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);
		}
	}
}