Feature: NSO-like Rewind Functionality

Delta/Database/Model/Human/SaveState.swift

@@ -19,6 +19,7 @@ import struct DSDeltaCore.DS
     case quick
     case general
     case locked
+    case rewind
 }
 
 @objc(SaveState)
@@ -128,7 +129,7 @@ extension SaveState: Syncable
         // self.game may be nil if being downloaded, so don't enforce it.
         // guard let identifier = self.game?.identifier else { return false }
 
-        let isSyncingEnabled = (self.type != .auto && self.type != .quick) && (self.game?.identifier != Game.melonDSBIOSIdentifier && self.game?.identifier != Game.melonDSDSiBIOSIdentifier)
+        let isSyncingEnabled = (self.type != .auto && self.type != .quick && self.type != .rewind) && (self.game?.identifier != Game.melonDSBIOSIdentifier && self.game?.identifier != Game.melonDSDSiBIOSIdentifier)
         return isSyncingEnabled
     }
 

Delta/Emulation/GameViewController.swift

@@ -112,6 +112,8 @@ class GameViewController: DeltaCore.GameViewController
             self.updateControllers()
 
             self.presentedGyroAlert = false
+
+            self.clearRewindSaveStates()
         }
     }
 
@@ -164,6 +166,8 @@ class GameViewController: DeltaCore.GameViewController
     private var sustainButtonsBackgroundView: RSTPlaceholderView!
     private var inputsToSustain = [AnyInput: Double]()
 
+    private var rewindTimer: Timer?
+
     private var isGyroActive = false
     private var presentedGyroAlert = false
 
@@ -210,6 +214,8 @@ class GameViewController: DeltaCore.GameViewController
     deinit
     {
         self.emulatorCore?.removeObserver(self, forKeyPath: #keyPath(EmulatorCore.state), context: &kvoContext)
+
+        self.invalidateRewindTimer()
     }
 
     // MARK: - GameControllerReceiver -
@@ -330,6 +336,8 @@ extension GameViewController
 
             UserDefaults.standard.desmumeDeprecatedAlertCount += 1
         }
+
+        self.activateRewindTimer()
     }
 
     override func viewWillTransition(to size: CGSize, with coordinator: UIViewControllerTransitionCoordinator)
@@ -338,7 +346,7 @@ extension GameViewController
 
         coordinator.animate(alongsideTransition: { (context) in
             self.updateControllerSkin()
-        }, completion: nil)        
+        }, completion: nil)
     }
 
     // MARK: - Segues
@@ -764,11 +772,45 @@ extension GameViewController: SaveStatesViewControllerDelegate
         }
     }
 
-    private func update(_ saveState: SaveState, with replacementSaveState: SaveStateProtocol? = nil)
+    private func clearRewindSaveStates(afterDate: Date? = nil)
+    {
+        guard let game = self.game as? Game else { return }
+
+        let fetchRequest = SaveState.fetchRequest(for: game, type: .rewind)
+        fetchRequest.includesPropertyValues = false
+
+        // if afterDate is included, we have rewound and should clear any rewind states that exist after our new time location
+        if let afterDate = afterDate
+        {
+            fetchRequest.predicate = NSPredicate(format: "%K == %@ AND %K >= %@", #keyPath(SaveState.type), NSNumber(value: SaveStateType.rewind.rawValue), #keyPath(SaveState.creationDate), afterDate as NSDate)
+        }
+        else
+        {
+            fetchRequest.predicate = NSPredicate(format: "%K == %@", #keyPath(SaveState.type), NSNumber(value: SaveStateType.rewind.rawValue))
+        }
+
+        DatabaseManager.shared.performBackgroundTask { (context) in
+            do
+            {
+                let saveStates = try context.fetch(fetchRequest)
+                for saveState in saveStates {
+                    let temporarySaveState = context.object(with: saveState.objectID)
+                    context.delete(temporarySaveState)
+                }
+                context.saveWithErrorLogging()
+            }
+            catch
+            {
+                print(error)
+            }
+        }
+    }
+
+    private func update(_ saveState: SaveState, with replacementSaveState: SaveStateProtocol? = nil, shouldSuspendEmulation: Bool = true)
     {
         let isRunning = (self.emulatorCore?.state == .running)
 
