[Init] Initial commit - NetMesh terminal manager

components/ui/virtualListMath.test.ts

@@ -0,0 +1,92 @@
+import assert from 'node:assert/strict';
+import test from 'node:test';
+
+import {
+  buildItemIndexToVisualIndexMap,
+  clampListIndex,
+  clampScrollTop,
+  getFixedSizeVirtualWindow,
+  stepListIndex,
+} from './virtualListMath.ts';
+
+test('clampScrollTop keeps the window on-content after a deep scroll + filter shrink', () => {
+  // User was deep in a long list (scrollTop large), then filter leaves few rows.
+  assert.equal(clampScrollTop(50_000, 10 * 44, 360), Math.max(0, 10 * 44 - 360));
+  assert.equal(clampScrollTop(-10, 1000, 200), 0);
+  assert.equal(clampScrollTop(100, 1000, 200), 100);
+  assert.equal(clampScrollTop(0, 0, 200), 0);
+});
+
+test('getFixedSizeVirtualWindow never starts past the last item after shrink', () => {
+  const deep = getFixedSizeVirtualWindow({
+    itemCount: 10_000,
+    itemHeight: 44,
+    scrollTop: 40_000,
+    viewportHeight: 300,
+    overscan: 6,
+  });
+  assert.ok(deep.startIndex < 10_000);
+  assert.ok(deep.endIndex - deep.startIndex < 100);
+  assert.ok(deep.endIndex <= 10_000);
+
+  const shrunk = getFixedSizeVirtualWindow({
+    itemCount: 8,
+    itemHeight: 44,
+    scrollTop: 40_000,
+    viewportHeight: 300,
+    overscan: 6,
+  });
+  assert.equal(shrunk.effectiveScrollTop, Math.max(0, 8 * 44 - 300));
+  assert.ok(shrunk.startIndex >= 0);
+  assert.ok(shrunk.startIndex < 8);
+  assert.equal(shrunk.endIndex, 8);
+  // Window must include at least one real item so the list never blanks.
+  assert.ok(shrunk.endIndex > shrunk.startIndex);
+});
+
+test('getFixedSizeVirtualWindow only materializes a viewport-sized slice for large lists', () => {
+  const window = getFixedSizeVirtualWindow({
+    itemCount: 8_000,
+    itemHeight: 44,
+    scrollTop: 0,
+    viewportHeight: 360,
+    overscan: 8,
+  });
+  const rendered = window.endIndex - window.startIndex;
+  assert.ok(rendered > 0);
+  assert.ok(rendered < 100, `expected viewport window, got ${rendered}`);
+  assert.equal(window.startIndex, 0);
+});
+
+test('clampListIndex and stepListIndex never produce -1 on empty or non-empty lists', () => {
+  assert.equal(clampListIndex(-1, 0), 0);
+  assert.equal(clampListIndex(5, 0), 0);
+  assert.equal(clampListIndex(-1, 5), 0);
+  assert.equal(clampListIndex(99, 5), 4);
+  assert.equal(clampListIndex(2, 5), 2);
+
+  assert.equal(stepListIndex(0, 0, 1), 0);
+  assert.equal(stepListIndex(0, 0, -1), 0);
+  // Empty list + ArrowDown must not go to -1 (QuickSwitcher regression).
+  assert.equal(stepListIndex(0, 0, 1), 0);
+  assert.equal(stepListIndex(0, 3, 1), 1);
+  assert.equal(stepListIndex(2, 3, 1), 2);
+  assert.equal(stepListIndex(0, 3, -1), 0);
+});
+
+test('buildItemIndexToVisualIndexMap skips headers for keyboard scroll targets', () => {
+  const visual = [
+    { kind: 'header' },
+    { kind: 'item' },
+    { kind: 'item' },
+    { kind: 'header' },
+    { kind: 'item' },
+  ];
+  const map = buildItemIndexToVisualIndexMap(visual);
+  assert.equal(map.get(0), 1);
+  assert.equal(map.get(1), 2);
+  assert.equal(map.get(2), 4);
+  assert.equal(map.size, 3);
+  // Keyboard index 1 scrolls to visual row 2 (second host, after first header).
+  assert.notEqual(map.get(1), 1);
+});