import logging
import os
import shutil

from django.conf import settings as conf
from django.contrib.auth.models import Group, Permission, User
from django.db import transaction
from django.db.models import signals, F
from django.db.models.functions import Concat, Substr
from django.dispatch import receiver
from django.utils import timezone as tz

from aircox import utils
from aircox.conf import settings
from .article import Article
from .diffusion import Diffusion
from .episode import Episode
from .page import Page
from .program import Program
from .schedule import Schedule
from .sound import Sound


logger = logging.getLogger("aircox")


# Add a default group to a user when it is created. It also assigns a list
# of permissions to the group if it is created.
#
# - group name: settings.AIRCOX_DEFAULT_USER_GROUP
# - group permissions: settings.AIRCOX_DEFAULT_USER_GROUP_PERMS
#
@receiver(signals.post_save, sender=User)
def user_default_groups(sender, instance, created, *args, **kwargs):
    """Set users to different default groups."""
    if not created or instance.is_superuser:
        return

    for group_name, permissions in settings.DEFAULT_USER_GROUPS.items():
        if instance.groups.filter(name=group_name).count():
            continue

        group, created = Group.objects.get_or_create(name=group_name)
        if created and permissions:
            for codename in permissions:
                permission = Permission.objects.filter(codename=codename).first()
                if permission:
                    group.permissions.add(permission)
            group.save()
        instance.groups.add(group)


# ---- page
@receiver(signals.post_save, sender=Page)
def page_post_save__child_page_defaults(sender, instance, created, *args, **kwargs):
    initial_cover = getattr(instance, "__initial_cover", None)
    if initial_cover is None and instance.cover is not None:
        Episode.objects.filter(parent=instance, cover__isnull=True).update(cover=instance.cover)
        Article.objects.filter(parent=instance, cover__isnull=True).update(cover=instance.cover)


# ---- program
@receiver(signals.post_save, sender=Program)
def program_post_save__clean_later_episodes(sender, instance, created, *args, **kwargs):
    if not instance.active:
        Diffusion.objects.program(instance).after(tz.now()).delete()
        Episode.objects.parent(instance).filter(diffusion__isnull=True).delete()


@receiver(signals.post_save, sender=Program)
def program_post_save__mv_sounds(sender, instance, created, *args, **kwargs):
    path_ = getattr(instance, "__initial_path", None)
    if path_ in (None, instance.path):
        return

    abspath = path_ and os.path.join(conf.MEDIA_ROOT, path_)
    if os.path.exists(abspath) and not os.path.exists(instance.abspath):
        logger.info(
            f"program #{instance.pk}'s dir changed to {instance.title} - update it.", instance.id, instance.title
        )

        shutil.move(abspath, instance.abspath)
        Sound.objects.filter(path__startswith=path_).update(file=Concat("file", Substr(F("file"), len(path_))))


# ---- schedule
@receiver(signals.pre_save, sender=Schedule)
def schedule_pre_save(sender, instance, *args, **kwargs):
    if getattr(instance, "pk") is not None and "raw" not in kwargs:
        instance._initial = Schedule.objects.get(pk=instance.pk)


@receiver(signals.post_save, sender=Schedule)
def schedule_post_save(sender, instance, created, *args, **kwargs):
    """Handles Schedule's time, duration and timezone changes and update
    corresponding diffusions accordingly."""
    initial = getattr(instance, "_initial", None)
    if not initial or (
        (instance.time, instance.duration, instance.timezone) == (initial.time, initial.duration, initial.timezone)
    ):
        return

    today = tz.datetime.today()
    delta = instance.normalize(today) - initial.normalize(today)
    duration = utils.to_timedelta(instance.duration)
    with transaction.atomic():
        qs = Diffusion.objects.filter(schedule=instance).after(tz.now())
        for diffusion in qs:
            diffusion.start = diffusion.start + delta
            diffusion.end = diffusion.start + duration
            diffusion.save()


@receiver(signals.pre_delete, sender=Schedule)
def schedule_pre_delete(sender, instance, *args, **kwargs):
    """Delete later corresponding diffusion to a changed schedule."""
    Diffusion.objects.filter(schedule=instance).after(tz.now()).delete()
    Episode.objects.filter(diffusion__isnull=True, content__isnull=True, episodesound__isnull=True).delete()


# ---- diffusion
@receiver(signals.post_delete, sender=Diffusion)
def diffusion_post_delete(sender, instance, *args, **kwargs):
    Episode.objects.filter(diffusion__isnull=True, content__isnull=True, episodesound__isnull=True).delete()


# ---- files
@receiver(signals.post_delete, sender=Sound)
def delete_file(sender, instance, *args, **kwargs):
    """Deletes file on `post_delete`"""
    if not instance.file:
        return

    path = instance.file.path
    qs = sender.objects.filter(file=path)
    if not qs.exists() and os.path.exists(path):
        os.remove(path)