Add fs.File implementation.

guest/fs.go

@@ -1,13 +1,20 @@
 package guest
 
 import (
+	"context"
 	"errors"
 	"io/fs"
+
+	"github.com/ipfs/boxo/files"
+	"github.com/ipfs/boxo/path"
+	iface "github.com/ipfs/kubo/core/coreiface"
 )
 
 var _ fs.FS = (*FS)(nil)
 
-type FS struct{}
+type FS struct {
+	IPFS iface.CoreAPI
+}
 
 // Open opens the named file.
 //
@@ -18,6 +25,32 @@ type FS struct{}
 // Open should reject attempts to open names that do not satisfy
 // ValidPath(name), returning a *PathError with Err set to
 // ErrInvalid or ErrNotExist.
-func (FS) Open(name string) (fs.File, error) {
-	return nil, errors.New("FS.Open::NOT IMPLEMENTED")
+func (fs FS) Open(name string) (fs.File, error) {
+	p, err := path.NewPath(name)
+	if err != nil {
+		return nil, err
+	}
+
+	n, err := fs.IPFS.Unixfs().Get(context.TODO(), p)
+	return fsNode{Node: n}, err
+}
+
+// fsNode provides access to a single file. The fs.File interface is the minimum
+// implementation required of the file. Directory files should also implement [ReadDirFile].
+// A file may implement io.ReaderAt or io.Seeker as optimizations.
+
+type fsNode struct {
+	files.Node
+}
+
+func (n fsNode) Stat() (fs.FileInfo, error) {
+	return nil, errors.New("fsNode.Stat::NOT IMPLEMENTED")
+}
+
+func (n fsNode) Read([]byte) (int, error) {
+	return 0, errors.New("fsNode.Read::NOT IMPLEMENTED")
+}
+
+func (n fsNode) Close() error {
+	return n.Node.Close()
 }