class PasswordManager {
    static let shared = PasswordManager() // singleton instance

    private lazy var protectionSpace: URLProtectionSpace = {
        return URLProtectionSpace(host: "somehost.com",
                                  port: 0,
                                  protocol: "http",
                                  realm: nil,
                                  authenticationMethod: nil)
    }()

    private init() { }

    func password(for userID: String) -> String? {
        guard let credentials = URLCredentialStorage.shared.credentials(for: protectionSpace) else { return nil }
        return credentials[userID]?.password
    }

    func set(password: String, for userID: String) {
        let credential = URLCredential(user: userID, password: password, persistence: .permanent)
        URLCredentialStorage.shared.set(credential, for: protectionSpace)
    }

    func clear(for userID: String) {
        if let password = password(for: userID) {
            let credential = URLCredential(user: userID, password: password, persistence: .permanent)
            URLCredentialStorage.shared.remove(credential, for: protectionSpace)
        }
    }
}