UserDefaults and app preferences

                  import Foundation

enum UserDefaultsKey: String {
    case username
    case isFirstLaunch
    case lastSyncDate
    case theme
    case fontSize
    case notificationsEnabled
    case selectedLanguage
}

class UserDefaultsManager {
    static let shared = UserDefaultsManager()
    private let defaults = UserDefaults.standard

    private init() {}

    // MARK: - Basic Types
    func set<T>(_ value: T, forKey key: UserDefaultsKey) {
        defaults.set(value, forKey: key.rawValue)
    }

    func get<T>(forKey key: UserDefaultsKey) -> T? {
        return defaults.object(forKey: key.rawValue) as? T
    }

    func remove(forKey key: UserDefaultsKey) {
        defaults.removeObject(forKey: key.rawValue)
    }

    // MARK: - Convenience Properties
    var username: String? {
        get { get(forKey: .username) }
        set { set(newValue, forKey: .username) }
    }

    var isFirstLaunch: Bool {
        get { get(forKey: .isFirstLaunch) ?? true }
        set { set(newValue, forKey: .isFirstLaunch) }
    }

    var lastSyncDate: Date? {
        get { get(forKey: .lastSyncDate) }
        set { set(newValue, forKey: .lastSyncDate) }
    }

    // MARK: - Codable Support
    func setCodable<T: Codable>(_ value: T, forKey key: String) {
        if let encoded = try? JSONEncoder().encode(value) {
            defaults.set(encoded, forKey: key)
        }
    }

    func getCodable<T: Codable>(forKey key: String) -> T? {
        guard let data = defaults.data(forKey: key) else { return nil }
        return try? JSONDecoder().decode(T.self, from: data)
    }

    // MARK: - App Group Support
    static func groupDefaults(suiteName: String) -> UserDefaults? {
        return UserDefaults(suiteName: suiteName)
    }
}

// MARK: - Type-safe wrapper
struct AppSettings: Codable {
    var theme: String
    var fontSize: Double
    var notificationsEnabled: Bool
    var selectedLanguage: String

    static func load() -> AppSettings {
        UserDefaultsManager.shared.getCodable(forKey: "appSettings") ?? AppSettings.default
    }

    func save() {
        UserDefaultsManager.shared.setCodable(self, forKey: "appSettings")
    }

    static var `default`: AppSettings {
        AppSettings(
            theme: "system",
            fontSize: 16,
            notificationsEnabled: true,
            selectedLanguage: "en"
        )
    }
}