NotificationScheduler.swift

//
//  NotificationScheduler.swift
//  LocationNotifier
//

import UIKit
import UserNotifications


protocol NotificationSchedulerDelegate: UNUserNotificationCenterDelegate {
    
    /// Called when the user has denied the notification permission prompt.
    func notificationPermissionDenied()
    /// Called when the notification request completed.
    ///
    /// - Parameter error: Optional error when trying to add the notification.
    func notificationScheduled(error: Error?)
}

struct NotificationInfo {
    
    // Identifiers
    let notificationId: String
    // Notification
    let title: String
    let body: String
    let data: [String: Any]?
}

class NotificationScheduler: NSObject, UNUserNotificationCenterDelegate {
    
    // MARK: - Public Properties
    
    weak var delegate: NotificationSchedulerDelegate? {
        didSet {
            UNUserNotificationCenter.current().delegate = self
        }
    }
    
    // MARK: - Private Properties
    
    
    // MARK: - Public Functions
    
    /// Request a geo location notification with optional data.
    ///
    /// - Parameter data: Data that will be sent with the notification.
    func requestNotification(with notificationInfo: NotificationInfo) {
        askForNotificationPermissions(notificationInfo: notificationInfo)
    }
    
    func userNotificationCenter(_ center: UNUserNotificationCenter,
                                willPresent notification: UNNotification,
                                withCompletionHandler completionHandler: @escaping (UNNotificationPresentationOptions) -> Void) {
        
        if (UIApplication.shared.applicationState == .inactive || UIApplication.shared.applicationState == .background) {
              if #available(iOS 14.0, *) {
                completionHandler([[.banner, .sound]])
              } else {
                completionHandler([.alert, .sound])
              }
            } else {
              if #available(iOS 14.0, *) {
                completionHandler([[.banner]])
              } else {
                completionHandler([.alert])
              }
            }
        
//        completionHandler([.alert, .sound, .badge])
    }
    
    func userNotificationCenter(_ center: UNUserNotificationCenter,
                                didReceive response: UNNotificationResponse,
                                withCompletionHandler completionHandler: @escaping () -> Void) {
        print(response.notification.request.content.userInfo)
        completionHandler()
    }
    
}

// MARK: - Private Functions

private extension NotificationScheduler {
    
    func askForNotificationPermissions(notificationInfo: NotificationInfo) {
        UNUserNotificationCenter.current().requestAuthorization(
            options: [.alert, .sound, .badge],
            completionHandler: { [weak self] granted, _ in
                guard granted else {
                    DispatchQueue.main.async {
                        self?.delegate?.notificationPermissionDenied()
                    }
                    return
                }
                self?.requestNotification(notificationInfo: notificationInfo)
        })
    }
    
    func requestNotification(notificationInfo: NotificationInfo) {
        let notification = notificationContent(notificationInfo: notificationInfo)
        let trigger = UNTimeIntervalNotificationTrigger.init(timeInterval: 5, repeats: false)
        let request = UNNotificationRequest(identifier: notificationInfo.notificationId,
                                            content: notification,
                                            trigger: trigger)
        
        UNUserNotificationCenter.current().add(request) { [weak self] (error) in
            DispatchQueue.main.async {
                self?.delegate?.notificationScheduled(error: error)
            }
        }
    }
    
    func notificationContent(notificationInfo: NotificationInfo) -> UNMutableNotificationContent {
        let notification = UNMutableNotificationContent()
        notification.title = notificationInfo.title
        notification.body = notificationInfo.body
        notification.sound = UNNotificationSound.default
        
        if let data = notificationInfo.data {
            notification.userInfo = data
        }
        return notification
    }
    
}

ViewController.swift

//
//  ViewController.swift
//  LocationNotifier
//

import UIKit
import UserNotifications

class ViewController: UIViewController {
    
    private let locationNotificationScheduler = NotificationScheduler()

    override func viewDidLoad() {
        super.viewDidLoad()
        locationNotificationScheduler.delegate = self
    }
    
    /// Center button to schedule a notification.
    ///
    /// - Parameter sender: Button sender.
    @IBAction func scheduleLocationNotification(_ sender: Any) {
        let notificationInfo = NotificationInfo(notificationId: "notification_id",
                                                                title: "Alert!",
                                                                body: "This is test notification.",
                                                                data: ["userInfo": "extra info"])
        
        locationNotificationScheduler.requestNotification(with: notificationInfo)
    }
}

extension ViewController: NotificationSchedulerDelegate {
    
    func notificationPermissionDenied() {
        let message = "The notification permission was not authorized. Please enable it in Settings to continue."
        presentSettingsAlert(message: message)
    }
    
    func notificationScheduled(error: Error?) {

    }
    
    private func presentSettingsAlert(message: String) {
        let alertController = UIAlertController(title: "Permissions Denied!",
                                                message: message,
                                                preferredStyle: .alert)
        
        let cancelAction = UIAlertAction(title: "Cancel", style: .cancel, handler: nil)
        let settingsAction = UIAlertAction(title: "Settings", style: .default) { (alertAction) in
            if let appSettings = URL(string: UIApplication.openSettingsURLString) {
                UIApplication.shared.open(appSettings)
            }
        }
        
        alertController.addAction(cancelAction)
        alertController.addAction(settingsAction)
        
        present(alertController, animated: true)
    }
}