content: package org.apache.lucene.search;
  
  /**
   * Licensed to the Apache Software Foundation (ASF) under one or more
   * contributor license agreements.  See the NOTICE file distributed with
   * this work for additional information regarding copyright ownership.
   * The ASF licenses this file to You 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.
   */
  
  import org.apache.lucene.index.IndexReader;
  import org.apache.lucene.index.Term;
  import org.apache.lucene.util.ToStringUtils;
  
  import java.io.IOException;
  import java.util.Set;
  
  
  /**
   * A query that applies a filter to the results of another query.
   *
   * <p>Note: the bits are retrieved from the filter each time this
   * query is used in a search - use a CachingWrapperFilter to avoid
   * regenerating the bits every time.
   *
   * <p>Created: Apr 20, 2004 8:58:29 AM
   *
   * @since   1.4
   * @see     CachingWrapperFilter
   */
  public class FilteredQuery
  extends Query {
  
    Query query;
    Filter filter;
  
    /**
     * Constructs a new query which applies a filter to the results of the original query.
     * Filter.getDocIdSet() will be called every time this query is used in a search.
     * @param query  Query to be filtered, cannot be <code>null</code>.
     * @param filter Filter to apply to query results, cannot be <code>null</code>.
     */
    public FilteredQuery (Query query, Filter filter) {
      this.query = query;
      this.filter = filter;
    }
  
    /**
     * Returns a Weight that applies the filter to the enclosed query's Weight.
     * This is accomplished by overriding the Scorer returned by the Weight.
     */
    @Override
    public Weight createWeight(final Searcher searcher) throws IOException {
      final Weight weight = query.createWeight (searcher);
      final Similarity similarity = query.getSimilarity(searcher);
      return new Weight() {
        private float value;
          
        // pass these methods through to enclosed query's weight
        @Override
        public float getValue() { return value; }
        
        @Override
        public boolean scoresDocsOutOfOrder() {
          return false;
        }
  
        public float sumOfSquaredWeights() throws IOException { 
          return weight.sumOfSquaredWeights() * getBoost() * getBoost(); // boost sub-weight
        }
  
        @Override
        public void normalize (float v) { 
          weight.normalize(v * getBoost()); // incorporate boost
          value = weight.getValue();
        }
  
        @Override
        public Explanation explain (IndexReader ir, int i) throws IOException {
          Explanation inner = weight.explain (ir, i);
          Filter f = FilteredQuery.this.filter;
          DocIdSet docIdSet = f.getDocIdSet(ir);
          DocIdSetIterator docIdSetIterator = docIdSet == null ? DocIdSet.EMPTY_DOCIDSET.iterator() : docIdSet.iterator();
          if (docIdSetIterator == null) {
            docIdSetIterator = DocIdSet.EMPTY_DOCIDSET.iterator();
          }
          if (docIdSetIterator.advance(i) == i) {
            return inner;
          } else {
            Explanation result = new Explanation
              (0.0f, "failure to match filter: " + f.toString());
            result.addDetail(inner);
            return result;
          }
        }
  
        // return this query
        @Override
        public Query getQuery() { return FilteredQuery.this; }
  
        // return a filtering scorer
        @Override
        public Scorer scorer(IndexReader indexReader, boolean scoreDocsInOrder, boolean topScorer) throws IOException {
          // Hackidy-Häck-Hack for backwards compatibility, as we cannot change IndexSearcher API in 3.x, but still want
          // to move the searchWithFilter implementation to this class: to enable access to our scorer() implementation
          // from IndexSearcher, we moved this method up to the main class. In Lucene trunk,
          // FilteredQuery#getFilteredScorer is inlined here - in 3.x we delegate:
          return FilteredQuery.getFilteredScorer(indexReader, similarity, weight, this, filter);
        }
      };
    }
    
