import Foundation
import UserNotifications

@MainActor
enum NotificationManager {
    /// Default reminder time (09:00) used when the user first enables a reminder.
    static var defaultTime: Date {
        Calendar.current.date(bySettingHour: 9, minute: 0, second: 0, of: .now) ?? .now
    }

    @discardableResult
    static func requestAuthorization() async -> Bool {
        do {
            return try await UNUserNotificationCenter.current()
                .requestAuthorization(options: [.alert, .sound, .badge])
        } catch {
            return false
        }
    }

    /// Cancels any existing reminder for the habit and, if it has a reminder
    /// time, schedules a new daily notification.
    static func reschedule(for habit: Habit) {
        let center = UNUserNotificationCenter.current()
        let id = identifier(for: habit)
        center.removePendingNotificationRequests(withIdentifiers: [id])

        guard let time = habit.reminderTime else { return }

        let content = UNMutableNotificationContent()
        content.title = habit.name
        content.body = "Zeit für deine Gewohnheit"
        content.sound = .default

        let components = Calendar.current.dateComponents([.hour, .minute], from: time)
        let trigger = UNCalendarNotificationTrigger(dateMatching: components, repeats: true)
        let request = UNNotificationRequest(identifier: id, content: content, trigger: trigger)
        center.add(request)
    }

    static func cancel(for habit: Habit) {
        UNUserNotificationCenter.current()
            .removePendingNotificationRequests(withIdentifiers: [identifier(for: habit)])
    }

    private static func identifier(for habit: Habit) -> String {
        "habit-\(habit.uuid.uuidString)"
    }
}