internal/store: expose save via handle

The handle is otherwise inaccessible without the compat interface. This change also moves compatibility methods to separate adapter structs to avoid inadvertently using them.

Signed-off-by: Ophestra <cat@gensokyo.uk>

internal/store/compat.go

@@ -22,20 +22,20 @@ type Compat interface {
 	List() (identities []int, err error)
 }
 
-func (s *Store) Do(identity int, f func(c Cursor)) (bool, error) {
-	if h, err := s.Handle(identity); err != nil {
-		return false, err
-	} else {
-		return h.do(f)
-	}
-}
-
 // storeAdapter satisfies [Compat] via [Store].
 type storeAdapter struct {
 	msg message.Msg
 	*Store
 }
 
+func (s storeAdapter) Do(identity int, f func(c Cursor)) (bool, error) {
+	if h, err := s.Handle(identity); err != nil {
+		return false, err
+	} else {
+		return handleAdapter{h}.do(f)
+	}
+}
+
 func (s storeAdapter) List() ([]int, error) {
 	segments, n, err := s.Segments()
 	if err != nil {
@@ -71,8 +71,11 @@ type Cursor interface {
 	Len() (int, error)
 }
 
+// handleAdapter satisfies [Cursor] via [Handle].
+type handleAdapter struct{ *Handle }
+
 // do implements [Compat.Do] on [Handle].
-func (h *Handle) do(f func(c Cursor)) (bool, error) {
+func (h handleAdapter) do(f func(c Cursor)) (bool, error) {
 	if unlock, err := h.Lock(); err != nil {
 		return false, err
 	} else {
@@ -85,15 +88,13 @@ func (h *Handle) do(f func(c Cursor)) (bool, error) {
 
 /* these compatibility methods must only be called while fileMu is held */
 
-func (h *Handle) Save(state *hst.State) error {
-	return (&EntryHandle{nil, h.Path.Append(state.ID.String()), state.ID}).Save(state)
-}
+func (h handleAdapter) Save(state *hst.State) error { _, err := h.Handle.Save(state); return err }
 
-func (h *Handle) Destroy(id hst.ID) error {
+func (h handleAdapter) Destroy(id hst.ID) error {
 	return (&EntryHandle{nil, h.Path.Append(id.String()), id}).Destroy()
 }
 
-func (h *Handle) Load() (map[hst.ID]*hst.State, error) {
+func (h handleAdapter) Load() (map[hst.ID]*hst.State, error) {
 	entries, n, err := h.Entries()
 	if err != nil {
 		return nil, err
@@ -114,7 +115,7 @@ func (h *Handle) Load() (map[hst.ID]*hst.State, error) {
 	return r, err
 }
 
-func (h *Handle) Len() (int, error) {
+func (h handleAdapter) Len() (int, error) {
 	entries, _, err := h.Entries()
 	if err != nil {
 		return -1, err

internal/store/segment.go

@@ -54,11 +54,11 @@ func (eh *EntryHandle) Destroy() error {
 	return nil
 }
 
-// Save encodes [hst.State] and writes it to the underlying file.
+// save encodes [hst.State] and writes it to the underlying file.
 // An error is returned if a file already exists with the same identifier.
-// Save does not validate the embedded [hst.Config].
-// A non-nil error returned by Save is of type [hst.AppError].
-func (eh *EntryHandle) Save(state *hst.State) error {
+// save does not validate the embedded [hst.Config].
+// A non-nil error returned by save is of type [hst.AppError].
+func (eh *EntryHandle) save(state *hst.State) error {
 	f, err := eh.open(os.O_RDWR|os.O_CREATE|os.O_EXCL, 0600)
 	if err != nil {
 		return err
@@ -123,6 +123,16 @@ func (h *Handle) Lock() (unlock func(), err error) {
 	return
 }
 
+// Save attempts to save [hst.State] as a segment entry, and returns its [EntryHandle].
+// Must be called while holding [Handle.Lock].
+// An error is returned if an entry already exists with the same identifier.
+// Save does not validate the embedded [hst.Config].
+// A non-nil error returned by Save is of type [hst.AppError].
+func (h *Handle) Save(state *hst.State) (*EntryHandle, error) {
+	eh := EntryHandle{nil, h.Path.Append(state.ID.String()), state.ID}
+	return &eh, eh.save(state)
+}
+
 // Entries returns an iterator over all [EntryHandle] held in this segment.
 // Must be called while holding [Handle.Lock].
 // A non-nil error attached to a [EntryHandle] indicates a malformed identifier and is of type [hst.AppError].

internal/store/segment_test.go

@@ -30,6 +30,9 @@ func newHandle(base *check.Absolute, identity int) *store.Handle
 //go:linkname open hakurei.app/internal/store.(*EntryHandle).open
 func open(eh *store.EntryHandle, flag int, perm os.FileMode) (*os.File, error)
 
+//go:linkname save hakurei.app/internal/store.(*EntryHandle).save
+func save(eh *store.EntryHandle, state *hst.State) error
+
 func TestStateEntryHandle(t *testing.T) {
 	t.Parallel()
 
@@ -44,7 +47,7 @@ func TestStateEntryHandle(t *testing.T) {
 		if err := eh.Destroy(); !reflect.DeepEqual(err, wantErr()) {
 			t.Errorf("destroy: error = %v, want %v", err, wantErr())
 		}
-		if err := eh.Save(nil); !reflect.DeepEqual(err, wantErr()) {
+		if err := save(&eh, nil); !reflect.DeepEqual(err, wantErr()) {
 			t.Errorf("save: error = %v, want %v", err, wantErr())
 		}
 		if _, err := eh.Load(nil); !reflect.DeepEqual(err, wantErr()) {
@@ -90,7 +93,7 @@ func TestStateEntryHandle(t *testing.T) {
 		eh := store.EntryHandle{Pathname: check.MustAbs(t.TempDir()).Append("entry"),
 			ID: newTemplateState().ID}
 
-		if err := eh.Save(newTemplateState()); err != nil {
+		if err := save(&eh, newTemplateState()); err != nil {
 			t.Fatalf("save: error = %v", err)
 		}