    /** Hackidy-Häck-Hack for backwards compatibility, as we cannot change IndexSearcher API in 3.x, but still want
     * to move the searchWithFilter implementation to this class: to enable access to our scorer() implementation
     * from IndexSearcher without instantiating a separate {@link Weight}, we make the inner implementation accessible.
     * @param indexReader the atomic reader
     * @param similarity the Similarity to use (deprecated)
     * @param weight the weight to wrap
     * @param wrapperWeight must be identical to {@code weight} for usage in {@link IndexSearcher}, but it is different inside this query
     * @param filter the Filter to wrap
     * @lucene.internal
     */
    static Scorer getFilteredScorer(final IndexReader indexReader, final Similarity similarity,
                                    final Weight weight, final Weight wrapperWeight, final Filter filter) throws IOException {
      assert filter != null;
  
      final DocIdSet filterDocIdSet = filter.getDocIdSet(indexReader);
      if (filterDocIdSet == null) {
        // this means the filter does not accept any documents.
        return null;
      }
      
      final DocIdSetIterator filterIter = filterDocIdSet.iterator();
      if (filterIter == null) {
        // this means the filter does not accept any documents.
        return null;
      }
  
      // we are gonna advance() this scorer, so we set inorder=true/toplevel=false
      final Scorer scorer = weight.scorer(indexReader, true, false);
      return (scorer == null) ? null : new Scorer(similarity, wrapperWeight) {
        private int scorerDoc = -1, filterDoc = -1;
        
        // optimization: we are topScorer and collect directly using short-circuited algo
        @Override
        public void score(Collector collector) throws IOException {
          int filterDoc = filterIter.nextDoc();
          int scorerDoc = scorer.advance(filterDoc);
          // the normalization trick already applies the boost of this query,
          // so we can use the wrapped scorer directly:
          collector.setScorer(scorer);
          for (;;) {
            if (scorerDoc == filterDoc) {
              // Check if scorer has exhausted, only before collecting.
              if (scorerDoc == DocIdSetIterator.NO_MORE_DOCS) {
                break;
              }
              collector.collect(scorerDoc);
              filterDoc = filterIter.nextDoc();
              scorerDoc = scorer.advance(filterDoc);
            } else if (scorerDoc > filterDoc) {
              filterDoc = filterIter.advance(scorerDoc);
            } else {
              scorerDoc = scorer.advance(filterDoc);
            }
          }
        }
        
        private int advanceToNextCommonDoc() throws IOException {
          for (;;) {
            if (scorerDoc < filterDoc) {
              scorerDoc = scorer.advance(filterDoc);
            } else if (scorerDoc == filterDoc) {
              return scorerDoc;
            } else {
              filterDoc = filterIter.advance(scorerDoc);
            }
          }
        }
  
        @Override
        public int nextDoc() throws IOException {
          filterDoc = filterIter.nextDoc();
          return advanceToNextCommonDoc();
        }
        
        @Override
        public int advance(int target) throws IOException {
          if (target > filterDoc) {
            filterDoc = filterIter.advance(target);
          }
          return advanceToNextCommonDoc();
        }
  
        @Override
        public int docID() {
          return scorerDoc;
        }
        
        @Override
        public float score() throws IOException {
          return scorer.score();
        }
      };
    }
  
    /** Rewrites the wrapped query. */
    @Override
    public Query rewrite(IndexReader reader) throws IOException {
      Query rewritten = query.rewrite(reader);
      if (rewritten != query) {
        FilteredQuery clone = (FilteredQuery)this.clone();
        clone.query = rewritten;
        return clone;
      } else {
        return this;
      }
    }
  
    public Query getQuery() {
      return query;
    }
  
    public Filter getFilter() {
      return filter;
    }
  
    // inherit javadoc
    @Override
    public void extractTerms(Set<Term> terms) {
        getQuery().extractTerms(terms);
    }
  
    /** Prints a user-readable version of this query. */
    @Override
    public String toString (String s) {
      StringBuilder buffer = new StringBuilder();
      buffer.append("filtered(");
      buffer.append(query.toString(s));
      buffer.append(")->");
      buffer.append(filter);
      buffer.append(ToStringUtils.boost(getBoost()));
      return buffer.toString();
    }
  
    /** Returns true iff <code>o</code> is equal to this. */
    @Override
    public boolean equals(Object o) {
      if (o instanceof FilteredQuery) {
        FilteredQuery fq = (FilteredQuery) o;
        return (query.equals(fq.query) && filter.equals(fq.filter) && getBoost()==fq.getBoost());
      }
      return false;
    }
  
    /** Returns a hash code value for this object. */
    @Override
    public int hashCode() {
      return query.hashCode() ^ filter.hashCode() + Float.floatToRawIntBits(getBoost());
    }
  }
  