fix: local sync task never runs on iOS (#21491)

* fix: local sync task never runs on iOS

* chore: rename ios register method

* refactor from using dart callback to dart entrypoint + more logs

* check if file exists before hashing

* reschedule local sync task

* chore: rename background worker logger

* refactor: move file exists check inside repo

---------

Co-authored-by: shenlong-tanwen <139912620+shalong-tanwen@users.noreply.github.com>

mobile/ios/Runner/AppDelegate.swift

@@ -24,7 +24,7 @@ import UIKit
     BackgroundServicePlugin.register(with: self.registrar(forPlugin: "BackgroundServicePlugin")!)
 
     BackgroundServicePlugin.registerBackgroundProcessing()
-    BackgroundWorkerApiImpl.registerBackgroundProcessing()
+    BackgroundWorkerApiImpl.registerBackgroundWorkers()
 
     BackgroundServicePlugin.setPluginRegistrantCallback { registry in
       if !registry.hasPlugin("org.cocoapods.path-provider-foundation") {

mobile/ios/Runner/Background/BackgroundWorker.g.swift

@@ -74,7 +74,7 @@ class BackgroundWorkerPigeonCodec: FlutterStandardMessageCodec, @unchecked Senda
 /// Generated protocol from Pigeon that represents a handler of messages from Flutter.
 protocol BackgroundWorkerFgHostApi {
   func enableSyncWorker() throws
-  func enableUploadWorker(callbackHandle: Int64) throws
+  func enableUploadWorker() throws
   func disableUploadWorker() throws
 }
 
@@ -99,11 +99,9 @@ class BackgroundWorkerFgHostApiSetup {
     }
     let enableUploadWorkerChannel = FlutterBasicMessageChannel(name: "dev.flutter.pigeon.immich_mobile.BackgroundWorkerFgHostApi.enableUploadWorker\(channelSuffix)", binaryMessenger: binaryMessenger, codec: codec)
     if let api = api {
-      enableUploadWorkerChannel.setMessageHandler { message, reply in
-        let args = message as! [Any?]
-        let callbackHandleArg = args[0] as! Int64
+      enableUploadWorkerChannel.setMessageHandler { _, reply in
         do {
-          try api.enableUploadWorker(callbackHandle: callbackHandleArg)
+          try api.enableUploadWorker()
           reply(wrapResult(nil))
         } catch {
           reply(wrapError(error))
@@ -130,6 +128,7 @@ class BackgroundWorkerFgHostApiSetup {
 /// Generated protocol from Pigeon that represents a handler of messages from Flutter.
 protocol BackgroundWorkerBgHostApi {
   func onInitialized() throws
+  func close() throws
 }
 
 /// Generated setup class from Pigeon to handle messages through the `binaryMessenger`.
@@ -151,6 +150,19 @@ class BackgroundWorkerBgHostApiSetup {
     } else {
       onInitializedChannel.setMessageHandler(nil)
     }
+    let closeChannel = FlutterBasicMessageChannel(name: "dev.flutter.pigeon.immich_mobile.BackgroundWorkerBgHostApi.close\(channelSuffix)", binaryMessenger: binaryMessenger, codec: codec)
+    if let api = api {
+      closeChannel.setMessageHandler { _, reply in
+        do {
+          try api.close()
+          reply(wrapResult(nil))
+        } catch {
+          reply(wrapError(error))
+        }
+      }
+    } else {
+      closeChannel.setMessageHandler(nil)
+    }
   }
 }
 /// Generated protocol from Pigeon that represents Flutter messages that can be called from Swift.

mobile/ios/Runner/Background/BackgroundWorker.swift

@@ -86,28 +86,10 @@ class BackgroundWorker: BackgroundWorkerBgHostApi {
    * starts the engine, and sets up a timeout timer if specified.
    */
   func run() {
-    // Retrieve the callback handle stored by the main Flutter app
-    // This handle points to the Flutter function that should be executed in the background
-    let callbackHandle = Int64(UserDefaults.standard.string(
-      forKey: BackgroundWorkerApiImpl.backgroundUploadCallbackHandleKey) ?? "0") ?? 0
-
-    if callbackHandle == 0 {
-      // Without a valid callback handle, we cannot start the Flutter background execution
-      complete(success: false)
-      return
-    }
-    
-    // Use the callback handle to retrieve the actual Flutter callback information
-    guard let callback = FlutterCallbackCache.lookupCallbackInformation(callbackHandle) else {
-      // The callback handle is invalid or the callback was not found
-      complete(success: false)
-      return
-    }
-           
     // Start the Flutter engine with the specified callback as the entry point
     let isRunning = engine.run(
-      withEntrypoint: callback.callbackName,
-      libraryURI: callback.callbackLibraryPath
+      withEntrypoint: "backgroundSyncNativeEntrypoint",
+      libraryURI: "package:immich_mobile/domain/services/background_worker.service.dart"
     )
     
