"""
This module defines `Celery`_ tasks to manage LDAP entities.

.. _Celery: http://www.celeryproject.org/

"""

from __future__ import absolute_import

from copy import deepcopy
from django.core.exceptions import ObjectDoesNotExist
from celery import shared_task
from celery.utils.log import get_task_logger
from celery.exceptions import Reject

from ldapentities.models import (
    LdapGroup,
    LdapUser,
)


_LOGGER = get_task_logger(__name__)


@shared_task
def create_ldap_group(groupname, gid, description):
    """
    This task creates an :py:class:`LDAP group <ldapentities.models.LdapGroup>`
    if it does not exist yet.

    If a group with the given name exists its group id and description
    attributes are updated.

    :param str groupname: the group name
    :param int gid: the group id
    :param str description: description text for the group
    :return: dictionary containing groupname, gid, description and
        :py:const:`group_dn` set to the distinguished name of the newly created
        or existing LDAP group
    :rtype: dict

    """
    try:
        ldapgroup = LdapGroup.objects.get(name=groupname)
        _LOGGER.info(
            'LDAP group %s with groupname %s already exists',
            ldapgroup.dn, groupname)
        ldapgroup.gid = gid
    except LdapGroup.DoesNotExist:
        ldapgroup = LdapGroup(gid=gid, name=groupname)
        _LOGGER.info('created LDAP group %s', ldapgroup.dn)
    ldapgroup.description = description
    ldapgroup.save()
    _LOGGER.info('set description of LDAP group %s', ldapgroup.dn)
    return {
        'groupname': groupname,
        'gid': gid,
        'description': description,
        'group_dn': ldapgroup.dn,
    }


@shared_task
def create_ldap_user(username, uid, gid, gecos, homedir, shell, password):
    """
    This task creates an :py:class:`LDAP user <ldapentities.models.LdapUser>`
    if it does not exist yet.

    The task is rejected if the primary group of the user is not defined.

    The user's fields are updated if the user already exists.

    :param str username: the user name
    :param int uid: the user id
    :param int gid: the user's primary group's id
    :param str gecos: the text for the GECOS field
    :param str homedir: the user's home directory
    :param str shell: the user's login shell
    :param str or None password: the clear text password, if :py:const:`None`
        is passed the password is not touched
    :raises celery.exceptions.Reject: if the specified primary group does not
        exist
    :return: dictionary containing username, uid, gid, gecos, homedir, shell,
        password and :py:const:`user_dn` set to the distinguished name of the
        newly created or existing LDAP user
    :rtype: dict

    """
    try:
        ldapuser = LdapUser.objects.get(username=username)
        _LOGGER.info(
            'LDAP user %s with username %s already exists',
            ldapuser.dn, username)
    except LdapUser.DoesNotExist:
        ldapuser = LdapUser(username=username)
    try:
        ldapgroup = LdapGroup.objects.get(gid=gid)
    except ObjectDoesNotExist as exc:
        _LOGGER.error('LDAP group with gid %d does not exist', gid)
        raise Reject(exc, requeue=False)
    ldapuser.uid = uid
    ldapuser.group = gid
    ldapuser.gecos = gecos
    ldapuser.home_directory = homedir
    ldapuser.login_shell = shell
    ldapuser.username = username
    ldapuser.common_name = username
    if password is not None:
        ldapuser.set_password(password)
        _LOGGER.info('set password for LDAP user %s', ldapuser.dn)
    ldapuser.save()
    _LOGGER.info('LDAP user %s created', ldapuser.dn)
    if ldapuser.username in ldapgroup.members:
        _LOGGER.info(
            'LDAP user %s is already member of LDAP group %s',
            ldapuser.dn, ldapgroup.dn)
    else:
        ldapgroup.members.append(ldapuser.username)
        ldapgroup.save()
        _LOGGER.info(
            'LDAP user %s has been added to LDAP group %s',
            ldapuser.dn, ldapgroup.dn)
    return {
        'username': username,
        'uid': uid,
        'gid': gid,
        'gecos': gecos,
        'homedir': homedir,
        'shell': shell,
        'user_dn': ldapuser.dn,
    }


@shared_task
def set_ldap_user_password(username, password):
    """
    This task sets the password of an existing :py:class:`LDAP user
    <ldapentities.models.LdapUser>`.

