src/Lucene.Net.Analysis.Common/Analysis/Snowball/SnowballAnalyzer.cs

using Lucene.Net.Analysis.Core;
using Lucene.Net.Analysis.En;
using Lucene.Net.Analysis.Standard;
using Lucene.Net.Analysis.Tr;
using Lucene.Net.Analysis.Util;
using Lucene.Net.Util;
using System;
using System.IO;

namespace Lucene.Net.Analysis.Snowball
{
    /*
	 * 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.
	 */

    /// <summary>
    /// Filters <seealso cref="StandardTokenizer"/> with <seealso cref="StandardFilter"/>, {@link
    /// LowerCaseFilter}, <seealso cref="StopFilter"/> and <seealso cref="SnowballFilter"/>.
    /// 
    /// Available stemmers are listed in org.tartarus.snowball.ext.  The name of a
    /// stemmer is the part of the class name before "Stemmer", e.g., the stemmer in
    /// <seealso cref="org.tartarus.snowball.ext.EnglishStemmer"/> is named "English".
    /// 
    /// <para><b>NOTE</b>: This class uses the same <seealso cref="Version"/>
    /// dependent settings as <seealso cref="StandardAnalyzer"/>, with the following addition:
    /// <ul>
    ///   <li> As of 3.1, uses <seealso cref="TurkishLowerCaseFilter"/> for Turkish language.
    /// </ul>
    /// </para> </summary>
    /// @deprecated (3.1) Use the language-specific analyzer in modules/analysis instead. 
    /// This analyzer will be removed in Lucene 5.0 
    [Obsolete("(3.1) Use the language-specific analyzer in modules/analysis instead.")]
    public sealed class SnowballAnalyzer : Analyzer
    {
        private string name;
        private CharArraySet stopSet;
        private readonly LuceneVersion matchVersion;

        /// <summary>
        /// Builds the named analyzer with no stop words. </summary>
        public SnowballAnalyzer(LuceneVersion matchVersion, string name)
        {
            this.name = name;
            this.matchVersion = matchVersion;
        }

        /// <summary>
        /// Builds the named analyzer with the given stop words. </summary>
        public SnowballAnalyzer(LuceneVersion matchVersion, string name, CharArraySet stopWords) : this(matchVersion, name)
        {
            stopSet = CharArraySet.UnmodifiableSet(CharArraySet.Copy(matchVersion, stopWords));
        }

        /// <summary>
        /// Constructs a <seealso cref="StandardTokenizer"/> filtered by a {@link
        ///    StandardFilter}, a <seealso cref="LowerCaseFilter"/>, a <seealso cref="StopFilter"/>,
        ///    and a <seealso cref="SnowballFilter"/> 
        /// </summary>
        public override TokenStreamComponents CreateComponents(string fieldName, TextReader reader)
        {
            Tokenizer tokenizer = new StandardTokenizer(matchVersion, reader);
            TokenStream result = new StandardFilter(matchVersion, tokenizer);
            // remove the possessive 's for english stemmers
            if (matchVersion.OnOrAfter(LuceneVersion.LUCENE_31) && (name.Equals("English") || name.Equals("Porter") || name.Equals("Lovins")))
            {
                result = new EnglishPossessiveFilter(result);
            }
            // Use a special lowercase filter for turkish, the stemmer expects it.
            if (matchVersion.OnOrAfter(LuceneVersion.LUCENE_31) && name.Equals("Turkish"))
            {
                result = new TurkishLowerCaseFilter(result);
            }
            else
            {
                result = new LowerCaseFilter(matchVersion, result);
            }
            if (stopSet != null)
            {
                result = new StopFilter(matchVersion, result, stopSet);
            }
            result = new SnowballFilter(result, name);
            return new TokenStreamComponents(tokenizer, result);
        }
    }
}