/*
 * C ABI between bunshin (Rust) and the microReticulum carrier shim.
 *
 * The shim owns the Reticulum run loop on a dedicated thread; every callback
 * below fires on that thread. link_id is always 16 bytes.
 */
#ifndef SMOLMAIL_RNS_H
#define SMOLMAIL_RNS_H

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

#ifdef __cplusplus
extern "C" {
#endif

/* Implemented in smolmail_rns.cpp, called from src/rns.rs.
 * identity: 64 bytes, x25519 private (32) || ed25519 private (32), the same
 * layout Identity::to_file writes and load_private_key expects.
 * udp_forward_host may be NULL: with no forward target the interface sends
 * to the source address of the last datagram received.
 * Returns 0 on success, negative on failure. */
int smolmail_rns_start(const uint8_t *identity,
                       const char *storage_dir,
                       const char *udp_listen_host, uint16_t udp_listen_port,
                       const char *udp_forward_host, uint16_t udp_forward_port,
                       uint8_t *destination_hash_out);

/* Pure computation, no Reticulum state: the 16-byte destination hash of
 * smolmail.server under this identity. microReticulum derives the identity's
 * x25519 public key with an unclamped scalar multiplication, which differs
 * from RFC 7748, so the hash must come from the library itself rather than
 * an independent Rust derivation. */
int smolmail_rns_destination_hash(const uint8_t *identity,
                                  uint8_t *destination_hash_out);

/* Implemented in src/rns.rs, called from the shim on the Reticulum loop
 * thread. A request is `op u8 || body` (RNS.md sec 1); the response placed
 * into the slot is `status u8 || payload`. on_request returns the response
 * length and leaves the bytes in the slot; the shim must copy them out with
 * take_response before the next on_request call. */
size_t smolmail_rns_on_request(const uint8_t *request, size_t request_len,
                               const uint8_t *link_id);
size_t smolmail_rns_take_response(uint8_t *out, size_t cap);

/* 0 = link admitted, 1 = over the concurrent-link cap (the shim tears the
 * link down after the current loop iteration). */
int smolmail_rns_on_link_opened(const uint8_t *link_id);
void smolmail_rns_on_link_closed(const uint8_t *link_id);

#ifdef __cplusplus
}
#endif

#endif /* SMOLMAIL_RNS_H */