src/Lucene.Net.Analysis.Common/Collation/CollationKeyAnalyzer.cs

#if FEATURE_COLLATION
using Icu.Collation;
using Lucene.Net.Analysis;
using Lucene.Net.Analysis.Core;
using Lucene.Net.Util;
using System;
using System.IO;

namespace Lucene.Net.Collation
{
    /*
     * 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>
    /// <para>
    ///   Configures <see cref="KeywordTokenizer"/> with <see cref="CollationAttributeFactory"/>.
    /// </para>
    /// <para>
    ///   Converts the token into its <see cref="System.Globalization.SortKey"/>, and then
    ///   encodes the <see cref="System.Globalization.SortKey"/> either directly or with 
    ///   <see cref="IndexableBinaryStringTools"/> (see version note below), to allow 
    ///   it to be stored as an index term.
    /// </para>
    /// <para>
    ///   <strong>WARNING:</strong> Make sure you use exactly the same <see cref="Collator"/> at
    ///   index and query time -- <see cref="System.Globalization.SortKey"/> are only comparable when produced by
    ///   the same <see cref="Collator"/>.  Since <c>java.text.RuleBasedCollators</c> are not
    ///   independently versioned, it is unsafe to search against stored
    ///   <see cref="System.Globalization.SortKey"/> unless the following are exactly the same (best practice is
    ///   to store this information with the index and check that they remain the
    ///   same at query time):
    /// </para>
    /// <list type="number">
    ///   <item><description>JVM vendor</description></item>
    ///   <item><description>JVM version, including patch version</description></item>
    ///   <item><description>
    ///     The language (and country and variant, if specified) of the Locale
    ///     used when constructing the collator via
    ///     <see cref="Collator.Create(System.Globalization.CultureInfo)"/>.
    ///   </description></item>
    ///   <item><description>
    ///     The collation strength used - see <see cref="Collator.Strength"/>
    ///   </description></item>
    /// </list> 
    /// <para>
    ///   The <c>ICUCollationKeyAnalyzer</c> in the analysis-icu package 
    ///   uses ICU4J's Collator, which makes its
    ///   its version available, thus allowing collation to be versioned
    ///   independently from the JVM.  ICUCollationKeyAnalyzer is also significantly
    ///   faster and generates significantly shorter keys than CollationKeyAnalyzer.
    ///   See <a href="http://site.icu-project.org/charts/collation-icu4j-sun"
    ///   >http://site.icu-project.org/charts/collation-icu4j-sun</a> for key
    ///   generation timing and key length comparisons between ICU4J and
    ///   <see cref="Collator"/> over several languages.
    /// </para>
    /// <para>
    ///   CollationKeys generated by <see cref="Collator"/> are not compatible
    ///   with those those generated by ICU Collators.  Specifically, if you use 
    ///   CollationKeyAnalyzer to generate index terms, do not use
    ///   ICUCollationKeyAnalyzer on the query side, or vice versa.
    /// </para>
    /// <para>You must specify the required <see cref="LuceneVersion"/>
    /// compatibility when creating <see cref="CollationKeyAnalyzer"/>:
    /// <list type="bullet">
    ///   <item><description> As of 4.0, Collation Keys are directly encoded as bytes. Previous
    ///   versions will encode the bytes with <see cref="IndexableBinaryStringTools"/>.</description></item>
    /// </list>
    /// </para>
    /// </summary>
    public sealed class CollationKeyAnalyzer : Analyzer
    {
        private readonly Collator collator;
        private readonly CollationAttributeFactory factory;
        private readonly LuceneVersion matchVersion;

        /// <summary>
        /// Create a new <see cref="CollationKeyAnalyzer"/>, using the specified collator.
        /// </summary>
        /// <param name="matchVersion"> See <see cref="CollationKeyAnalyzer"/> </param>
        /// <param name="collator"> <see cref="System.Globalization.SortKey"/> generator </param>
        public CollationKeyAnalyzer(LuceneVersion matchVersion, Collator collator)
        {
            this.matchVersion = matchVersion;
            this.collator = collator;
            this.factory = new CollationAttributeFactory(collator);
        }
        
        [Obsolete("Use <seealso cref=\"CollationKeyAnalyzer#CollationKeyAnalyzer(LuceneVersion, Collator)\"/> and specify a version instead. This ctor will be removed in Lucene 5.0")]
        public CollationKeyAnalyzer(Collator collator) 
            : this(LuceneVersion.LUCENE_31, collator)
        {
        }

        protected override TokenStreamComponents CreateComponents(string fieldName, TextReader reader)
        {
#pragma warning disable 612, 618
            if (this.matchVersion.OnOrAfter(LuceneVersion.LUCENE_40))
#pragma warning restore 612, 618
            {
                var tokenizer = new KeywordTokenizer(this.factory, reader, KeywordTokenizer.DEFAULT_BUFFER_SIZE);
                return new TokenStreamComponents(tokenizer, tokenizer);
            }
            else
            {
                var tokenizer = new KeywordTokenizer(reader);
                return new TokenStreamComponents(tokenizer,
#pragma warning disable 612, 618
                    new CollationKeyFilter(tokenizer, this.collator));
#pragma warning restore 612, 618
            }
        }
    }
}
#endif