[AltStore] Skip running apps when background refreshing

AltStore/AppDelegate.swift

@@ -12,11 +12,37 @@ import UserNotifications
 import AltSign
 import Roxas
 
+private extension CFNotificationName
+{
+    static let requestAppState = CFNotificationName("com.altstore.RequestAppState" as CFString)
+    static let appIsRunning = CFNotificationName("com.altstore.AppState.Running" as CFString)
+    
+    static func requestAppState(for appID: String) -> CFNotificationName
+    {
+        let name = String(CFNotificationName.requestAppState.rawValue) + "." + appID
+        return CFNotificationName(name as CFString)
+    }
+    
+    static func appIsRunning(for appID: String) -> CFNotificationName
+    {
+        let name = String(CFNotificationName.appIsRunning.rawValue) + "." + appID
+        return CFNotificationName(name as CFString)
+    }
+}
+
+private let ReceivedApplicationState: @convention(c) (CFNotificationCenter?, UnsafeMutableRawPointer?, CFNotificationName?, UnsafeRawPointer?, CFDictionary?) -> Void =
+{ (center, observer, name, object, userInfo) in
+    guard let appDelegate = UIApplication.shared.delegate as? AppDelegate, let name = name else { return }
+    appDelegate.receivedApplicationState(notification: name)
+}
+
 @UIApplicationMain
 class AppDelegate: UIResponder, UIApplicationDelegate {
 
     var window: UIWindow?
     
+    private var runningApplications: Set<String>?
+
     func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?) -> Bool
     {
         ServerManager.shared.startDiscovering()
@@ -75,7 +101,23 @@ extension AppDelegate
         let installedApps = InstalledApp.fetchAppsForBackgroundRefresh(in: DatabaseManager.shared.viewContext)
         guard !installedApps.isEmpty else { return completionHandler(.noData) }
         
-        print("Apps to refresh:", installedApps.map { $0.app.identifier })
+        self.runningApplications = []
+        
+        let identifiers = installedApps.compactMap { $0.app?.identifier }
+        print("Apps to refresh:", identifiers)
+        
+        DispatchQueue.global().async {
+            let notificationCenter = CFNotificationCenterGetDarwinNotifyCenter()
+            
+            for identifier in identifiers
+            {
+                let appIsRunningNotification = CFNotificationName.appIsRunning(for: identifier)
+                CFNotificationCenterAddObserver(notificationCenter, nil, ReceivedApplicationState, appIsRunningNotification.rawValue, nil, .deliverImmediately)
+                
+                let requestAppStateNotification = CFNotificationName.requestAppState(for: identifier)
+                CFNotificationCenterPostNotification(notificationCenter, requestAppStateNotification, nil, nil, true)
+            }
+        }
         
         ServerManager.shared.startDiscovering()
         
@@ -91,27 +133,13 @@ extension AppDelegate
             }
         }
         
+        // Sleep for three seconds to:
+        // a) give us time to discover AltServers
+        // b) give other processes a chance to respond to requestAppState notification
+        // NOTE: We need to sleep, *not* DispatchQueue.asyncAfter, or else background audio might fail to start.
+        Thread.sleep(forTimeInterval: 3)
+        
         BackgroundTaskManager.shared.performExtendedBackgroundTask { (taskResult, taskCompletionHandler) in
-            if let error = taskResult.error
-            {
-                print("Error starting extended background task. Aborting.", error)
-                
-                let content = UNMutableNotificationContent()
-                content.title = NSLocalizedString("Failed to refresh apps.", comment: "")
-                content.body = taskResult.error?.localizedDescription ?? ""
-                
-                let trigger = UNTimeIntervalNotificationTrigger(timeInterval: 0.01, repeats: false)
-                
-                let request = UNNotificationRequest(identifier: UUID().uuidString, content: content, trigger: trigger)
-                UNUserNotificationCenter.current().add(request) { (error) in
-                    if let error = error {
-                        print(error)
-                    }
-                }
-            }
-            
-            // Wait a few seconds so we have a chance to discover nearby AltServers.
-            DispatchQueue.main.asyncAfter(deadline: .now() + 3.0) {
             
             func finish(_ result: Result<[String: Result<InstalledApp, Error>], Error>)
             {
@@ -165,7 +193,18 @@ extension AppDelegate
                 taskCompletionHandler()
             }
             
-                let group = AppManager.shared.refresh(installedApps, presentingViewController: nil)
+            if let error = taskResult.error
+            {
+                print("Error starting extended background task. Aborting.", error)
+                finish(.failure(error))
+                return
+            }
+            
+            DispatchQueue.main.async {
+                let filteredApps = installedApps.filter { !(self.runningApplications?.contains($0.app.identifier) ?? false) }
+                print("Filtered Apps to Refresh:", filteredApps.map { $0.app.identifier })
+                
+                let group = AppManager.shared.refresh(filteredApps, presentingViewController: nil)
                 group.beginInstallationHandler = { (installedApp) in
                     guard installedApp.app.identifier == App.altstoreAppID else { return }
                     
@@ -191,4 +230,12 @@ extension AppDelegate
             }
         }
     }
+    
+    func receivedApplicationState(notification: CFNotificationName)
+    {
+        let baseName = String(CFNotificationName.appIsRunning.rawValue)
+        
+        let appID = String(notification.rawValue).replacingOccurrences(of: baseName + ".", with: "")
+        self.runningApplications?.insert(appID)
+    }
 }