푸시 알림: 곳곳에 숨은 조용한 실패

import Foundation

enum APNsEnvironment: String, Sendable {
    case sandbox, production
}

/// A wrong environment fails silently: the token registers, the relay sends, Apple drops it.
/// A simulator or a development-signed install carries embedded.mobileprovision and routes through
/// the sandbox; a TestFlight or App Store build carries none and routes through production.
func apnsEnvironment(isSimulator: Bool, bundleURL: URL) -> APNsEnvironment {
    if isSimulator { return .sandbox }
    let profile = bundleURL.appending(path: "embedded.mobileprovision")
    return FileManager.default.fileExists(atPath: profile.path) ? .sandbox : .production
}

/// Namespaced, so another family app's push can never be mistaken for this one's.
func noteID(fromPayload payload: [AnyHashable: Any]) -> String? {
    (payload["spark"] as? [String: Any])?["note_id"] as? String
}

/// The delegate exists before the app's model does. A tap from a cold launch waits here.
@MainActor
final class PushTapQueue {
    private var parked: String?
    private var deliver: ((String) -> Void)?

    func tapped(_ id: String) {
        if let deliver { deliver(id) } else { parked = id }   // a second early tap replaces the first
    }

    func attach(_ handler: @escaping (String) -> Void) {
        deliver = handler
        if let parked {
            self.parked = nil
            handler(parked)
        }
    }
}

import SwiftUI
import UIKit
import UserNotifications

@MainActor
class PushDelegate: NSObject, UIApplicationDelegate, UNUserNotificationCenterDelegate {
    let payloadKey: String
    let taps = PushTapQueue()

    init(payloadKey: String) {
        self.payloadKey = payloadKey
        super.init()
    }

    func application(_ application: UIApplication,
                     didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?) -> Bool {
        UNUserNotificationCenter.current().delegate = self
        return true
    }

    /// Not guaranteed on main. The async form means no completion handler crosses isolation;
    /// only the extracted id does.
    nonisolated func userNotificationCenter(_ center: UNUserNotificationCenter,
                                            didReceive response: UNNotificationResponse) async {
        guard let id = noteID(fromPayload: response.notification.request.content.userInfo) else { return }
        await taps.tapped(id)
    }
}

/// @UIApplicationDelegateAdaptor builds the delegate through the Objective-C -init slot.
/// `override init()` does not compile here, and a plain `init()` compiles and traps at launch.
final class SparkPushDelegate: PushDelegate {
    @objc init() { super.init(payloadKey: "spark") }
}

@main
struct SparkMobileApp: App {
    @UIApplicationDelegateAdaptor(SparkPushDelegate.self) private var pushDelegate: SparkPushDelegate

    var body: some Scene {
        WindowGroup {
            Text("Spark")
                .onAppear { pushDelegate.taps.attach { id in print("open note", id) } }
        }
    }
}