#!/usr/bin/python3
#
# This file is part of FreedomBox.
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU Affero General Public License as
# published by the Free Software Foundation, either version 3 of the
# License, or (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU Affero General Public License for more details.
#
# You should have received a copy of the GNU Affero General Public License
# along with this program.  If not, see <http://www.gnu.org/licenses/>.
#
"""
Configuration helper for the LDAP user directory
"""

import argparse
import augeas
import os
import re
import shutil
import subprocess
import sys

from plinth import action_utils

ACCESS_CONF = '/etc/security/access.conf'
LDAPSCRIPTS_CONF = '/etc/ldapscripts/freedombox-ldapscripts.conf'


def parse_arguments():
    """Return parsed command line arguments as dictionary"""
    parser = argparse.ArgumentParser()
    subparsers = parser.add_subparsers(dest='subcommand', help='Sub command')

    subparsers.add_parser('first-setup', help='Perform initial setup of LDAP')
    subparsers.add_parser('setup', help='Setup LDAP')

    subparser = subparsers.add_parser('create-user',
                                      help='Create an LDAP user')
    subparser.add_argument('username', help='Name of the LDAP user to create')

    subparser = subparsers.add_parser('remove-user',
                                      help='Delete an LDAP user')
    subparser.add_argument('username', help='Name of the LDAP user to delete')

    subparser = subparsers.add_parser('rename-user',
                                      help='Rename an LDAP user')
    subparser.add_argument('oldusername', help='Old name of the LDAP user')
    subparser.add_argument('newusername', help='New name of the LDAP user')

    subparser = subparsers.add_parser('set-user-password',
                                      help='Set the password of an LDAP user')
    subparser.add_argument(
        'username', help='Name of the LDAP user to set the password for')

    subparser = subparsers.add_parser('create-group',
                                      help='Create an LDAP group')
    subparser.add_argument('groupname',
                           help='Name of the LDAP group to create')

    subparser = subparsers.add_parser('remove-group',
                                      help='Delete an LDAP group')
    subparser.add_argument('groupname',
                           help='Name of the LDAP group to delete')

    subparser = subparsers.add_parser(
        'get-user-groups', help='Get all the LDAP groups for an LDAP user')
    subparser.add_argument('username',
                           help='LDAP user to retrieve the groups for')

    subparser = subparsers.add_parser('add-user-to-group',
                                      help='Add an LDAP user to an LDAP group')
    subparser.add_argument('username', help='LDAP user to add to group')
    subparser.add_argument('groupname', help='LDAP group to add the user to')

    subparser = subparsers.add_parser(
        'remove-user-from-group',
        help='Remove an LDAP user from an LDAP group')
    subparser.add_argument('username', help='LDAP user to remove from group')
    subparser.add_argument('groupname',
                           help='LDAP group to remove the user from')

    help_get_group_users = 'Get the list of all users in an LDAP group'
    subparser = subparsers.add_parser('get-group-users',
                                      help=help_get_group_users)
    subparser.add_argument(
        'groupname', help='name of the LDAP group to get the '
        'list of users')

    subparsers.required = True
    return parser.parse_args()


def subcommand_first_setup(_):
    """Perform initial setup of LDAP."""
    # Avoid reconfiguration of slapd during module upgrades, because
    # this will move the existing database.
    # XXX: Instead of a separate action that is conditionally called for a
    # version number, we can check if the domain currently configured is what
    # we want and then based on the value do a reconfiguration. This approach
    # will work better when FreedomBox state is reset etc.
    action_utils.dpkg_reconfigure('slapd', {'domain': 'thisbox'})


def subcommand_setup(_):
    """Setup LDAP."""
    # Update pam configs for access and mkhomedir.
    subprocess.run(['pam-auth-update', '--package'], check=True)

    configure_ldapscripts()

    configure_ldap_authentication()

    configure_ldap_structure()


def configure_ldap_authentication():
    """Configure LDAP authentication."""
    action_utils.dpkg_reconfigure('nslcd', {
        'ldap-uris': 'ldapi:///',
        'ldap-base': 'dc=thisbox',
        'ldap-auth-type': 'SASL',
        'ldap-sasl-mech': 'EXTERNAL'
    })
    action_utils.dpkg_reconfigure('libnss-ldapd',
                                  {'nsswitch': 'group, passwd, shadow'})
    action_utils.service_restart('nscd')