    :param str username: the user name
    :param str password: teh clear text password
    :return: dictionary containing the username and a flag
        :py:const:`password_set` that is set to  :py:const:`True` if the
        password has been set, :py:const:`False` if the user does not exist.
    :rtype: dict

    """
    retval = {'username': username, 'password_set': False}
    try:
        ldapuser = LdapUser.objects.get(username=username)
    except LdapUser.DoesNotExist:
        _LOGGER.info('there is no LDAP user with username %s', username)
        return retval
    ldapuser.set_password(password)
    ldapuser.save()
    _LOGGER.info("set new password for LDAP user %s", ldapuser.dn)
    retval['password_set'] = True
    return retval


@shared_task(bind=True)
def add_ldap_user_to_group(self, username, groupname):
    """
    This task adds the specified user to the given group.

    This task does nothing if the user is already member of the group.

    :param str username: the user name
    :param str groupname: the group name
    :raises celery.exceptions.Retry: if the user does not exist yet,
        :py:func:`create_ldap_user` should be called before
    :return: dictionary containing the username, groupname and a flag
        :py:const`added` that is as a :py:const:`True` if the user has been
        added to the group otherwise to :py:const:`False`
    :rtype: dict

    """
    retval = {'username': username, 'groupname': groupname, 'added': False}
    try:
        ldapgroup = LdapGroup.objects.get(name=groupname)
        ldapuser = LdapUser.objects.get(username=username)
    except LdapGroup.DoesNotExist:
        _LOGGER.error('LDAP group with groupname %s does not exist', groupname)
    except LdapUser.DoesNotExist as exc:
        _LOGGER.error('LDAP user with username %s does not exist', username)
        self.retry(exc=exc, time_limit=5)
    else:
        if ldapuser.username not in ldapgroup.members:
            ldapgroup.members.append(ldapuser.username)
            ldapgroup.save()
            _LOGGER.info(
                'LDAP user %s has been added to LDAP group %s',
                ldapuser.username, ldapgroup.dn)
        else:
            _LOGGER.info(
                'LDAP user %s is already in LDAP group %s',
                ldapuser.username, ldapgroup.dn)
        retval['added'] = True
    return retval


@shared_task
def remove_ldap_user_from_group(username, groupname):
    """
    This task removes the given user from the given group.

    :param str username: the user name
    :param str groupname: the group name
    :return: dictionary containing the input parameters and a flag
        :py:const:`removed` that is set to :py:const:`True` if the user has
        been removed, False otherwise
    :rtype: dict

    """
    retval = {'username': username, 'groupname': groupname, 'removed': False}
    try:
        ldapgroup = LdapGroup.objects.get(name=groupname)
        ldapuser = LdapUser.objects.get(username=username)
    except LdapGroup.DoesNotExist:
        _LOGGER.error('LDAP group with groupname %s does not exist', groupname)
    except LdapUser.DoesNotExist:
        _LOGGER.error('LDAP user with username %s does not exist', username)
    else:
        if ldapuser.username in ldapgroup.members:
            ldapgroup.members.remove(ldapuser.username)
            _LOGGER.info(
                'removed LDAP user %s from LDAP group %s',
                ldapuser.dn, ldapgroup.dn)
            ldapgroup.save()
            retval['removed'] = True
        else:
            _LOGGER.info(
                'LDAP user %s is not a member of LDAP group %s',
                ldapuser.dn, ldapgroup.dn)
    return retval


@shared_task
def delete_ldap_user(username, *args, **kwargs):
    """
    This task deletes the given user.

