// .NET Assembly Strong Name Replacer
// (C) 2004 Michael Giagnocavo
// www.atrevido.net

using System;
using System.Diagnostics;
using System.IO;
using System.Reflection;

public class SNReplace
{
	public static void Main(string[] args)
	{
		if (args.Length < 2)
		{
			Console.WriteLine("Usage: SNReplace <assembly> <keyfile>");
			return;
		}
		SNReplace snr = new SNReplace();
		snr.AssemblyFile			= args[0];
		snr.KeyFile					= args[1];
		snr.Replace();
	}


	public string KeyFile;
	public string AssemblyFile;

	byte[] currentKey;
	byte[] newKey;
		
	byte[] assembly;

	private int keyStart;

	public void Replace()
	{
		readKeys();
		readAssembly();
		findKeyStart();
		replaceKey();
		save();
		resign();
	}


	private void readKeys()
	{
		this.currentKey = AssemblyName.GetAssemblyName(this.AssemblyFile).GetPublicKey();

		FileStream keyStream = File.OpenRead(this.KeyFile);
		this.newKey = new StrongNameKeyPair(keyStream).PublicKey;
		keyStream.Close();
	}


	private void readAssembly()
	{
		using (FileStream fs = File.OpenRead(this.AssemblyFile))
		{
			this.assembly = new byte[fs.Length];
			fs.Read(this.assembly, 0, (int)fs.Length);
		}
	}
		

	private void findKeyStart()
	{
		// Yes, it's a slow algorithm.
		byte startByte = currentKey[0];
		for(int i = 0; i < this.assembly.Length; i++)
		{
			if (assembly[i] == startByte)
			{
				// Possible match
				if (isKeyFound(i)) 
				{
					this.keyStart = i;
					return;
				}
			}
		}
		// Not found...
		Console.WriteLine("Something's wrong. Public key not found.");
		Environment.Exit(1);
	}


	private bool isKeyFound(int startIndex)
	{
		for(int i = 0; i < currentKey.Length; i++)
		{
			if (currentKey[i] != assembly[i + startIndex])
			{
				return false;
			}
		}
		return true;
	}


	private void replaceKey()
	{
		for(int i = 0; i < newKey.Length; i++)
		{
			assembly[keyStart + i] = newKey[i];
		}
	}


	private void save()
	{
		using (FileStream fs = File.Create(this.AssemblyFile))
		{
			fs.Write(assembly, 0, assembly.Length);
		}
	}


	private void resign()
	{
		ProcessStartInfo si = new ProcessStartInfo("sn.exe");
		si.Arguments = string.Format("-R {0} {1}", this.AssemblyFile, this.KeyFile);
		try 
		{
			Process p = Process.Start(si);
			if (!p.WaitForExit(15000))
			{
				Console.WriteLine("Timeout while waiting for SN to resign the assembly.");
				p.Kill();
				Environment.Exit(2);
			}
		}
		catch (System.ComponentModel.Win32Exception)
		{
			Console.WriteLine("The assembly's public key has been replaced, but SN.exe could not be started. Ensure SN.exe (in the .NET Framework SDK) is in your path, then run SN -R <assembly> <keyfile>.");
		}
	}
}