DevDrive/FloppyFileSystem.cs

using System.Security.AccessControl;
using DokanNet;
using FileAccess = DokanNet.FileAccess;

namespace DevDrive;

public class FloppyFileSystem : IDokanOperations
{
    private const string DefaultVolumeName = "Dev Disk";
    private const string FileSystemName = "FAT";
    private const uint VolumeSerial = 0x19950101;

    private readonly FloppyStorage _storage;
    private readonly string _volumeName;

    public FloppyFileSystem(string? volumeName = null, long totalBytes = FloppyStorage.DefaultCapacity, long freeBytes = FloppyStorage.DefaultCapacity)
    {
        _storage = new FloppyStorage(totalBytes, freeBytes);
        _volumeName = volumeName ?? DefaultVolumeName;
    }

    public FloppyFileSystem(Dictionary<string, string>? symlinks, string? volumeName, long totalBytes, long freeBytes)
    {
        _storage = new FloppyStorage(totalBytes, freeBytes);
        _volumeName = volumeName ?? DefaultVolumeName;

        if (symlinks != null)
        {
            foreach (var (path, target) in symlinks)
            {
                _storage.CreateSymlink(path, target, true);
            }
        }
    }

    public NtStatus CreateFile(
        string fileName,
        FileAccess access,
        FileShare share,
        FileMode mode,
        FileOptions options,
        FileAttributes attributes,
        IDokanFileInfo info)
    {
        var path = FloppyStorage.NormalizePath(fileName);

        if (SymlinkHandler.TryResolveSymlink(path, _storage, out var realPath) && realPath != null)
        {
            return SymlinkHandler.CreateRealFileOrDirectory(realPath, info.IsDirectory, mode);
        }

        var node = _storage.GetNode(path);
        var parentPath = FloppyStorage.GetParentPath(path);
        var parentExists = _storage.Exists(parentPath);

        if (info.IsDirectory)
        {
            switch (mode)
            {
                case FileMode.CreateNew:
                    if (node != null)
                    {
                        return DokanResult.FileExists;
                    }
                    if (!parentExists)
                    {
                        return DokanResult.PathNotFound;
                    }
                    var newDir = _storage.CreateNode(path, true);
                    if (newDir == null)
                    {
                        return DokanResult.Error;
                    }
                    return DokanResult.Success;

                case FileMode.Open:
                    if (node == null)
                    {
                        return DokanResult.PathNotFound;
                    }
                    if (!node.IsDirectory)
                    {
                        return DokanResult.NotADirectory;
                    }
                    return DokanResult.Success;

                default:
                    return DokanResult.Success;
            }
        }

        var pathExists = node != null;
        var pathIsDirectory = node?.IsDirectory ?? false;

        switch (mode)
        {
            case FileMode.Open:
                if (!pathExists)
                {
                    return DokanResult.FileNotFound;
                }
                if (pathIsDirectory)
                {
                    info.IsDirectory = true;
                }
                break;

            case FileMode.CreateNew:
                if (pathExists)
                {
                    return DokanResult.FileExists;
                }
                if (!parentExists)
                {
                    return DokanResult.PathNotFound;
                }
                _storage.CreateNode(path, false);
                break;

            case FileMode.Create:
                if (pathExists && pathIsDirectory)
                {
                    return DokanResult.AccessDenied;
                }
                if (!parentExists)
                {
                    return DokanResult.PathNotFound;
                }
                if (pathExists)
                {
                    var existing = _storage.GetNode(path);
                    if (existing != null)
                    {
                        existing.Data = [];
                        existing.LastWriteTime = DateTime.Now;
                    }
                }
                else
                {
                    _storage.CreateNode(path, false);
                }
                break;

            case FileMode.OpenOrCreate:
                if (!pathExists)
                {
                    if (!parentExists)
                    {
                        return DokanResult.PathNotFound;
                    }
                    _storage.CreateNode(path, false);
                }
                else if (pathIsDirectory)
                {
                    info.IsDirectory = true;
                }
                break;

