from django.dispatch import receiver
from django.db.models.signals import post_save, post_delete, m2m_changed
from django.contrib.auth import get_user_model
from django.conf import settings
from .ldap_sync import make_ldap_conn, LDAPUserEntry, LDAPUserSyncer

User = get_user_model()

def synchronous_user_sync(user, remove=False):
    sync_enabled = getattr(settings, 'BAM_LDAP_SYNCHRONOUS_SYNC_ENABLED', True)
    if sync_enabled:
        uri = settings.BAM_LDAP_URI
        bind_dn = settings.BAM_LDAP_BIND_DN
        secret = settings.BAM_LDAP_SECRET
        base_dn_map = settings.BAM_LDAP_BASE_DN_MAP
        ldap_conn = make_ldap_conn(uri, bind_dn, secret)

        try:
            syncer = LDAPUserSyncer(ldap_conn, base_dn_map)
            if remove:
                syncer.remove_user(user)
            else:
                syncer.sync_user(user)
        finally:
            ldap_conn.unbind_s()

@receiver(post_save, sender=User)
def handle_user_save(sender, instance, created, raw, using, update_fields,
                     **kwargs):
    relevant_fields = LDAPUserEntry.get_mapped_fields()
    if update_fields is None or not update_fields.isdisjoint(relevant_fields):
        synchronous_user_sync(instance)

@receiver(post_delete, sender=User)
def handle_user_delete(sender, instance, **kwargs):
    synchronous_user_sync(instance, remove=True)

@receiver(m2m_changed, sender=User.groups.through)
def handle_user_groups_change(sender, instance, action, **kwargs):
    if action in ('post_add', 'post_remove'):
        synchronous_user_sync(instance)