axiom-now-playing-musickit

# MusicKit Integration (Apple Music)

**Time cost**: 5-10 minutes

## Key Insight

**MusicKit's ApplicationMusicPlayer automatically publishes to MPNowPlayingInfoCenter.** You don't need to manually update Now Playing info when playing Apple Music content.

## What's Automatic

When using `ApplicationMusicPlayer`:
- Track title, artist, album
- Artwork (Apple's album art)
- Duration and elapsed time
- Playback rate (playing/paused state)

The system handles all MPNowPlayingInfoCenter updates for you.

## What's NOT Automatic

- Custom metadata (chapter markers, custom artist notes)
- Remote command customization beyond standard controls
- Mixing MusicKit content with your own content

## GOOD Code (MusicKit Content)

```swift
import MusicKit

@MainActor
class MusicKitPlayer {
    private let player = ApplicationMusicPlayer.shared

    func play(song: Song) async throws {
        // ✅ Just play - MPNowPlayingInfoCenter updates automatically
        player.queue = [song]
        try await player.play()

        // ❌ DO NOT manually set nowPlayingInfo here
        // MPNowPlayingInfoCenter.default().nowPlayingInfo = [...] // WRONG!
    }
}
```

## Hybrid Apps (Own Content + Apple Music)

If your app plays both Apple Music and your own content:

```swift
import MusicKit

@MainActor
class HybridPlayer {
    private let musicKitPlayer = ApplicationMusicPlayer.shared
    private var avPlayer: AVPlayer?
    private var currentSource: ContentSource = .none

    enum ContentSource {
        case none
        case appleMusic      // MusicKit handles Now Playing
        case ownContent  // We handle Now Playing
    }

    func playAppleMusicSong(_ song: Song) async throws {
        // Switch to MusicKit
        avPlayer?.pause()
        currentSource = .appleMusic

        musicKitPlayer.queue = [song]
        try await musicKitPlayer.play()
        // ✅ MusicKit handles Now Playing automatically
    }

    func playOwnContent(_ url: URL) {
        // Switch to AVPlayer