// Windows sometimes needs to defer the replacement of in-use files until the
// next system start. It does this by keeping a list of (new file, old file)
// pairs in a REG_MULTI_SZ value at HKLM\SYSTEM\CurrentControlSet\Control\
// Session Manager\PendingFileRenameOperations, checking that list at startup
// and moving (renaming) the new files over the old ones. See
// http://ss64.com/nt/mv.html
//
// Unfortunately such moves will fail if the new and old files are not on
// the same drive, and this can cause some app updaters to break if e.g.
// %APPDATA% and %ProgramFiles% have been set up on different volumes.
//
// This script is designed to be run during system shutdown (e.g. from a
// Group Policy shutdown script). It scans the pending rename list for doomed
// cross-drive renames, and attempts to fix those by copying the new files
// onto the same drives as those they are to replace.
//
// Windows Home editions without the ability to use shutdown scripts can run
// this every few minutes from a scheduled task instead. Provided it gets to
// run at least once after creation of a broken rename list, it will fix it.
//
// Stephen Thomas <flabdablet@gmail.com>
// Last updated 3-Nov-2010
//
// This is free software. Do whatever you like with it except
// hold me accountable for any grief it causes you.




// Don't issue diagnostic spew when run from wscript

var host = WScript.Fullname;
var cscript = host.substr(host.length - 12).toLowerCase() == "\\cscript.exe";

// For FileSystemObject documentation, see
// http://msdn.microsoft.com/en-us/library/6kxy1a51

fso = new ActiveXObject("Scripting.FileSystemObject");

// Getting at the registry from jscript requires bizarre contortions: see
// http://msdn.microsoft.com/en-us/library/aa392722
// http://msdn.microsoft.com/en-us/library/aa389294
// http://msdn.microsoft.com/en-us/library/aa392730
// http://msdn.microsoft.com/en-us/library/aa394616

var registry = GetObject("winmgmts:{impersonationLevel=impersonate}!root/default:StdRegProv");

var HKCR = 0x80000000;
var HKCU = 0x80000001;
var HKLM = 0x80000002;
var HKU  = 0x80000003;
var HKCC = 0x80000005;



function ReadRegMultiSz(address) {
	var method = registry.Methods_.Item("GetMultiStringValue");
	var inParam = method.InParameters.SpawnInstance_();
	inParam.hDefKey = address[0];
	inParam.sSubKeyName = address[1];
	inParam.sValueName = address[2];
	var outParam = registry.ExecMethod_(method.Name, inParam);
	if (outParam.ReturnValue == 0) {
		return outParam.sValue.toArray();
	}
	else return [];
}



function WriteRegMultiSz(address, data) {

	// If the array passed as "data" contains any property other
	// than the actual array values, jscript will consider it
	// a sparse array, and passing it directly will make the
	// SetMultiStringValue method call fail with a Type Mismatch
	// error. Even reading the data array's length will cause
	// a .length property to spring into existence and make the
	// array sparse. Create a pristine fixed-size copy using
	// only numeric indices to work around this.

	var values = new Array(data.length);
	for (var i = 0; i < data.length; i++) {
		values[i] = data[i];
	}

	var method = registry.Methods_.Item("SetMultiStringValue");
	var inParam = method.InParameters.SpawnInstance_();
	inParam.hDefKey = address[0];
	inParam.sSubKeyName = address[1];
	inParam.sValueName = address[2];
	inParam.sValue = values;
	var outParam = registry.ExecMethod_(method.Name, inParam);
	return outParam.ReturnValue;
}



function Drive(path) {
	var drive = "";
	if (path) {
		drive = fso.GetDriveName(fso.GetAbsolutePathName(path)).toUpperCase();
	}
	return drive;
}



function RandomHex(bits) {
	var result = "0x";
	for (var i = 0; i < bits; i += 4) {
		result += "0123456789abcdef".charAt(16 * Math.random());
	}
	return result;
}



function Log(message) {
	if (cscript) {
		if (message instanceof Array) {
			WScript.Echo("[");
			for (var i = 0; i < message.length; i++) {
				WScript.Echo(" " + i + ": " + message[i]);
			}
			WScript.Echo("]");
		}
		else {
			WScript.Echo(message);
		}
	}
}



// Get the list of files to be renamed at next startup.

var renameListAddress = [HKLM, "SYSTEM\\CurrentControlSet\\Control\\Session Manager", "PendingFileRenameOperations"];
var renameList = ReadRegMultiSz(renameListAddress);
Log(renameList);

var changed = false;
var copied = new Array;
var tempFolders = new Array;

// Make a first pass over the rename list to find and fix doomed renames.

for (var i = 0; i < renameList.length; i += 2) {
	var source = renameList[i];
	var destn = renameList[i + 1];
	if (source.substr(0, 4) == "\\??\\" && destn.substr(0, 5) == "!\\??\\") {
		source = source.substr(4);
		destn = destn.substr(5);
		var sourceDrive = Drive(source);
		var destnDrive = Drive(destn);
		if (sourceDrive && destnDrive && sourceDrive != destnDrive) {

			// Rename won't work across drives, so the file needs
			// copying to a temp folder on the destination drive.
			// First, find or make the temp folder.

			var tempFolder;
			if (tempFolders[destnDrive]) {
				tempFolder = tempFolders[destnDrive];
			}
			else {
				// Drive has no existing temp folder, so make a
				// new one and schedule it for later deletion.

				tempFolder = destnDrive + "\\" + RandomHex(96);
				tempFolders[destnDrive] = tempFolder;
				fso.CreateFolder(tempFolder);
				renameList.push("\\??\\" + tempFolder, "");
				changed = true;
			}

			// Copy the file to the destination drive.
			// If the copy worked, remember it.

			try {
				newSource = tempFolder + "\\" + RandomHex(96);
				Log("\r\n" + source + "\r\n -> " + newSource);
				fso.CopyFile(source, newSource, false);
				copied["\\??\\" + source] = "\\??\\" + newSource;
			}
			catch (ex) {
				Log(ex.message);
			}
		}
	}
}

// Second pass edits all references to files that got copied,
// making them refer to the copies instead of the originals.

for (var i = 0; i < renameList.length; i += 2) {
	var source = renameList[i];
	if (copied[source]) {
		renameList[i] = copied[source];
	}
}

// Finish by prepending deletion requests for the originals of all
// copied files. Originals should't simply be deleted as we go, as
// app updaters might be testing for their continued existence.

for (var source in copied) {
	renameList.unshift(source, "");
}

// If the rename list was changed, write it back.

if (changed) {
	WriteRegMultiSz(renameListAddress, renameList)
	Log(renameList);
}