/*
 * 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.solr.handler.clustering.carrot2;

import java.io.IOException;
import java.io.Reader;
import java.lang.invoke.MethodHandles;
import java.util.regex.Pattern;

import org.apache.lucene.analysis.TokenStream;
import org.apache.lucene.analysis.Tokenizer;
import org.apache.lucene.analysis.tokenattributes.CharTermAttribute;
import org.carrot2.core.LanguageCode;
import org.carrot2.text.analysis.ExtendedWhitespaceTokenizer;
import org.carrot2.text.analysis.ITokenizer;
import org.carrot2.text.linguistic.ITokenizerFactory;
import org.carrot2.text.util.MutableCharArray;
import org.carrot2.util.ExceptionUtils;
import org.carrot2.util.ReflectionUtils;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * An implementation of Carrot2's {@link ITokenizerFactory} based on Lucene's
 * Smart Chinese tokenizer. If Smart Chinese tokenizer is not available in
 * classpath at runtime, the default Carrot2's tokenizer is used. Should the
 * Lucene APIs need to change, the changes can be made in this class.
 * 
 * @lucene.experimental
 */
public class LuceneCarrot2TokenizerFactory implements ITokenizerFactory {
  private static final Logger logger = LoggerFactory.getLogger(MethodHandles.lookup().lookupClass());

  @Override
  public ITokenizer getTokenizer(LanguageCode language) {
    switch (language) {
    case CHINESE_SIMPLIFIED:
      return ChineseTokenizerFactory.createTokenizer();

      /*
       * We use our own analyzer for Arabic. Lucene's version has special
       * support for Nonspacing-Mark characters (see
       * http://www.fileformat.info/info/unicode/category/Mn/index.htm), but we
       * have them included as letters in the parser.
       */
    case ARABIC:
      // Intentional fall-through.

    default:
      return new ExtendedWhitespaceTokenizer();
    }
  }

  /**
   * Creates tokenizers that adapt Lucene's Smart Chinese Tokenizer to Carrot2's
   * {@link ITokenizer}. If Smart Chinese is not available in the classpath, the
   * factory will fall back to the default white space tokenizer.
   */
  private static final class ChineseTokenizerFactory {
    static {
      try {
        ReflectionUtils.classForName(
            "org.apache.lucene.analysis.cn.smart.WordTokenFilter", false);
        ReflectionUtils.classForName(
            "org.apache.lucene.analysis.cn.smart.SentenceTokenizer", false);
      } catch (Throwable e) {
        logger
            .warn("Could not instantiate Smart Chinese Analyzer, clustering quality "
                + "of Chinese content may be degraded. For best quality clusters, "
                + "make sure Lucene's Smart Chinese Analyzer JAR is in the classpath");
        if (e instanceof Error) {
          throw (Error) e;
        }
      }
    }

    static ITokenizer createTokenizer() {
      try {
        return new ChineseTokenizer();
      } catch (Throwable e) {
        if (e instanceof OutOfMemoryError) {
          throw (OutOfMemoryError) e;
        }
        return new ExtendedWhitespaceTokenizer();
      }
    }

    private final static class ChineseTokenizer implements ITokenizer {
      private final static Pattern numeric = Pattern
          .compile("[\\-+'$]?\\d+([:\\-/,.]?\\d+)*[%$]?");

      private Tokenizer sentenceTokenizer;
      private TokenStream wordTokenFilter;
      private CharTermAttribute term = null;

      private final MutableCharArray tempCharSequence;
      private final Class<?> tokenFilterClass;

      private ChineseTokenizer() throws Exception {
        this.tempCharSequence = new MutableCharArray(new char[0]);

        // As Smart Chinese is not available during compile time,
        // we need to resort to reflection.
        final Class<?> tokenizerClass = ReflectionUtils.classForName(
            "org.apache.lucene.analysis.cn.smart.SentenceTokenizer", false);
        this.sentenceTokenizer = (Tokenizer) tokenizerClass.getConstructor(
            Reader.class).newInstance((Reader) null);
        this.tokenFilterClass = ReflectionUtils.classForName(
            "org.apache.lucene.analysis.cn.smart.WordTokenFilter", false);
      }

      @Override
      public short nextToken() throws IOException {
        final boolean hasNextToken = wordTokenFilter.incrementToken();
        if (hasNextToken) {
          short flags = 0;
          final char[] image = term.buffer();
          final int length = term.length();
          tempCharSequence.reset(image, 0, length);
          if (length == 1 && image[0] == ',') {
            // ChineseTokenizer seems to convert all punctuation to ','
            // characters
            flags = ITokenizer.TT_PUNCTUATION;
          } else if (numeric.matcher(tempCharSequence).matches()) {
            flags = ITokenizer.TT_NUMERIC;
          } else {
            flags = ITokenizer.TT_TERM;
          }
          return flags;
        }

        return ITokenizer.TT_EOF;
      }

      @Override
      public void setTermBuffer(MutableCharArray array) {
        array.reset(term.buffer(), 0, term.length());
      }

      @Override
      public void reset(Reader input) {
        try {
          sentenceTokenizer.setReader(input);
          wordTokenFilter = (TokenStream) tokenFilterClass.getConstructor(
              TokenStream.class).newInstance(sentenceTokenizer);
          term = wordTokenFilter.addAttribute(CharTermAttribute.class);
        } catch (Exception e) {
          throw ExceptionUtils.wrapAsRuntimeException(e);
        }
      }
    }
  }
}