/*
 * 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.cn.smart;


import java.io.IOException;
import java.text.BreakIterator;
import java.util.Iterator;
import java.util.Locale;

import org.apache.lucene.analysis.cn.smart.hhmm.SegToken;
import org.apache.lucene.analysis.tokenattributes.CharTermAttribute;
import org.apache.lucene.analysis.tokenattributes.OffsetAttribute;
import org.apache.lucene.analysis.tokenattributes.TypeAttribute;
import org.apache.lucene.analysis.util.SegmentingTokenizerBase;
import org.apache.lucene.util.AttributeFactory;

Tokenizer for Chinese or mixed Chinese-English text.

The analyzer uses probabilistic knowledge to find the optimal word segmentation for Simplified Chinese text.
The text is first broken into sentences, then each sentence is segmented into words.
/**
 * Tokenizer for Chinese or mixed Chinese-English text.
 * <p>
 * The analyzer uses probabilistic knowledge to find the optimal word segmentation for Simplified Chinese text.
 * The text is first broken into sentences, then each sentence is segmented into words.
 */
public class HMMChineseTokenizer extends SegmentingTokenizerBase {
  
used for breaking the text into sentences /** used for breaking the text into sentences */
  private static final BreakIterator sentenceProto = BreakIterator.getSentenceInstance(Locale.ROOT);
  
  private final CharTermAttribute termAtt = addAttribute(CharTermAttribute.class);
  private final OffsetAttribute offsetAtt = addAttribute(OffsetAttribute.class);
  private final TypeAttribute typeAtt = addAttribute(TypeAttribute.class);
  
  private final WordSegmenter wordSegmenter = new WordSegmenter();
  private Iterator<SegToken> tokens;

  
Creates a new HMMChineseTokenizer /** Creates a new HMMChineseTokenizer */
  public HMMChineseTokenizer() {
    this(DEFAULT_TOKEN_ATTRIBUTE_FACTORY);
  }
      
  
Creates a new HMMChineseTokenizer, supplying the AttributeFactory /** Creates a new HMMChineseTokenizer, supplying the AttributeFactory */
  public HMMChineseTokenizer(AttributeFactory factory) {
    super(factory, (BreakIterator)sentenceProto.clone());
  }

  @Override
  protected void setNextSentence(int sentenceStart, int sentenceEnd) {
    String sentence = new String(buffer, sentenceStart, sentenceEnd - sentenceStart);
    tokens = wordSegmenter.segmentSentence(sentence, offset + sentenceStart).iterator();
  }

  @Override
  protected boolean incrementWord() {
    if (tokens == null || !tokens.hasNext()) {
      return false;
    } else {
      SegToken token = tokens.next();
      clearAttributes();
      termAtt.copyBuffer(token.charArray, 0, token.charArray.length);
      offsetAtt.setOffset(correctOffset(token.startOffset), correctOffset(token.endOffset));
      typeAtt.setType("word");
      return true;
    }
  }
  
  @Override
  public void reset() throws IOException {
    super.reset();
    tokens = null;
  }
}