1 files changed, 82 insertions, 0 deletions
diff --git a/repository/open_refs.go b/repository/open_refs.go
new file mode 100644
index 00000000..296c503c
--- /dev/null
+++ b/repository/open_refs.go
@@ -0,0 +1,82 @@
+package repository
+
+import (
+	"errors"
+	"fmt"
+	"os"
+
+	"codeberg.org/lindenii/furgit/objectid"
+	"codeberg.org/lindenii/furgit/refstore"
+	refchain "codeberg.org/lindenii/furgit/refstore/chain"
+	refloose "codeberg.org/lindenii/furgit/refstore/loose"
+	refpacked "codeberg.org/lindenii/furgit/refstore/packed"
+	reftable "codeberg.org/lindenii/furgit/refstore/reftable"
+)
+
+func openRefStore(root *os.Root, algo objectid.Algorithm) (out refstore.Store, err error) {
+	hasReftable, err := hasReftableStack(root)
+	if err != nil {
+		return nil, err
+	}
+
+	if hasReftable {
+		reftableRoot, err := root.OpenRoot("reftable")
+		if err != nil {
+			return nil, fmt.Errorf("repository: open reftable: %w", err)
+		}
+
+		reftableStore, err := reftable.New(reftableRoot, algo)
+		if err != nil {
+			_ = reftableRoot.Close()
+
+			return nil, err
+		}
+
+		return reftableStore, nil
+	}
+
+	looseRoot, err := root.OpenRoot(".")
+	if err != nil {
+		return nil, fmt.Errorf("repository: open root for loose refs: %w", err)
+	}
+
+	looseStore, err := refloose.New(looseRoot, algo)
+	if err != nil {
+		_ = looseRoot.Close()
+
+		return nil, err
+	}
+
+	backends := []refstore.Store{looseStore}
+
+	_, err = root.Stat("packed-refs")
+	if err == nil {
+		packedStore, packedErr := refpacked.New(root, algo)
+		if packedErr != nil {
+			_ = looseStore.Close()
+
+			return nil, packedErr
+		}
+
+		backends = append(backends, packedStore)
+	} else if !errors.Is(err, os.ErrNotExist) {
+		_ = looseStore.Close()
+
+		return nil, fmt.Errorf("repository: stat packed-refs: %w", err)
+	}
+
+	return refchain.New(backends...), nil
+}
+
+func hasReftableStack(root *os.Root) (bool, error) {
+	_, err := root.Stat("reftable/tables.list")
+	if err == nil {
+		return true, nil
+	}
+
+	if errors.Is(err, os.ErrNotExist) {
+		return false, nil
+	}
+
+	return false, fmt.Errorf("repository: stat reftable/tables.list: %w", err)
+}