refactor(director): separate timing clocks and scene pack presentation

src/director/timeline.test.mjs

@@ -0,0 +1,51 @@
+import test from 'node:test';
+import assert from 'node:assert/strict';
+import {
+  sceneTimingForShot,
+  sceneSeekState,
+  cameraAtProgress,
+} from './timeline.js';
+const camera = (lon, heading) => ({
+  lat: 10,
+  lon,
+  alt: 1000,
+  heading,
+  pitch: -40,
+  roll: 0,
+});
+const scene = {
+  shots: [
+    { id: 'a', durationSec: 2, holdSec: 1, camera: camera(20, 350) },
+    { id: 'b', durationSec: 4, holdSec: 3, camera: camera(24, 10) },
+  ],
+};
+const duration = (_, shot) => shot.durationSec + shot.holdSec;
+const hold = (_, shot) => shot.holdSec;
+
+test('scene time accounts for flight and hold; exact boundaries select the next shot', () => {
+  const time = sceneTimingForShot(scene, scene.shots[1], duration);
+  assert.equal(time.startElapsedSec, 3);
+  assert.equal(time.endElapsedSec, 10);
+  const seek = (progress) => sceneSeekState(scene, progress, duration, hold);
+  assert.equal(seek(-1).shot.id, 'a');
+  assert.equal(seek(0.3).shot.id, 'b');
+  assert.equal(seek(0.3).cameraProgress, 0);
+  assert.equal(seek(0.5).cameraProgress, 0.5);
+  assert.equal(seek(0.5).camera.lon, 22);
+  assert.equal(seek(0.8).holdElapsedSec, 1);
+  assert.equal(seek(2).holdProgress, 1);
+  assert.equal(seek(0).sceneElapsedSec, 0);
+  assert.equal(sceneSeekState({ shots: [] }, 1, duration, hold), null);
+});
+
+test('camera seeking preserves cubic easing and shortest-angle orientation', () => {
+  assert.equal(
+    cameraAtProgress(camera(20, 350), camera(24, 10), 0.5).heading,
+    360,
+  );
+  assert.equal(
+    cameraAtProgress(camera(20, 350), camera(24, 10), 0.25).lon,
+    20.25,
+  );
+  assert.deepEqual(cameraAtProgress(null, camera(20, 350), 0), camera(20, 350));
+});