// Apple-only learning file: iOS 17+ target with a suitable Xcode SDK.
// Not compiled or run in this Windows/Linux review.
import SwiftUI
import CoreData

@objc(WorkshopNote) final class WorkshopNote: NSManagedObject { @NSManaged var label: String }
@MainActor final class MemoryStore {
    static let shared = MemoryStore()
    let container: NSPersistentContainer
    init() {
        let attribute = NSAttributeDescription()
        attribute.name = "label"; attribute.attributeType = .stringAttributeType; attribute.isOptional = false
        let entity = NSEntityDescription()
        entity.name = "WorkshopNote"; entity.managedObjectClassName = NSStringFromClass(WorkshopNote.self)
        entity.properties = [attribute]
        let model = NSManagedObjectModel(); model.entities = [entity]
        container = NSPersistentContainer(name: "WorkshopMemory", managedObjectModel: model)
        let store = NSPersistentStoreDescription(); store.type = NSInMemoryStoreType
        store.shouldAddStoreAsynchronously = false
        container.persistentStoreDescriptions = [store]
        container.loadPersistentStores { _, error in precondition(error == nil, "Memory store failed") }
    }
}

struct DemoView: View {
    @Environment(\.managedObjectContext) private var context
    @FetchRequest(sortDescriptors: []) private var notes: FetchedResults<WorkshopNote>
    @State private var notice = "In-memory notes only"
    var body: some View {
        VStack {
            List(notes, id: \.objectID) { Text($0.label) }
            Button("Add draft note") {
                let note = WorkshopNote(context: context)
                note.label = "Check glaze sample"
                do { try context.save(); notice = "Saved in this process only" }
                catch { context.rollback(); notice = "Save failed" }
            }
            Text(notice)
        }.environment(\.managedObjectContext, MemoryStore.shared.container.viewContext)
    }
}

@main
struct WorkshopDemoApp: App {
    var body: some Scene { WindowGroup { DemoView().environment(\.managedObjectContext, MemoryStore.shared.container.viewContext) } }
}