Add VFS

pkNX.Containers/VFS/FileSystems/LayeredFileSystem.cs

@@ -0,0 +1,83 @@
+using System;
+using System.Collections.Generic;
+using System.IO;
+using System.Linq;
+using System.Text;
+
+namespace pkNX.Containers.VFS;
+
+public class LayeredFileSystem : IFileSystem
+{
+    public IEnumerable<IFileSystem> FileSystems { get; }
+    public LayeredFileSystem(IEnumerable<IFileSystem> fileSystems)
+    {
+        FileSystems = fileSystems.ToArray();
+    }
+
+    public LayeredFileSystem(params IFileSystem[] fileSystems)
+    {
+        FileSystems = fileSystems.ToArray();
+    }
+
+    public void Dispose()
+    {
+        foreach (var fs in FileSystems)
+            fs.Dispose();
+
+        GC.SuppressFinalize(this);
+    }
+
+    public IEnumerable<FileSystemPath> GetEntities(FileSystemPath path)
+    {
+        var entities = new SortedList<FileSystemPath, FileSystemPath>();
+        foreach (var fs in FileSystems.Where(fs => fs.Exists(path)))
+        {
+            foreach (var entity in fs.GetEntities(path))
+            {
+                if (!entities.ContainsKey(entity))
+                    entities.Add(entity, entity);
+            }
+        }
+        return entities.Values;
+    }
+
+    public bool Exists(FileSystemPath path)
+    {
+        return FileSystems.Any(fs => fs.Exists(path));
+    }
+
+    public IFileSystem? GetFirst(FileSystemPath path)
+    {
+        return FileSystems.FirstOrDefault(fs => fs.Exists(path));
+    }
+
+    public Stream CreateFile(FileSystemPath path)
+    {
+        IFileSystem fs = GetFirst(path) ?? FileSystems.First();
+        return fs.CreateFile(path);
+    }
+
+    public Stream OpenFile(FileSystemPath path, FileAccess access)
+    {
+        IFileSystem? fs = GetFirst(path);
+        if (fs == null)
+            throw new FileNotFoundException();
+        return fs.OpenFile(path, access);
+    }
+
+    public void CreateDirectory(FileSystemPath path)
+    {
+        if (Exists(path))
+            throw new ArgumentException("The specified directory already exists.");
+        IFileSystem? fs = GetFirst(path.ParentPath);
+        if (fs == null)
+            throw new ArgumentException("The directory-parent does not exist.");
+        fs.CreateDirectory(path);
+    }
+
+    public void Delete(FileSystemPath path)
+    {
+        foreach (var fs in FileSystems.Where(fs => fs.Exists(path)))
+            fs.Delete(path);
+    }
+}