stemify/ios/Stemify/Playback/NowPlaying.swift

import Foundation
import MediaPlayer
import UIKit

/// Lock screen, Control Center, headphone and car controls: publishes the current track to
/// MPNowPlayingInfoCenter and routes MPRemoteCommandCenter back into [PlaybackManager].
/// Stands in for the Media3 session on Android.
final class NowPlaying: @unchecked Sendable {
    private let pm: PlaybackManager
    private let plex: PlexClient
    private let center = MPNowPlayingInfoCenter.default()
    private var artKey: String?
    private var artwork: MPMediaItemArtwork?

    init(pm: PlaybackManager, plex: PlexClient) {
        self.pm = pm
        self.plex = plex
        pm.addListener { [weak self] in self?.publish() }
        wireCommands()
        publish()
    }

    // ---- shared with CarPlay ---------------------------------------------------------

    /// The mix shown next to the artist: nil unless stems are playing or the mix is Full.
    var mixLabel: String? {
        guard pm.source == .Stems else { return nil }
        guard let p = MixPresets.current(pm.stemNames, pm.mix) else { return "Custom mix" }
        return p == MixPresets.full ? nil : p.label
    }

    var vocalsAvailable: Bool { pm.source == .Stems && pm.stemNames.contains("vocals") }
    var vocalsSilent: Bool { MixPresets.vocalsSilent(pm.stemNames, pm.mix) }
    var nextMix: MixPreset { MixPresets.next(pm.stemNames, pm.mix) }

    /// One tap: hear the vocals again, or take them out.
    func toggleVocals() {
        let names = pm.stemNames, mix = pm.mix
        let anySolo = names.contains { mix[$0]?.solo == true }
        if MixPresets.vocalsSilent(names, mix) {
            if mix["vocals"]?.muted == true && !anySolo { pm.toggleMute("vocals") } else { pm.applyMix([:]) }
        } else if anySolo {
            pm.applyMix(MixPresets.karaoke.build(names) ?? [:])
        } else {
            pm.toggleMute("vocals")
        }
    }

    func cycleMix() { pm.applyMix(nextMix.build(pm.stemNames) ?? [:]) }

    // ---- info --------------------------------------------------------------------------

    private func publish() {
        guard let t = pm.current?.track else {
            center.nowPlayingInfo = nil
            center.playbackState = .stopped
            return
        }
        var info: [String: Any] = [
            MPMediaItemPropertyTitle: t.title,
            MPMediaItemPropertyArtist: mixLabel.map { "\(t.artist) · \($0)" } ?? t.artist,
            MPMediaItemPropertyAlbumTitle: t.album,
            MPMediaItemPropertyPlaybackDuration: Double(max(pm.durationMs, t.durationMs)) / 1000,
            MPNowPlayingInfoPropertyElapsedPlaybackTime: Double(pm.positionMs()) / 1000,
            MPNowPlayingInfoPropertyPlaybackRate: pm.isPlaying && !pm.buffering ? 1.0 : 0.0,
            MPNowPlayingInfoPropertyDefaultPlaybackRate: 1.0,
            MPNowPlayingInfoPropertyMediaType: MPNowPlayingInfoMediaType.audio.rawValue,
            MPNowPlayingInfoPropertyPlaybackQueueIndex: max(pm.index, 0),
            MPNowPlayingInfoPropertyPlaybackQueueCount: pm.queue.count,
            MPNowPlayingInfoPropertyExternalContentIdentifier: t.ratingKey,
        ]
        if let n = t.index { info[MPMediaItemPropertyAlbumTrackNumber] = n }
        let key = t.thumb
        if key == artKey, let artwork { info[MPMediaItemPropertyArtwork] = artwork }
        center.nowPlayingInfo = info
        center.playbackState = pm.isPlaying ? .playing : .paused
        updateCommands()
        if key != artKey {
            artKey = key
            artwork = nil
            if let url = plex.artUrl(key, px: 600) {
                Task { @MainActor [weak self] in
                    guard let img = await ArtLoader.shared.image(url), let self, self.artKey == key else { return }
                    self.artwork = MPMediaItemArtwork(boundsSize: img.size) { _ in img }
                    self.publish()
                }
            }
        }
    }

    // ---- commands ----------------------------------------------------------------------

    private func wireCommands() {
        let c = MPRemoteCommandCenter.shared()
        func on(_ cmd: MPRemoteCommand, _ f: @escaping (MPRemoteCommandEvent) -> MPRemoteCommandHandlerStatus) {
            cmd.isEnabled = true
            cmd.addTarget { e in MainActor.assumeIsolated { f(e) } }
        }
        on(c.playCommand) { [pm] _ in pm.play(); return .success }
        on(c.pauseCommand) { [pm] _ in pm.pause(); return .success }
        on(c.stopCommand) { [pm] _ in pm.pause(); return .success }
        on(c.togglePlayPauseCommand) { [pm] _ in pm.togglePlay(); return .success }
        on(c.nextTrackCommand) { [pm] _ in pm.next(); return .success }
        on(c.previousTrackCommand) { [pm] _ in pm.previous(); return .success }
        on(c.changePlaybackPositionCommand) { [pm] e in
            guard let e = e as? MPChangePlaybackPositionCommandEvent else { return .commandFailed }
            pm.seekTo(Int64(e.positionTime * 1000))
            return .success
        }
        on(c.changeShuffleModeCommand) { [pm] e in
            guard let e = e as? MPChangeShuffleModeCommandEvent else { return .commandFailed }
            pm.setShuffle(e.shuffleType != .off)
            return .success
        }
        on(c.changeRepeatModeCommand) { [pm] e in
            guard let e = e as? MPChangeRepeatModeCommandEvent else { return .commandFailed }
            pm.setRepeat(e.repeatType == .one ? .One : e.repeatType == .all ? .All : .Off)
            return .success
        }
        c.skipForwardCommand.isEnabled = false
        c.skipBackwardCommand.isEnabled = false
        c.seekForwardCommand.isEnabled = false
        c.seekBackwardCommand.isEnabled = false
    }

    private func updateCommands() {
        let c = MPRemoteCommandCenter.shared()
        c.changeShuffleModeCommand.currentShuffleType = pm.shuffle ? .items : .off
        c.changeRepeatModeCommand.currentRepeatType = pm.repeatMode == .One ? .one : pm.repeatMode == .All ? .all : .off
        c.nextTrackCommand.isEnabled = pm.index + 1 < pm.queue.count || pm.repeatMode != .Off
        c.previousTrackCommand.isEnabled = pm.current != nil
    }
}