import Foundation
import Observation
import UserNotifications

/// Lokale tägliche Reminder. Reines `UNUserNotificationCenter` —
/// keine Push-Backend-Anbindung, keine Crash-Reporter, kein SaaS
/// (Compliance, siehe `mana/docs/COMPLIANCE.md`).
@MainActor
@Observable
final class NotificationManager {
    enum AuthorizationStatus: Sendable {
        case unknown
        case authorized
        case denied
    }

    private(set) var authorization: AuthorizationStatus = .unknown
    private let identifier = "ev.mana.cards.dailyReminder"
    private let store = UserDefaults.standard

    /// Persistiert User-Pref. Format: ISO-Stunde:Minute (default 18:00).
    var reminderHour: Int {
        get { store.object(forKey: "reminderHour") as? Int ?? 18 }
        set { store.set(newValue, forKey: "reminderHour") }
    }

    var reminderMinute: Int {
        get { store.object(forKey: "reminderMinute") as? Int ?? 0 }
        set { store.set(newValue, forKey: "reminderMinute") }
    }

    var remindersEnabled: Bool {
        get { store.bool(forKey: "remindersEnabled") }
        set { store.set(newValue, forKey: "remindersEnabled") }
    }

    func refreshAuthorization() async {
        let settings = await UNUserNotificationCenter.current().notificationSettings()
        switch settings.authorizationStatus {
        case .authorized, .provisional, .ephemeral:
            authorization = .authorized
        case .denied:
            authorization = .denied
        default:
            authorization = .unknown
        }
    }

    /// Permission anfragen. Beim ersten Aufruf zeigt iOS den System-Prompt.
    func requestAuthorization() async -> Bool {
        let center = UNUserNotificationCenter.current()
        do {
            let granted = try await center.requestAuthorization(options: [.alert, .badge, .sound])
            authorization = granted ? .authorized : .denied
            return granted
        } catch {
            authorization = .denied
            return false
        }
    }

    /// Tägliche Reminder neu planen. Bei `remindersEnabled = false`
    /// werden alle bestehenden Notifications gecancelt.
    func reschedule() async {
        let center = UNUserNotificationCenter.current()
        center.removePendingNotificationRequests(withIdentifiers: [identifier])
        guard remindersEnabled, authorization == .authorized else { return }

        let content = UNMutableNotificationContent()
        content.title = "Cards"
        content.body = "Ein paar Karten warten auf dich."
        content.sound = .default

        var components = DateComponents()
        components.hour = reminderHour
        components.minute = reminderMinute
        let trigger = UNCalendarNotificationTrigger(dateMatching: components, repeats: true)
        let request = UNNotificationRequest(identifier: identifier, content: content, trigger: trigger)

        do {
            try await center.add(request)
        } catch {
            Log.app.error("Notification schedule failed: \(error.localizedDescription, privacy: .public)")
        }
    }
}