using System;
using Lucene.Net.Analysis;
namespace Lucene.Net.Analysis.Ru
{
///
/// A filter that stems Russian words. The implementation was inspired by GermanStemFilter.
/// The input should be filtered by RussianLowerCaseFilter before passing it to RussianStemFilter,
/// because RussianStemFilter only works with lowercase part of any "russian" charset.
///
public sealed class RussianStemFilter : TokenFilter
{
///
/// The actual token in the input stream.
///
private Token token = null;
private RussianStemmer stemmer = null;
public RussianStemFilter(TokenStream _in, char[] charset) : base(_in)
{
stemmer = new RussianStemmer(charset);
}
///
///
///
/// Returns the next token in the stream, or null at EOS
public override Token Next()
{
if ((token = input.Next()) == null)
{
return null;
}
else
{
String s = stemmer.Stem(token.TermText());
if (!s.Equals(token.TermText()))
{
return new Token(s, token.StartOffset(), token.EndOffset(),
token.Type());
}
return token;
}
}
///
/// Set a alternative/custom RussianStemmer for this filter.
///
///
public void SetStemmer(RussianStemmer stemmer)
{
if (stemmer != null)
{
this.stemmer = stemmer;
}
}
}
}