refactor: use Cursor in query result sets

1 files changed, 36 insertions, 0 deletions

diff --git a/subprojects/store/src/main/java/tools/refinery/store/map/Cursors.java b/subprojects/store/src/main/java/tools/refinery/store/map/Cursors.java
new file mode 100644
index 00000000..fc8e628b
--- /dev/null
+++ b/subprojects/store/src/main/java/tools/refinery/store/map/Cursors.java
@@ -0,0 +1,36 @@
+package tools.refinery.store.map;
+
+public final class Cursors {
+    private Cursors() {
+        throw new IllegalStateException("This is a static utility class and should not be instantiated directly");
+    }
+
+    public static <K, V> Cursor<K, V> empty() {
+        return new Empty<>();
+    }
+
+    private static class Empty<K, V> implements Cursor<K, V> {
+        private boolean terminated = false;
+
+        @Override
+        public K getKey() {
+            return null;
+        }
+
+        @Override
+        public V getValue() {
+            return null;
+        }
+
+        @Override
+        public boolean isTerminated() {
+            return terminated;
+        }
+
+        @Override
+        public boolean move() {
+            terminated = true;
+            return false;
+        }
+    }
+}