    # XXX: Workaround for login issue
    action_utils.service_enable('slapd')
    action_utils.service_start('slapd')
    action_utils.service_enable('nslcd')
    action_utils.service_start('nslcd')


def configure_ldap_structure():
    """Configure LDAP basic structure."""
    was_running = action_utils.service_is_running('slapd')
    if not was_running:
        action_utils.service_start('slapd')

    setup_admin()
    create_organizational_unit('users')
    create_organizational_unit('groups')


def create_organizational_unit(unit):
    """Create an organizational unit in LDAP."""
    distinguished_name = 'ou={unit},dc=thisbox'.format(unit=unit)
    try:
        subprocess.run([
            'ldapsearch', '-Q', '-Y', 'EXTERNAL', '-H', 'ldapi:///', '-s',
            'base', '-b', distinguished_name, '(objectclass=*)'
        ], stdout=subprocess.DEVNULL, check=True)
        return  # Already exists
    except subprocess.CalledProcessError:
        input = '''
dn: ou={unit},dc=thisbox
objectClass: top
objectClass: organizationalUnit
ou: {unit}'''.format(unit=unit)
        subprocess.run(['ldapadd', '-Q', '-Y', 'EXTERNAL', '-H',
                        'ldapi:///'], input=input.encode(),
                       stdout=subprocess.DEVNULL, check=True)


def setup_admin():
    """Remove LDAP admin password and Allow root to modify the users."""
    process = subprocess.run([
        'ldapsearch', '-Q', '-L', '-L', '-L', '-Y', 'EXTERNAL', '-H',
        'ldapi:///', '-s', 'base', '-b', 'olcDatabase={1}mdb,cn=config',
        '(objectclass=*)', 'olcRootDN', 'olcRootPW'
    ], check=True, stdout=subprocess.PIPE)
    ldap_object = {}
    for line in process.stdout.decode().splitlines():
        if line:
            line = line.split(':')
            ldap_object[line[0]] = line[1]

    if 'olcRootPW' in ldap_object:
        subprocess.run(
            ['ldapmodify', '-Q', '-Y', 'EXTERNAL', '-H',
             'ldapi:///'], check=True, stdout=subprocess.DEVNULL, input=b'''
dn: olcDatabase={1}mdb,cn=config
changetype: modify
delete: olcRootPW''')

    root_dn = 'gidNumber=0+uidNumber=0,cn=peercred,cn=external,cn=auth'
    if ldap_object['olcRootDN'] != root_dn:
        subprocess.run(
            ['ldapmodify', '-Q', '-Y', 'EXTERNAL', '-H',
             'ldapi:///'], check=True, stdout=subprocess.DEVNULL, input=b'''
dn: olcDatabase={1}mdb,cn=config
changetype: modify
replace: olcRootDN
olcRootDN: gidNumber=0+uidNumber=0,cn=peercred,cn=external,cn=auth
''')


def configure_ldapscripts():
    """Set the configuration used by ldapscripts for later user management."""
    # modify a copy of the config file
    shutil.copy('/etc/ldapscripts/ldapscripts.conf', LDAPSCRIPTS_CONF)

    aug = augeas.Augeas(
        flags=augeas.Augeas.NO_LOAD + augeas.Augeas.NO_MODL_AUTOLOAD)
    aug.set('/augeas/load/Shellvars/lens', 'Shellvars.lns')
    aug.set('/augeas/load/Shellvars/incl[last() + 1]', LDAPSCRIPTS_CONF)
    aug.load()

    # XXX: Password setting on users is disabled as changing passwords
    # using SASL Auth is not supported.
    aug.set('/files' + LDAPSCRIPTS_CONF + '/SERVER', '"ldapi://"')
    aug.set('/files' + LDAPSCRIPTS_CONF + '/SASLAUTH', '"EXTERNAL"')
    aug.set('/files' + LDAPSCRIPTS_CONF + '/SUFFIX', '"dc=thisbox"')
    aug.set('/files' + LDAPSCRIPTS_CONF + '/USUFFIX', '"ou=Users"')
    aug.set('/files' + LDAPSCRIPTS_CONF + '/GSUFFIX', '"ou=Groups"')
    aug.set('/files' + LDAPSCRIPTS_CONF + '/PASSWORDGEN', '"true"')
    aug.save()


def read_password():
    """Read the password from stdin."""
    return ''.join(sys.stdin)


def subcommand_create_user(arguments):
    """Create an LDAP user, set password and flush cache."""
    _run(['ldapadduser', arguments.username, 'users'])
    set_user_password(arguments.username, read_password())
    flush_cache()


def subcommand_remove_user(arguments):
    """Remove an LDAP user."""
    username = arguments.username
    groups = get_user_groups(username)

    for group in groups:
        remove_user_from_group(username, group)

