package org.apache.lucene.analysis.tokenattributes;

/*
 * 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.util.Attribute;

/**
 * The start and end character offset of a Token. 
 */
public interface OffsetAttribute extends Attribute {
  /** 
   * Returns this Token's starting offset, the position of the first character
   * corresponding to this token in the source text.
   * <p>
   * Note that the difference between {@link #endOffset()} and <code>startOffset()</code> 
   * may not be equal to termText.length(), as the term text may have been altered by a
   * stemmer or some other filter.
   * @see #setOffset(int, int) 
   */
  public int startOffset();

  
  /** 
   * Set the starting and ending offset.
   * @throws IllegalArgumentException If <code>startOffset</code> or <code>endOffset</code>
   *         are negative, or if <code>startOffset</code> is greater than 
   *         <code>endOffset</code>
   * @see #startOffset()
   * @see #endOffset()
   */
  public void setOffset(int startOffset, int endOffset);
  

  /** 
   * Returns this Token's ending offset, one greater than the position of the
   * last character corresponding to this token in the source text. The length
   * of the token in the source text is (<code>endOffset()</code> - {@link #startOffset()}). 
   * @see #setOffset(int, int)
   */
  public int endOffset();
}
