Uses UTIs to determine whether apps are installed or not

AltStore now inserts an app-specific UTI when resigning apps, and it periodically checks whether that app has been deleted by checking whether UTTypeCopyDeclaration returns nil for the same app-specific UTI.

AltKit/Bundle+AltStore.swift

@@ -18,6 +18,7 @@ public extension Bundle
         public static let appGroups = "ALTAppGroups"
         
         public static let urlTypes = "CFBundleURLTypes"
+        public static let exportedUTIs = "UTExportedTypeDeclarations"
     }
 }
 

AltStore/Managing Apps/AppManager.swift

@@ -9,6 +9,7 @@
 import Foundation
 import UIKit
 import UserNotifications
+import MobileCoreServices
 
 import AltSign
 import AltKit
@@ -55,16 +56,19 @@ extension AppManager
         do
         {
             let installedApps = try context.fetch(fetchRequest)
-            for app in installedApps where app.storeApp != nil
+            for app in installedApps
             {
+                let uti = UTTypeCopyDeclaration(app.installedAppUTI as CFString)?.takeRetainedValue() as NSDictionary?
+                
                 if app.bundleIdentifier == StoreApp.altstoreAppID
                 {
                     self.scheduleExpirationWarningLocalNotification(for: app)
                 }
                 else
                 {
-                    if !UIApplication.shared.canOpenURL(app.openAppURL)
+                    if uti == nil
                     {
+                        // This UTI is not declared by any apps, which means this app has been deleted by the user.
                         context.delete(app)
                     }
                 }

AltStore/Model/InstalledApp.swift

@@ -187,6 +187,12 @@ extension InstalledApp
         return directoryURL
     }
     
+    class func installedAppUTI(forBundleIdentifier bundleIdentifier: String) -> String
+    {
+        let installedAppUTI = "io.altstore.Installed." + bundleIdentifier
+        return installedAppUTI
+    }
+    
     var directoryURL: URL {
         return InstalledApp.directoryURL(for: self)
     }
@@ -198,4 +204,8 @@ extension InstalledApp
     var refreshedIPAURL: URL {
         return InstalledApp.refreshedIPAURL(for: self)
     }
+    
+    var installedAppUTI: String {
+        return InstalledApp.installedAppUTI(forBundleIdentifier: self.resignedBundleIdentifier)
+    }
 }

AltStore/Operations/ResignAppOperation.swift

@@ -372,6 +372,17 @@ private extension ResignAppOperation
                 infoDictionary[Bundle.Info.appGroups] = appGroups
             }
             
+            // Add app-specific exported UTI so we can check later if this app (extension) is installed or not.
+            let installedAppUTI = ["UTTypeConformsTo": [],
+                                   "UTTypeDescription": "AltStore Installed App",
+                                   "UTTypeIconFiles": [],
+                                   "UTTypeIdentifier": InstalledApp.installedAppUTI(forBundleIdentifier: profile.bundleIdentifier),
+                                   "UTTypeTagSpecification": [:]] as [String : Any]
+            
+            var exportedUTIs = infoDictionary[Bundle.Info.exportedUTIs] as? [[String: Any]] ?? []
+            exportedUTIs.append(installedAppUTI)
+            infoDictionary[Bundle.Info.exportedUTIs] = exportedUTIs
+            
             try (infoDictionary as NSDictionary).write(to: bundle.infoPlistURL)
         }