import Foundation
import Security

/// Keychain-backed secure storage for auth tokens
enum SecureStorage {

    private static let service = "com.payfrit.beacon"

    struct Session {
        let token: String
        let userId: String
    }

    static func saveSession(token: String, userId: String) {
        save(key: "authToken", value: token)
        save(key: "userId", value: userId)
    }

    static func loadSession() -> Session? {
        guard let token = load(key: "authToken"),
              let userId = load(key: "userId") else { return nil }
        return Session(token: token, userId: userId)
    }

    static func clearSession() {
        delete(key: "authToken")
        delete(key: "userId")
    }

    // MARK: - Keychain Helpers

    private static func save(key: String, value: String) {
        guard let data = value.data(using: .utf8) else { return }
        delete(key: key) // Remove old value first

        let query: [String: Any] = [
            kSecClass as String: kSecClassGenericPassword,
            kSecAttrService as String: service,
            kSecAttrAccount as String: key,
            kSecValueData as String: data,
            kSecAttrAccessible as String: kSecAttrAccessibleWhenUnlockedThisDeviceOnly
        ]
        SecItemAdd(query as CFDictionary, nil)
    }

    private static func load(key: String) -> String? {
        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 else { return nil }
        return String(data: data, encoding: .utf8)
    }

    private static func delete(key: String) {
        let query: [String: Any] = [
            kSecClass as String: kSecClassGenericPassword,
            kSecAttrService as String: service,
            kSecAttrAccount as String: key
        ]
        SecItemDelete(query as CFDictionary)
    }
}