object/fetch: Port tree

1 files changed, 86 insertions, 0 deletions

diff --git a/object/fetch/tree.go b/object/fetch/tree.go
new file mode 100644
index 00000000..ef0f9e77
--- /dev/null
+++ b/object/fetch/tree.go
@@ -0,0 +1,86 @@
+package fetch
+
+import (
+	"lindenii.org/go/furgit/errs"
+	"lindenii.org/go/furgit/object/commit"
+	oid "lindenii.org/go/furgit/object/id"
+	"lindenii.org/go/furgit/object/stored"
+	"lindenii.org/go/furgit/object/tag"
+	"lindenii.org/go/furgit/object/tree"
+	"lindenii.org/go/furgit/object/typ"
+)
+
+// ExactTree reads, parses, and wraps the tree at id.
+//
+// Labels: Life-Parent.
+func (r *Fetcher) ExactTree(id oid.ObjectID) (*stored.Stored[*tree.Tree], error) {
+	parsed, err := r.parseObject(id)
+	if err != nil {
+		return nil, err
+	}
+
+	tree, ok := parsed.(*tree.Tree)
+	if !ok {
+		return nil, &errs.ObjectTypeError{OID: id, Got: parsed.ObjectType(), Want: typ.TypeTree}
+	}
+
+	return stored.New(id, tree), nil
+}
+
+// PeelToTree peels tags until it reaches a tree or commit. If it reaches a
+// commit, it returns the commit's root tree.
+//
+// Labels: Life-Parent.
+func (r *Fetcher) PeelToTree(id oid.ObjectID) (*stored.Stored[*tree.Tree], error) {
+	for {
+		obj, err := r.ExactObject(id)
+		if err != nil {
+			return nil, err
+		}
+
+		switch parsed := obj.Object().(type) {
+		case *tree.Tree:
+			return stored.New(id, parsed), nil
+		case *commit.Commit:
+			return r.ExactTree(parsed.Tree)
+		case *tag.Tag:
+			id = parsed.TargetID
+		default:
+			return nil, &errs.ObjectTypeError{OID: id, Got: parsed.ObjectType(), Want: typ.TypeTree}
+		}
+	}
+}
+
+// PeelToTreeID peels tags until it reaches a tree object ID, or a commit whose
+// root tree object ID is then returned.
+func (r *Fetcher) PeelToTreeID(id oid.ObjectID) (oid.ObjectID, error) {
+	for {
+		ty, _, err := r.Header(id)
+		if err != nil {
+			return oid.ObjectID{}, err
+		}
+
+		switch ty {
+		case typ.TypeTree:
+			return id, nil
+		case typ.TypeCommit:
+			commit, err := r.ExactCommit(id)
+			if err != nil {
+				return oid.ObjectID{}, err
+			}
+
+			return commit.Object().Tree, nil
+		case typ.TypeTag:
+			tag, err := r.ExactTag(id)
+			if err != nil {
+				return oid.ObjectID{}, err
+			}
+
+			id = tag.Object().TargetID
+		case typ.TypeUnknown, typ.TypeBlob:
+			return oid.ObjectID{}, &errs.ObjectTypeError{OID: id, Got: ty, Want: typ.TypeTree}
+		default:
+			return oid.ObjectID{}, &errs.ObjectTypeError{OID: id, Got: ty, Want: typ.TypeTree}
+		}
+	}
+}