#include "str_lib.h"

size_t mystrlen(const char *str) {
    if (!str) return 0;
    size_t len = 0;
    while (str[len] != '\0') {
        len++;
    }
    return len;
}

int mystr_idx(const char *str, const char *substr) {
    if (!str || !substr) return -1;
    
    size_t str_len = mystrlen(str);
    size_t substr_len = mystrlen(substr);
    
    if (substr_len == 0) return 0;
    if (substr_len > str_len) return -1;
    
    for (size_t i = 0; i <= str_len - substr_len; i++) {
        int found = 1;
        for (size_t j = 0; j < substr_len; j++) {
            if (str[i + j] != substr[j]) {
                found = 0;
                break;
            }
        }
        if (found) return i;
    }
    
    return -1;
}