Meshtastic-Apple/Meshtastic/Persistence/Persistence.swift

//
//  Persistence.swift
//  Meshtastic
//
//  Copyright(c) Garth Vander Houwen 11/28/21.
//

import CoreData

class PersistenceController {

	static let shared = PersistenceController()

	static var preview: PersistenceController = {
		let result = PersistenceController(inMemory: false)
		let viewContext = result.container.viewContext
		for _ in 0..<10 {
			let newItem = NodeInfoEntity(context: viewContext)
			newItem.lastHeard = Date()
		}
		do {
			try viewContext.save()
		} catch {
			// Replace this implementation with code to handle the error appropriately.
			// fatalError() causes the application to generate a crash log and terminate. You should not use this function in a shipping application, although it may be useful during development.
			let nsError = error as NSError
			fatalError("Unresolved error \(nsError), \(nsError.userInfo)")
		}
		return result
	}()

	let container: NSPersistentContainer

	init(inMemory: Bool = false) {

		container = NSPersistentContainer(name: "Meshtastic")

		if inMemory {
			container.persistentStoreDescriptions.first!.url = URL(fileURLWithPath: "/dev/null")
		}

		container.loadPersistentStores(completionHandler: { (_, error) in

			// Merge policy that favors in memory data over data in the db
			self.container.viewContext.mergePolicy = NSMergeByPropertyObjectTrumpMergePolicy
			self.container.viewContext.automaticallyMergesChangesFromParent = true

			if let error = error as NSError? {

				print("💥 CoreData Error: \(error.localizedDescription). Now attempting to truncate CoreData database.  All app data will be lost.")
				self.clearDatabase()
			}
		})
	}

	public func clearDatabase() {
		guard let url = self.container.persistentStoreDescriptions.first?.url else { return }

		let persistentStoreCoordinator = self.container.persistentStoreCoordinator

		 do {

			 try persistentStoreCoordinator.destroyPersistentStore(at: url, ofType: NSSQLiteStoreType, options: nil)
			 try persistentStoreCoordinator.addPersistentStore(ofType: NSSQLiteStoreType, configurationName: nil, at: url, options: nil)
			 print("💥 CoreData database truncated.  All app data has been erased.")

		} catch let error {
			print("💣 Failed to destroy CoreData database, delete the app and re-install to clear data. Attempted to clear persistent store: " + error.localizedDescription)
		}
	}
}

extension NSManagedObjectContext {

	/// Executes the given `NSBatchDeleteRequest` and directly merges the changes to bring the given managed object context up to date.
	///
	/// - Parameter batchDeleteRequest: The `NSBatchDeleteRequest` to execute.
	/// - Throws: An error if anything went wrong executing the batch deletion.
	public func executeAndMergeChanges(using batchDeleteRequest: NSBatchDeleteRequest) throws {
		batchDeleteRequest.resultType = .resultTypeObjectIDs

		let result = try execute(batchDeleteRequest) as? NSBatchDeleteResult
		let changes: [AnyHashable: Any] = [NSDeletedObjectsKey: result?.result as? [NSManagedObjectID] ?? []]

		NSManagedObjectContext.mergeChanges(fromRemoteContextSave: changes, into: [self])
	}
}