-        if isRunning
+        if isRunning && shouldSuspendEmulation
         {
             self.pauseEmulation()
         }
@@ -810,7 +852,7 @@ extension GameViewController: SaveStatesViewControllerDelegate
         saveState.modifiedDate = Date()
         saveState.coreIdentifier = self.emulatorCore?.deltaCore.identifier
 
-        if isRunning
+        if isRunning && shouldSuspendEmulation
         {
             self.resumeEmulation()
         }
@@ -867,6 +909,18 @@ extension GameViewController: SaveStatesViewControllerDelegate
             print(error)
         }
 
+        // delay by 0.5 so as not to interfere with other operations
+        DispatchQueue.main.asyncAfter(deadline: .now() + 0.5) {
+            if let rewindSaveState = saveState as? SaveState, rewindSaveState.type == .rewind
+            {
+                self.clearRewindSaveStates(afterDate: rewindSaveState.creationDate)
+            }
+            else
+            {
+                self.clearRewindSaveStates()
+            }
+        }
+
         if isRunning
         {
             self.resumeEmulation()
@@ -1232,3 +1286,77 @@ private extension UserDefaults
 {
     @NSManaged var desmumeDeprecatedAlertCount: Int
 }
+
+//MARK: - Timer -
+private extension GameViewController
+{
+    func activateRewindTimer()
+    {
+        self.invalidateRewindTimer()
+        guard Settings.isRewindEnabled == true else { return }
+        let interval = TimeInterval(Settings.rewindTimerInterval)
+        self.rewindTimer = Timer.scheduledTimer(timeInterval: interval, target: self, selector: #selector(rewindPollFunction), userInfo: nil, repeats: true)
+    }
+
+    func invalidateRewindTimer()
+    {
+        self.rewindTimer?.invalidate()
+    }
+
+    @objc func rewindPollFunction() {
+
+        guard Settings.isRewindEnabled == true,
+              self.emulatorCore?.state == .running,
+              let game = self.game as? Game else { return }
+
+        // first; cap number of rewind states to 30. do this by deleting oldest state if >= 30 exist
+        let fetchRequest: NSFetchRequest<SaveState> = SaveState.fetchRequest()
+        fetchRequest.returnsObjectsAsFaults = false
+        fetchRequest.sortDescriptors = [NSSortDescriptor(key: #keyPath(SaveState.creationDate), ascending: true)]
+
+        if let system = System(gameType: game.type)
+        {
+            fetchRequest.predicate = NSPredicate(format: "%K == %@ AND %K == %@ AND %K == %@", #keyPath(SaveState.game), game, #keyPath(SaveState.coreIdentifier), system.deltaCore.identifier, #keyPath(SaveState.type), NSNumber(value: SaveStateType.rewind.rawValue))
+        }
+        else
+        {
+            fetchRequest.predicate = NSPredicate(format: "%K == %@ AND %K == %@", #keyPath(SaveState.game), game, #keyPath(SaveState.type), NSNumber(value: SaveStateType.rewind.rawValue))
+        }
+
+        do
+        {
+            let rewindStateCount = try DatabaseManager.shared.viewContext.count(for: fetchRequest)
+            if rewindStateCount >= 30
+            {
+                fetchRequest.fetchLimit = 1
+                if let oldestRewindSaveState = try DatabaseManager.shared.viewContext.fetch(fetchRequest).first
+                {
+                    DatabaseManager.shared.performBackgroundTask { (context) in
+                        let temporarySaveState = context.object(with: oldestRewindSaveState.objectID)
+                        context.delete(temporarySaveState)
+                        context.saveWithErrorLogging()
+                    }
+                }
+            }
+        }
+        catch
+        {
+            print(error)
+        }
+
+        // second; save new state
+        let backgroundContext = DatabaseManager.shared.newBackgroundContext()
+        backgroundContext.perform {
+
+            let game = backgroundContext.object(with: game.objectID) as! Game
+
+            let saveState = SaveState(context: backgroundContext)
+            saveState.type = .rewind
+            saveState.game = game
+
+            self.update(saveState, shouldSuspendEmulation: false)
+
+            backgroundContext.saveWithErrorLogging()
+        }
+    }
+}

