feat: coordinate adaptive audio intent

src/composables/useAudioIntent.ts

@@ -0,0 +1,105 @@
+import {
+  onMounted,
+  onUnmounted,
+  readonly,
+  shallowRef,
+  watch,
+  type Ref,
+} from 'vue';
+import {
+  createAudioIntentCoordinator,
+  type AudioIntentCoordinator,
+  type AudioIntentUpdate,
+} from '@/audio/audio-intent-coordinator';
+import {
+  DEFAULT_DRIVE_ENERGY,
+  resolveChapterIntent,
+} from '@/audio/journey-music-state';
+import type { ChapterIntent, DriveEnergySample } from '@/audio/types';
+import type { JourneySectionsBinding } from '@/composables/useJourneySections';
+import type { SectionId } from '@/content/types';
+import type { NavigationState } from '@/journey/navigation-controller';
+import type { JourneySnapshot } from '@/journey/types';
+
+export interface AudioIntentSources {
+  readonly canonicalIds: readonly SectionId[];
+  readonly journey: JourneySectionsBinding;
+  readonly navigation: Readonly<Ref<NavigationState>>;
+}
+
+export interface AudioIntentBinding {
+  readonly chapter: Readonly<Ref<ChapterIntent>>;
+  readonly drive: Readonly<Ref<DriveEnergySample>>;
+}
+
+export function useAudioIntent(sources: AudioIntentSources): AudioIntentBinding {
+  const firstId = sources.canonicalIds[0];
+  if (firstId === undefined) throw new Error('Audio intent requires one section.');
+  const chapter = shallowRef(resolveChapterIntent(firstId));
+  const drive = shallowRef<DriveEnergySample>(DEFAULT_DRIVE_ENERGY);
+  let coordinator: AudioIntentCoordinator | null = null;
+  let removeFrame = (): void => {};
+
+  const publish = (update: AudioIntentUpdate): boolean => {
+    if (update.chapter !== null) chapter.value = update.chapter;
+    if (update.drive !== null) drive.value = update.drive;
+    return update.needsFrame;
+  };
+  const sample = (now: number, snapshot: JourneySnapshot): boolean => {
+    if (coordinator === null) {
+      coordinator = createAudioIntentCoordinator(
+        sources.canonicalIds,
+        snapshot.activeSectionId,
+        snapshot.sectionActivation.layoutRevision,
+        snapshot.scrollY,
+      );
+      const seeded = coordinator.current();
+      chapter.value = seeded.chapter;
+      drive.value = seeded.drive;
+    }
+    return publish(coordinator.sample({
+      now,
+      visible: document.visibilityState !== 'hidden',
+      scrollY: snapshot.scrollY,
+      activeSectionId: snapshot.activeSectionId,
+      acceleration: snapshot.acceleration,
+      sectionActivation: snapshot.sectionActivation,
+      navigation: sources.navigation.value,
+    }));
+  };
+
+  const stopNavigationWatch = watch(
+    sources.navigation,
+    () => sources.journey.requestFrame(),
+    { flush: 'sync' },
+  );
+  onMounted(() => {
+    removeFrame = sources.journey.subscribeFrame(sample);
+    const resetFromCurrentSnapshot = (): void => {
+      if (coordinator === null) return;
+      const snapshot = sources.journey.snapshot.value;
+      publish(coordinator.reset({
+        navigation: sources.navigation.value,
+        scrollY: snapshot.scrollY,
+        sectionActivation: snapshot.sectionActivation,
+      }));
+    };
+    const onVisibility = (): void => {
+      resetFromCurrentSnapshot();
+      if (document.visibilityState !== 'hidden') sources.journey.requestFrame();
+    };
+    document.addEventListener('visibilitychange', onVisibility);
+    removeFrame = combineCleanup(removeFrame, () =>
+      document.removeEventListener('visibilitychange', onVisibility));
+    sources.journey.requestFrame();
+  });
+  onUnmounted(() => {
+    stopNavigationWatch();
+    removeFrame();
+  });
+  return { chapter: readonly(chapter), drive: readonly(drive) };
+}
+
+function combineCleanup(left: () => void, right: () => void): () => void {
+  return () => { left(); right(); };
+}