/*
    * Copyright 2004-2022 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
    *
    *    https://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.ibatis.sqlmap.engine.cache.lru;
  
  import com.ibatis.sqlmap.engine.cache.CacheController;
  import com.ibatis.sqlmap.engine.cache.CacheModel;
  
  import java.util.Collections;
  import java.util.HashMap;
  import java.util.LinkedList;
  import java.util.List;
  import java.util.Map;
  import java.util.Properties;
  
  /**
   * LRU (least recently used) cache controller implementation.
   */
  public class LruCacheController implements CacheController {
  
    /** The cache size. */
    private int cacheSize;
  
    /** The cache. */
    private Map cache;
  
    /** The key list. */
    private List keyList;
  
    /**
     * Default constructor.
     */
    public LruCacheController() {
      this.cacheSize = 100;
      this.cache = Collections.synchronizedMap(new HashMap());
      this.keyList = Collections.synchronizedList(new LinkedList());
    }
  
    /**
     * Gets the cache size.
     *
     * @return the cache size
     */
    public int getCacheSize() {
      return cacheSize;
    }
  
    /**
     * Sets the cache size.
     *
     * @param cacheSize
     *          the new cache size
     */
    public void setCacheSize(int cacheSize) {
      this.cacheSize = cacheSize;
    }
  
    /**
     * Configures the cache
     *
     * @param props
     *          Optionally can contain properties [reference-type=WEAK|SOFT|STRONG]
     */
    public void setProperties(Properties props) {
      String size = props.getProperty("cache-size");
      if (size == null) {
        size = props.getProperty("size");
      }
      if (size != null) {
        cacheSize = Integer.parseInt(size);
      }
    }
  
    /**
     * Add an object to the cache
     *
     * @param cacheModel
     *          The cacheModel
     * @param key
     *          The key of the object to be cached
     * @param value
     *          The object to be cached
     */
    public void putObject(CacheModel cacheModel, Object key, Object value) {
      cache.put(key, value);
      keyList.add(key);
      if (keyList.size() > cacheSize) {
       try {
         Object oldestKey = keyList.remove(0);
         cache.remove(oldestKey);
       } catch (IndexOutOfBoundsException e) {
         // ignore
       }
     }
   }
 
   /**
    * Get an object out of the cache.
    *
    * @param cacheModel
    *          The cache model
    * @param key
    *          The key of the object to be returned
    *
    * @return The cached object (or null)
    */
   public Object getObject(CacheModel cacheModel, Object key) {
     Object result = cache.get(key);
     keyList.remove(key);
     if (result != null) {
       keyList.add(key);
     }
     return result;
   }
 
   public Object removeObject(CacheModel cacheModel, Object key) {
     keyList.remove(key);
     return cache.remove(key);
   }
 
   /**
    * Flushes the cache.
    *
    * @param cacheModel
    *          The cache model
    */
   public void flush(CacheModel cacheModel) {
     cache.clear();
     keyList.clear();
   }
 
 }