functional carplay experience in simulators

ios/Runner/CarPlaySceneDelegate.swift

@@ -16,9 +16,44 @@ import UIKit
  */
 class CarPlaySceneDelegate: UIResponder, CPTemplateApplicationSceneDelegate, CPListTemplateDelegate {
 
+  private struct Snapshot {
+    var playbackStatus: String
+    var title: String
+    var subtitle: String
+    var album: String
+
+    init(playbackStatus: String, title: String, subtitle: String, album: String) {
+      self.playbackStatus = playbackStatus
+      self.title = title
+      self.subtitle = subtitle
+      self.album = album
+    }
+
+    static let `default` = Snapshot(
+      playbackStatus: "stopped",
+      title: "KRYZ Live Stream",
+      subtitle: "KRYZ Radio",
+      album: "Live"
+    )
+
+    init(payload: [String: Any]?) {
+      let base = Snapshot.default
+      let status = (payload?["playbackStatus"] as? String)?.trimmingCharacters(in: .whitespacesAndNewlines)
+      let title = (payload?["title"] as? String)?.trimmingCharacters(in: .whitespacesAndNewlines)
+      let subtitle = (payload?["subtitle"] as? String)?.trimmingCharacters(in: .whitespacesAndNewlines)
+      let album = (payload?["album"] as? String)?.trimmingCharacters(in: .whitespacesAndNewlines)
+
+      playbackStatus = (status?.isEmpty == false) ? status! : base.playbackStatus
+      self.title = (title?.isEmpty == false) ? title! : base.title
+      self.subtitle = (subtitle?.isEmpty == false) ? subtitle! : base.subtitle
+      self.album = (album?.isEmpty == false) ? album! : base.album
+    }
+  }
+
   private var carPlayInterfaceController: CPInterfaceController?
   private var listTemplate: CPListTemplate?
   private var streamItem: CPListItem?
+  private var snapshot: Snapshot = .default
 
   // MARK: - CPTemplateApplicationSceneDelegate
 
@@ -26,7 +61,10 @@ class CarPlaySceneDelegate: UIResponder, CPTemplateApplicationSceneDelegate, CPL
     _ templateApplicationScene: CPTemplateApplicationScene,
     didConnect interfaceController: CPInterfaceController
   ) {
+    appDelegate?.ensureFlutterBridgeReadyForCarPlay()
     carPlayInterfaceController = interfaceController
+    snapshot = Snapshot(payload: appDelegate?.currentCarPlaySnapshot())
+
     let rootTemplate = makeListTemplate()
     if #available(iOS 14.0, *) {
       interfaceController.setRootTemplate(rootTemplate, animated: false, completion: nil)
@@ -34,12 +72,25 @@ class CarPlaySceneDelegate: UIResponder, CPTemplateApplicationSceneDelegate, CPL
       // iOS 13 fallback: use API variant available before iOS 14.
       interfaceController.setRootTemplate(rootTemplate, animated: false)
     }
+
+    NotificationCenter.default.addObserver(
+      self,
+      selector: #selector(handleCarPlaySnapshotChanged(_:)),
+      name: AppDelegate.carPlaySnapshotDidChangeNotification,
+      object: nil
+    )
+    appDelegate?.requestCarPlaySnapshot()
   }
 
   func templateApplicationScene(
     _ templateApplicationScene: CPTemplateApplicationScene,
     didDisconnectInterfaceController interfaceController: CPInterfaceController
   ) {
+    NotificationCenter.default.removeObserver(
+      self,
+      name: AppDelegate.carPlaySnapshotDidChangeNotification,
+      object: nil
+    )
     carPlayInterfaceController = nil
     listTemplate = nil
     appDelegate?.invokeStop()
@@ -52,8 +103,8 @@ class CarPlaySceneDelegate: UIResponder, CPTemplateApplicationSceneDelegate, CPL
       .withRenderingMode(.alwaysOriginal)
 
     let item = CPListItem(
-      text: "KRYZ Live Stream",
-      detailText: "KRYZ Radio",
+      text: snapshot.title,
+      detailText: detailText(for: snapshot),
       image: icon
     )
     streamItem = item
@@ -82,10 +133,57 @@ class CarPlaySceneDelegate: UIResponder, CPTemplateApplicationSceneDelegate, CPL
     return template
   }
 
+  private func detailText(for snapshot: Snapshot) -> String {
+    let statusText: String = switch snapshot.playbackStatus {
+    case "playing":
+      "Playing"
+    case "buffering":
+      "Buffering"
+    default:
+      "Stopped"
+    }
+
+    if snapshot.subtitle.trimmingCharacters(in: .whitespacesAndNewlines).isEmpty {
+      return statusText
+    }
+
+    return "\(snapshot.subtitle) • \(statusText)"
+  }
+
+  @objc private func handleCarPlaySnapshotChanged(_ notification: Notification) {
+    guard
+      let payload = notification.userInfo?[AppDelegate.carPlaySnapshotUserInfoKey] as? [String: Any]
+    else {
+      return
+    }
+
+    snapshot = Snapshot(payload: payload)
+    refreshTemplatesForSnapshot()
+  }
+
+  private func refreshTemplatesForSnapshot() {
+    guard let interfaceController = carPlayInterfaceController else {
+      return
+    }
+
+    if #available(iOS 14.0, *), interfaceController.topTemplate is CPNowPlayingTemplate {
+      // Preserve Now Playing navigation stack while metadata updates are flowing.
+      return
+    }
+
+    let updatedTemplate = makeListTemplate()
+    if #available(iOS 14.0, *) {
+      interfaceController.setRootTemplate(updatedTemplate, animated: false, completion: nil)
+    } else {
+      interfaceController.setRootTemplate(updatedTemplate, animated: false)
+    }
+  }
+
   // MARK: - Playback
 
   private func handleStreamItemTapped() {
     appDelegate?.invokePlay()
+    appDelegate?.requestCarPlaySnapshot()
     guard let interfaceController = carPlayInterfaceController else {
       return
     }