src/Lucene.Net.Analysis.Common/Analysis/Hi/HindiNormalizer.cs

using Lucene.Net.Analysis.Util;

namespace Lucene.Net.Analysis.Hi
{
    /*
     * 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>
    /// Normalizer for Hindi.
    /// <para>
    /// Normalizes text to remove some differences in spelling variations.
    /// </para>
    /// <para>
    /// Implements the Hindi-language specific algorithm specified in:
    /// <c>Word normalization in Indian languages</c>
    /// Prasad Pingali and Vasudeva Varma.
    /// http://web2py.iiit.ac.in/publications/default/download/inproceedings.pdf.3fe5b38c-02ee-41ce-9a8f-3e745670be32.pdf
    /// </para>
    /// <para>
    /// with the following additions from <c>Hindi CLIR in Thirty Days</c>
    /// Leah S. Larkey, Margaret E. Connell, and Nasreen AbdulJaleel.
    /// http://maroo.cs.umass.edu/pub/web/getpdf.php?id=454:
    /// <list type="bullet">
    ///     <item><description>Internal Zero-width joiner and Zero-width non-joiners are removed</description></item>
    ///     <item><description>In addition to chandrabindu, NA+halant is normalized to anusvara</description></item>
    /// </list>
    /// </para>
    /// </summary>
    public class HindiNormalizer
    {
        /// <summary>
        /// Normalize an input buffer of Hindi text
        /// </summary>
        /// <param name="s"> input buffer </param>
        /// <param name="len"> length of input buffer </param>
        /// <returns> length of input buffer after normalization </returns>
        public virtual int Normalize(char[] s, int len)
        {
            for (int i = 0; i < len; i++)
            {
                switch (s[i])
                {
                    // dead n -> bindu
                    case '\u0928':
                        if (i + 1 < len && s[i + 1] == '\u094D')
                        {
                            s[i] = '\u0902';
                            len = StemmerUtil.Delete(s, i + 1, len);
                        }
                        break;
                    // candrabindu -> bindu
                    case '\u0901':
                        s[i] = '\u0902';
                        break;
                    // nukta deletions
                    case '\u093C':
                        len = StemmerUtil.Delete(s, i, len);
                        i--;
                        break;
                    case '\u0929':
                        s[i] = '\u0928';
                        break;
                    case '\u0931':
                        s[i] = '\u0930';
                        break;
                    case '\u0934':
                        s[i] = '\u0933';
                        break;
                    case '\u0958':
                        s[i] = '\u0915';
                        break;
                    case '\u0959':
                        s[i] = '\u0916';
                        break;
                    case '\u095A':
                        s[i] = '\u0917';
                        break;
                    case '\u095B':
                        s[i] = '\u091C';
                        break;
                    case '\u095C':
                        s[i] = '\u0921';
                        break;
                    case '\u095D':
                        s[i] = '\u0922';
                        break;
                    case '\u095E':
                        s[i] = '\u092B';
                        break;
                    case '\u095F':
                        s[i] = '\u092F';
                        break;
                    // zwj/zwnj -> delete
                    case '\u200D':
                    case '\u200C':
                        len = StemmerUtil.Delete(s, i, len);
                        i--;
                        break;
                    // virama -> delete
                    case '\u094D':
                        len = StemmerUtil.Delete(s, i, len);
                        i--;
                        break;
                    // chandra/short -> replace
                    case '\u0945':
                    case '\u0946':
                        s[i] = '\u0947';
                        break;
                    case '\u0949':
                    case '\u094A':
                        s[i] = '\u094B';
                        break;
                    case '\u090D':
                    case '\u090E':
                        s[i] = '\u090F';
                        break;
                    case '\u0911':
                    case '\u0912':
                        s[i] = '\u0913';
                        break;
                    case '\u0972':
                        s[i] = '\u0905';
                        break;
                    // long -> short ind. vowels
                    case '\u0906':
                        s[i] = '\u0905';
                        break;
                    case '\u0908':
                        s[i] = '\u0907';
                        break;
                    case '\u090A':
                        s[i] = '\u0909';
                        break;
                    case '\u0960':
                        s[i] = '\u090B';
                        break;
                    case '\u0961':
                        s[i] = '\u090C';
                        break;
                    case '\u0910':
                        s[i] = '\u090F';
                        break;
                    case '\u0914':
                        s[i] = '\u0913';
                        break;
                    // long -> short dep. vowels
                    case '\u0940':
                        s[i] = '\u093F';
                        break;
                    case '\u0942':
                        s[i] = '\u0941';
                        break;
                    case '\u0944':
                        s[i] = '\u0943';
                        break;
                    case '\u0963':
                        s[i] = '\u0962';
                        break;
                    case '\u0948':
                        s[i] = '\u0947';
                        break;
                    case '\u094C':
                        s[i] = '\u094B';
                        break;
                    default:
                        break;
                }
            }

            return len;
        }
    }
}