            case FileMode.Truncate:
                if (!pathExists)
                {
                    return DokanResult.FileNotFound;
                }
                if (pathIsDirectory)
                {
                    return DokanResult.AccessDenied;
                }
                var truncNode = _storage.GetNode(path);
                if (truncNode != null)
                {
                    truncNode.Data = [];
                    truncNode.LastWriteTime = DateTime.Now;
                }
                break;

            case FileMode.Append:
                if (!pathExists)
                {
                    if (!parentExists)
                    {
                        return DokanResult.PathNotFound;
                    }
                    _storage.CreateNode(path, false);
                }
                break;
        }

        return DokanResult.Success;
    }

    public void Cleanup(string fileName, IDokanFileInfo info)
    {
        if (info.IsDirectory && _storage.Exists(FloppyStorage.NormalizePath(fileName)))
        {
            return;
        }
    }

    public void CloseFile(string fileName, IDokanFileInfo info)
    {
    }

    public NtStatus ReadFile(
        string fileName,
        byte[] buffer,
        out int bytesRead,
        long offset,
        IDokanFileInfo info)
    {
        var path = FloppyStorage.NormalizePath(fileName);

        if (SymlinkHandler.TryResolveSymlink(path, _storage, out var realPath) && realPath != null)
        {
            return SymlinkHandler.ReadRealFile(realPath, buffer, out bytesRead, offset);
        }

        var node = _storage.GetNode(path);

        if (node == null || node.IsDirectory)
        {
            bytesRead = 0;
            return DokanResult.FileNotFound;
        }

        node.LastAccessTime = DateTime.Now;

        if (offset >= node.Data.Length)
        {
            bytesRead = 0;
            return DokanResult.Success;
        }

        var toRead = Math.Min(buffer.Length, (int)(node.Data.Length - offset));
        Array.Copy(node.Data, offset, buffer, 0, toRead);
        bytesRead = toRead;

        return DokanResult.Success;
    }

    public NtStatus WriteFile(
        string fileName,
        byte[] buffer,
        out int bytesWritten,
        long offset,
        IDokanFileInfo info)
    {
        var path = FloppyStorage.NormalizePath(fileName);

        if (SymlinkHandler.TryResolveSymlink(path, _storage, out var realPath) && realPath != null)
        {
            return SymlinkHandler.WriteRealFile(realPath, buffer, out bytesWritten, offset);
        }

        var node = _storage.GetNode(path);

        if (node == null || node.IsDirectory)
        {
            bytesWritten = 0;
            return DokanResult.FileNotFound;
        }

        if (info.PagingIo)
        {
            if (offset >= node.Data.Length)
            {
                bytesWritten = 0;
                return DokanResult.Success;
            }
            var toWrite = Math.Min(buffer.Length, (int)(node.Data.Length - offset));
            Array.Copy(buffer, 0, node.Data, offset, toWrite);
            bytesWritten = toWrite;
            return DokanResult.Success;
        }

        var newLength = offset + buffer.Length;
        var additionalBytes = newLength - node.Data.Length;

        if (additionalBytes > 0 && !_storage.HasEnoughSpace(additionalBytes))
        {
            bytesWritten = 0;
            return DokanResult.DiskFull;
        }

        if (newLength > node.Data.Length)
        {
            var newData = new byte[newLength];
            Array.Copy(node.Data, newData, node.Data.Length);
            node.Data = newData;
        }

