/*************************************************************************
 * ModernUO                                                              *
 * Copyright 2019-2020 - ModernUO Development Team                       *
 * Email: hi@modernuo.com                                                *
 * File: HexStringConverter.cs                                           *
 *                                                                       *
 * This program is free software: you can redistribute it and/or modify  *
 * it under the terms of the GNU General Public License as published by  *
 * the Free Software Foundation, either version 3 of the License, or     *
 * (at your option) any later version.                                   *
 *                                                                       *
 * You should have received a copy of the GNU General Public License     *
 * along with this program.  If not, see <http://www.gnu.org/licenses/>. *
 *************************************************************************/

using System;

namespace Server.Text
{
    public static class HexStringConverter
    {
        public static readonly uint[] m_Lookup32Chars = CreateLookup32Chars();

        private static uint[] CreateLookup32Chars()
        {
            var result = new uint[256];
            for (var i = 0; i < 256; i++)
            {
                var s = i.ToString("X2");
                if (BitConverter.IsLittleEndian)
                {
                    result[i] = s[0] + ((uint)s[1] << 16);
                }
                else
                {
                    result[i] = s[1] + ((uint)s[0] << 16);
                }
            }

            return result;
        }

        public static string ToHexString(this byte[] bytes) => new ReadOnlySpan<byte>(bytes).ToHexString();

        public static string ToHexString(this Span<byte> bytes) => ((ReadOnlySpan<byte>)bytes).ToHexString();

        public static unsafe string ToHexString(this ReadOnlySpan<byte> bytes)
        {
            var result = new string((char)0, bytes.Length * 2);
            fixed (char* resultP = result)
            {
                var resultP2 = (uint*)resultP;
                for (var i = 0; i < bytes.Length; i++)
                {
                    resultP2[i] = m_Lookup32Chars[bytes[i]];
                }
            }

            return result;
        }

        public static string ToDelimitedHexString(this byte[] bytes) => ((ReadOnlySpan<byte>)bytes).ToDelimitedHexString();

        public static unsafe string ToDelimitedHexString(this ReadOnlySpan<byte> bytes)
        {
            const uint delimiter = 0x20002C; // ", "
            const char openBracket = '[';
            const char closeBracket = ']';
            var length = Math.Max(2, bytes.Length * 4); // len * 2 + (len - 1) * 2 + 2

            var result = new string((char)0, length);
            fixed (char* resultP = result)
            {
                resultP[0] = openBracket;
                resultP[length - 1] = closeBracket;

                var resultP2 = (uint*)(resultP + 1);
                for (int a = 0, i = 0; a < bytes.Length; a++, i++)
                {
                    if (a > 0)
                    {
                        resultP2[i++] = delimiter;
                    }

                    resultP2[i] = m_Lookup32Chars[bytes[a]];
                }
            }

            return result;
        }

        public static unsafe void GetBytes(this string str, Span<byte> bytes)
        {
            fixed (char* strP = str)
            {
                var i = 0;
                var j = 0;
                while (i < str.Length)
                {
                    int chr1 = strP[i++];
                    int chr2 = strP[i++];
                    if (BitConverter.IsLittleEndian)
                    {
                        bytes[j++] = (byte)(((chr1 - (chr1 >= 65 ? 55 : 48)) << 4) | (chr2 - (chr2 >= 65 ? 55 : 48)));
                    }
                    else
                    {
                        bytes[j++] = (byte)((chr1 - (chr1 >= 65 ? 55 : 48)) | ((chr2 - (chr2 >= 65 ? 55 : 48)) << 4));
                    }
                }
            }
        }
    }
}
