/* uring.h — io_uring lifecycle (the kernel-facing seam, part 2).
 *
 * Thin ownership wrapper over liburing so the rest of the engine never calls
 * io_uring_* directly — that keeps the "Linux-only now, portable later" seam
 * intact (a future epoll/kqueue backend implements the same reactor contract).
 * Each reactor thread owns exactly one naut_ring for both network and disk.
 */
#ifndef NAUT_URING_H
#define NAUT_URING_H

#include "naut/common.h"
#include "naut/buf.h"
#include <liburing.h>

typedef struct naut_ring {
    struct io_uring ring;
    bool sqpoll;
    bool send_zc;
    bool msg_ring;
    bool buffers_registered;
    bool recv_fixed;
} naut_ring;

/* entries: SQ depth (rounded up to a power of two by the kernel).
 * sqpoll: dedicate a kernel thread to submission polling — removes the
 * io_uring_enter syscall from the hot path once the queue is warm (needs
 * CAP_SYS_NICE or /proc/sys tuning on some setups; falls back if it can't). */
naut_err naut_ring_init(naut_ring *r, unsigned entries, bool sqpoll);
naut_err naut_ring_init_cpu(naut_ring *r, unsigned entries, bool sqpoll,
                            int sqpoll_cpu);
void     naut_ring_close(naut_ring *r);

/* Detect kernel support for the features the data path relies on. Logs a
 * summary; returns NAUT_ERR_NOSYS if a hard requirement is missing. */
naut_err naut_ring_probe(naut_ring *r);

/* Register the pool's contiguous slab as fixed buffer index 0. Registration
 * may fail under a low RLIMIT_MEMLOCK; callers can continue in degraded mode. */
naut_err naut_ring_register_bufpool(naut_ring *r, const naut_bufpool *pool);
void     naut_ring_unregister_buffers(naut_ring *r);

/* Prepare a send using SEND_ZC when supported and requested, otherwise normal
 * SEND. Returns true when the caller must retain the buffer until a CQE with
 * IORING_CQE_F_NOTIF arrives. */
bool naut_ring_prep_send(naut_ring *r, struct io_uring_sqe *sqe, int fd,
                         const void *buf, size_t len, int flags,
                         bool prefer_zero_copy);
/* Returns true when this recv was armed against the registered fixed buffer.
 * Some kernels accept READ_FIXED but reject IORING_RECVSEND_FIXED_BUF on plain
 * recv with -EINVAL; the caller should remember this per-operation so it can
 * distinguish "fixed-buffer unsupported, retry unfixed" from a real error
 * (rather than tearing the connection down). */
bool naut_ring_prep_recv(naut_ring *r, struct io_uring_sqe *sqe, int fd,
                         void *buf, size_t len, int flags);

#endif /* NAUT_URING_H */