src/Lucene.Net.Analysis.Common/Analysis/Ngram/EdgeNGramTokenizerFactory.cs

using Lucene.Net.Analysis.Util;
using Lucene.Net.Util;
using System;
using System.Collections.Generic;
using System.IO;

namespace Lucene.Net.Analysis.Ngram
{
    /*
	 * 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>
    /// Creates new instances of <seealso cref="EdgeNGramTokenizer"/>.
    /// <pre class="prettyprint">
    /// &lt;fieldType name="text_edgngrm" class="solr.TextField" positionIncrementGap="100"&gt;
    ///   &lt;analyzer&gt;
    ///     &lt;tokenizer class="solr.EdgeNGramTokenizerFactory" minGramSize="1" maxGramSize="1"/&gt;
    ///   &lt;/analyzer&gt;
    /// &lt;/fieldType&gt;</pre>
    /// </summary>
    public class EdgeNGramTokenizerFactory : TokenizerFactory
    {
        private readonly int maxGramSize;
        private readonly int minGramSize;
        private readonly string side;

        /// <summary>
        /// Creates a new EdgeNGramTokenizerFactory </summary>
        public EdgeNGramTokenizerFactory(IDictionary<string, string> args) : base(args)
        {
            minGramSize = GetInt(args, "minGramSize", EdgeNGramTokenizer.DEFAULT_MIN_GRAM_SIZE);
            maxGramSize = GetInt(args, "maxGramSize", EdgeNGramTokenizer.DEFAULT_MAX_GRAM_SIZE);
            side = Get(args, "side", EdgeNGramTokenFilter.Side.FRONT.ToString());
            if (args.Count > 0)
            {
                throw new System.ArgumentException("Unknown parameters: " + args);
            }
        }

        public override Tokenizer Create(AttributeSource.AttributeFactory factory, TextReader input)
        {
            if (luceneMatchVersion.OnOrAfter(LuceneVersion.LUCENE_44))
            {
                EdgeNGramTokenFilter.Side sideEnum;
                if (!Enum.TryParse(this.side, true, out sideEnum))
                {
                    throw new System.ArgumentException(typeof(EdgeNGramTokenizer).Name + " does not support backward n-grams as of Lucene 4.4");
                }
                return new EdgeNGramTokenizer(luceneMatchVersion, input, minGramSize, maxGramSize);
            }
            else
            {
                return new Lucene43EdgeNGramTokenizer(luceneMatchVersion, input, side, minGramSize, maxGramSize);
            }
        }
    }
}