// ── Notification Scheduling ────────────────────────────────────
// UNUserNotificationCenter wrapper for pre-warning cascade + timer fire
// iOS-native notification system

import Foundation
import UserNotifications

// MARK: - Notification Manager

@MainActor
final class CMNotificationManager: ObservableObject {
    static let shared = CMNotificationManager()

    @Published var isAuthorized = false

    private init() {}

    // MARK: - Permission

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

    func checkPermission() async {
        let settings = await UNUserNotificationCenter.current().notificationSettings()
        isAuthorized = settings.authorizationStatus == .authorized
    }

    // MARK: - Schedule Timer Notifications

    /// Schedule all cascade warnings + final fire notification for a timer
    func scheduleNotifications(for timer: CMTimer) {
        // Remove existing notifications for this timer
        removeNotifications(for: timer.id)

        // Schedule cascade warnings
        for warning in timer.warnings where !warning.fired {
            scheduleWarning(timer: timer, warning: warning)
        }

        // Schedule fire notification
        scheduleFireNotification(timer: timer)
    }

    /// Remove all scheduled notifications for a timer
    func removeNotifications(for timerId: String) {
        let center = UNUserNotificationCenter.current()
        // Remove all notifications with this timer's ID prefix
        center.getPendingNotificationRequests { requests in
            let ids = requests
                .filter { $0.identifier.hasPrefix("cm-\(timerId)") }
                .map { $0.identifier }
            center.removePendingNotificationRequests(withIdentifiers: ids)
        }
    }

    /// Remove all ChronoMind notifications
    func removeAllNotifications() {
        UNUserNotificationCenter.current().removeAllPendingNotificationRequests()
    }

    // MARK: - Private

    private func scheduleWarning(timer: CMTimer, warning: CascadeWarning) {
        let content = UNMutableNotificationContent()
        let timeStr = formatMinutesBefore(warning.minutesBefore)
        content.title = "⏰ \(timer.label) in \(timeStr)"
        content.body = "Pre-warning: \"\(timer.label)\" fires in \(timeStr)"
        content.sound = soundForUrgency(timer.urgency, isWarning: true)
        content.categoryIdentifier = "TIMER_WARNING"
        content.userInfo = [
            "timerId": timer.id,
            "warningId": warning.id,
            "type": "warning",
        ]

        // Use the warning's scheduled time
        let trigger = UNTimeIntervalNotificationTrigger(
            timeInterval: max(1, warning.scheduledTime.timeIntervalSinceNow),
            repeats: false
        )

        let request = UNNotificationRequest(
            identifier: "cm-\(timer.id)-warning-\(warning.id)",
            content: content,
            trigger: trigger
        )

        UNUserNotificationCenter.current().add(request)
    }

    private func scheduleFireNotification(timer: CMTimer) {
        let content = UNMutableNotificationContent()
        content.title = "🔔 \(timer.label) — NOW!"
        content.body = "Timer \"\(timer.label)\" is firing!"
        content.sound = soundForUrgency(timer.urgency, isWarning: false)
        content.categoryIdentifier = "TIMER_FIRE"
        content.userInfo = [
            "timerId": timer.id,
            "type": "fire",
        ]

        // Interrupt level for important/critical
        if #available(iOS 15.0, *) {
            switch timer.urgency {
            case .critical:
                content.interruptionLevel = .critical
            case .important:
                content.interruptionLevel = .timeSensitive
            case .standard:
                content.interruptionLevel = .active
            case .gentle:
                content.interruptionLevel = .passive
            case .passive:
                content.interruptionLevel = .passive
            }
        }

        let trigger = UNTimeIntervalNotificationTrigger(
            timeInterval: max(1, timer.targetTime.timeIntervalSinceNow),
            repeats: false
        )

        let request = UNNotificationRequest(
            identifier: "cm-\(timer.id)-fire",
            content: content,
            trigger: trigger
        )

        UNUserNotificationCenter.current().add(request)
    }

    private func soundForUrgency(_ urgency: UrgencyLevel, isWarning: Bool) -> UNNotificationSound {
        let config = getUrgencyConfig(urgency)
        guard config.soundEnabled else { return .none }

        if urgency == .critical && !isWarning {
            // Critical fires get the default critical alert sound
            if #available(iOS 12.0, *) {
                return .defaultCritical
            }
        }

        return .default
    }

    // MARK: - Notification Categories

    func registerCategories() {
        let snooze5 = UNNotificationAction(
            identifier: "SNOOZE_5",
            title: "Snooze 5m",
            options: []
        )
        let snooze15 = UNNotificationAction(
            identifier: "SNOOZE_15",
            title: "Snooze 15m",
            options: []
        )
        let dismiss = UNNotificationAction(
            identifier: "DISMISS",
            title: "Dismiss",
            options: [.destructive]
        )

        let fireCategory = UNNotificationCategory(
            identifier: "TIMER_FIRE",
            actions: [snooze5, snooze15, dismiss],
            intentIdentifiers: [],
            options: []
        )

        let warningCategory = UNNotificationCategory(
            identifier: "TIMER_WARNING",
            actions: [dismiss],
            intentIdentifiers: [],
            options: []
        )

        UNUserNotificationCenter.current().setNotificationCategories([fireCategory, warningCategory])
    }
}