#include <pwd.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

static struct passwd pwd;
static FILE* f { nullptr };
static char buf[4096];

extern "C"
{
    struct passwd* getpwent()
    {
        if (!f)
        {
            f = fopen("/etc/passwd", "r");
            if (!f) return nullptr;
        }

        while (true)
        {
            char* rc = fgets(buf, sizeof(buf), f);
            if (!rc) return nullptr;

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

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

            char* uid = strtok(nullptr, ":\n");
            if (!uid) continue;

            char* gid = strtok(nullptr, ":\n");
            if (!gid) continue;

            char* gecos = strtok(nullptr, ":\n");
            if (!gecos) continue;

            char* dir = strtok(nullptr, ":\n");
            if (!dir) continue;

            char* shell = strtok(nullptr, ":\n");
            if (!shell) continue;

            pwd.pw_name = name;
            pwd.pw_passwd = passwd;
            pwd.pw_uid = (uid_t)strtoul(uid, NULL, 10);
            pwd.pw_gid = (gid_t)strtoul(gid, NULL, 10);
            pwd.pw_gecos = gecos;
            pwd.pw_dir = dir;
            pwd.pw_shell = shell;

            return &pwd;
        }
    }

    struct passwd* getpwnam(const char* name)
    {
        setpwent();

        struct passwd* entry;

        while ((entry = getpwent()))
        {
            if (!strcmp(entry->pw_name, name))
            {
                endpwent();
                return entry;
            }
        }

        endpwent();
        return entry;
    }

    struct passwd* getpwuid(uid_t uid)
    {
        setpwent();

        struct passwd* entry;

        while ((entry = getpwent()))
        {
            if (entry->pw_uid == uid)
            {
                endpwent();
                return entry;
            }
        }

        endpwent();
        return entry;
    }

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

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