refstore/loose: Add loose refs implementation

1 files changed, 87 insertions, 0 deletions

diff --git a/refstore/loose/resolve.go b/refstore/loose/resolve.go
new file mode 100644
index 00000000..f54ab5a4
--- /dev/null
+++ b/refstore/loose/resolve.go
@@ -0,0 +1,87 @@
+package loose
+
+import (
+	"errors"
+	"fmt"
+	"os"
+	"strings"
+
+	"codeberg.org/lindenii/furgit/objectid"
+	"codeberg.org/lindenii/furgit/ref"
+	"codeberg.org/lindenii/furgit/refstore"
+)
+
+// Resolve resolves a loose reference name to symbolic or detached form.
+func (store *Store) Resolve(name string) (ref.Ref, error) {
+	if name == "" {
+		return nil, refstore.ErrReferenceNotFound
+	}
+	resolved, err := store.resolveOne(name)
+	if err != nil {
+		return nil, err
+	}
+	return resolved, nil
+}
+
+// ResolveFully resolves symbolic references within the loose backend only.
+func (store *Store) ResolveFully(name string) (ref.Detached, error) {
+	if name == "" {
+		return ref.Detached{}, refstore.ErrReferenceNotFound
+	}
+
+	cur := name
+	seen := make(map[string]struct{})
+	for {
+		if _, ok := seen[cur]; ok {
+			return ref.Detached{}, fmt.Errorf("refstore/loose: symbolic reference cycle at %q", cur)
+		}
+		seen[cur] = struct{}{}
+
+		resolved, err := store.resolveOne(cur)
+		if err != nil {
+			return ref.Detached{}, err
+		}
+		switch resolved := resolved.(type) {
+		case ref.Detached:
+			return resolved, nil
+		case ref.Symbolic:
+			target := strings.TrimSpace(resolved.Target)
+			if target == "" {
+				return ref.Detached{}, fmt.Errorf("refstore/loose: symbolic reference %q has empty target", resolved.Name())
+			}
+			cur = target
+		default:
+			return ref.Detached{}, fmt.Errorf("refstore/loose: unsupported reference type %T", resolved)
+		}
+	}
+}
+
+// resolveOne resolves one loose ref file without symbolic recursion.
+func (store *Store) resolveOne(name string) (ref.Ref, error) {
+	data, err := store.root.ReadFile(name)
+	if err != nil {
+		if errors.Is(err, os.ErrNotExist) {
+			return nil, refstore.ErrReferenceNotFound
+		}
+		return nil, err
+	}
+	line := strings.TrimSpace(string(data))
+	if strings.HasPrefix(line, "ref: ") {
+		target := strings.TrimSpace(line[len("ref: "):])
+		if target == "" {
+			return nil, fmt.Errorf("refstore/loose: symbolic reference %q has empty target", name)
+		}
+		return ref.Symbolic{
+			RefName: name,
+			Target:  target,
+		}, nil
+	}
+	id, err := objectid.ParseHex(store.algo, line)
+	if err != nil {
+		return nil, fmt.Errorf("refstore/loose: invalid detached reference %q: %w", name, err)
+	}
+	return ref.Detached{
+		RefName: name,
+		ID:      id,
+	}, nil
+}