package de.mpg.mpiwg.berlin.mpdl.analysis;

import org.apache.lucene.analysis.*;
import org.apache.lucene.analysis.standard.StandardFilter;
import org.apache.lucene.analysis.standard.StandardTokenizer;

import java.io.File;
import java.io.IOException;
import java.io.Reader;
import java.util.Set;

/**
 * StandardAnalyzer which is case insensitive (no LowerCaseFilter in method tokenStream 
 * and reusableTokenStream)
 *
 */
public class MpdlStandardAnalyzer extends Analyzer {
  private Set stopSet;
  /** An array containing some common English words that are usually not
  useful for searching. */
  public static final String[] STOP_WORDS = StopAnalyzer.ENGLISH_STOP_WORDS;

  /** Builds an analyzer with the default stop words ({@link #STOP_WORDS}). */
  public MpdlStandardAnalyzer() {
    this(STOP_WORDS);
  }

  /** Builds an analyzer with the given stop words. */
  public MpdlStandardAnalyzer(Set stopWords) {
    stopSet = stopWords;
  }

  /** Builds an analyzer with the given stop words. */
  public MpdlStandardAnalyzer(String[] stopWords) {
    stopSet = StopFilter.makeStopSet(stopWords);
  }

  /** Builds an analyzer with the stop words from the given file.
   * @see WordlistLoader#getWordSet(File)
   */
  public MpdlStandardAnalyzer(File stopwords) throws IOException {
    stopSet = WordlistLoader.getWordSet(stopwords);
  }

  /** Builds an analyzer with the stop words from the given reader.
   * @see WordlistLoader#getWordSet(Reader)
   */
  public MpdlStandardAnalyzer(Reader stopwords) throws IOException {
    stopSet = WordlistLoader.getWordSet(stopwords);
  }

  /** Constructs a {@link StandardTokenizer} filtered by a {@link
  StandardFilter}, not a {@link LowerCaseFilter} and a {@link StopFilter}. */
  public TokenStream tokenStream(String fieldName, Reader reader) {
    StandardTokenizer tokenStream = new StandardTokenizer(reader);
    tokenStream.setMaxTokenLength(maxTokenLength);
    TokenStream result = new StandardFilter(tokenStream);
    result = new StopFilter(result, stopSet);
    return result;
  }

  private static final class SavedStreams {
    StandardTokenizer tokenStream;
    TokenStream filteredTokenStream;
  }

  /** Default maximum allowed token length */
  public static final int DEFAULT_MAX_TOKEN_LENGTH = 255;

  private int maxTokenLength = DEFAULT_MAX_TOKEN_LENGTH;

  /**
   * Set maximum allowed token length.  If a token is seen
   * that exceeds this length then it is discarded.  This
   * setting only takes effect the next time tokenStream or
   * reusableTokenStream is called.
   */
  public void setMaxTokenLength(int length) {
    maxTokenLength = length;
  }
    
  /**
   * @see #setMaxTokenLength
   */
  public int getMaxTokenLength() {
    return maxTokenLength;
  }
  
  public TokenStream reusableTokenStream(String fieldName, Reader reader) throws IOException {
    SavedStreams streams = (SavedStreams) getPreviousTokenStream();
    if (streams == null) {
      streams = new SavedStreams();
      setPreviousTokenStream(streams);
      streams.tokenStream = new StandardTokenizer(reader);
      streams.filteredTokenStream = new StandardFilter(streams.tokenStream);
      streams.filteredTokenStream = new StopFilter(streams.filteredTokenStream, stopSet);
    } else {
      streams.tokenStream.reset(reader);
    }
    streams.tokenStream.setMaxTokenLength(maxTokenLength);
    return streams.filteredTokenStream;
  }
}