FamilyMealPlanner/MealMoodWatch/MealMoodWatchApp.swift

import SwiftUI
import WatchConnectivity
import WidgetKit

@main
struct MealMoodWatchApp: App {
    @StateObject private var store = WatchWeekStore.shared

    var body: some Scene {
        WindowGroup {
            TabView {
                TodayView()
                WeekView()
            }
            .tabViewStyle(.verticalPage)
            .environmentObject(store)
        }
    }
}

/// Receives the week snapshot from the iPhone and persists it in the watch's
/// app group so the complication can read it too.
final class WatchWeekStore: NSObject, ObservableObject, WCSessionDelegate {
    static let shared = WatchWeekStore()

    @Published var payload: WatchWeekPayload?

    private override init() {
        super.init()
        payload = WatchWeekPayload.stored()
        guard WCSession.isSupported() else { return }
        WCSession.default.delegate = self
        WCSession.default.activate()
    }

    private func apply(_ data: Data) {
        guard let received = WatchWeekPayload.decode(data) else { return }
        DispatchQueue.main.async {
            self.payload = received
            received.store()
            WidgetCenter.shared.reloadAllTimelines()
        }
    }

    func session(_ session: WCSession, activationDidCompleteWith activationState: WCSessionActivationState, error: Error?) {
        // Pick up a context delivered while the app wasn't running.
        if let data = session.receivedApplicationContext[WatchWeekPayload.storageKey] as? Data {
            apply(data)
        }
    }

    func session(_ session: WCSession, didReceiveApplicationContext applicationContext: [String: Any]) {
        if let data = applicationContext[WatchWeekPayload.storageKey] as? Data {
            apply(data)
        }
    }
}