src/Lucene.Net.Analysis.Common/Analysis/Pattern/PatternCaptureGroupFilterFactory.cs

using Lucene.Net.Analysis.Util;
using System.Collections.Generic;
using System.Text.RegularExpressions;

namespace Lucene.Net.Analysis.Pattern
{
    /*
	 * 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>
    /// Factory for <see cref="PatternCaptureGroupTokenFilter"/>. 
    /// <code>
    /// &lt;fieldType name="text_ptncapturegroup" class="solr.TextField" positionIncrementGap="100"&gt;
    ///   &lt;analyzer&gt;
    ///     &lt;tokenizer class="solr.KeywordTokenizerFactory"/&gt;
    ///     &lt;filter class="solr.PatternCaptureGroupFilterFactory" pattern="([^a-z])" preserve_original="true"/&gt;
    ///   &lt;/analyzer&gt;
    /// &lt;/fieldType&gt;</code>
    /// </summary>
    /// <seealso cref="PatternCaptureGroupTokenFilter"/>
    public class PatternCaptureGroupFilterFactory : TokenFilterFactory
    {
        private Regex pattern;
        private bool preserveOriginal = true;

        public PatternCaptureGroupFilterFactory(IDictionary<string, string> args) 
            : base(args)
        {
            pattern = GetPattern(args, "pattern");
            preserveOriginal = args.TryGetValue("preserve_original", out string value) ? bool.Parse(value) : true;
        }

        public override TokenStream Create(TokenStream input)
        {
            return new PatternCaptureGroupTokenFilter(input, preserveOriginal, pattern);
        }
    }
}