/* queue.c -- FIFO queue (circular buffer). */
#include "queue.h"

#include <stdlib.h>

int queue_init(Queue *q, size_t capacity) {
    if (!q || capacity == 0) return -1;
    q->data = malloc(capacity * sizeof(int));
    if (!q->data) return -1;
    q->capacity = capacity;
    q->head = 0;
    q->tail = 0;
    q->size = 0;
    return 0;
}

void queue_destroy(Queue *q) {
    if (!q) return;
    free(q->data);
    q->data = NULL;
    q->capacity = 0;
    q->head = q->tail = q->size = 0;
}

int queue_enqueue(Queue *q, int value) {
    if (!q || q->size >= q->capacity) return -1;
    q->data[q->tail] = value;
    q->tail = (q->tail + 1) % q->capacity;
    q->size++;
    return 0;
}

int queue_dequeue(Queue *q, int *out) {
    if (!q || q->size == 0) return -1;
    if (out) *out = q->data[q->head];
    q->head = (q->head + 1) % q->capacity;
    q->size--;
    return 0;
}

int queue_is_empty(const Queue *q) {
    return !q || q->size == 0;
}

size_t queue_size(const Queue *q) {
    return q ? q->size : 0;
}