    _run(['ldapdeleteuser', username])
    flush_cache()


def subcommand_rename_user(arguments):
    """Rename an LDAP user."""
    old_username = arguments.oldusername
    new_username = arguments.newusername
    groups = get_user_groups(old_username)

    for group in groups:
        remove_user_from_group(old_username, group)

    _run(['ldaprenameuser', old_username, new_username])

    for group in groups:
        add_user_to_group(new_username, group)

    flush_cache()


def set_user_password(username, password):
    """Set a user's password."""
    process = _run(['slappasswd', '-s', password], stdout=subprocess.PIPE)
    password = process.stdout.decode().strip()
    _run(['ldapsetpasswd', username, password])


def subcommand_set_user_password(arguments):
    """Set a user's password."""
    set_user_password(arguments.username, read_password())


def get_user_groups(username):
    """Returns only the supplementary groups of the given user.

    Exclude the 'users' primary group from the returned list."""
    process = _run(['ldapid', username], stdout=subprocess.PIPE, check=False)
    output = process.stdout.decode().strip()
    if output:
        groups_part = output.split(' ')[2]
        groups = groups_part.split('=')[1]
        group_names = [
            user.strip('()') for user in re.findall('\(.*?\)', groups)
        ]
        group_names.remove('users')
        return group_names

    return []


def subcommand_get_user_groups(arguments):
    """Return list of a given user's groups."""
    groups = get_user_groups(arguments.username)
    if groups:
        print(*groups, sep='\n')


def group_exists(groupname):
    """Return whether a group already exits."""
    process = _run(['ldapgid', groupname], check=False)
    return process.returncode == 0


def create_group(groupname):
    """Add an LDAP group."""
    if not group_exists(groupname):
        _run(['ldapaddgroup', groupname])


def subcommand_create_group(arguments):
    """Add an LDAP group."""
    create_group(arguments.groupname)
    flush_cache()


def subcommand_remove_group(arguments):
    """Remove an LDAP group."""
    if group_exists(arguments.groupname):
        _run(['ldapdeletegroup', arguments.groupname])

    flush_cache()


def add_user_to_group(username, groupname):
    """Add an LDAP user to an LDAP group."""
    create_group(groupname)
    _run(['ldapaddusertogroup', username, groupname])


def subcommand_add_user_to_group(arguments):
    """Add an LDAP user to an LDAP group."""
    add_user_to_group(arguments.username, arguments.groupname)
    flush_cache()


def remove_user_from_group(username, groupname):
    """Remove an LDAP user from an LDAP group."""
    _run(['ldapdeleteuserfromgroup', username, groupname])


def subcommand_remove_user_from_group(arguments):
    """Remove an LDAP user from an LDAP group."""
    remove_user_from_group(arguments.username, arguments.groupname)
    flush_cache()


def subcommand_get_group_users(arguments):
    """ Get the list of users of an LDAP group."""
    process = _run(['ldapgid', '-P', arguments.groupname],
                   stdout=subprocess.PIPE)
    output = process.stdout.decode()
    users = output.rsplit(':')[-1]
    if users:
        for user in users.strip().split(','):
            print(user)


def flush_cache():
    """Flush nscd cache."""
    _run(['nscd', '--invalidate=passwd'])
    _run(['nscd', '--invalidate=group'])


def _run(arguments, **kwargs):
    """Run a command. Check return code and suppress output by default."""
    env = dict(os.environ, LDAPSCRIPTS_CONF=LDAPSCRIPTS_CONF)
    kwargs['stdout'] = kwargs.get('stdout', subprocess.DEVNULL)
    kwargs['stderr'] = kwargs.get('stderr', subprocess.DEVNULL)
    kwargs['check'] = kwargs.get('check', True)
    return subprocess.run(arguments, env=env, **kwargs)


def main():
    """Parse arguments and perform all duties"""
    arguments = parse_arguments()

    subcommand = arguments.subcommand.replace('-', '_')
    subcommand_method = globals()['subcommand_' + subcommand]

    subcommand_method(arguments)


if __name__ == '__main__':
    main()