/**
 * IK 中文分词  版本 5.0
 * IK Analyzer release 5.0
 * <p>
 * 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
 * <p>
 * http://www.apache.org/licenses/LICENSE-2.0
 * <p>
 * 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.
 * <p>
 * 源代码由林良益(linliangyi2005@gmail.com)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.query;

import java.io.IOException;
import java.io.StringReader;
import java.util.ArrayList;
import java.util.List;

import org.apache.lucene.analysis.standard.StandardAnalyzer;
import org.apache.lucene.queryparser.classic.ParseException;
import org.apache.lucene.queryparser.classic.QueryParser;
import org.apache.lucene.search.Query;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.wltea.analyzer.core.IKSegmenter;
import org.wltea.analyzer.core.Lexeme;

/**
 * Single Word Multi Char Query Builder
 * IK分词算法专用
 *
 * @author linliangyi
 */
public class SWMCQueryBuilder {

    private static final Logger LOG = LoggerFactory.getLogger(SWMCQueryBuilder.class);

    /**
     * 生成SWMCQuery
     *
     * @param fieldName
     * @param keywords
     * @param quickMode
     *
     * @return Lucene Query
     */
    public static Query create(String fieldName, String keywords, boolean quickMode) {
        if (fieldName == null || keywords == null) {
            throw new IllegalArgumentException("参数 fieldName 、 keywords 不能为null.");
        }
        //1.对keywords进行分词处理
        List<Lexeme> lexemes = doAnalyze(keywords);
        //2.根据分词结果，生成SWMCQuery
        Query swmcQuery = getSWMCQuery(fieldName, lexemes, quickMode);
        return swmcQuery;
    }

    /**
     * 分词切分，并返回结链表
     *
     * @param keywords
     *
     * @return
     */
    private static List<Lexeme> doAnalyze(String keywords) {
        List<Lexeme> lexemes = new ArrayList<Lexeme>();
        IKSegmenter ikSeg = new IKSegmenter(new StringReader(keywords), true);
        try {
            Lexeme l;
            while ((l = ikSeg.next()) != null) {
                lexemes.add(l);
            }
        } catch (IOException e) {
            LOG.error("io error.", e);
        }
        return lexemes;
    }

    /**
     * 根据分词结果生成SWMC搜索
     *
     * @param fieldName
     * @param lexemes
     * @param quickMode
     *
     * @return
     */
    private static Query getSWMCQuery(String fieldName, List<Lexeme> lexemes, boolean quickMode) {
        //构造SWMC的查询表达式
        StringBuffer keywordBuffer = new StringBuffer();
        //精简的SWMC的查询表达式
        StringBuffer keywordBuffer_Short = new StringBuffer();
        //记录最后词元长度
        int lastLexemeLength = 0;
        //记录最后词元结束位置
        int lastLexemeEnd = -1;

        int shortCount = 0;
        int totalCount = 0;
        for (Lexeme l : lexemes) {
            totalCount += l.getLength();
            //精简表达式
            if (l.getLength() > 1) {
                keywordBuffer_Short.append(' ').append(l.getLexemeText());
                shortCount += l.getLength();
            }

            if (lastLexemeLength == 0) {
                keywordBuffer.append(l.getLexemeText());
            } else if (lastLexemeLength == 1 && l.getLength() == 1
                    && lastLexemeEnd == l.getBeginPosition()) {//单字位置相邻，长度为一，合并)
                keywordBuffer.append(l.getLexemeText());
            } else {
                keywordBuffer.append(' ').append(l.getLexemeText());

            }
            lastLexemeLength = l.getLength();
            lastLexemeEnd = l.getEndPosition();
        }

        //借助lucene queryparser 生成SWMC Query
        QueryParser qp = new QueryParser(fieldName, new StandardAnalyzer());
        qp.setDefaultOperator(QueryParser.AND_OPERATOR);
        qp.setSplitOnWhitespace(true);
        qp.setAutoGeneratePhraseQueries(true);

        if (quickMode && (shortCount * 1.0f / totalCount) > 0.5f) {
            try {
                Query q = qp.parse(keywordBuffer_Short.toString());
                return q;
            } catch (ParseException e) {
                LOG.error("parse error", e);
            }

        } else {
            if (keywordBuffer.length() > 0) {
                try {
                    Query q = qp.parse(keywordBuffer.toString());
                    return q;
                } catch (ParseException e) {
                    LOG.error("parse error", e);
                }
            }
        }
        return null;
    }
}
