import Foundation
#if os(iOS)
import Security
#endif

/// Small generic Keychain wrapper (iOS) with a UserDefaults fallback on other
/// platforms (macOS test target), namespaced by `service`+`key`.
enum KeychainStore {
    static func save(_ value: String, service: String, key: String) {
#if os(iOS)
        guard let data = value.data(using: .utf8) else { return }
        let query: [String: Any] = [
            kSecClass as String: kSecClassGenericPassword,
            kSecAttrService as String: service,
            kSecAttrAccount as String: key
        ]
        SecItemDelete(query as CFDictionary)
        var attributes = query
        attributes[kSecValueData as String] = data
        SecItemAdd(attributes as CFDictionary, nil)
#else
        UserDefaults.standard.set(value, forKey: "\(service).\(key)")
#endif
    }

    static func load(service: String, key: String) -> String? {
#if os(iOS)
        let query: [String: Any] = [
            kSecClass as String: kSecClassGenericPassword,
            kSecAttrService as String: service,
            kSecAttrAccount as String: key,
            kSecReturnData as String: true,
            kSecMatchLimit as String: kSecMatchLimitOne
        ]
        var result: AnyObject?
        let status = SecItemCopyMatching(query as CFDictionary, &result)
        guard status == errSecSuccess,
              let data = result as? Data,
              let value = String(data: data, encoding: .utf8) else {
            return nil
        }
        return value
#else
        UserDefaults.standard.string(forKey: "\(service).\(key)")
#endif
    }

    static func delete(service: String, key: String) {
#if os(iOS)
        let query: [String: Any] = [
            kSecClass as String: kSecClassGenericPassword,
            kSecAttrService as String: service,
            kSecAttrAccount as String: key
        ]
        SecItemDelete(query as CFDictionary)
#else
        UserDefaults.standard.removeObject(forKey: "\(service).\(key)")
#endif
    }
}