#ifndef VMSIG_ADAPTER_UTIL_H
#define VMSIG_ADAPTER_UTIL_H
#include <stddef.h>

/* adapter_util.h — shared primitive "blocking API -> completion eventfd".
 *
 * A bridge turning a synchronous CPU-bound / blocking neighbor call (vmie,
 * vmctl) into a readiness source for the epoll core: the loop thread posts a request, a
 * separate worker thread runs the blocking work and signals a completion eventfd; on it
 * the loop wakes and collects the result in on_readiness. Reused by the memctx
 * (off-loop bootstrap) and input adapters. */

typedef struct vmsig_worker vmsig_worker;

#define VMSIG_WORK_SLOT 256   /* req/res slot size (POD, copied) */

/* Callback run IN the worker thread: req -> res (both POD <= VMSIG_WORK_SLOT).
 * Returns 0/-1 (the code is stored alongside, see vmsig_worker_poll). Must not touch
 * core structures — only compute res from req. */
typedef int (*vmsig_work_fn)(void* user, const void* req, void* res);

/* Create a worker pool of nthreads threads over a shared queue (nthreads>=1). vmie
 * allows parallel read-only readers; for a serial channel (QMP) use 1. max_depth — the
 * request-queue depth ceiling (<=0 => default): submit beyond it is rejected (-1) so an
 * untrusted flood does not grow into OOM. NULL on error. */
vmsig_worker* vmsig_worker_new(vmsig_work_fn fn, void* user, int nthreads, int max_depth);

/* Stop the threads (join) and free. Safe on NULL. */
void          vmsig_worker_free(vmsig_worker* w);

/* completion eventfd: the adapter registers it as a VMSIG_RDY_EVENTFD source. */
int  vmsig_worker_evfd(const vmsig_worker* w);

/* loop thread: post a request (copied, len <= VMSIG_WORK_SLOT). 0/-1. */
int  vmsig_worker_submit(vmsig_worker* w, const void* req, size_t len);

/* loop thread (in on_readiness): drain the completion eventfd. */
void vmsig_worker_ack(vmsig_worker* w);

/* loop thread: collect a ready result. 1 — written to res (+ *rc = fn code),
 * 0 — empty, -1 — error. Drain in a loop until 0. */
int  vmsig_worker_poll(vmsig_worker* w, void* res, size_t cap, int* rc);

#endif /* VMSIG_ADAPTER_UTIL_H */