import UserNotifications
import Foundation

class NotificationService {
    static let shared = NotificationService()

    // MARK: - Permission

    func requestPermission() async -> Bool {
        do {
            let granted = try await UNUserNotificationCenter.current().requestAuthorization(options: [.alert, .badge, .sound])
            return granted
        } catch {
            return false
        }
    }

    func isAuthorized() async -> Bool {
        let settings = await UNUserNotificationCenter.current().notificationSettings()
        return settings.authorizationStatus == .authorized
    }

    // MARK: - Morning Reminder

    func scheduleMorningReminder(hour: Int, minute: Int) {
        let content = UNMutableNotificationContent()
        content.title = "Доброе утро!"
        content.body = "Посмотри свои привычки и задачи на сегодня"
        content.sound = .default

        var components = DateComponents()
        components.hour = hour
        components.minute = minute

        let trigger = UNCalendarNotificationTrigger(dateMatching: components, repeats: true)
        let request = UNNotificationRequest(identifier: "morning_reminder", content: content, trigger: trigger)

        UNUserNotificationCenter.current().add(request)
    }

    // MARK: - Evening Reminder

    func scheduleEveningReminder(hour: Int, minute: Int) {
        let content = UNMutableNotificationContent()
        content.title = "Итоги дня"
        content.body = "Проверь, все ли привычки выполнены сегодня"
        content.sound = .default

        var components = DateComponents()
        components.hour = hour
        components.minute = minute

        let trigger = UNCalendarNotificationTrigger(dateMatching: components, repeats: true)
        let request = UNNotificationRequest(identifier: "evening_reminder", content: content, trigger: trigger)

        UNUserNotificationCenter.current().add(request)
    }

    // MARK: - Task Deadline Reminder

    func scheduleTaskReminder(taskId: Int, title: String, dueDate: Date) {
        let content = UNMutableNotificationContent()
        content.title = "Задача скоро"
        content.body = title
        content.sound = .default

        // За 1 час до дедлайна
        let reminderDate = dueDate.addingTimeInterval(-3600)
        guard reminderDate > Date() else { return }

        let components = Calendar.current.dateComponents([.year, .month, .day, .hour, .minute], from: reminderDate)
        let trigger = UNCalendarNotificationTrigger(dateMatching: components, repeats: false)
        let request = UNNotificationRequest(identifier: "task_\(taskId)", content: content, trigger: trigger)

        UNUserNotificationCenter.current().add(request)
    }

    // MARK: - Habit Reminder

    func scheduleHabitReminder(habitId: Int, name: String, hour: Int, minute: Int) {
        let content = UNMutableNotificationContent()
        content.title = "Привычка"
        content.body = name
        content.sound = .default

        var components = DateComponents()
        components.hour = hour
        components.minute = minute

        let trigger = UNCalendarNotificationTrigger(dateMatching: components, repeats: true)
        let request = UNNotificationRequest(identifier: "habit_\(habitId)", content: content, trigger: trigger)

        UNUserNotificationCenter.current().add(request)
    }

    // MARK: - Cancel

    func cancelReminder(_ identifier: String) {
        UNUserNotificationCenter.current().removePendingNotificationRequests(withIdentifiers: [identifier])
    }

    func cancelAllReminders() {
        UNUserNotificationCenter.current().removeAllPendingNotificationRequests()
    }

    // MARK: - Payment Reminders

    func schedulePaymentReminders(payments: [MonthlyPaymentDetail]) {
        cancelPaymentReminders()

        let cal = Calendar.current
        let now = Date()

        for payment in payments {
            let day = payment.day
            guard day >= 1, day <= 28 else { continue }

            // Build due date for this month
            var components = cal.dateComponents([.year, .month], from: now)
            components.day = day
            components.hour = 11
            components.minute = 0
            guard let dueDate = cal.date(from: components) else { continue }

            let offsets = [(-5, "через 5 дней"), (-1, "завтра"), (0, "сегодня")]

            for (offset, label) in offsets {
                guard let notifDate = cal.date(byAdding: .day, value: offset, to: dueDate),
                      notifDate > now else { continue }

                let content = UNMutableNotificationContent()
                content.title = "Платёж \(label)"
                content.body = "\(payment.categoryName): \(Int(payment.amount)) ₽ — \(day) числа"
                content.sound = .default

                let trigger = UNCalendarNotificationTrigger(
                    dateMatching: cal.dateComponents([.year, .month, .day, .hour, .minute], from: notifDate),
                    repeats: false
                )
                let id = "payment_\(payment.categoryId)_\(offset)"
                UNUserNotificationCenter.current().add(UNNotificationRequest(identifier: id, content: content, trigger: trigger))
            }
        }
    }

    func cancelPaymentReminders() {
        let center = UNUserNotificationCenter.current()
        center.getPendingNotificationRequests { requests in
            let ids = requests.filter { $0.identifier.hasPrefix("payment_") }.map(\.identifier)
            center.removePendingNotificationRequests(withIdentifiers: ids)
        }
    }

    // MARK: - Update from settings

    func updateSchedule(morning: Bool, morningTime: String, evening: Bool, eveningTime: String) {
        cancelReminder("morning_reminder")
        cancelReminder("evening_reminder")

        if morning {
            let parts = morningTime.split(separator: ":").compactMap { Int($0) }
            if parts.count == 2 { scheduleMorningReminder(hour: parts[0], minute: parts[1]) }
        }
        if evening {
            let parts = eveningTime.split(separator: ":").compactMap { Int($0) }
            if parts.count == 2 { scheduleEveningReminder(hour: parts[0], minute: parts[1]) }
        }
    }
}