mysubstr task

#include <string.h>

#define STAR_CHR '*'
int
mysubstr(char *needle, char *haystack)
{
    char *star = strchr(needle, STAR_CHR);
    if (star != NULL) {
        // separate two parts of the string
        *star = 0;
        // now needle is he first part
        // and star + 1 is the second part
    }
    char *res = strstr(haystack, needle);
    // NOTE: strstr uses reverse args order
    if (star == NULL) {
        // if there was no star, we're done
        return res == NULL ? -1 : res - haystack;
    }
    if (res == NULL) {
        *star = STAR_CHR;
        return -1;
    }
    // search for the second part of the needle
    // in the remaining part of the haystack
    char *second_part = strstr(res + strlen(needle), star + 1);
    *star = STAR_CHR;
    return second_part == NULL ? -1 : res - haystack;
}

#ifdef DEBUG
#include <stdio.h>
int main(void) {
    char needle[80];
    char haystack[80];
    scanf("%s%s", needle, haystack);
    printf("%d\n", mysubstr(needle, haystack));
    return 0;
}
#endif