// tun_if.h - TUN interface management for utun
#ifndef TUN_IF_H
#define TUN_IF_H

#include <stdint.h>
#include <stddef.h>
#include <sys/types.h>

// Forward declarations
struct UTUN_INSTANCE;

#ifdef __cplusplus
extern "C" {
#endif

#define MAX_PACKET_SIZE 1500

// TUN interface configuration
struct tun_config {
    char ifname[16];           // Interface name (e.g., "tun12")
    char ip_addr[64];          // IP address with mask (e.g., "10.0.0.1/24")
    int mtu;                   // MTU size
    int fd;                    // File descriptor
    uint8_t is_up;             // 1 if interface is up
    // Statistics
    uint64_t bytes_read;          // Bytes read from TUN
    uint64_t bytes_written;       // Bytes written to TUN
    uint32_t packets_read;        // Packets read from TUN
    uint32_t packets_written;     // Packets written to TUN
    uint32_t read_errors;         // Read errors
    uint32_t write_errors;        // Write errors
};

/**
 * @brief Create and configure TUN interface
 * @param config TUN configuration (ifname can be empty for auto)
 * @return 0 on success, -1 on error
 */
int tun_create(struct tun_config *config);

/**
 * @brief Configure IP address on TUN interface
 * @param ifname Interface name
 * @param ip_addr IP address with mask (e.g., "10.0.0.1/24")
 * @return 0 on success, -1 on error
 */
int tun_set_ip(const char *ifname, const char *ip_addr);

/**
 * @brief Bring TUN interface up
 * @param ifname Interface name
 * @return 0 on success, -1 on error
 */
int tun_set_up(const char *ifname);

/**
 * @brief Set MTU on TUN interface
 * @param ifname Interface name
 * @param mtu MTU value
 * @return 0 on success, -1 on error
 */
int tun_set_mtu(const char *ifname, int mtu);

/**
 * @brief Read packet from TUN interface
 * @param fd TUN file descriptor
 * @param buffer Buffer to store packet
 * @param size Buffer size
 * @return Number of bytes read, -1 on error
 */
ssize_t tun_read(int fd, uint8_t *buffer, size_t size);

/**
 * @brief Write packet to TUN interface
 * @param fd TUN file descriptor
 * @param buffer Packet data
 * @param size Packet size
 * @return Number of bytes written, -1 on error
 */
ssize_t tun_write(int fd, const uint8_t *buffer, size_t size);

/**
 * @brief Close TUN interface
 * @param config TUN configuration
 */
void tun_close(struct tun_config *config);

/**
 * @brief Get current TUN configuration
 * @param ifname Interface name
 * @param config Output configuration
 * @return 0 on success, -1 on error
 */
int tun_get_config(const char *ifname, struct tun_config *config);

int utun_instance_register_sockets(struct UTUN_INSTANCE *instance);
void utun_instance_unregister_sockets(struct UTUN_INSTANCE *instance);

// TUN callback function
void tun_read_callback(int fd, void* user_arg);


#ifdef __cplusplus
}
#endif

#endif /* TUN_IF_H */