Delta/Pause Menu/PauseViewController.swift

@@ -19,7 +19,7 @@ class PauseViewController: UIViewController, PauseInfoProviding
     }
 
     var pauseItems: [MenuItem] {
-        return [self.saveStateItem, self.loadStateItem, self.cheatCodesItem, self.fastForwardItem, self.sustainButtonsItem].compactMap { $0 }
+        return [self.saveStateItem, self.loadStateItem, self.cheatCodesItem, self.fastForwardItem, self.sustainButtonsItem, self.rewindItem].compactMap { $0 }
     }
 
     /// Pause Items
@@ -28,6 +28,7 @@ class PauseViewController: UIViewController, PauseInfoProviding
     var cheatCodesItem: MenuItem?
     var fastForwardItem: MenuItem?
     var sustainButtonsItem: MenuItem?
+    var rewindItem: MenuItem?
 
     /// PauseInfoProviding
     var pauseText: String?
@@ -114,9 +115,9 @@ extension PauseViewController
         case "saveStates":
             let saveStatesViewController = segue.destination as! SaveStatesViewController
             saveStatesViewController.delegate = self.saveStatesViewControllerDelegate
+            saveStatesViewController.mode = self.saveStatesViewControllerMode
             saveStatesViewController.game = self.emulatorCore?.game as? Game
             saveStatesViewController.emulatorCore = self.emulatorCore
-            saveStatesViewController.mode = self.saveStatesViewControllerMode
 
         case "cheats":
             let cheatsViewController = segue.destination as! CheatsViewController
@@ -160,6 +161,7 @@ private extension PauseViewController
         self.cheatCodesItem = nil
         self.sustainButtonsItem = nil
         self.fastForwardItem = nil
+        self.rewindItem = nil
 
         guard self.emulatorCore != nil else { return }
 
@@ -173,6 +175,14 @@ private extension PauseViewController
             self.performSegue(withIdentifier: "saveStates", sender: self)
         })
 
+        if Settings.isRewindEnabled
+        {
+            self.rewindItem = MenuItem(text: NSLocalizedString("Rewind", comment: ""), image: #imageLiteral(resourceName: "Rewind"), action: { [unowned self] _ in
+                self.saveStatesViewControllerMode = .rewind
+                self.performSegue(withIdentifier: "saveStates", sender: self)
+            })
+        }
+
         self.cheatCodesItem = MenuItem(text: NSLocalizedString("Cheat Codes", comment: ""), image: #imageLiteral(resourceName: "CheatCodes"), action: { [unowned self] _ in
             self.performSegue(withIdentifier: "cheats", sender: self)
         })

Delta/Pause Menu/Save States/SaveStatesViewController.swift

@@ -24,6 +24,7 @@ extension SaveStatesViewController
     {
         case saving
         case loading
+        case rewind
     }
 
     enum Section: Int
@@ -32,6 +33,7 @@ extension SaveStatesViewController
         case quick
         case general
         case locked
+        case rewind
     }
 }
 
@@ -111,6 +113,11 @@ extension SaveStatesViewController
             self.title = NSLocalizedString("Load State", comment: "")
             self.placeholderView.detailTextLabel.text = NSLocalizedString("You can create a new save state by pressing the Save State option in the pause menu.", comment: "")
             self.navigationItem.rightBarButtonItems?.removeFirst()
+
+        case .rewind:
+            self.title = NSLocalizedString("Rewind State", comment: "")
+            self.placeholderView.detailTextLabel.text = NSLocalizedString("Rewind States will appear here as gameplay advances.", comment: "")
+            self.navigationItem.rightBarButtonItems?.removeFirst()
         }
 
         // Manually update prototype cell properties
@@ -132,7 +139,7 @@ extension SaveStatesViewController
         self.navigationController?.toolbar.barStyle = .blackTranslucent
 
         self.update()
-    }    
+    }
 
     override func viewWillDisappear(_ animated: Bool)
     {
@@ -204,13 +211,15 @@ private extension SaveStatesViewController
         fetchRequest.returnsObjectsAsFaults = false
         fetchRequest.sortDescriptors = [NSSortDescriptor(key: #keyPath(SaveState.type), ascending: true), NSSortDescriptor(key: #keyPath(SaveState.creationDate), ascending: Settings.sortSaveStatesByOldestFirst)]
 
