Connect Apple Music and Spotify-via-Last.fm on iPhone

- Local Expo module (Swift): MusicKit authorization, Music User Token via
  MusicUserTokenProvider, and live Music app now-playing while the app is
  open (MediaPlayer notifications), reported through the device endpoint
- One-tap Apple Music onboarding on iOS; Apple Music row in Settings
- Sign in with Last.fm, plus a guided Spotify-via-Last.fm flow when direct
  Spotify sign-in is capped
- Device registration moved to shared code used by Android and iOS
Not yet compiled for iOS (no Xcode here); needs an EAS build.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01MzFywujuH9TiuXbr9vjoX8

apps/mobile/modules/apple-music/expo-module.config.json

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+{
+  "platforms": ["apple"],
+  "apple": {
+    "modules": ["AppleMusicModule"]
+  }
+}

apps/mobile/modules/apple-music/index.ts

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+// iOS-only native module; the default export is null where it is unavailable.
+export { default } from './src/AppleMusicModule';
+export * from './src/AppleMusic.types';

apps/mobile/modules/apple-music/ios/AppleMusic.podspec

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+Pod::Spec.new do |s|
+  s.name           = 'AppleMusic'
+  s.version        = '1.0.0'
+  s.summary        = 'Apple Music authorization, user token and Music app now-playing'
+  s.description    = 'Local Expo module for musicshare'
+  s.author         = ''
+  s.homepage       = 'https://docs.expo.dev/modules/'
+  s.platforms      = {
+    :ios => '16.4',
+    :tvos => '16.4'
+  }
+  s.source         = { git: '' }
+  s.static_framework = true
+
+  s.dependency 'ExpoModulesCore'
+  s.frameworks = 'MusicKit', 'MediaPlayer'
+
+  # Swift/Objective-C compatibility
+  s.pod_target_xcconfig = {
+    'DEFINES_MODULE' => 'YES',
+  }
+
+  s.source_files = "**/*.{h,m,mm,swift,hpp,cpp}"
+end

apps/mobile/modules/apple-music/ios/AppleMusicModule.swift

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+import ExpoModulesCore
+import MediaPlayer
+import MusicKit
+
+/**
+ * Apple Music for the iOS app:
+ *  - the one-tap "Allow access to Apple Music" prompt (MusicKit authorization)
+ *  - the Music User Token the server needs to read recently played
+ *  - live now-playing from the Music app while our app is open
+ *    (iOS doesn't let apps observe the Music app in the background)
+ */
+public class AppleMusicModule: Module {
+  private var observers: [NSObjectProtocol] = []
+
+  public func definition() -> ModuleDefinition {
+    Name("AppleMusic")
+
+    Events("onNowPlayingChange")
+
+    Function("authorizationStatus") { () -> String in
+      Self.describe(MusicAuthorization.currentStatus)
+    }
+
+    AsyncFunction("requestAuthorization") { () async -> String in
+      Self.describe(await MusicAuthorization.request())
+    }
+
+    /// developerToken comes from our server (signed with the MusicKit key).
+    AsyncFunction("getUserToken") { (developerToken: String) async throws -> String in
+      try await MusicUserTokenProvider().userToken(for: developerToken, options: .ignoreCache)
+    }
+
+    AsyncFunction("getNowPlaying") { () async -> [String: Any] in
+      await MainActor.run { Self.snapshot() }
+    }
+
+    OnStartObserving {
+      DispatchQueue.main.async { self.startObserving() }
+    }
+
+    OnStopObserving {
+      DispatchQueue.main.async { self.stopObserving() }
+    }
+  }
+
+  private func startObserving() {
+    guard observers.isEmpty, MusicAuthorization.currentStatus == .authorized else { return }
+    let player = MPMusicPlayerController.systemMusicPlayer
+    player.beginGeneratingPlaybackNotifications()
+    let center = NotificationCenter.default
+    for name in [Notification.Name.MPMusicPlayerControllerNowPlayingItemDidChange,
+                 Notification.Name.MPMusicPlayerControllerPlaybackStateDidChange] {
+      observers.append(center.addObserver(forName: name, object: player, queue: .main) { [weak self] _ in
+        self?.sendEvent("onNowPlayingChange", Self.snapshot())
+      })
+    }
+  }
+
+  private func stopObserving() {
+    observers.forEach { NotificationCenter.default.removeObserver($0) }
+    observers.removeAll()
+    MPMusicPlayerController.systemMusicPlayer.endGeneratingPlaybackNotifications()
+  }
+
+  /// Must be called on the main thread.
+  private static func snapshot() -> [String: Any] {
+    let player = MPMusicPlayerController.systemMusicPlayer
+    guard let item = player.nowPlayingItem, let title = item.title, !title.isEmpty else {
+      return ["state": "stopped"]
+    }
+    let state: String
+    switch player.playbackState {
+    case .playing, .seekingForward, .seekingBackward: state = "playing"
+    case .paused, .interrupted: state = "paused"
+    default: state = "stopped"
+    }
+    return [
+      "state": state,
+      "title": title,
+      "artist": item.artist ?? "",
+      "album": item.albumTitle ?? "",
+      "durationMs": item.playbackDuration * 1000,
+      "storeId": item.playbackStoreID,
+    ]
+  }
+
+  private static func describe(_ status: MusicAuthorization.Status) -> String {
+    switch status {
+    case .authorized: return "authorized"
+    case .denied: return "denied"
+    case .restricted: return "restricted"
+    case .notDetermined: return "notDetermined"
+    @unknown default: return "unknown"
+    }
+  }
+}

apps/mobile/modules/apple-music/src/AppleMusic.types.ts

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+export type AppleMusicAuthorization = 'authorized' | 'denied' | 'restricted' | 'notDetermined' | 'unknown';
+
+export type MusicAppPlayback =
+  | { state: 'stopped' }
+  | {
+      state: 'playing' | 'paused' | 'stopped';
+      title: string;
+      artist: string;
+      album: string;
+      durationMs: number;
+      storeId: string;
+    };
+
+export type AppleMusicModuleEvents = {
+  onNowPlayingChange: (playback: MusicAppPlayback) => void;
+};

apps/mobile/modules/apple-music/src/AppleMusicModule.ts

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+import { NativeModule, requireOptionalNativeModule } from 'expo';
+
+import type { AppleMusicAuthorization, AppleMusicModuleEvents, MusicAppPlayback } from './AppleMusic.types';
+
+declare class AppleMusicModule extends NativeModule<AppleMusicModuleEvents> {
+  authorizationStatus(): AppleMusicAuthorization;
+  requestAuthorization(): Promise<AppleMusicAuthorization>;
+  getUserToken(developerToken: string): Promise<string>;
+  getNowPlaying(): Promise<MusicAppPlayback>;
+}
+
+/** iOS only. null on Android, web and Expo Go, so callers must feature-check. */
+export default requireOptionalNativeModule<AppleMusicModule>('AppleMusic');