/*
 *
 * 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.
 *
*/

using System;

namespace Lucene.Net.Analysis.Ru
{
	/// <summary>
	/// RussianCharsets class contains encodings schemes (charsets) and ToLowerCase() method implementation
	/// for russian characters in Unicode, KOI8 and CP1252.
	/// Each encoding scheme contains lowercase (positions 0-31) and uppercase (position 32-63) characters.
	/// One should be able to add other encoding schemes (like ISO-8859-5 or customized) by adding a new charset
	/// and adding logic to ToLowerCase() method for that charset.
	/// </summary>
	public class RussianCharsets
	{
		/// <summary>
		/// Unicode Russian charset (lowercase letters only)
		/// </summary>
		public static char[] UnicodeRussian = {
												  '\u0430',
												  '\u0431',
												  '\u0432',
												  '\u0433',
												  '\u0434',
												  '\u0435',
												  '\u0436',
												  '\u0437',
												  '\u0438',
												  '\u0439',
												  '\u043A',
												  '\u043B',
												  '\u043C',
												  '\u043D',
												  '\u043E',
												  '\u043F',
												  '\u0440',
												  '\u0441',
												  '\u0442',
												  '\u0443',
												  '\u0444',
												  '\u0445',
												  '\u0446',
												  '\u0447',
												  '\u0448',
												  '\u0449',
												  '\u044A',
												  '\u044B',
												  '\u044C',
												  '\u044D',
												  '\u044E',
												  '\u044F',
												  // upper case
												  '\u0410',
												  '\u0411',
												  '\u0412',
												  '\u0413',
												  '\u0414',
												  '\u0415',
												  '\u0416',
												  '\u0417',
												  '\u0418',
												  '\u0419',
												  '\u041A',
												  '\u041B',
												  '\u041C',
												  '\u041D',
												  '\u041E',
												  '\u041F',
												  '\u0420',
												  '\u0421',
												  '\u0422',
												  '\u0423',
												  '\u0424',
												  '\u0425',
												  '\u0426',
												  '\u0427',
												  '\u0428',
												  '\u0429',
												  '\u042A',
												  '\u042B',
												  '\u042C',
												  '\u042D',
												  '\u042E',
												  '\u042F'
											  };

		/// <summary>
		/// KOI8 charset
		/// </summary>
		public static char[] KOI8 = {
										(char)0xc1,
										(char)0xc2,
										(char)0xd7,
										(char)0xc7,
										(char)0xc4,
										(char)0xc5,
										(char)0xd6,
										(char)0xda,
										(char)0xc9,
										(char)0xca,
										(char)0xcb,
										(char)0xcc,
										(char)0xcd,
										(char)0xce,
										(char)0xcf,
										(char)0xd0,
										(char)0xd2,
										(char)0xd3,
										(char)0xd4,
										(char)0xd5,
										(char)0xc6,
										(char)0xc8,
										(char)0xc3,
										(char)0xde,
										(char)0xdb,
										(char)0xdd,
										(char)0xdf,
										(char)0xd9,
										(char)0xd8,
										(char)0xdc,
										(char)0xc0,
										(char)0xd1,
										// upper case
										(char)0xe1,
										(char)0xe2,
										(char)0xf7,
										(char)0xe7,
										(char)0xe4,
										(char)0xe5,
										(char)0xf6,
										(char)0xfa,
										(char)0xe9,
										(char)0xea,
										(char)0xeb,
										(char)0xec,
										(char)0xed,
										(char)0xee,
										(char)0xef,
										(char)0xf0,
										(char)0xf2,
										(char)0xf3,
										(char)0xf4,
										(char)0xf5,
										(char)0xe6,
										(char)0xe8,
										(char)0xe3,
										(char)0xfe,
										(char)0xfb,
										(char)0xfd,
										(char)0xff,
										(char)0xf9,
										(char)0xf8,
										(char)0xfc,
										(char)0xe0,
										(char)0xf1
									};

		/// <summary>
		/// CP1251 Charset
		/// </summary>
		public static char[] CP1251 = {
										  (char)0xE0,
										  (char)0xE1,
										  (char)0xE2,
										  (char)0xE3,
										  (char)0xE4,
										  (char)0xE5,
										  (char)0xE6,
										  (char)0xE7,
										  (char)0xE8,
										  (char)0xE9,
										  (char)0xEA,
										  (char)0xEB,
										  (char)0xEC,
										  (char)0xED,
										  (char)0xEE,
										  (char)0xEF,
										  (char)0xF0,
										  (char)0xF1,
										  (char)0xF2,
										  (char)0xF3,
										  (char)0xF4,
										  (char)0xF5,
										  (char)0xF6,
										  (char)0xF7,
										  (char)0xF8,
										  (char)0xF9,
										  (char)0xFA,
										  (char)0xFB,
										  (char)0xFC,
										  (char)0xFD,
										  (char)0xFE,
										  (char)0xFF,
										  // upper case
										  (char)0xC0,
										  (char)0xC1,
										  (char)0xC2,
										  (char)0xC3,
										  (char)0xC4,
										  (char)0xC5,
										  (char)0xC6,
										  (char)0xC7,
										  (char)0xC8,
										  (char)0xC9,
										  (char)0xCA,
										  (char)0xCB,
										  (char)0xCC,
										  (char)0xCD,
										  (char)0xCE,
										  (char)0xCF,
										  (char)0xD0,
										  (char)0xD1,
										  (char)0xD2,
										  (char)0xD3,
										  (char)0xD4,
										  (char)0xD5,
										  (char)0xD6,
										  (char)0xD7,
										  (char)0xD8,
										  (char)0xD9,
										  (char)0xDA,
										  (char)0xDB,
										  (char)0xDC,
										  (char)0xDD,
										  (char)0xDE,
										  (char)0xDF
									  };

		public static char ToLowerCase(char letter, char[] charset)
		{
			if (charset == UnicodeRussian)
			{
				if (letter >= '\u0430' && letter <= '\u044F')
				{
					return letter;
				}
				if (letter >= '\u0410' && letter <= '\u042F')
				{
					return (char) (letter + 32);
				}
			}

			if (charset == KOI8)
			{
				if (letter >= 0xe0 && letter <= 0xff)
				{
					return (char) (letter - 32);
				}
				if (letter >= 0xc0 && letter <= 0xdf)
				{
					return letter;
				}

			}

			if (charset == CP1251)
			{
				if (letter >= 0xC0 && letter <= 0xDF)
				{
					return (char) (letter + 32);
				}
				if (letter >= 0xE0 && letter <= 0xFF)
				{
					return letter;
				}

			}

			return Char.ToLower(letter);
		}
	}
}