"""User existence and attribute probes."""

import pwd
import grp


def user_exists(username: str) -> bool:
    """Check if a system user exists."""
    try:
        pwd.getpwnam(username)
        return True
    except KeyError:
        return False


def user_uid(username: str) -> int | None:
    try:
        return pwd.getpwnam(username).pw_uid
    except KeyError:
        return None

def user_gid(username: str) -> int | None:
    try:
        return pwd.getpwnam(username).pw_gid
    except KeyError:
        return None

def user_in_group(username: str, groupname: str) -> bool:
    """Check if a user is a member of a group."""
    try:
        group = grp.getgrnam(groupname)
        return username in group.gr_mem
    except KeyError:
        return False


def user_shell(username: str) -> str | None:
    try:
        return pwd.getpwnam(username).pw_shell
    except KeyError:
        return None