/*
 *  Copyright 2004 Clinton Begin
 *
 *  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.ibatis.sqlmap.engine.cache.memory;

import com.ibatis.sqlmap.engine.cache.CacheController;
import com.ibatis.sqlmap.engine.cache.CacheModel;

import java.lang.ref.SoftReference;
import java.lang.ref.WeakReference;
import java.util.Collections;
import java.util.HashMap;
import java.util.Map;
import java.util.Properties;

/**
 * Memory-based implementation of CacheController
 */
public class MemoryCacheController implements CacheController {

  private MemoryCacheLevel cacheLevel = MemoryCacheLevel.WEAK;
  private Map cache = Collections.synchronizedMap(new HashMap());

  /**
   * Configures the cache
   *
   * @param props Optionally can contain properties [reference-type=WEAK|SOFT|STRONG]
   */
  public void configure(Properties props) {
    String refType = props.getProperty("reference-type");
    if (refType == null) {
      refType = props.getProperty("referenceType");
    }
    if (refType != null) {
      cacheLevel = MemoryCacheLevel.getByReferenceType(refType);
    }
  }

  /**
   * 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) {
    Object reference = null;
    if (cacheLevel.equals(MemoryCacheLevel.WEAK)) {
      reference = new WeakReference(value);
    } else if (cacheLevel.equals(MemoryCacheLevel.SOFT)) {
      reference = new SoftReference(value);
    } else if (cacheLevel.equals(MemoryCacheLevel.STRONG)) {
      reference = new StrongReference(value);
    }
    cache.put(key, reference);
  }

  /**
   * 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 value = null;
    Object ref = cache.get(key);
    if (ref != null) {
      if (ref instanceof StrongReference) {
        value = ((StrongReference) ref).get();
      } else if (ref instanceof SoftReference) {
        value = ((SoftReference) ref).get();
      } else if (ref instanceof WeakReference) {
        value = ((WeakReference) ref).get();
      }
    }
    return value;
  }

  public Object removeObject(CacheModel cacheModel, Object key) {
    Object value = null;
    Object ref = cache.remove(key);
    if (ref != null) {
      if (ref instanceof StrongReference) {
        value = ((StrongReference) ref).get();
      } else if (ref instanceof SoftReference) {
        value = ((SoftReference) ref).get();
      } else if (ref instanceof WeakReference) {
        value = ((WeakReference) ref).get();
      }
    }
    return value;
  }

  /**
   * Flushes the cache.
   *
   * @param cacheModel The cache model
   */
  public void flush(CacheModel cacheModel) {
    cache.clear();
  }

  /**
   * Class to implement a strong (permanent) reference.
   */
  private static class StrongReference {
    private Object object;

    /**
     * StrongReference constructor for an object
     * @param object - the Object to store
     */
    public StrongReference(Object object) {
      this.object = object;
    }

    /**
     * Getter to get the object stored in the StrongReference
     * @return - the stored Object
     */
    public Object get() {
      return object;
    }
  }

}