content: /**
   * 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.
   */
  
  package org.apache.solr.search;
  
  import org.apache.lucene.search.Filter;
  import org.apache.lucene.search.DocIdSet;
  import org.apache.lucene.index.Term;
  import org.apache.lucene.index.IndexReader;
  import org.apache.lucene.index.TermEnum;
  import org.apache.lucene.index.TermDocs;
  import org.apache.lucene.util.OpenBitSet;
  
  import java.io.IOException;
  
  /**
   * @version $Id: PrefixFilter.java 922957 2010-03-14 20:58:32Z markrmiller $
   */
  public class PrefixFilter extends Filter {
    protected final Term prefix;
  
    PrefixFilter(Term prefix) {
      this.prefix = prefix;
    }
  
    Term getPrefix() { return prefix; }
  
   @Override
    public DocIdSet getDocIdSet(IndexReader reader) throws IOException {
      final OpenBitSet bitSet = new OpenBitSet(reader.maxDoc());
      new PrefixGenerator(prefix) {
        public void handleDoc(int doc) {
          bitSet.set(doc);
        }
      }.generate(reader);
      return bitSet;
    }
  
    @Override
    public boolean equals(Object o) {
      return o instanceof PrefixFilter && ((PrefixFilter)o).prefix.equals(this.prefix);
    }
  
    @Override
    public int hashCode() {
      return 0xcecf7fe2 + prefix.hashCode();
    }
  
    @Override
    public String toString () {
      StringBuilder sb = new StringBuilder();
      sb.append("PrefixFilter(");
      sb.append(prefix.toString());
      sb.append(")");
      return sb.toString();
    }
  }
  
  // keep this protected until I decide if it's a good way
  // to separate id generation from collection (or should
  // I just reuse hitcollector???)
  interface IdGenerator {
    public void generate(IndexReader reader) throws IOException;
    public void handleDoc(int doc);
  }
  
  
  abstract class PrefixGenerator implements IdGenerator {
    protected final Term prefix;
  
    PrefixGenerator(Term prefix) {
      this.prefix = prefix;
    }
  
    public void generate(IndexReader reader) throws IOException {
      TermEnum enumerator = reader.terms(prefix);
      TermDocs termDocs = reader.termDocs();
  
      try {
  
        String prefixText = prefix.text();
        String prefixField = prefix.field();
        do {
          Term term = enumerator.term();
          if (term != null &&
              term.text().startsWith(prefixText) &&
              term.field() == prefixField)
          {
            termDocs.seek(term);
            while (termDocs.next()) {
              handleDoc(termDocs.doc());
            }
          } else {
            break;
          }
        } while (enumerator.next());
      } finally {
        termDocs.close();
        enumerator.close();
      }
    }
  }
  