fs: add DirWrapper for wrapping Directory-s with optional methods

fs/dir_wrapper.go

@@ -0,0 +1,79 @@
+package fs
+
+import (
+	"context"
+	"time"
+)
+
+// DirWrapper wraps a Directory object so the Remote can be overridden
+type DirWrapper struct {
+	Directory        // Directory we are wrapping
+	remote    string // name of the directory
+}
+
+// NewDirWrapper creates a wrapper for a directory object
+//
+// This passes through optional methods and should be used for
+// wrapping backends to wrap native directories.
+func NewDirWrapper(remote string, d Directory) *DirWrapper {
+	return &DirWrapper{
+		Directory: d,
+		remote:    remote,
+	}
+}
+
+// String returns the name
+func (d *DirWrapper) String() string {
+	return d.remote
+}
+
+// Remote returns the remote path
+func (d *DirWrapper) Remote() string {
+	return d.remote
+}
+
+// SetRemote sets the remote
+func (d *DirWrapper) SetRemote(remote string) *DirWrapper {
+	d.remote = remote
+	return d
+}
+
+// Metadata returns metadata for an DirEntry
+//
+// It should return nil if there is no Metadata
+func (d *DirWrapper) Metadata(ctx context.Context) (Metadata, error) {
+	do, ok := d.Directory.(Metadataer)
+	if !ok {
+		return nil, nil
+	}
+	return do.Metadata(ctx)
+}
+
+// SetMetadata sets metadata for an DirEntry
+//
+// It should return fs.ErrorNotImplemented if it can't set metadata
+func (d *DirWrapper) SetMetadata(ctx context.Context, metadata Metadata) error {
+	do, ok := d.Directory.(SetMetadataer)
+	if !ok {
+		return ErrorNotImplemented
+	}
+	return do.SetMetadata(ctx, metadata)
+}
+
+// SetModTime sets the metadata on the DirEntry to set the modification date
+//
+// If there is any other metadata it does not overwrite it.
+func (d *DirWrapper) SetModTime(ctx context.Context, t time.Time) error {
+	do, ok := d.Directory.(SetModTimer)
+	if !ok {
+		return ErrorNotImplemented
+	}
+	return do.SetModTime(ctx, t)
+}
+
+// Check interfaces
+var (
+	_ DirEntry      = (*DirWrapper)(nil)
+	_ Directory     = (*DirWrapper)(nil)
+	_ FullDirectory = (*DirWrapper)(nil)
+)