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 java.io.IOException;
  
  import org.apache.lucene.index.IndexReader;
  import org.apache.lucene.index.Term;
  
  abstract class TermCollectingRewrite<Q extends Query> extends MultiTermQuery.RewriteMethod {
    
    /** Return a suitable top-level Query for holding all expanded terms. */
    protected abstract Q getTopLevelQuery() throws IOException;
    
    /** Add a MultiTermQuery term to the top-level query */
    protected abstract void addClause(Q topLevel, Term term, float boost) throws IOException;
    
    protected final void collectTerms(IndexReader reader, MultiTermQuery query, TermCollector collector) throws IOException {
      final FilteredTermEnum enumerator = query.getEnum(reader);
      try {
        do {
          final Term t = enumerator.term();
          if (t == null || !collector.collect(t, enumerator.difference()))
            break;
        } while (enumerator.next());    
      } finally {
        enumerator.close();
      }
    }
    
    protected interface TermCollector {
      /** return false to stop collecting */
      boolean collect(Term t, float boost) throws IOException;
    }
  }
  