rbd: add manager GetSnapshotByID and SnapshotResolver interface

A (CSI) VolumeGroupSnapshot object contains references to Snapshot IDs
(or CSI Snapshot handles). In order to work with a VolumeGroupSnapshot
struct, the Snapshot IDs need to be resolved into rbdSnapshot structs.

Signed-off-by: Niels de Vos <ndevos@ibm.com>

internal/rbd/manager.go

@@ -139,6 +139,31 @@ func (mgr *rbdManager) GetVolumeByID(ctx context.Context, id string) (types.Volu
 	return volume, nil
 }
 
+func (mgr *rbdManager) GetSnapshotByID(ctx context.Context, id string) (types.Snapshot, error) {
+	creds, err := mgr.getCredentials()
+	if err != nil {
+		return nil, err
+	}
+
+	snapshot, err := genSnapFromSnapID(ctx, id, creds, mgr.secrets)
+	if err != nil {
+		switch {
+		case errors.Is(err, ErrImageNotFound):
+			err = fmt.Errorf("volume %s not found: %w", id, err)
+
+			return nil, err
+		case errors.Is(err, util.ErrPoolNotFound):
+			err = fmt.Errorf("pool %s not found for %s: %w", snapshot.Pool, id, err)
+
+			return nil, err
+		default:
+			return nil, fmt.Errorf("failed to get volume from id %q: %w", id, err)
+		}
+	}
+
+	return snapshot, nil
+}
+
 func (mgr *rbdManager) GetVolumeGroupByID(ctx context.Context, id string) (types.VolumeGroup, error) {
 	creds, err := mgr.getCredentials()
 	if err != nil {

internal/rbd/types/manager.go

@@ -26,6 +26,12 @@ type VolumeResolver interface {
 	GetVolumeByID(ctx context.Context, id string) (Volume, error)
 }
 
+// SnapshotResolver can be used to construct a Snapshot from a CSI SnapshotId.
+type SnapshotResolver interface {
+	// GetSnapshotByID uses the CSI SnapshotId to resolve the returned Snapshot.
+	GetSnapshotByID(ctx context.Context, id string) (Snapshot, error)
+}
+
 // Manager provides a way for other packages to get Volumes and VolumeGroups.
 // It handles the operations on the backend, and makes sure the journal
 // reflects the expected state.
@@ -33,6 +39,9 @@ type Manager interface {
 	// VolumeResolver is fully implemented by the Manager.
 	VolumeResolver
 
+	// SnapshotResolver is fully implemented by the Manager.
+	SnapshotResolver
+
 	// Destroy frees all resources that the Manager allocated.
 	Destroy(ctx context.Context)