import Foundation
import UserNotifications
import UIKit

class NotificationService: ObservableObject {
    static let shared = NotificationService()

    @Published var isAuthorized = false
    @Published var pendingCount = 0

    private let center = UNUserNotificationCenter.current()

    private init() {
        checkAuthorizationStatus()
    }

    // MARK: - Authorization

    func checkAuthorizationStatus() {
        center.getNotificationSettings { [weak self] settings in
            DispatchQueue.main.async {
                self?.isAuthorized = settings.authorizationStatus == .authorized
            }
        }
    }

    func requestAuthorization() async -> Bool {
        do {
            let granted = try await center.requestAuthorization(options: [.alert, .badge, .sound])
            await MainActor.run {
                self.isAuthorized = granted
            }
            return granted
        } catch {
            print("Notification authorization error: \(error)")
            return false
        }
    }

    // MARK: - Schedule Notifications

    func scheduleReminder(for source: InvestmentSource) {
        guard let nextDate = source.nextReminderDate else { return }
        guard source.frequency != .never else { return }

        // Remove existing notification for this source
        cancelReminder(for: source)

        // Get notification time from settings
        let settings = AppSettings.getOrCreate(in: CoreDataStack.shared.viewContext)
        let notificationTime = settings.defaultNotificationTime ?? defaultNotificationTime()

        // Combine date and time
        let calendar = Calendar.current
        var components = calendar.dateComponents([.year, .month, .day], from: nextDate)
        let timeComponents = calendar.dateComponents([.hour, .minute], from: notificationTime)
        components.hour = timeComponents.hour
        components.minute = timeComponents.minute

        guard let triggerDate = calendar.date(from: components) else { return }

        // Create notification content
        let content = UNMutableNotificationContent()
        content.title = "Investment Update Reminder"
        content.body = "Time to update \(source.name). Tap to add a new snapshot."
        content.sound = .default
        content.badge = NSNumber(value: pendingCount + 1)
        content.userInfo = [
            "sourceId": source.id.uuidString,
            "sourceName": source.name
        ]

        // Create trigger
        let triggerComponents = calendar.dateComponents(
            [.year, .month, .day, .hour, .minute],
            from: triggerDate
        )
        let trigger = UNCalendarNotificationTrigger(dateMatching: triggerComponents, repeats: false)

        // Create request
        let request = UNNotificationRequest(
            identifier: notificationIdentifier(for: source),
            content: content,
            trigger: trigger
        )

        // Schedule
        center.add(request) { error in
            if let error = error {
                print("Failed to schedule notification: \(error)")
            } else {
                print("Scheduled reminder for \(source.name) on \(triggerDate)")
                FirebaseService.shared.logNotificationScheduled(frequency: source.notificationFrequency)
            }
        }
    }

    func scheduleAllReminders(for sources: [InvestmentSource]) {
        for source in sources {
            scheduleReminder(for: source)
        }
    }

    // MARK: - Cancel Notifications

    func cancelReminder(for source: InvestmentSource) {
        center.removePendingNotificationRequests(
            withIdentifiers: [notificationIdentifier(for: source)]
        )
    }

    func cancelAllReminders() {
        center.removeAllPendingNotificationRequests()
    }

    // MARK: - Badge Management

    func updateBadgeCount() {
        let repository = InvestmentSourceRepository()
        let needsUpdate = repository.fetchSourcesNeedingUpdate()
        pendingCount = needsUpdate.count

        DispatchQueue.main.async {
            UIApplication.shared.applicationIconBadgeNumber = self.pendingCount
        }
    }

    func clearBadge() {
        pendingCount = 0
        DispatchQueue.main.async {
            UIApplication.shared.applicationIconBadgeNumber = 0
        }
    }

    // MARK: - Pending Notifications

    func getPendingNotifications() async -> [UNNotificationRequest] {
        await center.pendingNotificationRequests()
    }

    // MARK: - Helpers

    private func notificationIdentifier(for source: InvestmentSource) -> String {
        "investment_reminder_\(source.id.uuidString)"
    }

    private func defaultNotificationTime() -> Date {
        var components = DateComponents()
        components.hour = 9
        components.minute = 0
        return Calendar.current.date(from: components) ?? Date()
    }
}

// MARK: - Deep Link Handler

extension NotificationService {
    func handleNotificationResponse(_ response: UNNotificationResponse) {
        let userInfo = response.notification.request.content.userInfo

        guard let sourceIdString = userInfo["sourceId"] as? String,
              let sourceId = UUID(uuidString: sourceIdString) else {
            return
        }

        // Post notification for deep linking
        NotificationCenter.default.post(
            name: .openSourceDetail,
            object: nil,
            userInfo: ["sourceId": sourceId]
        )
    }
}

// MARK: - Notification Names

extension Notification.Name {
    static let openSourceDetail = Notification.Name("openSourceDetail")
}

// MARK: - Background Refresh

extension NotificationService {
    func performBackgroundRefresh() {
        updateBadgeCount()

        // Reschedule any missed notifications
        let repository = InvestmentSourceRepository()
        let sources = repository.fetchActiveSources()
        scheduleAllReminders(for: sources)
    }
}