/**
 * @file se050_tai64n.h
 * @brief TAI64N Timestamp Encoding (WireGuard Protocol)
 * 
 * TAI64N: 64-bit TAI + 32-bit nanoseconds
 * Total: 12 bytes (big-endian)
 */

#ifndef SE050_TAI64N_H
#define SE050_TAI64N_H

#include <stdint.h>
#include <stddef.h>

#ifdef __cplusplus
extern "C" {
#endif

#define TAI64N_SIZE 12

/**
 * @brief Encode a timestamp to TAI64N format
 * @param out Output buffer (12 bytes)
 * @param seconds Unix timestamp seconds
 * @param nanoseconds Nanoseconds (0-999999999)
 */
void se050_tai64n_encode(uint8_t out[12], uint64_t seconds, uint32_t nanoseconds);

/**
 * @brief Decode TAI64N format to Unix timestamp
 * @param in Input buffer (12 bytes)
 * @param seconds Output seconds (Unix timestamp)
 * @param nanoseconds Output nanoseconds
 * @return 0 on success, -1 on error
 */
int se050_tai64n_decode(const uint8_t in[12], uint64_t *seconds, uint32_t *nanoseconds);

/**
 * @brief Get current time as TAI64N
 * @param out Output buffer (12 bytes)
 * @return 0 on success, -1 on error
 */
int se050_tai64n_now(uint8_t out[12]);

/**
 * @brief Check if TAI64N timestamp is within acceptable window
 * @param timestamp Received timestamp
 * @param current Current timestamp
 * @param window Acceptable window in seconds
 * @return 1 if valid, 0 if expired/replay, -1 on error
 */
int se050_tai64n_check_window(const uint8_t timestamp[12],
                              const uint8_t current[12],
                              uint32_t window);

#ifdef __cplusplus
}
#endif

#endif /* SE050_TAI64N_H */