        Array.Copy(buffer, 0, node.Data, offset, buffer.Length);
        bytesWritten = buffer.Length;
        node.LastWriteTime = DateTime.Now;

        return DokanResult.Success;
    }

    public NtStatus FlushFileBuffers(string fileName, IDokanFileInfo info)
    {
        return DokanResult.Success;
    }

    public NtStatus GetFileInformation(
        string fileName,
        out FileInformation fileInfo,
        IDokanFileInfo info)
    {
        var path = FloppyStorage.NormalizePath(fileName);

        if (SymlinkHandler.TryResolveSymlink(path, _storage, out var realPath) && realPath != null)
        {
            if (SymlinkHandler.GetRealFileInfo(realPath, out fileInfo))
            {
                return DokanResult.Success;
            }
            return DokanResult.FileNotFound;
        }

        var node = _storage.GetNode(path);

        if (node == null)
        {
            fileInfo = default;
            return DokanResult.FileNotFound;
        }

        fileInfo = new FileInformation
        {
            FileName = node.Name,
            Attributes = node.Attributes,
            CreationTime = node.CreationTime,
            LastAccessTime = node.LastAccessTime,
            LastWriteTime = node.LastWriteTime,
            Length = node.FileSize
        };

        return DokanResult.Success;
    }

    public NtStatus FindFiles(
        string fileName,
        out IList<FileInformation> files,
        IDokanFileInfo info)
    {
        var path = FloppyStorage.NormalizePath(fileName);

        if (SymlinkHandler.TryResolveSymlink(path, _storage, out var realPath) && realPath != null)
        {
            files = SymlinkHandler.ListRealDirectory(realPath);
            return DokanResult.Success;
        }

        var children = _storage.GetChildren(path);

        files = children.Select(node => new FileInformation
        {
            FileName = node.Name,
            Attributes = node.Attributes,
            CreationTime = node.CreationTime,
            LastAccessTime = node.LastAccessTime,
            LastWriteTime = node.LastWriteTime,
            Length = node.FileSize
        }).ToList();

        return DokanResult.Success;
    }

    public NtStatus FindFilesWithPattern(
        string fileName,
        string searchPattern,
        out IList<FileInformation> files,
        IDokanFileInfo info)
    {
        files = [];
        return DokanResult.NotImplemented;
    }

    public NtStatus SetFileAttributes(
        string fileName,
        FileAttributes attributes,
        IDokanFileInfo info)
    {
        var path = FloppyStorage.NormalizePath(fileName);
        var node = _storage.GetNode(path);

        if (node == null)
        {
            return DokanResult.FileNotFound;
        }

        node.Attributes = attributes;
        return DokanResult.Success;
    }

    public NtStatus SetFileTime(
        string fileName,
        DateTime? creationTime,
        DateTime? lastAccessTime,
        DateTime? lastWriteTime,
        IDokanFileInfo info)
    {
        var path = FloppyStorage.NormalizePath(fileName);
        var node = _storage.GetNode(path);

        if (node == null)
        {
            return DokanResult.FileNotFound;
        }

        if (creationTime.HasValue)
        {
            node.CreationTime = creationTime.Value;
        }
        if (lastAccessTime.HasValue)
        {
            node.LastAccessTime = lastAccessTime.Value;
        }
        if (lastWriteTime.HasValue)
        {
            node.LastWriteTime = lastWriteTime.Value;
        }

        return DokanResult.Success;
    }

    public NtStatus DeleteFile(string fileName, IDokanFileInfo info)
    {
        var path = FloppyStorage.NormalizePath(fileName);
        var node = _storage.GetNode(path);

        if (node == null)
        {
            return DokanResult.FileNotFound;
        }

        if (node.IsDirectory)
        {
            return DokanResult.AccessDenied;
        }

        return DokanResult.Success;
    }

    public NtStatus DeleteDirectory(string fileName, IDokanFileInfo info)
    {
        var path = FloppyStorage.NormalizePath(fileName);
        var node = _storage.GetNode(path);

        if (node == null)
        {
            return DokanResult.PathNotFound;
        }

        if (!node.IsDirectory)
        {
            return DokanResult.NotADirectory;
        }

        var children = _storage.GetChildren(path);
        if (children.Any())
        {
            return DokanResult.DirectoryNotEmpty;
        }

        return DokanResult.Success;
    }

    public NtStatus MoveFile(
        string oldName,
        string newName,
        bool replace,
        IDokanFileInfo info)
    {
        var success = _storage.MoveNode(oldName, newName, replace);
        return success ? DokanResult.Success : DokanResult.FileNotFound;
    }

