lucene/highlighter/src/java/org/apache/lucene/search/uhighlight/CustomSeparatorBreakIterator.java

/*
 * 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.search.uhighlight;

import java.text.BreakIterator;
import java.text.CharacterIterator;

/**
 * A {@link BreakIterator} that breaks the text whenever a certain separator, provided as a constructor argument, is found.
 */
public final class CustomSeparatorBreakIterator extends BreakIterator {

  private final char separator;
  private CharacterIterator text;
  private int current;

  public CustomSeparatorBreakIterator(char separator) {
    this.separator = separator;
  }

  @Override
  public int current() {
    return current;
  }

  @Override
  public int first() {
    text.setIndex(text.getBeginIndex());
    return current = text.getIndex();
  }

  @Override
  public int last() {
    text.setIndex(text.getEndIndex());
    return current = text.getIndex();
  }

  @Override
  public int next() {
    if (text.getIndex() == text.getEndIndex()) {
      return DONE;
    } else {
      return advanceForward();
    }
  }

  private int advanceForward() {
    char c;
    while ((c = text.next()) != CharacterIterator.DONE) {
      if (c == separator) {
        return current = text.getIndex() + 1;
      }
    }
    assert text.getIndex() == text.getEndIndex();
    return current = text.getIndex();
  }

  @Override
  public int following(int pos) {
    if (pos < text.getBeginIndex() || pos > text.getEndIndex()) {
      throw new IllegalArgumentException("offset out of bounds");
    } else if (pos == text.getEndIndex()) {
      // this conflicts with the javadocs, but matches actual behavior (Oracle has a bug in something)
      // https://bugs.openjdk.java.net/browse/JDK-8015110
      text.setIndex(text.getEndIndex());
      current = text.getIndex();
      return DONE;
    } else {
      text.setIndex(pos);
      current = text.getIndex();
      return advanceForward();
    }
  }

  @Override
  public int previous() {
    if (text.getIndex() == text.getBeginIndex()) {
      return DONE;
    } else {
      return advanceBackward();
    }
  }

  private int advanceBackward() {
    char c;
    while ((c = text.previous()) != CharacterIterator.DONE) {
      if (c == separator) {
        return current = text.getIndex() + 1;
      }
    }
    assert text.getIndex() == text.getBeginIndex();
    return current = text.getIndex();
  }

  @Override
  public int preceding(int pos) {
    if (pos < text.getBeginIndex() || pos > text.getEndIndex()) {
      throw new IllegalArgumentException("offset out of bounds");
    } else if (pos == text.getBeginIndex()) {
      // this conflicts with the javadocs, but matches actual behavior (Oracle has a bug in something)
      // https://bugs.openjdk.java.net/browse/JDK-8015110
      text.setIndex(text.getBeginIndex());
      current = text.getIndex();
      return DONE;
    } else {
      text.setIndex(pos);
      current = text.getIndex();
      return advanceBackward();
    }
  }

  @Override
  public int next(int n) {
    if (n < 0) {
      for (int i = 0; i < -n; i++) {
        previous();
      }
    } else {
      for (int i = 0; i < n; i++) {
        next();
      }
    }
    return current();
  }

  @Override
  public CharacterIterator getText() {
    return text;
  }

  @Override
  public void setText(CharacterIterator newText) {
    text = newText;
    current = text.getBeginIndex();
  }
}