/*
 * Copyright (c) 2026, Chloe M.
 * Provided under the BSD-3 clause
 */

#include <sys/types.h>
#include <stdint.h>
#include <stddef.h>
#include <string.h>
#include <errno.h>
#include "cescal/tokbuf.h"

int
tokbuf_init(struct tokbuf *tokbuf)
{
    if (tokbuf == NULL) {
        errno = EINVAL;
        return -1;
    }

    memset(tokbuf->buf, 0, sizeof(tokbuf->buf));
    tokbuf->head = 0;
    return 0;
}

int
tokbuf_push(struct tokbuf *tokbuf, struct token *tok)
{
    if (tokbuf == NULL || tok == NULL) {
        return -1;
    }

    if ((tokbuf->head++) >= TOKBUF_CAP) {
        tokbuf->head = 0;
    }

    tokbuf->buf[tokbuf->head] = *tok;
    return 0;
}

int
tokbuf_noff(struct tokbuf *tokbuf, size_t noff, struct token *res)
{
    ssize_t off;

    if (tokbuf == NULL || res == NULL) {
        errno = EINVAL;
        return -1;
    }

    if (noff == 0) {
        *res = tokbuf->buf[tokbuf->head + 1];
        return 0;
    }

    if ((off = (tokbuf->head - noff + 1)) < 0) {
        off = 0;
    }

    *res = tokbuf->buf[off];
    return 0;
}