- ReleaseTracks: Added in-app ReleaseTracks switching support

AltStoreCore/Model/ReleaseTrack.swift

@@ -0,0 +1,114 @@
+//
+//  AppreleaseTrack.swift
+//  AltStore
+//
+//  Created by Magesh K on 19/01/25.
+//  Copyright © 2025 SideStore. All rights reserved.
+//
+
+import CoreData
+
+// created for 0.6.0
+@objc(ReleaseTrack)
+public class ReleaseTrack: BaseEntity, Decodable
+{
+    // attributes
+    @NSManaged @objc(track) private var _track: String?
+    
+    // RelationShips
+    @NSManaged @objc(releases) private var _releases: NSOrderedSet?
+    @NSManaged public private(set) var storeApp: StoreApp?
+    
+    private enum CodingKeys: String, CodingKey, CaseIterable {
+        case track
+        case releases
+    }
+    
+    public var track: String? {
+        return _track?.isEmpty == false ? _track : nil
+    }
+    
+    public var releases:[AppVersion]? {
+        return _releases?.array as? [AppVersion]
+    }
+        
+    // Required initializer for Core Data (context saves)
+    private override init(entity: NSEntityDescription, insertInto context: NSManagedObjectContext?) {
+        super.init(entity: entity, insertInto: context)
+    }
+
+    public required init(from decoder: Decoder) throws{
+        guard let context = decoder.managedObjectContext else {
+            preconditionFailure("Decoder must have non-nil NSManagedObjectContext.")
+        }
+        
+        // Must initialize with context in order for child context saves to work correctly.
+        super.init(entity: ReleaseTrack.entity(), insertInto: context)
+        
+        do
+        {
+            let container = try decoder.container(keyedBy: CodingKeys.self)
+            
+            self._track = try container.decode(String.self, forKey: .track)
+            
+            let releases = try container.decode([AppVersion].self, forKey: .releases)
+            guard releases.count > 0 else
+            {
+                throw DecodingError.dataCorruptedError(forKey: .releases, in: container, debugDescription: "At least one version is required in key: releases")
+            }
+            self._releases = NSOrderedSet(array: releases)
+        }
+        catch
+        {
+            if let context = self.managedObjectContext
+            {
+                context.delete(self)
+            }
+            throw error
+        }
+    }
+}
+
+public extension ReleaseTrack{
+    
+    /// Warning:
+    /// - Special handling required for deleted objects:
+    ///   - CoreData sets all properties to nil during deletion
+    ///   - This triggers KVO and could cause "mutating removed object" errors
+    ///   - We guard against this by checking deletion state before updates
+    ///
+    internal func updateVersions(for storeApp: StoreApp?) {
+        guard let storeApp = storeApp else { return }
+        
+            releases?.forEach { version in
+                // never mutate objects that are being deleted or is already deleted
+                guard let context = version.managedObjectContext,
+                      !version.isDeleted, !context.deletedObjects.contains(version) else
+                {
+                    return
+                }
+                
+                // update it into the appVersion
+                _ = version.mutateForData(channel: track, appBundleID: storeApp.bundleIdentifier)
+            }
+    }
+    
+    /// Defer updates to fields that require storeApp inverse relationship to be set, which is not available in init(),
+    /// by observing changes to the prop and update the data later
+    ///
+    /// NOTE: We use KVO here only coz, ReleaseTrack already has an inverse relationship to StoreAppV2
+    ///       So coredata will actually set the storeApp but only issue is that it happens after init() is complete
+    ///       hence we are using KVO so that one doesn't need to manually set the value via a setter method
+    ///
+    /// However this caused an issue when an object is marked deleted during merge policy conflict resolution, all its props are set to nil by coredata.
+    /// this causes this KVO observer to be triggered and mutating the deleted entity causing a "coredata error: Mutating removed object"
+    /// which is now handled by checking if context.deletedObjects doesn't contain it and version.isDeleted is not true yet
+    /// 
+    override func didChangeValue(forKey key: String) {
+        super.didChangeValue(forKey: key)
+        if key == NSExpression(forKeyPath: #keyPath(ReleaseTrack.storeApp)).keyPath
+        {
+            updateVersions(for: storeApp)
+        }
+    }
+}