"""
User management for tljh.

Supports minimal user & group management
"""
import pwd
import grp
import subprocess


def ensure_user(username):
    """
    Make sure a given user exists
    """
    # Check if user exists
    try:
        pwd.getpwnam(username)
        # User exists, nothing to do!
        return
    except KeyError:
        # User doesn't exist, time to create!
        pass

    subprocess.check_call([
        'useradd',
        username
    ])


def remove_user(username):
    """
    Remove user from system if exists
    """
    try:
        pwd.getpwnam(username)
    except KeyError:
        # User doesn't exist, nothing to do
        return

    subprocess.check_call([
        'deluser',
        '--quiet',
        username
    ])


def ensure_group(groupname):
    """
    Ensure given group exists
    """
    subprocess.check_call([
        'groupadd',
        '--force',
        groupname
    ])


def remove_group(groupname):
    """
    Remove user from system if exists
    """
    try:
        grp.getgrnam(groupname)
    except KeyError:
        # Group doesn't exist, nothing to do
        return

    subprocess.check_call([
        'delgroup',
        '--quiet',
        groupname
    ])


def ensure_user_group(username, groupname):
    """
    Ensure given user is member of given group

    Group and User must already exist.
    """
    group = grp.getgrnam(groupname)
    if username in group.gr_mem:
        return

    subprocess.check_call([
        'usermod',
        '--append',
        '--groups',
        groupname,
        username
    ])


def remove_user_group(username, groupname):
    """
    Ensure given user is *not* a member of given group
    """
    group = grp.getgrnam(groupname)
    if username not in group.gr_mem:
        return

    subprocess.check_call([
        'deluser',
        '--quiet',
        username,
        groupname
    ])