From 5c6c66c9a1a6de75c7b6c43ac319baced63238f8 Mon Sep 17 00:00:00 2001
From: Riley Testut <riley@rileytestut.com>
Date: Mon, 26 Dec 2016 15:56:33 -0600
Subject: [PATCH] Fixes crashes when loading Game or SaveState that had been
 overwritten by a duplicate entry

When Core Data detects a duplicate entry, it deletes the previous entry. This caused Delta to delete the associated ROM and Save State files. Now, there is a check in prepareForDeletion to make sure the object being deleted is not simply being replaced by a newer entry during a merge.
---
 Delta/Database/Model/Human/Game.swift      | 39 ++++++++++++----------
 Delta/Database/Model/Human/SaveState.swift |  6 ++++
 2 files changed, 27 insertions(+), 18 deletions(-)

diff --git a/Delta/Database/Model/Human/Game.swift b/Delta/Database/Model/Human/Game.swift
index d65975d..7234bb6 100644
--- a/Delta/Database/Model/Human/Game.swift
+++ b/Delta/Database/Model/Human/Game.swift
@@ -30,6 +30,12 @@ extension Game
     {
         super.prepareForDeletion()
         
+        guard let managedObjectContext = self.managedObjectContext else { return }
+        
+        // If a game with the same identifier is also currently being inserted, Core Data is more than likely resolving a conflict by deleting the previous instance
+        // In this case, we make sure we DON'T delete the game file + misc other Core Data relationships, or else we'll just lose all that data
+        guard !managedObjectContext.insertedObjects.contains(where: { ($0 as? Game)?.identifier == self.identifier }) else { return }
+        
         guard FileManager.default.fileExists(atPath: self.fileURL.path) else { return }
         
         do
@@ -41,25 +47,22 @@ extension Game
             print(error)
         }
         
-        if let managedObjectContext = self.managedObjectContext
+        for collection in self.gameCollections where collection.games.count == 1
         {
-            for collection in self.gameCollections where collection.games.count == 1
-            {
-                // Once this game is deleted, collection will have 0 games, so we should delete it
-                managedObjectContext.delete(collection)
-            }
-            
-            // Manually cascade deletion since SaveState.fileURL references Game, and so we need to ensure we delete SaveState's before Game
-            // Otherwise, we crash when accessing SaveState.game since it is nil
-            for saveState in self.saveStates
-            {
-                managedObjectContext.delete(saveState)
-            }
-            
-            if managedObjectContext.hasChanges
-            {
-                managedObjectContext.saveWithErrorLogging()
-            }
+            // Once this game is deleted, collection will have 0 games, so we should delete it
+            managedObjectContext.delete(collection)
+        }
+        
+        // Manually cascade deletion since SaveState.fileURL references Game, and so we need to ensure we delete SaveState's before Game
+        // Otherwise, we crash when accessing SaveState.game since it is nil
+        for saveState in self.saveStates
+        {
+            managedObjectContext.delete(saveState)
+        }
+        
+        if managedObjectContext.hasChanges
+        {
+            managedObjectContext.saveWithErrorLogging()
         }
     }
 }
diff --git a/Delta/Database/Model/Human/SaveState.swift b/Delta/Database/Model/Human/SaveState.swift
index 26b27d9..acdfd55 100644
--- a/Delta/Database/Model/Human/SaveState.swift
+++ b/Delta/Database/Model/Human/SaveState.swift
@@ -60,6 +60,12 @@ public class SaveState: _SaveState, SaveStateProtocol
         // In rare cases, game may actually be nil if game is corrupted, so we ensure it is non-nil first
         guard self.game != nil else { return }
         
+        guard let managedObjectContext = self.managedObjectContext else { return }
+        
+        // If a save state with the same identifier is also currently being inserted, Core Data is more than likely resolving a conflict by deleting the previous instance
+        // In this case, we make sure we DON'T delete the save state file + misc other Core Data relationships, or else we'll just lose all that data
+        guard !managedObjectContext.insertedObjects.contains(where: { ($0 as? SaveState)?.identifier == self.identifier }) else { return }
+        
         guard FileManager.default.fileExists(atPath: self.fileURL.path) else { return }
         
         do