Merge pull request #1144 from kiwix/1107-liveactivities-backgroundprocess

Handle background downloads to update live activities

App/App_iOS.swift

@@ -17,6 +17,8 @@
 import SwiftUI
 import Combine
 import UserNotifications
+import BackgroundTasks
+import os
 
 @main
 struct Kiwix: App {
@@ -33,7 +35,7 @@ struct Kiwix: App {
         // MARK: - live activities
         switch AppType.current {
         case .kiwix:
-            activityService = ActivityService()
+            activityService = ActivityService.shared()
         case .custom:
             activityService = nil
         }
@@ -114,12 +116,69 @@ struct Kiwix: App {
     }
 
     private class AppDelegate: NSObject, UIApplicationDelegate, UNUserNotificationCenterDelegate {
+        
         /// Storing background download completion handler sent to application delegate
         func application(_ application: UIApplication,
                          handleEventsForBackgroundURLSession identifier: String,
                          completionHandler: @escaping () -> Void) {
             DownloadService.shared.backgroundCompletionHandler = completionHandler
         }
+        
+        func application(
+            _ application: UIApplication,
+            didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]? = nil
+        ) -> Bool {
+            registerBackgroundTask()
+            return true
+        }
+        
+        // Background download task
+        func applicationDidFinishLaunching(_ application: UIApplication) {
+            registerBackgroundTask()
+        }
+        func applicationDidEnterBackground(_ application: UIApplication) {
+            registerBackgroundTask()
+        }
+            
+        private func registerBackgroundTask() {
+            guard case .kiwix = AppType.current else { return }
+            let isRegistered = BGTaskScheduler.shared.register(
+                forTaskWithIdentifier: BackgroundDownloads.identifier,
+                using: .main) { [self] _ in
+                    // update the live activities, if any
+                    ActivityService.shared().start()
+                    // reschedule
+                    reScheduleBackgroundDownloadTask()
+                }
+            if isRegistered {
+                os_log("BackgroundDownloads registered", log: Log.DownloadService, type: .debug)
+            } else {
+                os_log("BackgroundDownloads registering failed: %s", log: Log.DownloadService, type: .error)
+            }
+        }
+        
+        private func reScheduleBackgroundDownloadTask() {
+                do {
+                    let date = BackgroundDownloads.nextDate()
+                    let request = BGAppRefreshTaskRequest(identifier: BackgroundDownloads.identifier)
+                    request.earliestBeginDate = date
+                    os_log(
+                        "BackgroundDownloads task re-scheduled for: %s",
+                        log: Log.DownloadService,
+                        type: .debug,
+                        date.formatted()
+                    )
+
+                    try BGTaskScheduler.shared.submit(request)
+                } catch {
+                    os_log(
+                        "BackgroundDownloads re-schedule failed: %s",
+                        log: Log.DownloadService,
+                        type: .error,
+                        error.localizedDescription
+                    )
+                }
+            }
 
         /// Handling file download complete notification
         func userNotificationCenter(_ center: UNUserNotificationCenter,

Model/Downloads/BackgroundDownloads.swift

@@ -0,0 +1,28 @@
+// This file is part of Kiwix for iOS & macOS.
+//
+// Kiwix is free software; you can redistribute it and/or modify it
+// under the terms of the GNU General Public License as published by
+// the Free Software Foundation; either version 3 of the License, or
+// any later version.
+//
+// Kiwix is distributed in the hope that it will be useful, but
+// WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+// General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with Kiwix; If not, see https://www.gnu.org/licenses/.
+
+#if os(iOS)
+import Foundation
+import BackgroundTasks
+
+enum BackgroundDownloads {
+    static let identifier = "org.kiwix.downloads_to_liveactivity"
+    
+    static func nextDate() -> Date {
+        .now + 2 // after 2 seconds
+    }
+}
+
+#endif

Support/Info.plist

@@ -6,7 +6,7 @@
 	<string>id997079563</string>
 	<key>BGTaskSchedulerPermittedIdentifiers</key>
 	<array>
-		<string>org.kiwix.library_refresh</string>
+		<string>org.kiwix.downloads_to_liveactivity</string>
 	</array>
 	<key>CFBundleDocumentTypes</key>
 	<array>

Views/LiveActivity/ActivityService.swift

@@ -22,6 +22,7 @@ import QuartzCore
 @MainActor
 final class ActivityService {
     
+    private static var instance: ActivityService?
     private var cancellables = Set<AnyCancellable>()
     private var activity: Activity<DownloadActivityAttributes>?
     private var lastUpdate = CACurrentMediaTime()
@@ -31,12 +32,30 @@ final class ActivityService {
     private var isStarted: Bool = false
     private var downloadTimes: [UUID: DownloadTime] = [:]
     
-    init(
+    public static func shared(
         publisher: @MainActor @escaping () -> CurrentValueSubject<[UUID: DownloadState], Never> = {
             DownloadService.shared.progress.publisher
         },
         updateFrequency: Double = 2,
         averageDownloadSpeedFromLastSeconds: Double = 30
+    ) -> ActivityService {
+        if let instance = Self.instance {
+            return instance
+        } else {
+            let instance = ActivityService(
+                publisher: publisher,
+                updateFrequency: updateFrequency,
+                averageDownloadSpeedFromLastSeconds: averageDownloadSpeedFromLastSeconds
+            )
+            Self.instance = instance
+            return instance
+        }
+    }
+    
+    private init(
+        publisher: @MainActor @escaping () -> CurrentValueSubject<[UUID: DownloadState], Never>,
+        updateFrequency: Double,
+        averageDownloadSpeedFromLastSeconds: Double
     ) {
         assert(updateFrequency > 0)
         assert(averageDownloadSpeedFromLastSeconds > 0)