refstore/chain: Split

1 files changed, 66 insertions, 0 deletions

diff --git a/refstore/chain/resolve.go b/refstore/chain/resolve.go
new file mode 100644
index 00000000..66ba821e
--- /dev/null
+++ b/refstore/chain/resolve.go
@@ -0,0 +1,66 @@
+package chain
+
+import (
+	"errors"
+	"fmt"
+
+	"codeberg.org/lindenii/furgit/ref"
+	"codeberg.org/lindenii/furgit/refstore"
+)
+
+// Resolve resolves a reference from the first backend that has it.
+func (chain *Chain) Resolve(name string) (ref.Ref, error) {
+	for i, backend := range chain.backends {
+		if backend == nil {
+			continue
+		}
+
+		resolved, err := backend.Resolve(name)
+		if err == nil {
+			return resolved, nil
+		}
+
+		if errors.Is(err, refstore.ErrReferenceNotFound) {
+			continue
+		}
+
+		return nil, fmt.Errorf("refstore: backend %d resolve: %w", i, err)
+	}
+
+	return nil, refstore.ErrReferenceNotFound
+}
+
+// ResolveFully resolves symbolic references through Resolve until detached.
+//
+// It intentionally does not call backend ResolveFully. This allows symbolic
+// references to cross backends in the chain.
+func (chain *Chain) ResolveFully(name string) (ref.Detached, error) {
+	cur := name
+
+	seen := map[string]struct{}{}
+	for {
+		if _, ok := seen[cur]; ok {
+			return ref.Detached{}, fmt.Errorf("refstore: symbolic reference cycle at %q", cur)
+		}
+
+		seen[cur] = struct{}{}
+
+		resolved, err := chain.Resolve(cur)
+		if err != nil {
+			return ref.Detached{}, err
+		}
+
+		switch resolved := resolved.(type) {
+		case ref.Detached:
+			return resolved, nil
+		case ref.Symbolic:
+			if resolved.Target == "" {
+				return ref.Detached{}, fmt.Errorf("refstore: symbolic reference %q has empty target", resolved.Name())
+			}
+
+			cur = resolved.Target
+		default:
+			return ref.Detached{}, fmt.Errorf("refstore: unsupported reference type %T", resolved)
+		}
+	}
+}