     // Verify that the Flutter engine started successfully
@@ -127,7 +109,7 @@ class BackgroundWorker: BackgroundWorkerBgHostApi {
     if maxSeconds != nil {
         // Schedule a timer to cancel the task after the specified timeout period
         Timer.scheduledTimer(withTimeInterval: TimeInterval(maxSeconds!), repeats: false) { _ in
-          self.cancel()
+          self.close()
         }
     }
   }
@@ -156,7 +138,7 @@ class BackgroundWorker: BackgroundWorkerBgHostApi {
    * Sends a cancel signal to the Flutter side and sets up a fallback timer to ensure
    * the completion handler is eventually called even if Flutter doesn't respond.
    */
-  func cancel() {
+  func close() {
     if isComplete {
       return
     }
@@ -182,7 +164,7 @@ class BackgroundWorker: BackgroundWorkerBgHostApi {
   private func handleHostResult(result: Result<Void, PigeonError>) {
     switch result {
       case .success(): self.complete(success: true)
-      case .failure(_): self.cancel()
+      case .failure(_): self.close()
     }
   }
 

mobile/ios/Runner/Background/BackgroundWorkerApiImpl.swift

@@ -6,10 +6,8 @@ class BackgroundWorkerApiImpl: BackgroundWorkerFgHostApi {
     print("BackgroundUploadImpl:enableSyncWorker Local Sync worker scheduled")
   }
   
-  func enableUploadWorker(callbackHandle: Int64) throws {
+  func enableUploadWorker() throws {
     BackgroundWorkerApiImpl.updateUploadEnabled(true)
-    // Store the callback handle for later use when starting background Flutter isolates
-    BackgroundWorkerApiImpl.updateUploadCallbackHandle(callbackHandle)
     
     BackgroundWorkerApiImpl.scheduleRefreshUpload()
     BackgroundWorkerApiImpl.scheduleProcessingUpload()
@@ -23,7 +21,6 @@ class BackgroundWorkerApiImpl: BackgroundWorkerFgHostApi {
   }
   
   public static let backgroundUploadEnabledKey = "immich:background:backup:enabled"
-  public static let backgroundUploadCallbackHandleKey = "immich:background:backup:callbackHandle"
   
   private static let localSyncTaskID = "app.alextran.immich.background.localSync"
   private static let refreshUploadTaskID = "app.alextran.immich.background.refreshUpload"
@@ -33,17 +30,13 @@ class BackgroundWorkerApiImpl: BackgroundWorkerFgHostApi {
     return UserDefaults.standard.set(isEnabled, forKey: BackgroundWorkerApiImpl.backgroundUploadEnabledKey)
   }
 
-  private static func updateUploadCallbackHandle(_ callbackHandle: Int64) {
-    return UserDefaults.standard.set(String(callbackHandle), forKey: BackgroundWorkerApiImpl.backgroundUploadCallbackHandleKey)
-  }
-
   private static func cancelUploadTasks() {
     BackgroundWorkerApiImpl.updateUploadEnabled(false)
     BGTaskScheduler.shared.cancel(taskRequestWithIdentifier: refreshUploadTaskID);
     BGTaskScheduler.shared.cancel(taskRequestWithIdentifier: processingUploadTaskID);
   }
 
-  public static func registerBackgroundProcessing() {
+  public static func registerBackgroundWorkers() {
       BGTaskScheduler.shared.register(
           forTaskWithIdentifier: processingUploadTaskID, using: nil) { task in
           if task is BGProcessingTask {
@@ -102,9 +95,22 @@ class BackgroundWorkerApiImpl: BackgroundWorkerFgHostApi {
   }
   
   private static func handleBackgroundRefresh(task: BGAppRefreshTask, taskType: BackgroundTaskType) {
-    scheduleRefreshUpload()
-    // Restrict the refresh task to run only for a maximum of 20 seconds
-    runBackgroundWorker(task: task, taskType: taskType, maxSeconds: 20)
+    let maxSeconds: Int?
+    
+    switch taskType {
+    case .localSync:
+      maxSeconds = 15
+      scheduleLocalSync()
+    case .refreshUpload:
+      maxSeconds = 20
+      scheduleRefreshUpload()
+    case .processingUpload:
+      print("Unexpected background refresh task encountered")
+      return;
+    }
+
+    // Restrict the refresh task to run only for a maximum of (maxSeconds) seconds
+    runBackgroundWorker(task: task, taskType: taskType, maxSeconds: maxSeconds)
   }
   
   private static func handleBackgroundProcessing(task: BGProcessingTask) {
@@ -134,7 +140,7 @@ class BackgroundWorkerApiImpl: BackgroundWorkerFgHostApi {
 
     task.expirationHandler = {
       DispatchQueue.main.async {
-        backgroundWorker.cancel()
+        backgroundWorker.close()
       }
       isSuccess = false