// JQCApp.swift
// ------------
// App entry point.

import SwiftUI
import SwiftData
import BackgroundTasks
import UserNotifications
import Combine

// ── AppearanceManager ─────────────────────────────────────────────────────────
// Persists the user's preferred colour scheme to UserDefaults and exposes it
// as a @Published property so the root view can apply .preferredColorScheme.
// "system" (nil) means the app follows iOS system appearance — the default.

enum AppearanceMode: String, CaseIterable {
    case system = "system"
    case light  = "light"
    case dark   = "dark"

    var displayName: String {
        switch self {
        case .system: return "System"
        case .light:  return "Light"
        case .dark:   return "Dark"
        }
    }

    /// The SwiftUI ColorScheme value to pass to .preferredColorScheme().
    /// nil = follow the OS (system default).
    var colorScheme: ColorScheme? {
        switch self {
        case .system: return nil
        case .light:  return .light
        case .dark:   return .dark
        }
    }
}

final class AppearanceManager: ObservableObject {
    static let shared = AppearanceManager()
    private static let defaultsKey = "jqc.appearanceMode"

    @Published var mode: AppearanceMode {
        didSet {
            UserDefaults.standard.set(mode.rawValue, forKey: Self.defaultsKey)
        }
    }

    private init() {
        let saved = UserDefaults.standard.string(forKey: Self.defaultsKey) ?? ""
        mode = AppearanceMode(rawValue: saved) ?? .system
    }
}

// ── AppDelegate — runtime orientation lock ────────────────────────────────────
// Info.plist must declare all 4 orientations so iPad multitasking is supported
// (App Store requirement). This delegate restricts the app to landscape-only
// at runtime by returning only the two landscape masks.
// Portrait is intentionally excluded: the grid-based inspection form is
// designed for landscape and does not adapt well to portrait on iPad.

final class AppDelegate: NSObject, UIApplicationDelegate {
    func application(
        _ application: UIApplication,
        supportedInterfaceOrientationsFor window: UIWindow?
    ) -> UIInterfaceOrientationMask {
        return [.landscapeLeft, .landscapeRight]
    }
}

@main
struct JanitorialQCApp: App {

    @UIApplicationDelegateAdaptor(AppDelegate.self) var appDelegate

    @StateObject private var auth       = AuthManager.shared
    @StateObject private var sync       = SyncManager.shared
    @StateObject private var appearance = AppearanceManager.shared

    init() {
        registerBackgroundTasks()
        requestNotificationPermission()
        // Set delegate so notifications display as banners when the app is in
        // the foreground. Without this iOS silently drops them.
        UNUserNotificationCenter.current().delegate = NotificationDelegate.shared
    }

    var body: some Scene {
        WindowGroup {
            ContentView()
                .environmentObject(auth)
                .environmentObject(sync)
                .environmentObject(appearance)
                .preferredColorScheme(appearance.mode.colorScheme)
        }
        .modelContainer(for: [
            LocalFacility.self,
            LocalArea.self,
            LocalTemplate.self,
            LocalInspection.self,
            LocalIssue.self,
            LocalScheduledInspection.self,
            PendingPhoto.self,
            SyncQueueEntry.self,
        ], isUndoEnabled: false) { result in
            switch result {
            case .success(let container):
                // Only set the model context here — do NOT await anything.
                // Session restore and sync are triggered by ContentView.task{}
                // which runs on the MainActor inside the SwiftUI lifecycle,
                // guaranteeing isLoading changes are seen by the view immediately.
                SyncManager.shared.modelContext = container.mainContext
            case .failure(let error):
                fatalError("SwiftData container failed: \(error)")
            }
        }
    }

    // ── Local notification permission ─────────────────────────────────────

    private func requestNotificationPermission() {
        UNUserNotificationCenter.current().requestAuthorization(
            options: [.alert, .sound, .badge]
        ) { granted, error in
            if let error { print("[JQC] Notification permission error: \(error)") }
        }
    }

    private func registerBackgroundTasks() {
        // register() returns false when the identifier is not declared in
        // BGTaskSchedulerPermittedIdentifiers or the `processing` background
        // mode is missing. Both are easy to lose in a project settings change
        // and the failure is otherwise completely silent, so it is logged.
        let registered = BGTaskScheduler.shared.register(
            forTaskWithIdentifier: "com.jqc.sync",
            using: nil
        ) { task in
            guard let processingTask = task as? BGProcessingTask else {
                task.setTaskCompleted(success: false)
                return
            }
            handleBackgroundSync(task: processingTask)
        }
        if !registered {
            print("[JQC] BGTaskScheduler.register FAILED for com.jqc.sync — "
                  + "check UIBackgroundModes contains 'processing' and "
                  + "BGTaskSchedulerPermittedIdentifiers contains com.jqc.sync")
        }
    }

    private func handleBackgroundSync(task: BGProcessingTask) {
        // Re-arm first: if anything below throws or the task is killed, a
        // request is already queued for the next opportunity.
        scheduleBackgroundSync()

        let syncTask = Task { @MainActor in
            // A BGTaskScheduler launch does not render ContentView, so the
            // `.task { restoreSession() }` there never runs and
            // AuthManager.isAuthenticated is still false. triggerSync() guards
            // on it and would return having done nothing at all.
            if !AuthManager.shared.isAuthenticated {
                await AuthManager.shared.restoreSession()
            }

            // The SwiftData container is created by the `.modelContainer`
            // scene modifier, so on a COLD background launch (process was
            // terminated, no scene connected) there is no context to drain.
            // The common case — app suspended but still resident — has one.
            guard SyncManager.shared.modelContext != nil else {
                print("[JQC] background sync skipped — no model context "
                      + "(cold launch, no scene)")
                return
            }

            await SyncManager.shared.triggerSync()
        }

        task.expirationHandler = {
            syncTask.cancel()
        }

        Task {
            await syncTask.value
            task.setTaskCompleted(success: !syncTask.isCancelled)
        }
    }
}

// ── Notification delegate ─────────────────────────────────────────────────────
// Allows local notifications to appear as banners while the app is in the
// foreground. Without this delegate iOS discards them silently.

final class NotificationDelegate: NSObject, UNUserNotificationCenterDelegate {
    static let shared = NotificationDelegate()
    private override init() {}

    func userNotificationCenter(
        _ center: UNUserNotificationCenter,
        willPresent notification: UNNotification,
        withCompletionHandler completionHandler:
            @escaping (UNNotificationPresentationOptions) -> Void
    ) {
        // Show banner + play sound even when the app is active in foreground.
        completionHandler([.banner, .sound])
    }
}

func scheduleBackgroundSync() {
    let request = BGProcessingTaskRequest(identifier: "com.jqc.sync")
    request.requiresNetworkConnectivity = true
    request.requiresExternalPower       = false
    do {
        try BGTaskScheduler.shared.submit(request)
    } catch {
        // Was `try?`. Submitting without the `processing` background mode fails
        // with BGTaskSchedulerError.notPermitted, which is exactly how this
        // whole path stayed dead unnoticed. Never swallow it again.
        print("[JQC] BGTaskScheduler.submit failed: \(error)")
    }
}