content: package org.apache.lucene.search.regex;
  
  /**
   * 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.search.FilteredTermEnum;
  import org.apache.lucene.index.IndexReader;
  import org.apache.lucene.index.Term;
  
  import java.io.IOException;
  
  /**
   * Subclass of FilteredTermEnum for enumerating all terms that match the
   * specified regular expression term using the specified regular expression
   * implementation.
   * <p>
   * Term enumerations are always ordered by Term.compareTo().  Each term in
   * the enumeration is greater than all that precede it.
   */
  
  public class RegexTermEnum extends FilteredTermEnum {
    private String field = "";
    private String pre = "";
    private boolean endEnum = false;
    private RegexCapabilities regexImpl;
  
    public RegexTermEnum(IndexReader reader, Term term, RegexCapabilities regexImpl) throws IOException {
      super();
      field = term.field();
      String text = term.text();
      this.regexImpl = regexImpl;
  
      regexImpl.compile(text);
  
      pre = regexImpl.prefix();
      if (pre == null) pre = "";
  
      setEnum(reader.terms(new Term(term.field(), pre)));
    }
  
    @Override
    protected final boolean termCompare(Term term) {
      if (field == term.field()) {
        String searchText = term.text();
        if (searchText.startsWith(pre)) {
          return regexImpl.match(searchText);
        }
      }
      endEnum = true;
      return false;
    }
  
    @Override
    public final float difference() {
  // TODO: adjust difference based on distance of searchTerm.text() and term().text()
      return 1.0f;
    }
  
    @Override
    public final boolean endEnum() {
      return endEnum;
    }
  
    @Override
    public void close() throws IOException {
      super.close();
      field = null;
    }
  }
  