Tonight

frontend/src/lib/h3-selection.test.ts

@@ -0,0 +1,46 @@
+import { cellToChildren, cellToLatLng, latLngToCell } from 'h3-js';
+import { describe, expect, it } from 'vitest';
+import type { HexagonData } from '../types';
+import { findOverlappingMatchingHexagon, hasMatchingHexagonAtResolution } from './h3-selection';
+
+function hexagonData(h3: string, count: number): HexagonData {
+  const [lat, lon] = cellToLatLng(h3);
+  return { h3, count, lat, lon };
+}
+
+describe('h3 selection helpers', () => {
+  it('finds a matching higher-resolution hexagon that overlaps the previous hexagon', () => {
+    const parent = latLngToCell(51.5, -0.1, 8);
+    const children = cellToChildren(parent, 9);
+    const selected = findOverlappingMatchingHexagon(
+      parent,
+      [hexagonData(children[0], 0), hexagonData(children[1], 4)],
+      9
+    );
+
+    expect(selected?.h3).toBe(children[1]);
+  });
+
+  it('rejects candidates that do not overlap or have no matches', () => {
+    const parent = latLngToCell(51.5, -0.1, 8);
+    const nearbyChild = cellToChildren(parent, 9)[0];
+    const distant = latLngToCell(52.2, -0.1, 9);
+
+    expect(
+      findOverlappingMatchingHexagon(
+        parent,
+        [hexagonData(nearbyChild, 0), hexagonData(distant, 12)],
+        9
+      )
+    ).toBeNull();
+  });
+
+  it('detects when target-resolution matching data is loaded', () => {
+    const parent = latLngToCell(51.5, -0.1, 8);
+    const child = cellToChildren(parent, 9)[0];
+
+    expect(hasMatchingHexagonAtResolution([hexagonData(child, 1)], 9)).toBe(true);
+    expect(hasMatchingHexagonAtResolution([hexagonData(child, 0)], 9)).toBe(false);
+    expect(hasMatchingHexagonAtResolution([hexagonData(parent, 1)], 9)).toBe(false);
+  });
+});