Add support for AirPlay (#22)

Fixes #21

Plug/AudioPlayer.swift

@@ -1,8 +1,9 @@
 import Cocoa
 import AVFoundation
 import CoreMedia
-import HypeMachineAPI
 import UserNotifications
+import Combine
+import HypeMachineAPI
 
 typealias OnShuffleChangedSwignal = Swignal1Arg<Bool>
 typealias OnTrackPlaying = Swignal1Arg<Bool>
@@ -13,7 +14,18 @@ typealias OnSkipBackward = Swignal1Arg<Bool>
 final class AudioPlayer: NSObject {
 	static let shared = AudioPlayer()
 
-	var player: AVPlayer?
+	private var playerDidChangeSubject = PassthroughSubject<Void, Never>()
+
+	var playerDidChangePublisher: AnyPublisher<Void, Never> {
+		playerDidChangeSubject.eraseToAnyPublisher()
+	}
+
+	var player: AVPlayer? {
+		didSet {
+			playerDidChangeSubject.send()
+		}
+	}
+
 	var playerItem: AVPlayerItem?
 
 	var currentDataSource: TracksDataSource? {

Plug/FooterViewController.swift

@@ -1,10 +1,15 @@
 import Cocoa
+import AVKit
+import Combine
 
 final class FooterViewController: NSViewController {
 	var volumeIcon: VolumeIconView!
 	var volumeSlider: NSSlider!
 	var shuffleButton: SwissArmyButton!
 
+	private var cancellables = Set<AnyCancellable>()
+	private let routeDetector = AVRouteDetector()
+
 	func toggleShuffle() {
 		AudioPlayer.shared.toggleShuffle()
 	}
@@ -34,6 +39,8 @@ final class FooterViewController: NSViewController {
 	override func loadView() {
 		view = NSView(frame: .zero)
 
+		routeDetector.isRouteDetectionEnabled = true
+
 		let backgroundView = DraggableVisualEffectsView()
 		backgroundView.blendingMode = .withinWindow
 		view.addSubview(backgroundView)
@@ -75,6 +82,37 @@ final class FooterViewController: NSViewController {
 			make.left.equalTo(backgroundView).offset(40)
 		}
 
+		let airPlayButton = AVRoutePickerView()
+		airPlayButton.isHidden = !routeDetector.multipleRoutesDetected
+		airPlayButton.isRoutePickerButtonBordered = false
+		airPlayButton.setRoutePickerButtonColor(.tertiaryLabelColor, for: .normal)
+		airPlayButton.setRoutePickerButtonColor(.secondaryLabelColor, for: .normalHighlighted)
+		airPlayButton.player = AudioPlayer.shared.player
+		backgroundView.addSubview(airPlayButton)
+
+		airPlayButton.snp.makeConstraints { make in
+			make.centerY.equalTo(backgroundView)
+			make.left.equalTo(volumeSlider).offset(70)
+		}
+
+		NotificationCenter.default.publisher(for: .AVRouteDetectorMultipleRoutesDetectedDidChange)
+			.receive(on: DispatchQueue.main)
+			.sink { [weak self] _ in
+				guard let self = self else {
+					return
+				}
+
+				airPlayButton.isHidden = !self.routeDetector.multipleRoutesDetected
+			}
+			.store(in: &cancellables)
+
+		AudioPlayer.shared.playerDidChangePublisher
+			.receive(on: DispatchQueue.main)
+			.sink {
+				airPlayButton.player = AudioPlayer.shared.player
+			}
+			.store(in: &cancellables)
+
 		shuffleButton = SwissArmyButton(frame: .zero)
 		let shuffleCell = TransparentButtonCell(textCell: "")
 		shuffleCell.allowsSelectedState = true