import CoreData
import CloudKit

struct PersistenceController {
    static let shared = PersistenceController()

    let container: NSPersistentCloudKitContainer

    // CloudKit container identifier - same as iOS app for sync
    static let cloudKitContainerIdentifier = "iCloud.dev.rzen.indie.Workouts"

    var viewContext: NSManagedObjectContext {
        container.viewContext
    }

    // MARK: - Preview Support

    static var preview: PersistenceController = {
        let controller = PersistenceController(inMemory: true)
        let viewContext = controller.container.viewContext

        // Create sample data for previews
        let split = Split(context: viewContext)
        split.name = "Upper Body"
        split.color = "blue"
        split.systemImage = "dumbbell.fill"
        split.order = 0

        let exercise = Exercise(context: viewContext)
        exercise.name = "Bench Press"
        exercise.sets = 3
        exercise.reps = 10
        exercise.weight = 135
        exercise.order = 0
        exercise.loadType = Int32(LoadType.weight.rawValue)
        exercise.split = split

        do {
            try viewContext.save()
        } catch {
            let nsError = error as NSError
            fatalError("Unresolved error \(nsError), \(nsError.userInfo)")
        }

        return controller
    }()

    // MARK: - Initialization

    init(inMemory: Bool = false, cloudKitEnabled: Bool = true) {
        container = NSPersistentCloudKitContainer(name: "Workouts")

        guard let description = container.persistentStoreDescriptions.first else {
            fatalError("Failed to retrieve a persistent store description.")
        }

        if inMemory {
            description.url = URL(fileURLWithPath: "/dev/null")
            description.cloudKitContainerOptions = nil
        } else if cloudKitEnabled {
            // Check if CloudKit is available before enabling
            let cloudKitAvailable = FileManager.default.ubiquityIdentityToken != nil

            if cloudKitAvailable {
                // Set CloudKit container options
                let cloudKitOptions = NSPersistentCloudKitContainerOptions(
                    containerIdentifier: Self.cloudKitContainerIdentifier
                )
                description.cloudKitContainerOptions = cloudKitOptions
            } else {
                // CloudKit not available (not signed in, etc.)
                description.cloudKitContainerOptions = nil
                print("CloudKit not available - using local storage only")
            }

            // Enable persistent history tracking (useful even without CloudKit)
            description.setOption(true as NSNumber, forKey: NSPersistentHistoryTrackingKey)
            description.setOption(true as NSNumber, forKey: NSPersistentStoreRemoteChangeNotificationPostOptionKey)
        } else {
            // CloudKit explicitly disabled
            description.cloudKitContainerOptions = nil
        }

        container.loadPersistentStores { storeDescription, error in
            if let error = error as NSError? {
                // In production, handle this more gracefully
                print("CoreData error: \(error), \(error.userInfo)")
                #if DEBUG
                fatalError("Unresolved error \(error), \(error.userInfo)")
                #endif
            }
        }

        // Configure view context
        container.viewContext.automaticallyMergesChangesFromParent = true
        container.viewContext.mergePolicy = NSMergeByPropertyObjectTrumpMergePolicy

        // Pin the viewContext to the current generation token
        do {
            try container.viewContext.setQueryGenerationFrom(.current)
        } catch {
            print("Failed to pin viewContext to the current generation: \(error)")
        }
    }

    // MARK: - Save Context

    func save() {
        let context = container.viewContext
        if context.hasChanges {
            do {
                try context.save()
            } catch {
                let nsError = error as NSError
                print("Save error: \(nsError), \(nsError.userInfo)")
            }
        }
    }
}