1 files changed, 39 insertions, 0 deletions
diff --git a/object/fetch/peel_to_blob_id.go b/object/fetch/peel_to_blob_id.go
new file mode 100644
index 00000000..9d13f640
--- /dev/null
+++ b/object/fetch/peel_to_blob_id.go
@@ -0,0 +1,39 @@
+package fetch
+
+import (
+	"fmt"
+
+	objectid "codeberg.org/lindenii/furgit/object/id"
+	objecttype "codeberg.org/lindenii/furgit/object/type"
+)
+
+// PeelToBlobID peels tags until it reaches a blob object ID.
+func (r *Fetcher) PeelToBlobID(id objectid.ObjectID) (objectid.ObjectID, error) {
+	for {
+		ty, _, err := r.store.ReadHeader(id)
+		if err != nil {
+			return objectid.ObjectID{}, err
+		}
+
+		switch ty {
+		case objecttype.TypeBlob:
+			return id, nil
+		case objecttype.TypeTag:
+			tag, err := r.ExactTag(id)
+			if err != nil {
+				return objectid.ObjectID{}, err
+			}
+
+			id = tag.Object().Target
+		case objecttype.TypeInvalid,
+			objecttype.TypeCommit,
+			objecttype.TypeTree,
+			objecttype.TypeFuture,
+			objecttype.TypeOfsDelta,
+			objecttype.TypeRefDelta:
+			return objectid.ObjectID{}, fmt.Errorf("object/fetch: expected blob-ish object %s, got %v", id, ty)
+		default:
+			return objectid.ObjectID{}, fmt.Errorf("object/fetch: expected blob-ish object %s, got %v", id, ty)
+		}
+	}
+}