refactor(radio): separate directory and playback components

src/layers/radio/presentation.js

@@ -0,0 +1,105 @@
+export function createPresentation({
+  state: layerState,
+  services,
+  parts,
+  source,
+}) {
+  /** Return the deeply immutable healthy catalog generation shared with tuner consumers. */
+
+  function getRadioAcceptedCatalogSnapshot() {
+    return layerState._acceptedCatalogSnapshot;
+  }
+
+  /** Return an immutable snapshot consumed by the right-rail UI. */
+
+  function getRadioUIState() {
+    const visible = parts.queries.visibleStations();
+    const selected = parts.queries.selectedStation();
+    return Object.freeze({
+      enabled: layerState._enabled,
+      loading: layerState._loading,
+      stale: layerState._stale,
+      degraded: layerState._degraded,
+      error: layerState._error,
+      updatedAt: layerState._updatedAt,
+      filter: layerState._filter,
+      categories: layerState._categories,
+      acceptedCatalogGeneration: layerState._acceptedCatalogSnapshot.generation,
+      presentationActive: parts.interaction.radioPresentationAllowed(),
+      stationCount: layerState._stations.length,
+      filteredCount: visible.length,
+      selected,
+      selectedIndex: selected
+        ? visible.findIndex((station) => station.id === selected.id)
+        : -1,
+      audioState: layerState._audioState,
+      audioError: layerState._audioError,
+      playingStationId: layerState._audioStationId,
+      volume: layerState._userVolume,
+      effectiveVolume:
+        layerState._audio?.volume ??
+        (layerState._voiceDucked ? 0 : layerState._userVolume),
+      voiceDucked: layerState._voiceDucked,
+      voiceRestoring: layerState._voiceRestoring,
+      tuningActive: layerState._tuningActive,
+      tuningStatic: layerState._tuningStatic,
+      tuningAwaitingStationId: layerState._tuningAwaitingStationId,
+      tuningPreviewStationId: layerState._tuningPreviewId,
+      tuningRestoredStationId:
+        layerState._cancelledTuningPresentationStation?.id || null,
+      tuningCatalogGeneration: layerState._tuningResolutionSnapshot.generation,
+      tuningUnavailableStationId: layerState._tuningUnavailableStationId,
+    });
+  }
+
+  function emitState() {
+    const snapshot = getRadioUIState();
+    for (const listener of layerState._listeners) {
+      try {
+        listener(snapshot);
+      } catch {
+        // A broken consumer must not break playback or rendering.
+      }
+    }
+  }
+
+  /** Subscribe to radio state; the current state is delivered immediately. */
+
+  function subscribeToRadio(listener) {
+    if (typeof listener !== 'function') return () => {};
+    layerState._listeners.add(listener);
+    listener(getRadioUIState());
+    return () => layerState._listeners.delete(listener);
+  }
+
+  /** Subscribe to explicit playback controls so voice handoffs cannot undo them. */
+
+  function subscribeToRadioPlaybackControls(listener) {
+    if (typeof listener !== 'function') return () => {};
+    layerState._playbackControlListeners.add(listener);
+    return () => layerState._playbackControlListeners.delete(listener);
+  }
+
+  function emitPlaybackControl(
+    action,
+    origin,
+    attemptId = layerState._activePlaybackAttempt?.id || null,
+  ) {
+    const event = { action, origin, attemptId };
+    for (const listener of layerState._playbackControlListeners) {
+      try {
+        listener(event);
+      } catch {
+        // Playback controls must remain usable if an observer fails.
+      }
+    }
+  }
+  return {
+    getRadioAcceptedCatalogSnapshot,
+    getRadioUIState,
+    emitState,
+    subscribeToRadio,
+    subscribeToRadioPlaybackControls,
+    emitPlaybackControl,
+  };
+}