ReverseDocComparatorSource.java

package com.browseengine.bobo.sort;

import java.io.IOException;
import java.io.Serializable;

import org.apache.lucene.index.AtomicReader;
import org.apache.lucene.search.ScoreDoc;

public class ReverseDocComparatorSource extends DocComparatorSource {
  private final DocComparatorSource _inner;

  public ReverseDocComparatorSource(DocComparatorSource inner) {
    _inner = inner;
  }

  @Override
  public DocComparator getComparator(AtomicReader reader, int docbase) throws IOException {
    return new ReverseDocComparator(_inner.getComparator(reader, docbase));
  }

  public static class ReverseDocComparator extends DocComparator {
    private final DocComparator _comparator;

    public ReverseDocComparator(DocComparator comparator) {
      _comparator = comparator;
    }

    @Override
    public int compare(ScoreDoc doc1, ScoreDoc doc2) {
      return -_comparator.compare(doc1, doc2);
    }

    @Override
    public Comparable<?> value(final ScoreDoc doc) {
      return new ReverseComparable(_comparator.value(doc));

    }

    @SuppressWarnings("rawtypes")
    public static class ReverseComparable implements Comparable, Serializable {
      /**
       *
       */
      private static final long serialVersionUID = 1L;

      final Comparable _inner;

      ReverseComparable(Comparable<?> inner) {
        _inner = inner;
      }

      @SuppressWarnings("unchecked")
      @Override
      public int compareTo(Object o) {
        if (o instanceof ReverseComparable) {
          Comparable inner = ((ReverseComparable) o)._inner;
          return -_inner.compareTo(inner);
        } else {
          throw new IllegalStateException("expected instanace of " + ReverseComparable.class);
        }
      }

      @Override
      public String toString() {
        StringBuilder buf = new StringBuilder();
        buf.append("!").append(_inner);
        return buf.toString();
      }
    }

  }

}