#include <fcntl.h>
#include <shadow.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

static struct spwd spwd;
static FILE* f { nullptr };
static char s_buf[4096];

extern char* _strtok_once(char* str, const char* delim);

extern "C"
{
    struct spwd* getspent()
    {
        struct spwd* result;

        if (getspent_r(&spwd, s_buf, sizeof(s_buf), &result) < 0) return nullptr;

        return result;
    }

    int getspent_r(struct spwd* spbuf, char* buf, size_t buflen, struct spwd** spbufp)
    {
        *spbufp = nullptr;

        if (!f)
        {
            f = fopen("/etc/shadow", "r");
            if (!f) return -1;
            fcntl(fileno(f), F_SETFD, FD_CLOEXEC);
        }

        return fgetspent_r(f, spbuf, buf, buflen, spbufp);
    }

    int fgetspent_r(FILE* stream, struct spwd* spbuf, char* buf, size_t buflen, struct spwd** spbufp)
    {
        *spbufp = nullptr;

        while (true)
        {
            char* rc = fgets(buf, buflen, stream);
            if (!rc) return -1;

            char* name = _strtok_once(rc, ":\n");
            if (!name) continue;

            char* passwd = _strtok_once(nullptr, ":\n");
            if (!passwd) continue;

            char* lstchg = _strtok_once(nullptr, ":\n");
            if (!lstchg) continue;

            char* min = _strtok_once(nullptr, ":\n");
            if (!min) continue;

            char* max = _strtok_once(nullptr, ":\n");
            if (!max) continue;

            char* warn = _strtok_once(nullptr, ":\n");
            if (!warn) continue;

            char* inact = _strtok_once(nullptr, ":\n");
            if (!inact) continue;

            char* expire = _strtok_once(nullptr, ":\n");
            if (!expire) continue;

            char* flag = _strtok_once(nullptr, ":\n");
            if (!flag) continue;

            spbuf->sp_namp = name;
            spbuf->sp_pwdp = passwd;
            spbuf->sp_lstchg = (long)strtol(lstchg, nullptr, 10);
            spbuf->sp_min = (long)strtol(min, nullptr, 10);
            spbuf->sp_max = (long)strtol(max, nullptr, 10);
            spbuf->sp_warn = (long)strtol(warn, nullptr, 10);
            spbuf->sp_inact = (long)strtol(inact, nullptr, 10);
            spbuf->sp_expire = (long)strtol(expire, nullptr, 10);
            spbuf->sp_flag = (unsigned long)strtoul(flag, nullptr, 10);

            *spbufp = spbuf;
            return 0;
        }
    }

    struct spwd* getspnam(const char* name)
    {
        setspent();

        struct spwd* entry;

        while ((entry = getspent()))
        {
            if (!strcmp(entry->sp_namp, name)) { return entry; }
        }

        return entry;
    }

    void setspent()
    {
        if (f) rewind(f);
    }

    void endspent()
    {
        if (f)
        {
            fclose(f);
            f = nullptr;
        }
    }
}