fix(store): Tail aware HasAt

Author: Wondertan

store/store.go

@@ -324,8 +324,22 @@ func (s *Store[H]) Has(ctx context.Context, hash header.Hash) (bool, error) {
 	return ok, err
 }
 
-func (s *Store[H]) HasAt(_ context.Context, height uint64) bool {
-	return height != uint64(0) && s.Height() >= height
+func (s *Store[H]) HasAt(ctx context.Context, height uint64) bool {
+	if height == uint64(0) {
+		return false
+	}
+
+	head, err := s.Head(ctx)
+	if err != nil {
+		return false
+	}
+
+	tail, err := s.Tail(ctx)
+	if err != nil {
+		return false
+	}
+
+	return head.Height() >= height && height >= tail.Height()
 }
 
 // DeleteTo implements [header.Store] interface.

store/store_test.go

@@ -829,3 +829,41 @@ func TestStoreInit(t *testing.T) {
 	err = reopenedStore.Stop(ctx)
 	require.NoError(t, err)
 }
+
+func TestStore_HasAt(t *testing.T) {
+	ctx, cancel := context.WithTimeout(context.Background(), time.Second*5)
+	t.Cleanup(cancel)
+
+	suite := headertest.NewTestSuite(t)
+
+	ds := sync.MutexWrap(datastore.NewMapDatastore())
+	store, err := NewStore[*headertest.DummyHeader](ds)
+	require.NoError(t, err)
+
+	err = store.Start(ctx)
+	require.NoError(t, err)
+
+	headers := suite.GenDummyHeaders(100)
+
+	err = store.Append(ctx, headers...)
+	require.NoError(t, err)
+	time.Sleep(100 * time.Millisecond)
+
+	err = store.DeleteTo(ctx, 50)
+	require.NoError(t, err)
+
+	has := store.HasAt(ctx, 100)
+	assert.True(t, has)
+
+	has = store.HasAt(ctx, 50)
+	assert.True(t, has)
+
+	has = store.HasAt(ctx, 49)
+	assert.False(t, has)
+
+	has = store.HasAt(ctx, 10)
+	assert.False(t, has)
+
+	has = store.HasAt(ctx, 0)
+	assert.False(t, has)
+}