    :param str username: the user name
    :return: dictionary containing the username and a flag :py:const:`deleted`
        that is set to :py:const:`True` if the user has been deleted and is set
        to :py:const:`False` otherwise
    :rtype: dict

    .. note::

        This variant can only be used at the beginning of a Celery task chain
        or as a standalone task.

        Use :py:func:`ldaptasks.tasks.delete_ldap_user_chained` at other
        positions in the task chain

    """
    retval = {'username': username, 'deleted': False}
    try:
        ldapuser = LdapUser.objects.get(username=username)
    except LdapUser.DoesNotExist:
        _LOGGER.info('there is no LDAP user with username %s', username)
    else:
        try:
            ldapgroup = LdapGroup.objects.get(gid=ldapuser.group)
        except LdapGroup.DoesNotExist:
            _LOGGER.info(
                'LDAP group %s of LDAP user %s does not exist',
                ldapuser.group, ldapuser.dn)
        else:
            if ldapuser.username in ldapgroup.members:
                ldapgroup.members.remove(ldapuser.username)
                ldapgroup.save()
                _LOGGER.info(
                    'removed LDAP user %s from LDAP group %s',
                    ldapuser.dn, ldapgroup.dn)
        userdn = ldapuser.dn
        ldapuser.delete()
        _LOGGER.info('deleted LDAP user %s', userdn)
        retval['deleted'] = True
    return retval


@shared_task
def delete_ldap_user_chained(previous_result, *args, **kwargs):
    """
    This task deletes the given user.

    :param dict previous_result: a dictionary describing the result of the
        previous step in the Celery task chain. This dictionary must contain a
        :py:const:`username` key
    :return: a copy of the :py:obj:`previous_result` dictionary with a new
        :py:const:`deleted` key set to :py:const:`True` if the user has been
        deleted and set to :py:const:`False` otherwise
    :rtype: dict

    """
    username = previous_result['username']
    retval = deepcopy(previous_result)
    retval.update(delete_ldap_user(username))
    return retval


@shared_task
def delete_ldap_group_if_empty(groupname):
    """
    This task deletes the given group if it is empty.

    :param str groupname: the group name
    :return: dictionary that contains the groupname and a flag
        :py:const:`deleted` that is set to :py:const:`True` if the group has
        been deleted and is set to :py:const:`False` otherwise
    :rtype: dict

    """
    retval = {'groupname': groupname, 'deleted': False}
    try:
        ldapgroup = LdapGroup.objects.get(name=groupname)
    except LdapGroup.DoesNotExist:
        _LOGGER.info('LDAP group with groupname %s does not exist', groupname)
    else:
        if len(ldapgroup.members) == 0:
            groupdn = ldapgroup.dn
            ldapgroup.delete()
            _LOGGER.info(
                'deleted LDAP group %s', groupdn)
            retval['deleted'] = True
        else:
            _LOGGER.info(
                'LDAP group %s has not been deleted. It still has %d members',
                ldapgroup.dn, len(ldapgroup.members))
    return retval


@shared_task
def delete_ldap_group(groupname):
    """
    This task deletes the given group.

    :param str groupname: the group name
    :return: dictionary that contains the groupname and a flag
        :py:const:`deleted` that is set to :py:const:`True` if the group has
        been deleted and is set to :py:const:`False` otherwise
    :rtype: dict

    """
    retval = {'groupname': groupname, 'deleted': False}
    try:
        ldapgroup = LdapGroup.objects.get(name=groupname)
    except LdapGroup.DoesNotExist:
        _LOGGER.info('LDAP group with name %s does not exist', groupname)
    else:
        groupdn = ldapgroup.dn
        ldapgroup.delete()
        _LOGGER.info('deleted LDAP group %s', groupdn)
        retval['deleted'] = True
    return retval