Add VFS

pkNX.Containers/VFS/VirtualFileSystem.cs

@@ -0,0 +1,80 @@
+using System;
+using System.Collections.Generic;
+using System.IO;
+using System.Linq;
+
+namespace pkNX.Containers.VFS;
+
+public record MountPoint(FileSystemPath Path, IFileSystem FileSystem) : IComparable<MountPoint>
+{
+    public int CompareTo(MountPoint? other)
+    {
+        return other?.Path.CompareTo(Path) ?? 1;
+    }
+}
+
+public class VirtualFileSystem : IFileSystem
+{
+    public bool IsReadOnly => Mounts.All(x => x.FileSystem.IsReadOnly);
+
+    public SortedSet<MountPoint> Mounts { get; }
+
+    public VirtualFileSystem(IEnumerable<MountPoint> mounts)
+    {
+        Mounts = new SortedSet<MountPoint>(mounts);
+    }
+
+    public VirtualFileSystem(params MountPoint[] mounts) :
+        this(mounts.AsEnumerable())
+    { }
+
+    protected MountPoint Get(FileSystemPath path)
+    {
+        return Mounts.First(pair => pair.Path == path || pair.Path.IsParentOf(path));
+    }
+
+    public void Dispose()
+    {
+        foreach (var fs in Mounts.Select(x => x.FileSystem))
+            fs.Dispose();
+
+        GC.SuppressFinalize(this);
+    }
+
+    public IEnumerable<FileSystemPath> GetEntities(FileSystemPath path)
+    {
+        MountPoint point = Get(path);
+        IEnumerable<FileSystemPath> entities = point.FileSystem.GetEntities(path.IsRoot ? path : path.RemoveParent(point.Path));
+        return entities.Select(p => point.Path.AppendPath(p));
+    }
+
+    public bool Exists(FileSystemPath path)
+    {
+        var pair = Get(path);
+        return pair.FileSystem.Exists(path.RemoveParent(pair.Path));
+    }
+
+    public Stream CreateFile(FileSystemPath path)
+    {
+        var pair = Get(path);
+        return pair.FileSystem.CreateFile(path.RemoveParent(pair.Path));
+    }
+
+    public Stream OpenFile(FileSystemPath path, FileAccess access)
+    {
+        var pair = Get(path);
+        return pair.FileSystem.OpenFile(path.RemoveParent(pair.Path), access);
+    }
+
+    public void CreateDirectory(FileSystemPath path)
+    {
+        var pair = Get(path);
+        pair.FileSystem.CreateDirectory(path.RemoveParent(pair.Path));
+    }
+
+    public void Delete(FileSystemPath path)
+    {
+        var pair = Get(path);
+        pair.FileSystem.Delete(path.RemoveParent(pair.Path));
+    }
+}