# VirtualFS

VirtualFS is a .NET library for composing multiple file-like data sources into one virtual hierarchy.

The core model is:

- every backend implements `IFileSystem`
- a `RootFileSystem` mounts many backends under virtual paths
- callers interact with virtual paths like `/assets/logo.png`
- reads and writes are dispatched to the mounted backend that owns that path

It behaves more like a small VFS layer than a thin `System.IO` wrapper.

## Status

The project currently targets:

- `netstandard2.0`
- `net472`
- `net6.0`
- `net8.0`
- `net10.0`

The test project targets `net10.0`.

## Key Rules

- paths are always rooted
- `/foo/` is a directory
- `/foo` is a file
- trailing `/` defines directory vs file
- path separator is always `/`
- mounted filesystems can overlap
- mount priority controls lookup order

## Minimal Example

```csharp
using System.IO;
using VirtualFS;
using VirtualFS.Implementation;
using VirtualFS.Memory;
using VirtualFS.Physical;

var root = new RootFileSystem();

root.Mount(new PhysicalFileSystem(new DirectoryInfo("./content")), "/");
root.Mount(new MemoryFileSystem { Priority = FileSystemMountPriority.High }, "/");

root.Root.FileCreate("runtime.txt").WriteAllText("generated at runtime");

foreach (var entry in root.Root.GetEntries())
{
    Console.WriteLine($"{entry.FullPath} readonly={entry.IsReadOnly}");
}
```

## Documentation

Detailed documentation is split into the `docs/` folder:

- [Documentation Index](./docs/README.md)
- [Architecture](./docs/architecture.md)
- [Usage](./docs/usage.md)
- [Backends](./docs/backends.md)
- [Development](./docs/development.md)

## Build and Test

The repository includes a Docker-based build/test flow using the official .NET 10 SDK image.

```bash
docker build --target test -t virtualfs:test .
```

The repository CI runs the same Docker target on pushes and pull requests.

## License

The project metadata declares the MIT license.