#define _GNU_SOURCE

#include <dlfcn.h>
#include <errno.h>
#include <pwd.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/types.h>

int strlcpy(char *restrict dest, const char *restrict src, size_t bufsize) {
    size_t i;
    for (i = 0; i < bufsize; ++i) {
        dest[i] = src[i];
        if (src[i] == '\0') {
            return 0;
        }
    }
    return ERANGE;
}

char *getlogin(void) {
    return getenv("USER");
}

int getlogin_r(char *buf, size_t bufsize) {
    const char *login = getlogin();
    if (login == NULL) {
        return ENOENT;
    }
    return strlcpy(buf, login, bufsize);
}

struct passwd *getpwuid(uid_t uid) {
    struct passwd *(*getpwuid)(uid_t) = dlsym(RTLD_NEXT, "getpwuid");
    if (getpwuid == NULL) {
        fprintf(stderr, "Unable to find the adress of the getpwuid function: %s\n", dlerror());
        return NULL;
    }
    struct passwd *pass = getpwuid(uid);
    char *name = getenv("USER");
    if (name == NULL) {
        fprintf(stderr, "Could not find the USER environment variable. Using the real username.\n");
        return pass;
    }
    pass->pw_name = name;
    return pass;
}