Group notifications from background polling

Session/Notifications/AppNotifications.swift

@@ -37,6 +37,7 @@ struct AppNotificationUserInfoKey {
     static let threadId = "Signal.AppNotificationsUserInfoKey.threadId"
     static let callBackNumber = "Signal.AppNotificationsUserInfoKey.callBackNumber"
     static let localCallId = "Signal.AppNotificationsUserInfoKey.localCallId"
+    static let threadNotificationCounter = "Session.AppNotificationsUserInfoKey.threadNotificationCounter"
 }
 
 extension AppNotificationCategory {
@@ -80,9 +81,9 @@ extension AppNotificationAction {
     }
 }
 
-// Delay notification of incoming messages when it's likely to be read by a linked device to
-// avoid notifying a user on their phone while a conversation is actively happening on desktop.
-let kNotificationDelayForRemoteRead: TimeInterval = 5
+// Delay notification of incoming messages when it's a background polling to
+// avoid too many notifications fired at the same time
+let kNotificationDelayForBackgroumdPoll: TimeInterval = 5
 
 let kAudioNotificationsThrottleCount = 2
 let kAudioNotificationsThrottleInterval: TimeInterval = 5
@@ -201,6 +202,8 @@ public class NotificationPresenter: NSObject, NotificationsProtocol {
                 owsFailDebug("unexpected thread: \(thread)")
                 return
             }
+        default:
+            notificationTitle = "Session"
         }
 
         var notificationBody: String?
@@ -209,6 +212,8 @@ public class NotificationPresenter: NSObject, NotificationsProtocol {
             notificationBody = NotificationStrings.incomingMessageBody
         case .namePreview:
             notificationBody = messageText
+        default:
+            notificationBody = NotificationStrings.incomingMessageBody
         }
 
         guard let threadId = thread.uniqueId else {
@@ -220,7 +225,7 @@ public class NotificationPresenter: NSObject, NotificationsProtocol {
 
         // Don't reply from lockscreen if anyone in this conversation is
         // "no longer verified".
-        var category = AppNotificationCategory.incomingMessage
+        let category = AppNotificationCategory.incomingMessage
 
         let userInfo = [
             AppNotificationUserInfoKey.threadId: threadId

Session/Notifications/UserNotificationsAdaptee.swift

@@ -96,17 +96,18 @@ extension UserNotificationPresenterAdaptee: NotificationPresenterAdaptee {
         let content = UNMutableNotificationContent()
         content.categoryIdentifier = category.identifier
         content.userInfo = userInfo
+        let isReplacingNotification = replacingIdentifier != nil
+        var isBackgroudPoll = false
+        if let threadIdentifier = userInfo[AppNotificationUserInfoKey.threadId] as? String {
+            content.threadIdentifier = threadIdentifier
+            isBackgroudPoll = replacingIdentifier == threadIdentifier
+        }
         let isAppActive = UIApplication.shared.applicationState == .active
         if let sound = sound, sound != OWSSound.none {
             content.sound = sound.notificationSound(isQuiet: isAppActive)
         }
-
-        var notificationIdentifier: String = UUID().uuidString
-        if let replacingIdentifier = replacingIdentifier {
-            notificationIdentifier = replacingIdentifier
-            Logger.debug("replacing notification with identifier: \(notificationIdentifier)")
-            cancelNotification(identifier: notificationIdentifier)
-        }
+        
+        let notificationIdentifier = isReplacingNotification ? replacingIdentifier! : UUID().uuidString
 
         if shouldPresentNotification(category: category, userInfo: userInfo) {
             if let displayableTitle = title?.filterForDisplay {
@@ -119,10 +120,26 @@ extension UserNotificationPresenterAdaptee: NotificationPresenterAdaptee {
             // Play sound and vibrate, but without a `body` no banner will show.
             Logger.debug("supressing notification body")
         }
+        
+        let trigger: UNNotificationTrigger?
+        if isBackgroudPoll {
+            trigger = UNTimeIntervalNotificationTrigger(timeInterval: kNotificationDelayForBackgroumdPoll, repeats: false)
+            let numberOfNotifications: Int
+            if let lastRequest = notifications[notificationIdentifier], let counter = lastRequest.content.userInfo[AppNotificationUserInfoKey.threadNotificationCounter] as? Int  {
+                numberOfNotifications = counter + 1
+            } else {
+                numberOfNotifications = 1
+            }
+            content.userInfo[AppNotificationUserInfoKey.threadNotificationCounter] = numberOfNotifications
+            content.body = "\(numberOfNotifications) new messages."
+        } else {
+            trigger = nil
+        }
 
-        let request = UNNotificationRequest(identifier: notificationIdentifier, content: content, trigger: nil)
+        let request = UNNotificationRequest(identifier: notificationIdentifier, content: content, trigger: trigger)
 
         Logger.debug("presenting notification with identifier: \(notificationIdentifier)")
+        if isReplacingNotification { cancelNotification(identifier: notificationIdentifier) }
         notificationCenter.add(request)
         notifications[notificationIdentifier] = request
     }

SessionMessagingKit/Sending & Receiving/MessageReceiver+Handling.swift

@@ -342,7 +342,9 @@ extension MessageReceiver {
         // Notify the user if needed
         guard (isMainAppAndActive || isBackgroundPoll), let tsIncomingMessage = TSMessage.fetch(uniqueId: tsMessageID, transaction: transaction) as? TSIncomingMessage,
             let thread = TSThread.fetch(uniqueId: threadID, transaction: transaction) else { return tsMessageID }
-        tsIncomingMessage.setNotificationIdentifier(UUID().uuidString, transaction: transaction)
+        // Use the same identifier for notifications when in backgroud polling to prevent spam
+        let notificationIdentifier = isBackgroundPoll ? thread.uniqueId : UUID().uuidString
+        tsIncomingMessage.setNotificationIdentifier(notificationIdentifier, transaction: transaction)
         DispatchQueue.main.async {
             Storage.read { transaction in
                 SSKEnvironment.shared.notificationsManager!.notifyUser(for: tsIncomingMessage, in: thread, transaction: transaction)