import Foundation
import UserNotifications
import Firebase

class MessageManager: NSObject,
UNUserNotificationCenterDelegate, MessagingDelegate {
    
    private static var mInstance: MessageManager?
    var isMessageEnable = true
    
    private override init() {
        //註冊推播，告訴APNs這個App要註冊推播，每次啟動App都應調用，因token會不定期更換
        UIApplication.shared.registerForRemoteNotifications()
    }
    
    // MARK: Public method
    static func sharedInstance() -> MessageManager {
        if mInstance == nil {
            mInstance = MessageManager()
        }
        return mInstance!
    }
    
    //取得User設定的通知權限(denied拒絕、authorized允許、notDetermined沒有決定)
    func getMessengerStatus() {
        UNUserNotificationCenter.current().getNotificationSettings { (settings) in
            self.isMessageEnable = (settings.authorizationStatus != .denied) ? true : false

            if settings.authorizationStatus == .notDetermined {
                DispatchQueue.main.async {
                    self.setupMessenger()
                }
            }
        }
    }
    
    //取得FCMToken，deviceToken是屬於APNs辨識用，在FCM中也有專屬的Token
    func getFcmToken() -> String? {
        return Messaging.messaging().fcmToken
    }
    
    //開啟App推播權限設定畫面
    func openAppSetting() {
        let url = URL(string: UIApplicationOpenSettingsURLString)!
        if UIApplication.shared.canOpenURL(url) {
            UIApplication.shared.open(url, options: [:], completionHandler: nil)
        }
    }
    
    //向使用者請求推播權限，通常在第一次使用App就會詢問
    private func setupMessenger() {
        UNUserNotificationCenter.current().delegate = self
        
        //要求推播中的哪些權限(alert提示內容、badge角標數字、sound音效)
        let authOptions: UNAuthorizationOptions = [.alert, .badge, .sound]
        UNUserNotificationCenter.current().requestAuthorization(
            options: authOptions,
            completionHandler: {_, _ in })
        
        Messaging.messaging().delegate = self //FCM委派
    }
    
    //當App在前景模式下收到推播時的處理，這裡設定成也同樣顯示推播
    func userNotificationCenter(_ center: UNUserNotificationCenter, willPresent notification: UNNotification, withCompletionHandler completionHandler: @escaping (UNNotificationPresentationOptions) -> Void) {
        completionHandler([.badge, .sound, .alert])
    }
    
    //當User點擊推播後的處理，預設為開啟App
    func userNotificationCenter(_ center: UNUserNotificationCenter, didReceive response: UNNotificationResponse, withCompletionHandler completionHandler: @escaping () -> Void) {
        completionHandler()
    }
}

import Foundation
import Firebase

class DatabaseManager: NSObject {
    private static var mInstance: DatabaseManager?
    private var dbRef: DatabaseReference?
    
    override private init() {
        super.init()
        self.dbRef = Database.database().reference()
    }
    
    // MARK: Public method
    static func sharedInstance() -> DatabaseManager {
        if mInstance == nil {
            mInstance = DatabaseManager()
        }
        return mInstance!
    }
    
    func uploadToken(_ token: String) {
        dbRef?.child("token").setValue(token)
    }
}

import Foundation
import UIKit

typealias AlertActionType = (UIAlertAction?) -> ()
extension UIAlertController {
    
    //MARK: Alert
    class func alert(title: String? = "提示", message: String?) -> UIAlertController  {
        let alertController = UIAlertController(title: title, message: message, preferredStyle: .alert)
        return alertController
    }
    
    //MARK: Actions
    func cancelHandle(title: String? = "取消", style: UIAlertActionStyle? = .cancel, alertAction: AlertActionType?) -> UIAlertController {
        
        let alert = UIAlertAction(title: title, style: style!) { (action) in
            if alertAction != nil{
                alertAction!(action)
            }
        }
        self.addAction(alert)
        return self
    }
    
    func otherHandle(title: String? = "確定", style: UIAlertActionStyle? = .default, alertAction: AlertActionType?) -> UIAlertController {
        let alert = UIAlertAction(title: title, style: style!) { (action) in
            if alertAction != nil{
                alertAction!(action)
            }
        }
        self.addAction(alert)
        return self
    }
    
    func show(currentVC: UIViewController)  {
        currentVC.present(self, animated: true, completion: nil)
    }
}

import UIKit
import Firebase //匯入Firebase模組

@UIApplicationMain
class AppDelegate: UIResponder, UIApplicationDelegate {

    var window: UIWindow?

    func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplicationLaunchOptionsKey: Any]?) -> Bool {
        FirebaseApp.configure() //配置Firebase
        MessageManager.sharedInstance().getMessengerStatus() //取得推播權限狀態
        return true
    }

    func applicationWillResignActive(_ application: UIApplication) {
    }

    func applicationDidEnterBackground(_ application: UIApplication) {
    }

    func applicationWillEnterForeground(_ application: UIApplication) {
    }

    func applicationDidBecomeActive(_ application: UIApplication) {
    }

    func applicationWillTerminate(_ application: UIApplication) {
    }
    
    //當推播註冊成功就會調用，並取得deviceToken，一有deviceToken就會產生FCMToken
    func application(_ application: UIApplication, didRegisterForRemoteNotificationsWithDeviceToken deviceToken: Data) {
        let fcmToken = MessageManager.sharedInstance().getFcmToken() //取得FCMToken
        DatabaseManager.sharedInstance().uploadToken(fcmToken!) //上傳到Firebase
    }
}

import UIKit

class ViewController: UIViewController {

    override func viewDidLoad() {
        super.viewDidLoad()

        //確保在主線程中執行
        DispatchQueue.main.async {
            //判斷推播權限設定的狀態，如果是不允許則跳出提醒，按確定後前往設定權限畫面
            if !MessageManager.sharedInstance().isMessageEnable {
                self.showAlert(message: "為了避免遺漏重要訊息\n請點選確定以打開通知功能", completion:
                    {
                        MessageManager.sharedInstance().openAppSetting()
                })
            }
        }
    }

    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
    }
    
    //提醒視窗
    func showAlert(message: String!, completion:@escaping () -> Void) {
        UIAlertController.alert(message: message).otherHandle(alertAction: { (action) in
            completion()
        }).cancelHandle(alertAction: nil ).show(currentVC: self)
    }
}