#!/usr/bin/python3
# -*- mode: python -*-
#
# This file is part of Plinth.
#
# 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 subprocess

import augeas
from plinth import action_utils

ACCESS_CONF = '/etc/security/access.conf'
LDAPSCRIPTS_CONF = '/etc/ldapscripts/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(
        'pre-install',
        help='Preseed debconf values before packages are installed')
    subparsers.add_parser('setup', help='Setup LDAP')

    return parser.parse_args()


def subcommand_pre_install(_):
    """Preseed debconf values before packages are installed."""
    subprocess.run(
        ['debconf-set-selections'],
        input=b'slapd slapd/domain string thisbox',
        check=True)
    subprocess.run(
        ['debconf-set-selections'],
        input=b'nslcd nslcd/ldap-uris string "ldapi:///"',
        check=True)
    subprocess.run(
        ['debconf-set-selections'],
        input=b'nslcd nslcd/ldap-base string "dc=thisbox"',
        check=True)
    subprocess.run(
        ['debconf-set-selections'],
        input=b'nslcd nslcd/ldap-auth-type select SASL',
        check=True)
    subprocess.run(
        ['debconf-set-selections'],
        input=b'nslcd nslcd/ldap-sasl-mech select EXTERNAL',
        check=True)
    subprocess.run(
        ['debconf-set-selections'],
        input=b'libnss-ldapd libnss-ldapd/nsswitch multiselect '
        b'group, passwd, shadow',
        check=True)


def subcommand_setup(_):
    """Setup LDAP."""
    configure_access_conf()

    # Update pam configs for access and mkhomedir.
    subprocess.run(['pam-auth-update', '--package'], check=True)

    configure_ldapscripts()

    configure_slapd()


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

    try:
        setup_admin()
        create_organizational_unit('users')
        create_organizational_unit('groups')
    finally:
        if not was_running:
            action_utils.service_stop('slapd')


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_access_conf():
    """Restrict console login to users in admin or sudo group."""
    with open(ACCESS_CONF, 'r') as conffile:
        lines = conffile.readlines()

    for line in lines:
        if '-:ALL EXCEPT root fbx (admin) (sudo):ALL' in line:
            return

    with open(ACCESS_CONF, 'a') as conffile:
        conffile.write('-:ALL EXCEPT root fbx (admin) (sudo):ALL\n')


def configure_ldapscripts():
    """Set the configuration used by ldapscripts for later user management."""
    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 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()