#include "queue.h"
#include <stdatomic.h>
#include <stdbool.h>

void queue_init(spsc_queue_t *q) {
  /* nothing to allocate, just ensure head/tail start at 0 */
  q->head = 0;
  q->tail = 0;
}

bool queue_push(spsc_queue_t *q, command_t cmd) {
  int h = atomic_load_explicit(&q->head, memory_order_relaxed);
  int t = atomic_load_explicit(&q->tail, memory_order_acquire);
  int next = (h + 1) % QUEUE_CAPACITY;
  if (next == t)
    return false; /* queue full */
  q->buffer[h] = cmd;
  atomic_store_explicit(&q->head, next, memory_order_release);
  return true;
}

bool queue_pop(spsc_queue_t *q, command_t *cmd) {
  int t = atomic_load_explicit(&q->tail, memory_order_relaxed);
  int h = atomic_load_explicit(&q->head, memory_order_acquire);
  if (t == h)
    return false; /* queue empty */
  *cmd = q->buffer[t];
  atomic_store_explicit(&q->tail, (t + 1) % QUEUE_CAPACITY,
                        memory_order_release);
  return true;
}