using System;
using System.Collections.Generic;
using System.Security.Cryptography;
using System.Text;

namespace GenerateBootImage
{
  class Startup
  {
    private const int _MIN_ARGUMENTS = 2;
    private const int _MAX_ARGUMENTS = 3;
    private const int _PAGE_SIZE = 0x4000;
    private const int _HASH_SIZE = 0x10;

    static void Main(string[] args)
    {
      if (args.Length < _MIN_ARGUMENTS || args.Length > _MAX_ARGUMENTS)
      {
        _DisplayUsage();
      }
      else
      {
        try
        {
          //Open the first dump, verify its size, get the data, and hash it
          var buffer1 = new byte[_PAGE_SIZE];
          var rdr1 = new System.IO.FileStream(args[1], System.IO.FileMode.Open);
          if (rdr1.Length != _PAGE_SIZE)
            throw new InvalidOperationException(String.Format("First dump is not {0} bytes!", _PAGE_SIZE));
          rdr1.Read(buffer1, 0, _PAGE_SIZE);
          rdr1.Close();
          var d1 = MD5.Create();
          var hash1 = d1.ComputeHash(buffer1, 0, _PAGE_SIZE);

          //If we have it, open the second dump, verify its size, get the data, and hash it
          var buffer2 = new byte[_PAGE_SIZE];
          var d2 = MD5.Create();
          byte[] hash2 = null;
          if (args.Length > 2)
          {
            var rdr2 = new System.IO.FileStream(args[2], System.IO.FileMode.Open);
            if (rdr2.Length != _PAGE_SIZE)
              throw new InvalidOperationException(String.Format("Second dump is not {0} bytes!", _PAGE_SIZE));
            rdr2.Read(buffer2, 0, _PAGE_SIZE);
            rdr2.Close();
            hash2 = d2.ComputeHash(buffer2, 0, _PAGE_SIZE);
          }

          int outputFileSize = _PAGE_SIZE + _HASH_SIZE;
          if (args.Length > 2) outputFileSize *= 2;

          //Now write the output file
          var outfile = new System.IO.FileStream(args[0], System.IO.FileMode.Create);
          outfile.Write(buffer1, 0, _PAGE_SIZE);
          outfile.Write(hash1, 0, _HASH_SIZE);
          if (args.Length > 2)
          {
            outfile.Write(buffer2, 0, _PAGE_SIZE);
            outfile.Write(hash2, 0, _HASH_SIZE);
          }
          outfile.Close();
        }
        catch (Exception ex)
        {
          Console.WriteLine("ERROR: " + ex.Message + "\r\n" + ex.ToString());
        }
      }
    }

    static void _DisplayUsage()
    {
        Console.WriteLine("GenerateBootImage");
        Console.WriteLine("Brandon Wilson");
        Console.WriteLine();
        Console.WriteLine("Generates a boot image BIN file given a page 0x1F/0x3F/0x7F (and optionally 0x2F/0x6F) dump(s).");
        Console.WriteLine("Usage: GenerateBootImage.exe [output BIN filename] [page 0x1F/0x3F/0x7F image]");
        Console.WriteLine("                             [page 0x2F/0x6F image]");
    }

    static void _ReverseHash(ref byte[] hash)
    {
      for (int i = 0; i < hash.Length / 2; i++)
      {
        var tmp = hash[i];
        hash[i] = hash[hash.Length - i - 1];
        hash[hash.Length - i - 1] = tmp;
      }
    }
  }
}