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 java.text.Collator;
  
  import org.apache.lucene.index.IndexReader;
  import org.apache.lucene.index.Term;
  import org.apache.lucene.util.StringHelper;
  
  /**
   * Subclass of FilteredTermEnum for enumerating all terms that match the
   * specified range parameters.
   * <p>
   * Term enumerations are always ordered by Term.compareTo().  Each term in
   * the enumeration is greater than all that precede it.
   * @since 2.9
   */
  public class TermRangeTermEnum extends FilteredTermEnum {
  
    private Collator collator = null;
    private boolean endEnum = false;
    private String field;
    private String upperTermText;
    private String lowerTermText;
    private boolean includeLower;
    private boolean includeUpper;
  
    /**
     * Enumerates all terms greater/equal than <code>lowerTerm</code>
     * but less/equal than <code>upperTerm</code>. 
     * 
     * If an endpoint is null, it is said to be "open". Either or both 
     * endpoints may be open.  Open endpoints may not be exclusive 
     * (you can't select all but the first or last term without 
     * explicitly specifying the term to exclude.)
     * 
     * @param reader
     * @param field
     *          An interned field that holds both lower and upper terms.
     * @param lowerTermText
     *          The term text at the lower end of the range
     * @param upperTermText
     *          The term text at the upper end of the range
     * @param includeLower
     *          If true, the <code>lowerTerm</code> is included in the range.
     * @param includeUpper
     *          If true, the <code>upperTerm</code> is included in the range.
     * @param collator
     *          The collator to use to collate index Terms, to determine their
     *          membership in the range bounded by <code>lowerTerm</code> and
     *          <code>upperTerm</code>.
     * 
     * @throws IOException
     */
    public TermRangeTermEnum(IndexReader reader, String field, String lowerTermText, String upperTermText, 
      boolean includeLower, boolean includeUpper, Collator collator) throws IOException {
      this.collator = collator;
      this.upperTermText = upperTermText;
      this.lowerTermText = lowerTermText;
      this.includeLower = includeLower;
      this.includeUpper = includeUpper;
      this.field = StringHelper.intern(field);
      
      // do a little bit of normalization...
      // open ended range queries should always be inclusive.
      if (this.lowerTermText == null) {
        this.lowerTermText = "";
        this.includeLower = true;
      }
      
      if (this.upperTermText == null) {
        this.includeUpper = true;
      }
  
      String startTermText = collator == null ? this.lowerTermText : "";
      setEnum(reader.terms(new Term(this.field, startTermText)));
    }
  
    @Override
    public float difference() {
      return 1.0f;
    }
  
    @Override
    protected boolean endEnum() {
      return endEnum;
    }
  
    @Override
    protected boolean termCompare(Term term) {
      if (collator == null) {
        // Use Unicode code point ordering
        boolean checkLower = false;
        if (!includeLower) // make adjustments to set to exclusive
          checkLower = true;
        if (term != null && term.field() == field) { // interned comparison
          if (!checkLower || null==lowerTermText || term.text().compareTo(lowerTermText) > 0) {
            checkLower = false;
            if (upperTermText != null) {
              int compare = upperTermText.compareTo(term.text());
              /*
               * if beyond the upper term, or is exclusive and this is equal to
               * the upper term, break out
               */
              if ((compare < 0) ||
                  (!includeUpper && compare==0)) {
                endEnum = true;
                return false;
              }
            }
            return true;
          }
        } else {
          // break
          endEnum = true;
          return false;
        }
        return false;
      } else {
        if (term != null && term.field() == field) { // interned comparison
          if ((lowerTermText == null
              || (includeLower
                  ? collator.compare(term.text(), lowerTermText) >= 0
                  : collator.compare(term.text(), lowerTermText) > 0))
             && (upperTermText == null
                 || (includeUpper
                     ? collator.compare(term.text(), upperTermText) <= 0
                     : collator.compare(term.text(), upperTermText) < 0))) {
            return true;
          }
          return false;
        }
        endEnum = true;
        return false;
      }
    }
  }
  