package org.apache.lucene.search;

/* ====================================================================
 * The Apache Software License, Version 1.1
 *
 * Copyright (c) 2001 The Apache Software Foundation.  All rights
 * reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 *
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 *
 * 3. The end-user documentation included with the redistribution,
 *    if any, must include the following acknowledgment:
 *       "This product includes software developed by the
 *        Apache Software Foundation (http://www.apache.org/)."
 *    Alternately, this acknowledgment may appear in the software itself,
 *    if and wherever such third-party acknowledgments normally appear.
 *
 * 4. The names "Apache" and "Apache Software Foundation" and
 *    "Apache Lucene" must not be used to endorse or promote products
 *    derived from this software without prior written permission. For
 *    written permission, please contact apache@apache.org.
 *
 * 5. Products derived from this software may not be called "Apache",
 *    "Apache Lucene", nor may "Apache" appear in their name, without
 *    prior written permission of the Apache Software Foundation.
 *
 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED.  IN NO EVENT SHALL THE APACHE SOFTWARE FOUNDATION OR
 * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
 * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 * ====================================================================
 *
 * This software consists of voluntary contributions made by many
 * individuals on behalf of the Apache Software Foundation.  For more
 * information on the Apache Software Foundation, please see
 * <http://www.apache.org/>.
 */

import org.apache.lucene.index.IndexReader;
import java.util.BitSet;
import java.util.WeakHashMap;
import java.util.Map;
import java.io.IOException;

/**
 * @todo add documentation after this is fully accepted
 */
public class CachingWrapperFilter extends Filter {
  private Filter filter;

  /**
   * @todo What about serialization in RemoteSearchable?  Caching won't work.
   *       Should transient be removed?
   */
  private transient Map cache;

  /**
   * @param filter Filter to cache results of
   * @todo Do we want another constructor to allow user to supply
   *       a backing caching Map implementation?
   */
  public CachingWrapperFilter(Filter filter) {
    this.filter = filter;
  }

  public BitSet bits(IndexReader reader) throws IOException {
    if (cache == null) {
      cache = new WeakHashMap();
    }

    synchronized (cache) {  // check cache
      BitSet cached = (BitSet) cache.get(reader);
      if (cached != null) {
        return cached;
      }
    }

    final BitSet bits = filter.bits(reader);

    synchronized (cache) {  // update cache
      cache.put(reader, bits);
    }

    return bits;
  }
}

@@ -2860,60 +2860,259 @@
 %0A * 
-@todo add documentation after this is fully accepted
+Wraps another filters result and caches it.  The caching%0A * behavior is like %7B@link QueryFilter%7D.  The purpose is to allow%0A * filters to simply filter, and then wrap with this class to add%0A * caching, keeping the two concerns decoupled yet composable.
 %0A */
@@ -3407,123 +3407,8 @@
  of%0A
-   * @todo Do we want another constructor to allow user to supply%0A   *       a backing caching Map implementation?%0A
    *

Add some javadoc