using System;
using System.IO;
using System.Text;

namespace WR
{
    internal static class Program
    {
        private const string BkpSuffix = "_BKP";
        private const string WormsreloadedExe = "WormsReloaded.exe";
        private const string LanguageFile = "DataPC/Language/AllTextWR.bin";
        private static readonly byte[] Orgepattern = new byte[] {0x41, 0x6c, 0x6c, 0x54, 0x65, 0x78, 0x74, 0x25, 0x73};

        private static readonly byte[] ReplacePattern = new byte[]
                                                            {0x57, 0x52};

        private static void Main()
        {
            try
            {
                string curentDir = Directory.GetCurrentDirectory();
                string wrExeFile = Path.Combine(curentDir, WormsreloadedExe);
                if (!File.Exists(wrExeFile))
                {
                    Console.WriteLine("Can't find " + WormsreloadedExe);
                    return;
                }

                if (!File.Exists(wrExeFile + BkpSuffix))
                {
                    File.Copy(wrExeFile, wrExeFile + BkpSuffix);
                }

                Stream exeStream = new FileStream(wrExeFile, FileMode.Open, FileAccess.ReadWrite);
                Console.WriteLine("Searching for pattern '" + Encoding.UTF8.GetString(Orgepattern) + "' in " +
                                  WormsreloadedExe);
                long pos = ReadTo(Orgepattern, exeStream);
                if (pos == -1)
                {
                    Console.WriteLine("Can't find pattern!");
                    return;
                }
                Console.WriteLine("Found! Modyfying file... " + Encoding.UTF8.GetString(Orgepattern) + " -> " +
                                  Encoding.UTF8.GetString(ReplacePattern));
                exeStream.Seek(-ReplacePattern.Length, SeekOrigin.Current);
                exeStream.Write(ReplacePattern, 0, ReplacePattern.Length);
                Console.WriteLine("Done!");
                exeStream.Flush();
                exeStream.Close();
                if (!File.Exists(Path.Combine(curentDir, LanguageFile)))
                {
                    Console.WriteLine("Remember about creating " + LanguageFile + " !");
                }
            }
            catch (Exception)
            {
                Console.WriteLine("Something went teribbly wrong...");
            }
            Console.Read();
        }

        private static long ReadTo(byte[] pattern, Stream stream)
        {
            int[] f = KmpFailureFunction(pattern);
            int j = 0;
            int tmp = stream.ReadByte();
            if (tmp < 0)
                return tmp;
            byte t = (byte) tmp;

            while (stream.Position < stream.Length + 1)
            {
                if (pattern[j] == t)
                {
                    if (j == pattern.Length - 1)
                        return stream.Position - pattern.Length;

                    tmp = stream.ReadByte();
                    if (tmp < 0)
                        return tmp;
                    t = (byte) tmp;
                    j++;
                }
                else if (j > 0)
                {
                    j = f[j - 1];
                }
                else
                {
                    tmp = stream.ReadByte();
                    if (tmp < 0)
                        return tmp;
                    t = (byte) tmp;
                }
            }
            return -1;
        }

        private static int[] KmpFailureFunction(byte[] pattern)
        {
            int i = 1;
            int j = 0;
            int[] f = new int[pattern.Length];
            if (f.Length > 0)
                f[0] = 0;
            while (i < pattern.Length)
            {
                if (pattern[j] == pattern[i])
                {
                    f[i] = j + 1;
                    i++;
                    j++;
                }
                else if (j > 0)
                {
                    j = f[j - 1];
                }
                else
                {
                    f[i] = 0;
                    i++;
                }
            }
            return f;
        }
    }
}