COVIDSafe code from version 1.4 (#3)

CovidSafe/EncounterDB.swift

@@ -0,0 +1,75 @@
+//
+//  EncounterDB.swift
+//  CovidSafe
+//
+//  Copyright © 2020 Australian Government. All rights reserved.
+//
+
+import UIKit
+import CoreData
+
+class EncounterDB {
+    static let shared = EncounterDB()
+    private let modelName = "tracer"
+    private var localStoreUrl: URL?
+    private var _persistentContainer: CovidPersistentContainer?
+    var migrationDelegate: EncounterDBMigrationProgress?
+    var backgroundTask: UIBackgroundTaskIdentifier = .invalid
+    
+    
+    private lazy var managedObjectModel: NSManagedObjectModel = {
+        guard let modelURL = Bundle.main.url(forResource: self.modelName, withExtension: "momd") else {
+            fatalError("Unable to Find Data Model")
+        }
+
+        guard let managedObjectModel = NSManagedObjectModel(contentsOf: modelURL) else {
+            fatalError("Unable to Load Data Model")
+        }
+
+        return managedObjectModel
+    }()
+    
+    public var persistentContainer: CovidPersistentContainer? {
+        get {
+            if let container = _persistentContainer {
+                return container
+            }
+            //check if we need to migrate store first
+            if let localStoreUrl = self.localStoreUrl {
+                if FileManager.default.fileExists(atPath: localStoreUrl.path) &&
+                    store(localStoreUrl, isCompatibleWithModel: self.managedObjectModel) == false {
+                    return nil // Don't return a store if it's not compatible with the model
+                }
+            }
+
+            let container = CovidPersistentContainer(name: self.modelName)
+            container.loadPersistentStores(completionHandler: { (storeDescription, error) in
+                if let error = error as NSError? {
+                    fatalError("Unresolved error \(error), \(error.userInfo)")
+                }
+            })
+            _persistentContainer = container
+            return _persistentContainer
+        }
+    }
+    
+    func registerBackgroundTask() {
+        backgroundTask = UIApplication.shared.beginBackgroundTask { [weak self] in
+            self?.endBackgroundTask()
+        }
+        assert(backgroundTask != .invalid)
+    }
+      
+    func endBackgroundTask() {
+        if(backgroundTask != .invalid){
+            UIApplication.shared.endBackgroundTask(backgroundTask)
+            backgroundTask = .invalid
+        }
+    }
+    
+    func setup(migrationDelegate: EncounterDBMigrationProgress?) {
+        self.migrationDelegate = migrationDelegate
+        self.localStoreUrl = CovidPersistentContainer.defaultDirectoryURL().appendingPathComponent(self.modelName, isDirectory: true).appendingPathExtension("sqlite")
+        migrateStoreIfNecessary(storeURL: self.localStoreUrl!, destinationModel: self.managedObjectModel)
+    }
+}