import Foundation
import Security

enum KeychainService {
    private static let serviceName = "com.aiusage.app"

    static func save(_ value: String, account: String) throws {
        let data = Data(value.utf8)
        let query: [String: Any] = [
            kSecClass as String: kSecClassGenericPassword,
            kSecAttrService as String: serviceName,
            kSecAttrAccount as String: account,
        ]

        SecItemDelete(query as CFDictionary)

        var addQuery = query
        addQuery[kSecValueData as String] = data
        addQuery[kSecAttrAccessible as String] = kSecAttrAccessibleAfterFirstUnlock

        let status = SecItemAdd(addQuery as CFDictionary, nil)
        guard status == errSecSuccess else {
            throw KeychainError.unhandled(status)
        }
    }

    static func load(account: String) -> String? {
        let query: [String: Any] = [
            kSecClass as String: kSecClassGenericPassword,
            kSecAttrService as String: serviceName,
            kSecAttrAccount as String: account,
            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 string = String(data: data, encoding: .utf8)
        else {
            return nil
        }
        return string
    }

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

    static func keychainAccount(provider: ProviderID, authMode: AuthMode) -> String {
        "\(provider.rawValue).\(authMode.rawValue)"
    }
}

enum KeychainError: Error, LocalizedError {
    case unhandled(OSStatus)

    var errorDescription: String? {
        switch self {
        case .unhandled(let status):
            "Keychain error (\(status))"
        }
    }
}