#ifndef SELFCHECK_H
#define SELFCHECK_H

#define SELFCHECK_CHALLENGE_LEN   16
#define SELFCHECK_RECV_TIMEOUT_S  2
#define SELFCHECK_FAIL_THRESHOLD  3
#define SELFCHECK_DRIFT_THRESHOLD 10
#define SELFCHECK_COOLDOWN_S      60

/*
 * Init challenge buffer and start UDP socket listener thread.
 * The socket discards any datagram and always
 * responsds with the challenge bytes.
 *
 * Returns 0 on success.
 * Returns -1 on failure.
 */
int selfcheck_start_listener(int port);

/*
 * Checks if the random challenge bytes are received
 * when sending an empty datagram to the domain and port.
 *
 * Returns 0 if the response matches.
 * Returns -1 on DNS failure, send failure, or timeout.
 * Returns -2 if the response did not match.
 */
int selfcheck_domain(const char *domain, int port);

/*
 * Same as selfcheck_domain but sends directly to `ip` without DNS.
 *
 * Returns 0 if the response matches.
 * Returns -1 on send failure or timeout.
 * Returns -2 if the response did not match.
 */
int selfcheck_ip_str(const char *ip, int port);

#endif /* SELFCHECK_H */