    public NtStatus SetEndOfFile(string fileName, long length, IDokanFileInfo info)
    {
        var path = FloppyStorage.NormalizePath(fileName);
        var node = _storage.GetNode(path);

        if (node == null || node.IsDirectory)
        {
            return DokanResult.FileNotFound;
        }

        var additionalBytes = length - node.Data.Length;
        if (additionalBytes > 0 && !_storage.HasEnoughSpace(additionalBytes))
        {
            return DokanResult.DiskFull;
        }

        if (length != node.Data.Length)
        {
            var newData = new byte[length];
            var copyLength = Math.Min(length, node.Data.Length);
            Array.Copy(node.Data, newData, copyLength);
            node.Data = newData;
            node.LastWriteTime = DateTime.Now;
        }

        return DokanResult.Success;
    }

    public NtStatus SetAllocationSize(string fileName, long length, IDokanFileInfo info)
    {
        var path = FloppyStorage.NormalizePath(fileName);
        var node = _storage.GetNode(path);

        if (node == null || node.IsDirectory)
        {
            return DokanResult.FileNotFound;
        }

        if (length < node.Data.Length)
        {
            var newData = new byte[length];
            Array.Copy(node.Data, newData, length);
            node.Data = newData;
            node.LastWriteTime = DateTime.Now;
        }

        return DokanResult.Success;
    }

    public NtStatus LockFile(
        string fileName,
        long offset,
        long length,
        IDokanFileInfo info)
    {
        return DokanResult.Success;
    }

    public NtStatus UnlockFile(
        string fileName,
        long offset,
        long length,
        IDokanFileInfo info)
    {
        return DokanResult.Success;
    }

    public NtStatus GetDiskFreeSpace(
        out long freeBytesAvailable,
        out long totalNumberOfBytes,
        out long totalNumberOfFreeBytes,
        IDokanFileInfo info)
    {
        freeBytesAvailable = _storage.FreeSpace;
        totalNumberOfBytes = _storage.Capacity;
        totalNumberOfFreeBytes = _storage.FreeSpace;
        return DokanResult.Success;
    }

    public NtStatus GetVolumeInformation(
        out string volumeLabel,
        out FileSystemFeatures features,
        out string fileSystemName,
        out uint maximumComponentLength,
        IDokanFileInfo info)
    {
        volumeLabel = _volumeName;
        fileSystemName = FileSystemName;
        maximumComponentLength = 255;

        features = FileSystemFeatures.CasePreservedNames
                   | FileSystemFeatures.UnicodeOnDisk;

        return DokanResult.Success;
    }

    public NtStatus GetFileSecurity(
        string fileName,
        out FileSystemSecurity? security,
        AccessControlSections sections,
        IDokanFileInfo info)
    {
        var path = FloppyStorage.NormalizePath(fileName);
        var node = _storage.GetNode(path);

        if (node == null)
        {
            security = null;
            return DokanResult.FileNotFound;
        }

        security = node.Security;
        return DokanResult.Success;
    }

    public NtStatus SetFileSecurity(
        string fileName,
        FileSystemSecurity security,
        AccessControlSections sections,
        IDokanFileInfo info)
    {
        var path = FloppyStorage.NormalizePath(fileName);
        var node = _storage.GetNode(path);

        if (node == null)
        {
            return DokanResult.FileNotFound;
        }

        node.Security = security;
        return DokanResult.Success;
    }

    public NtStatus Mounted(string mountPoint, IDokanFileInfo info)
    {
        Console.WriteLine($"Drive mounted at {mountPoint}");
        return DokanResult.Success;
    }

    public NtStatus Unmounted(IDokanFileInfo info)
    {
        Console.WriteLine("Drive unmounted");
        return DokanResult.Success;
    }

    public NtStatus FindStreams(
        string fileName,
        out IList<FileInformation> streams,
        IDokanFileInfo info)
    {
        streams = [];
        return DokanResult.NotImplemented;
    }
}