feat: integrate authored nightdrive soundtrack

tests/unit/soundtrack-transport.test.ts

@@ -0,0 +1,51 @@
+import { describe, expect, it } from 'vitest';
+import {
+  MAIN_PHRASE_BARS,
+  MUSIC_BAR_SECONDS,
+  INTRO_IN_END_SECONDS,
+  SOUNDTRACK_SAMPLE_RATE,
+  mainPhraseOffsetSeconds,
+  nextSafeBarTime,
+  resolveInitialPlayback,
+} from '@/audio/soundtrack-transport';
+
+describe('soundtrack transport decisions', () => {
+  it('starts at the intro only on Start and otherwise chooses the matching main phrase', () => {
+    expect(resolveInitialPlayback({
+      atStart: true,
+      bias: 'open',
+      entryPhrase: 0,
+      intensity: 0,
+    })).toEqual({ kind: 'intro' });
+
+    expect(resolveInitialPlayback({
+      atStart: false,
+      bias: 'shadow',
+      entryPhrase: 3,
+      intensity: 0.5,
+    })).toEqual({ kind: 'main', offsetSeconds: mainPhraseOffsetSeconds(3) });
+
+    expect(mainPhraseOffsetSeconds(Number.NaN)).toBe(0);
+    const finalPhraseSample = Math.round(
+      7 * MAIN_PHRASE_BARS * MUSIC_BAR_SECONDS * SOUNDTRACK_SAMPLE_RATE,
+    );
+    expect(mainPhraseOffsetSeconds(99)).toBe(finalPhraseSample / SOUNDTRACK_SAMPLE_RATE);
+  });
+
+  it('coalesces an exit onto the next bar with enough time for a clean crossfade', () => {
+    const anchorTime = 1;
+    const now = anchorTime + MUSIC_BAR_SECONDS * 2 + 0.1;
+    const transitionTime = nextSafeBarTime(now, anchorTime, 0.25);
+
+    expect(transitionTime).toBeCloseTo(anchorTime + MUSIC_BAR_SECONDS * 3, 8);
+    expect(transitionTime).toBeGreaterThanOrEqual(now + 0.25);
+    expect(nextSafeBarTime(anchorTime, anchorTime, 0)).toBe(anchorTime);
+
+    const earliestIntroExit = nextSafeBarTime(
+      anchorTime + INTRO_IN_END_SECONDS - 0.35,
+      anchorTime,
+      0.35,
+    );
+    expect(earliestIntroExit).toBeCloseTo(anchorTime + MUSIC_BAR_SECONDS * 2, 8);
+  });
+});