import Foundation

/// Actor that handles all UserDefaults operations.
/// Provides thread-safe access to UserDefaults with suite support.
actor UserDefaultsHelper {
    
    public static let shared = UserDefaultsHelper()
    
    private init() {}
    
    // MARK: - Public Interface
    
    /// Stores data in UserDefaults.
    /// - Parameters:
    ///   - data: The data to store.
    ///   - key: The key to store the data under.
    ///   - suite: Optional suite name. Nil uses standard UserDefaults.
    /// - Throws: `StorageError.invalidUserDefaultsSuite` if suite is invalid.
    public func set(_ data: Data, forKey key: String, suite: String?) throws {
        let defaults = try userDefaults(for: suite)
        defaults.set(data, forKey: key)
    }
    
    /// Retrieves data from UserDefaults.
    /// - Parameters:
    ///   - key: The key to retrieve.
    ///   - suite: Optional suite name.
    /// - Returns: The stored data, or nil if not found.
    /// - Throws: `StorageError.invalidUserDefaultsSuite` if suite is invalid.
    public func get(forKey key: String, suite: String?) throws -> Data? {
        let defaults = try userDefaults(for: suite)
        return defaults.data(forKey: key)
    }
    
    /// Removes data from UserDefaults.
    /// - Parameters:
    ///   - key: The key to remove.
    ///   - suite: Optional suite name.
    /// - Throws: `StorageError.invalidUserDefaultsSuite` if suite is invalid.
    public func remove(forKey key: String, suite: String?) throws {
        let defaults = try userDefaults(for: suite)
        defaults.removeObject(forKey: key)
    }
    
    /// Checks if a key exists in UserDefaults.
    /// - Parameters:
    ///   - key: The key to check.
    ///   - suite: Optional suite name.
    /// - Returns: True if the key exists.
    /// - Throws: `StorageError.invalidUserDefaultsSuite` if suite is invalid.
    public func exists(forKey key: String, suite: String?) throws -> Bool {
        let defaults = try userDefaults(for: suite)
        return defaults.object(forKey: key) != nil
    }
    
    /// Gets all keys in UserDefaults for a given suite.
    /// - Parameter suite: Optional suite name.
    /// - Returns: An array of all keys.
    /// - Throws: `StorageError.invalidUserDefaultsSuite` if suite is invalid.
    public func allKeys(suite: String?) throws -> [String] {
        let defaults = try userDefaults(for: suite)
        return Array(defaults.dictionaryRepresentation().keys)
    }
    
    // MARK: - Private Helpers
    
    private func userDefaults(for suite: String?) throws -> UserDefaults {
        guard let suite else {
            return .standard
        }
        
        guard let defaults = UserDefaults(suiteName: suite) else {
            throw StorageError.invalidUserDefaultsSuite(suite)
        }
        
        return defaults
    }
}