musicshare/apps/mobile/src/lib/appleMusic.ts

import { useEffect } from 'react';
import { AppState } from 'react-native';
import AppleMusic, { type MusicAppPlayback } from '@/modules/apple-music';
import { api } from './api';
import { reportPlayback } from './device';

/** True on iOS builds that include the native module (not Android, web, or Expo Go). */
export const appleMusicAvailable = AppleMusic !== null;

export class AppleMusicPermissionError extends Error {}

/**
 * The whole Apple Music setup: one system prompt. Asks for access, exchanges
 * our developer token for the user's Music User Token, and hands it to the
 * server, which then follows recently played in the background.
 */
export async function connectAppleMusic() {
  if (!AppleMusic) throw new Error('Apple Music is only available in the iPhone app');
  let status = AppleMusic.authorizationStatus();
  if (status === 'notDetermined') status = await AppleMusic.requestAuthorization();
  if (status !== 'authorized') {
    throw new AppleMusicPermissionError(
      status === 'restricted'
        ? 'Apple Music access is restricted on this iPhone (Screen Time or a device profile).'
        : 'Turn on Media & Apple Music for musicshare in the Settings app, then try again.',
    );
  }
  const { token } = await api.appleMusicDeveloperToken();
  const musicUserToken = await AppleMusic.getUserToken(token);
  return api.connectAppleMusic(musicUserToken);
}

const HEARTBEAT_MS = 4 * 60_000; // the server expires silent phones after 9 minutes
let lastSent: { key: string; at: number } | null = null;

function report(playback: MusicAppPlayback) {
  const key = 'title' in playback ? `${playback.state}|${playback.title}|${playback.artist}` : 'stopped';
  const now = Date.now();
  if (lastSent?.key === key && (playback.state !== 'playing' || now - lastSent.at < HEARTBEAT_MS)) return;
  if (!lastSent && key === 'stopped') return; // nothing was shared yet; no need to say "stopped"
  lastSent = { key, at: now };
  reportPlayback(
    'title' in playback && playback.state !== 'stopped'
      ? {
          app: 'com.apple.Music',
          appName: 'Apple Music',
          state: playback.state,
          track: {
            title: playback.title,
            artist: playback.artist,
            album: playback.album || null,
            durationMs: playback.durationMs > 0 ? Math.round(playback.durationMs) : null,
          },
        }
      : { app: 'com.apple.Music', appName: 'Apple Music', state: 'stopped' },
  ).catch(() => {
    lastSent = null; // retry on the next change
  });
}

/**
 * While the app is open, mirror the Music app exactly. iOS doesn't let us watch
 * it in the background; then the server's recently-played polling takes over.
 */
export function useAppleMusicLive(enabled: boolean) {
  useEffect(() => {
    if (!enabled || !AppleMusic || AppleMusic.authorizationStatus() !== 'authorized') return;
    const music = AppleMusic;
    const check = () => music.getNowPlaying().then(report).catch(() => {});
    check();
    const changes = music.addListener('onNowPlayingChange', report);
    const foreground = AppState.addEventListener('change', (s) => s === 'active' && check());
    const heartbeat = setInterval(check, HEARTBEAT_MS);
    return () => {
      changes.remove();
      foreground.remove();
      clearInterval(heartbeat);
    };
  }, [enabled]);
}