DevDrive/SymlinkHandler.cs

using DokanNet;

namespace DevDrive;

/// <summary>
/// Handles passthrough operations for symlinks to real file system paths.
/// </summary>
public static class SymlinkHandler
{
    public static bool TryResolveSymlink(string virtualPath, FloppyStorage storage, out string? realPath)
    {
        realPath = null;
        virtualPath = FloppyStorage.NormalizePath(virtualPath);

        var node = storage.GetNode(virtualPath);
        if (node?.IsSymlink == true)
        {
            realPath = node.SymlinkTarget;
            return true;
        }

        var parts = virtualPath.Split('\\', StringSplitOptions.RemoveEmptyEntries);
        var currentPath = "\\";

        for (var i = 0; i < parts.Length; i++)
        {
            currentPath = currentPath == "\\" ? "\\" + parts[i] : currentPath + "\\" + parts[i];
            var currentNode = storage.GetNode(currentPath);

            if (currentNode?.IsSymlink == true)
            {
                var remainingPath = string.Join("\\", parts.Skip(i + 1));
                realPath = string.IsNullOrEmpty(remainingPath)
                    ? currentNode.SymlinkTarget
                    : Path.Combine(currentNode.SymlinkTarget!, remainingPath);
                return true;
            }
        }

        return false;
    }

    public static IList<FileInformation> ListRealDirectory(string realPath)
    {
        var files = new List<FileInformation>();

        try
        {
            if (!Directory.Exists(realPath))
            {
                return files;
            }

            foreach (var entry in new DirectoryInfo(realPath).EnumerateFileSystemInfos())
            {
                files.Add(new FileInformation
                {
                    FileName = entry.Name,
                    Attributes = entry.Attributes,
                    CreationTime = entry.CreationTime,
                    LastAccessTime = entry.LastAccessTime,
                    LastWriteTime = entry.LastWriteTime,
                    Length = entry is FileInfo fi ? fi.Length : 0
                });
            }
        }
        catch
        {
        }

        return files;
    }

    public static bool GetRealFileInfo(string realPath, out FileInformation fileInfo)
    {
        fileInfo = default;

        try
        {
            if (File.Exists(realPath))
            {
                var fi = new FileInfo(realPath);
                fileInfo = new FileInformation
                {
                    FileName = fi.Name,
                    Attributes = fi.Attributes,
                    CreationTime = fi.CreationTime,
                    LastAccessTime = fi.LastAccessTime,
                    LastWriteTime = fi.LastWriteTime,
                    Length = fi.Length
                };
                return true;
            }

            if (Directory.Exists(realPath))
            {
                var di = new DirectoryInfo(realPath);
                fileInfo = new FileInformation
                {
                    FileName = di.Name,
                    Attributes = di.Attributes,
                    CreationTime = di.CreationTime,
                    LastAccessTime = di.LastAccessTime,
                    LastWriteTime = di.LastWriteTime,
                    Length = 0
                };
                return true;
            }
        }
        catch
        {
        }

        return false;
    }

    public static NtStatus ReadRealFile(string realPath, byte[] buffer, out int bytesRead, long offset)
    {
        bytesRead = 0;

        try
        {
            using var stream = new FileStream(realPath, System.IO.FileMode.Open, System.IO.FileAccess.Read, FileShare.ReadWrite);
            stream.Seek(offset, SeekOrigin.Begin);
            bytesRead = stream.Read(buffer, 0, buffer.Length);
            return DokanResult.Success;
        }
        catch (FileNotFoundException)
        {
            return DokanResult.FileNotFound;
        }
        catch (UnauthorizedAccessException)
        {
            return DokanResult.AccessDenied;
        }
        catch
        {
            return DokanResult.Error;
        }
    }

    public static NtStatus WriteRealFile(string realPath, byte[] buffer, out int bytesWritten, long offset)
    {
        bytesWritten = 0;

        try
        {
            using var stream = new FileStream(realPath, System.IO.FileMode.OpenOrCreate, System.IO.FileAccess.Write, FileShare.ReadWrite);
            stream.Seek(offset, SeekOrigin.Begin);
            stream.Write(buffer, 0, buffer.Length);
            bytesWritten = buffer.Length;
            return DokanResult.Success;
        }
        catch (UnauthorizedAccessException)
        {
            return DokanResult.AccessDenied;
        }
        catch
        {
            return DokanResult.Error;
        }
    }

    public static NtStatus CreateRealFileOrDirectory(string realPath, bool isDirectory, FileMode mode)
    {
        try
        {
            if (isDirectory)
            {
                if (mode == FileMode.CreateNew)
                {
                    Directory.CreateDirectory(realPath);
                }
                return DokanResult.Success;
            }

            switch (mode)
            {
                case FileMode.CreateNew:
                    using (File.Create(realPath)) { }
                    break;
                case FileMode.Create:
                case FileMode.OpenOrCreate:
                    using (new FileStream(realPath, System.IO.FileMode.OpenOrCreate, System.IO.FileAccess.ReadWrite)) { }
                    break;
                default:
                    break;
            }

            return DokanResult.Success;
        }
        catch (UnauthorizedAccessException)
        {
            return DokanResult.AccessDenied;
        }
        catch
        {
            return DokanResult.Error;
        }
    }
}