/*
 * 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.lucene.analysis.miscellaneous;


import java.io.IOException;

import org.apache.lucene.analysis.TokenFilter;
import org.apache.lucene.analysis.TokenStream;
import org.apache.lucene.analysis.tokenattributes.OffsetAttribute;

Lets all tokens pass through until it sees one with a start offset <= a
configured limit, which won't pass and ends the stream.  This can be useful to
limit highlighting, for example.
 By default, this filter ignores any tokens in the wrapped TokenStream once the limit has been exceeded, which can result in reset() being called prior to incrementToken() returning false. For most TokenStream implementations this should be acceptable, and faster then consuming the full stream. If you are wrapping a TokenStream which requires that the full stream of tokens be exhausted in order to function properly, use the LimitTokenOffsetFilter(TokenStream, int, boolean) option. /**
 * Lets all tokens pass through until it sees one with a start offset &lt;= a
 * configured limit, which won't pass and ends the stream.  This can be useful to
 * limit highlighting, for example.
 * <p>
 * By default, this filter ignores any tokens in the wrapped {@code TokenStream}
 * once the limit has been exceeded, which can result in {@code reset()} being
 * called prior to {@code incrementToken()} returning {@code false}.  For most
 * {@code TokenStream} implementations this should be acceptable, and faster
 * then consuming the full stream. If you are wrapping a {@code TokenStream}
 * which requires that the full stream of tokens be exhausted in order to
 * function properly, use the
 * {@link #LimitTokenOffsetFilter(TokenStream, int, boolean)} option.
 */
public final class LimitTokenOffsetFilter extends TokenFilter {

  private final OffsetAttribute offsetAttrib = addAttribute(OffsetAttribute.class);
  private int maxStartOffset;
  private final boolean consumeAllTokens;

  // some day we may limit by end offset too but no need right now

  
Lets all tokens pass through until it sees one with a start offset <= maxStartOffset which won't pass and ends the stream. It won't consume any tokens afterwards. 
Params:
maxStartOffset – the maximum start offset allowed/**
   * Lets all tokens pass through until it sees one with a start offset &lt;= {@code maxStartOffset}
   * which won't pass and ends the stream. It won't consume any tokens afterwards.
   *
   * @param maxStartOffset the maximum start offset allowed
   */
  public LimitTokenOffsetFilter(TokenStream input, int maxStartOffset) {
    this(input, maxStartOffset, false);
  }

  public LimitTokenOffsetFilter(TokenStream input, int maxStartOffset, boolean consumeAllTokens) {
    super(input);
    if (maxStartOffset < 0) {
      throw new IllegalArgumentException("maxStartOffset must be >= zero");
    }
    this.maxStartOffset = maxStartOffset;
    this.consumeAllTokens = consumeAllTokens;
  }

  @Override
  public boolean incrementToken() throws IOException {
    if (!input.incrementToken()) {
      return false;
    }
    if (offsetAttrib.startOffset() <= maxStartOffset) {
      return true;
    }
    if (consumeAllTokens) {
      while (input.incrementToken()) {
        // no-op
      }
    }
    return false;
  }
}