/**
 * Audio-route detection.
 *
 * AirPlay is not Cast: it is an audio session route. The local engine keeps
 * playing and keeps owning transport — the sound simply comes out somewhere
 * else. Nothing here installs an output or takes commands away from the engine,
 * which is exactly what distinguishes it from a Cast session.
 *
 * Detection is structural: decisions read `portType`, never the localized
 * port name.
 */
import type { AudioSession } from '../specs/AudioSession.nitro';
import type { OutputPresence } from './outputPresence';

type CallbackGuard = () => boolean;

export interface RouteWiring {
  wireAirPlayDetection(
    session: AudioSession,
    isCurrentEvent?: CallbackGuard
  ): void;
}

export function createRouteWiring(presence: OutputPresence): RouteWiring {
  let onAirPlay = false;

  return {
    wireAirPlayDetection(
      session: AudioSession,
      isCurrentEvent: CallbackGuard = () => true
    ): void {
      session.onRouteChange((event) => {
        if (!isCurrentEvent()) return;

        // Only on genuine transitions: route changes fire for reasons that
        // have nothing to do with AirPlay, and republishing on each would
        // churn every useCastState subscriber.
        if (
          event.reason === 'newDeviceAvailable' &&
          event.output?.portType === 'airplay'
        ) {
          if (onAirPlay) return;
          onAirPlay = true;
          presence.setRoute({
            name: event.output.name ?? 'AirPlay',
            type: 'airplay',
          });
        } else if (
          event.reason === 'oldDeviceUnavailable' &&
          event.removedOutput?.portType === 'airplay'
        ) {
          if (!onAirPlay) return;
          onAirPlay = false;
          presence.setRoute(undefined);
        }
      });
    },
  };
}