+        let rewindEvaluationOperator = self.mode == .rewind ? "==" : "!="
+
         if let system = System(gameType: self.game.type)
         {
-            fetchRequest.predicate = NSPredicate(format: "%K == %@ AND %K == %@", #keyPath(SaveState.game), self.game, #keyPath(SaveState.coreIdentifier), system.deltaCore.identifier)
+            fetchRequest.predicate = NSPredicate(format: "%K == %@ AND %K == %@ AND %K \(rewindEvaluationOperator) %@", #keyPath(SaveState.game), game, #keyPath(SaveState.coreIdentifier), system.deltaCore.identifier, #keyPath(SaveState.type), NSNumber(value: SaveStateType.rewind.rawValue))
         }
         else
         {
-            fetchRequest.predicate = NSPredicate(format: "%K == %@", #keyPath(SaveState.game), self.game)
+            fetchRequest.predicate = NSPredicate(format: "%K == %@ AND %K \(rewindEvaluationOperator) %@", #keyPath(SaveState.game), game, #keyPath(SaveState.type), NSNumber(value: SaveStateType.rewind.rawValue))
         }
 
         self.dataSource.fetchedResultsController = NSFetchedResultsController(fetchRequest: fetchRequest, managedObjectContext: DatabaseManager.shared.viewContext, sectionNameKeyPath: #keyPath(SaveState.type), cacheName: nil)
@@ -259,15 +268,23 @@ private extension SaveStatesViewController
         case .translucent:
             cell.isTextLabelVibrancyEnabled = true
             cell.isImageViewVibrancyEnabled = true
-        }        
+        }
 
         let deltaCore = Delta.core(for: self.game.type)!
 
         let dimensions = deltaCore.videoFormat.dimensions
         cell.maximumImageSize = CGSize(width: self.prototypeCellWidthConstraint.constant, height: (self.prototypeCellWidthConstraint.constant / dimensions.width) * dimensions.height)
 
         cell.textLabel.font = UIFont.preferredFont(forTextStyle: .subheadline)
-        cell.textLabel.text = saveState.localizedName
+        if self.mode == .rewind
+        {
+            let differenceInSeconds = Int(Date().timeIntervalSince(saveState.modifiedDate))
+            cell.textLabel.text = "\(differenceInSeconds)s Ago"
+        }
+        else
+        {
+            cell.textLabel.text = saveState.localizedName
+        }
     }
 
     func configure(_ headerView: SaveStatesCollectionHeaderView, forSection section: Int)
@@ -282,6 +299,7 @@ private extension SaveStatesViewController
         case .quick: title = NSLocalizedString("Quick Save", comment: "")
         case .general: title = NSLocalizedString("General", comment: "")
         case .locked: title = NSLocalizedString("Locked", comment: "")
+        case .rewind: title = NSLocalizedString("Rewind", comment: "")
         }
 
         headerView.textLabel.text = title
@@ -494,7 +512,7 @@ private extension SaveStatesViewController
 
     func actionsForSaveState(_ saveState: SaveState) -> [Action]?
     {
-        guard saveState.type != .auto else { return nil }
+        guard saveState.type != .auto && saveState.type != .rewind else { return nil }
 
         let isPreviewAvailable: Bool
 
@@ -550,6 +568,7 @@ private extension SaveStatesViewController
                 self.unlockSaveState(saveState)
             })
             actions.append(unlockAction)
+        case .rewind: break
         }
 
         let deleteAction = Action(title: NSLocalizedString("Delete", comment: ""), style: .destructive, image: UIImage(symbolNameIfAvailable: "trash"), action: { [unowned self] action in
@@ -720,7 +739,7 @@ extension SaveStatesViewController
             let section = self.correctedSectionForSectionIndex(indexPath.section)
             switch section
             {
-            case .auto: break
+            case .auto, .rewind: break
             case .quick, .general:
                 let backgroundContext = DatabaseManager.shared.newBackgroundContext()
                 backgroundContext.performAndWait() {
@@ -736,6 +755,7 @@ extension SaveStatesViewController
             }
 
         case .loading: self.loadSaveState(saveState)
+        case .rewind: self.loadSaveState(saveState)
         }
     }
 }