/**
 * IK 中文分词  版本 5.0
 * IK Analyzer release 5.0
 * 
 * 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.
 *
 * 源代码由林良益([email protected])提供
 * 版权声明 2012，乌龙茶工作室
 * provided by Linliangyi and copyright 2012 by Oolong studio
 * 

 * 
 */
package org.wltea.analyzer.lucene;

import java.io.IOException;
import java.io.Reader;

import org.apache.lucene.analysis.Tokenizer;
import org.apache.lucene.analysis.tokenattributes.CharTermAttribute;
import org.apache.lucene.analysis.tokenattributes.OffsetAttribute;

import org.wltea.analyzer.core.IKSegmenter;
import org.wltea.analyzer.core.Lexeme;

/**
 * IK分词器 Lucene Tokenizer适配器类
 * 兼容Lucene 3.1以上版本
 */
public final class IKTokenizer extends Tokenizer {
	
	//IK分词器实现
	private IKSegmenter _IKImplement;
	//词元文本属性
	private CharTermAttribute termAtt;
	//词元位移属性
	private OffsetAttribute offsetAtt;
	//记录最后一个词元的结束位置
	private int finalOffset;
	
	/**
	 * Lucene 3.5 Tokenizer适配器类构造函数
	 *
	 * @param in a {@link java.io.Reader} object.
	 * @param useSmart a boolean.
	 */
	public IKTokenizer(Reader in , boolean useSmart){
	    super(in);
	    offsetAtt = addAttribute(OffsetAttribute.class);
	    termAtt = addAttribute(CharTermAttribute.class);
		_IKImplement = new IKSegmenter(in , useSmart);
	}

	/* (non-Javadoc)
	 * @see org.apache.lucene.analysis.TokenStream#incrementToken()
	 */
	/** {@inheritDoc} */
	@Override
	public boolean incrementToken() throws IOException {
		//清除所有的词元属性
		clearAttributes();
		Lexeme nextLexeme = _IKImplement.next();
		if(nextLexeme != null){
			//将Lexeme转成Attributes
			//设置词元文本
			termAtt.append(nextLexeme.getLexemeText());
			//设置词元长度
			termAtt.setLength(nextLexeme.getLength());
			//设置词元位移
			offsetAtt.setOffset(nextLexeme.getBeginPosition(), nextLexeme.getEndPosition());
			//记录分词的最后位置
			finalOffset = nextLexeme.getEndPosition();
			//返会true告知还有下个词元
			return true;
		}
		//返会false告知词元输出完毕
		return false;
	}

	
	/*
	 * (non-Javadoc)
	 * @see org.apache.lucene.analysis.Tokenizer#reset(java.io.Reader)
	 */
	/** {@inheritDoc} */
	public void reset(Reader input) throws IOException {
		super.reset(input);
		_IKImplement.reset(input);
	}	
	
	/** {@inheritDoc} */
	@Override
	public final void end() {
	    // set final offset 
		offsetAtt.setOffset(finalOffset, finalOffset);
	}
}