/* This software is licensed by the MIT License, see LICENSE file */
/*                                Copyright © 2022 Gregory Lirent */

#include "include.h"

char* at_string(const str_t* s, ssize_t i) {
    char *e, *p;
    size_t n, l;

    if (is_null(s->buffer) || !*s->buffer)
        return nullptr;

    n = strasciilen(s->buffer);
    e = s->buffer + n;

    if (i > n) {
        p = s->buffer + n;
        e = p + strlen(p);

        do { p = next_char(p); } while (--i && p < e);
        return (!i) ? p : nullptr;

    } else if (i < 0 && n < (l = strlen(s->buffer))) {
        p = s->buffer + l;

        do { p = prev_char(p); } while (++i && p >= s->buffer);
        return (!i) ? p : nullptr;

    } else if (i < 0 && (i += l) < 0) i = 0;

    return s->buffer + i;
}


ssize_t libcdsb_string_indexof(const str_t* x, const char* s) {
    char *e, *p;
    size_t n;

    if (is_null(x->buffer) || is_null(s) || !*x->buffer || !*s) {
        return 0;
    }

    if (!is_null(p = strstr(x->buffer, s))) {
        n = strasciilen(x->buffer);
        e = x->buffer + n;

        if (e >= p) return p - x->buffer;

        do {
            e = next_char(e);
            ++n;
        } while (e < p);

        if (e != p) {
        /* Trying to find index of inconsistent string part
         * It is not make a sense on that abstract level */
        } else return n;
    }

    return -1;
}