get feature highlighting working both ways

From the editor to the viewer and from the viewer to the editor

src/lib/utils.test.ts

@@ -0,0 +1,19 @@
+import { isOverlapping } from "./utils";
+import { Range } from "../useStore";
+
+describe("testing isOverlapping", () => {
+  testBothOrders([0, 5], [3, 10]);
+  testBothOrders([0, 5], [3, 4]);
+  testBothOrders([0, 5], [5, 10]);
+  testBothOrders([0, 5], [6, 10], false);
+  testBothOrders([0, 5], [-1, 1]);
+  testBothOrders([0, 5], [-1, 0]);
+  testBothOrders([0, 5], [-2, -1], false);
+});
+
+function testBothOrders(a: Range, b: Range, result = true) {
+  it(`test is overlapping ${a} ${b}`, () => {
+    expect(isOverlapping(a, b)).toBe(result);
+    expect(isOverlapping(b, a)).toBe(result);
+  });
+}