  }

  private void cycleKeyList(Object key) {

    keyList.addLast(key);

    if (keyList.size() > size) {

      Object oldestKey = keyList.removeFirst();

      delegate.removeObject(oldestKey);

    }

  }

}