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

using Lucene.Net.Analysis.Util;
using Lucene.Net.Util;
using System.Collections.Generic;
using System;
using System.IO;
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="PatternTokenizer"/>.
    /// This tokenizer uses regex pattern matching to construct distinct tokens
    /// for the input stream.  It takes two arguments:  "pattern" and "group".
    /// <para/>
    /// <list type="bullet">
    ///     <item><description>"pattern" is the regular expression.</description></item>
    ///     <item><description>"group" says which group to extract into tokens.</description></item>
    /// </list>
    /// <para>
    /// group=-1 (the default) is equivalent to "split".  In this case, the tokens will
    /// be equivalent to the output from (without empty tokens):
    /// <see cref="Regex.Replace(string, string)"/>
    /// </para>
    /// <para>
    /// Using group &gt;= 0 selects the matching group as the token.  For example, if you have:<br/>
    /// <code>
    ///     pattern = \'([^\']+)\'
    ///     group = 0
    ///     input = aaa 'bbb' 'ccc'
    /// </code>
    /// the output will be two tokens: 'bbb' and 'ccc' (including the ' marks).  With the same input
    /// but using group=1, the output would be: bbb and ccc (no ' marks)
    /// </para>
    /// <para>NOTE: This Tokenizer does not output tokens that are of zero length.</para>
    /// 
    /// <code>
    /// &lt;fieldType name="text_ptn" class="solr.TextField" positionIncrementGap="100"&gt;
    ///   &lt;analyzer&gt;
    ///     &lt;tokenizer class="solr.PatternTokenizerFactory" pattern="\'([^\']+)\'" group="1"/&gt;
    ///   &lt;/analyzer&gt;
    /// &lt;/fieldType&gt;</code> 
    /// 
    /// @since solr1.2
    /// </summary>
    /// <seealso cref="PatternTokenizer"/>
    public class PatternTokenizerFactory : TokenizerFactory
    {
        public const string PATTERN = "pattern";
        public const string GROUP = "group";

        protected readonly Regex m_pattern;
        protected readonly int m_group;

        /// <summary>
        /// Creates a new <see cref="PatternTokenizerFactory"/> </summary>
        public PatternTokenizerFactory(IDictionary<string, string> args) 
            : base(args)
        {
            m_pattern = GetPattern(args, PATTERN);
            m_group = GetInt32(args, GROUP, -1);
            if (args.Count > 0)
            {
                throw new ArgumentException("Unknown parameters: " + args);
            }
        }

        /// <summary>
        /// Split the input using configured pattern
        /// </summary>
        public override Tokenizer Create(AttributeSource.AttributeFactory factory, TextReader input)
        {
            return new PatternTokenizer(factory, input, m_pattern, m_group);
        }
    }
}