#
# Copyright 2023 © AE UTBM
# ae@utbm.fr / ae.info@utbm.fr
#
# This file is part of the website of the UTBM Student Association (AE UTBM),
# https://ae.utbm.fr.
#
# You can find the source code of the website at https://github.com/ae-utbm/sith
#
# LICENSED UNDER THE GNU GENERAL PUBLIC LICENSE VERSION 3 (GPLv3)
# SEE : https://raw.githubusercontent.com/ae-utbm/sith/master/LICENSE
# OR WITHIN THE LOCAL FILE "LICENSE"
#
#

from __future__ import annotations

import contextlib
from io import BytesIO
from typing import ClassVar, Self

from django.conf import settings
from django.core.cache import cache
from django.db import models
from django.db.models import Exists, OuterRef
from django.urls import reverse
from django.utils import timezone
from django.utils.functional import cached_property
from django.utils.translation import gettext_lazy as _
from PIL import Image

from core.models import Group, Notification, User
from core.utils import exif_auto_rotate, resize_image


def get_directory(instance: SasFile, filename: str):
    return f"./{instance.parent_path}/{filename}"


def get_compressed_directory(instance: SasFile, filename: str):
    return f"./.compressed/{instance.parent_path}/{filename}"


def get_thumbnail_directory(instance: SasFile, filename: str):
    if isinstance(instance, Album):
        name, extension = filename.rsplit(".", 1)
        filename = f"{name}/thumb.{extension}"
    return f"./.thumbnails/{instance.parent_path}/{filename}"


class SasFile(models.Model):
    """Abstract model for SAS files

    May be used to have logic that should be shared by both
    [Picture][sas.models.Picture] and [Album][sas.models.Album].
    """

    class Meta:
        abstract = True

    def can_be_viewed_by(self, user):
        if user.is_anonymous:
            return False
        cache_key = (
            f"sas:{self._meta.model_name}_viewable_by_{user.id}_in_{self.parent_id}"
        )
        viewable: list[int] | None = cache.get(cache_key)
        if viewable is None:
            viewable = list(
                self.__class__.objects.filter(parent_id=self.parent_id)
                .viewable_by(user)
                .values_list("pk", flat=True)
            )
            cache.set(cache_key, viewable, timeout=10)
        return self.id in viewable

    def can_be_edited_by(self, user):
        return user.is_root or user.is_in_group(pk=settings.SITH_GROUP_SAS_ADMIN_ID)

    @cached_property
    def parent_path(self) -> str:
        return "/".join(["SAS", *[p.name for p in self.parent_list]])

    @cached_property
    def parent_list(self) -> list[Self]:
        parents = []
        current = self.parent
        while current is not None:
            parents.append(current)
            current = current.parent
        return parents


class AlbumQuerySet(models.QuerySet):
    def viewable_by(self, user: User) -> Self:
        """Filter the albums that this user can view.

        Warning:
            Calling this queryset method may add several additional requests.
        """
        if user.is_root or user.is_in_group(pk=settings.SITH_GROUP_SAS_ADMIN_ID):
            return self.all()
        if user.was_subscribed:
            return self.filter(
                Exists(Picture.objects.filter(parent=OuterRef("pk"), is_moderated=True))
            )
        # known bug : if all children of an album are also albums
        # then this album is excluded, even if one of the sub-albums should be visible.
        # The fs-like navigation is likely to be half-broken for non-subscribers,
        # but that's ok, since non-subscribers are expected to see only the albums
        # containing pictures on which they have been identified (hence, very few).
        # Most, if not all, of their albums will be displayed on the
        # `latest albums` section of the SAS.
        # Moreover, they will still see all of their picture in their profile.
        return self.filter(
            Exists(Picture.objects.filter(parent_id=OuterRef("pk")).viewable_by(user))
        )

    def annotate_is_moderated(self) -> Self:
        # an album is moderated if it has at least one moderated photo
        # if there is no photo at all, the album isn't considered as non-moderated
        # (it's just empty)
        return self.annotate(
            is_moderated=Exists(
                Picture.objects.filter(parent=OuterRef("pk"), is_moderated=True)
            )
            | ~Exists(Picture.objects.filter(parent=OuterRef("pk")))
        )


class Album(SasFile):
    NAME_MAX_LENGTH: ClassVar[int] = 50

    name = models.CharField(_("name"), max_length=100)
    parent = models.ForeignKey(
        "self",
        related_name="children",
        verbose_name=_("parent"),
        null=True,
        blank=True,
        on_delete=models.CASCADE,
    )
    thumbnail = models.FileField(
        upload_to=get_thumbnail_directory, verbose_name=_("thumbnail"), max_length=256
    )
    view_groups = models.ManyToManyField(
        Group, related_name="viewable_albums", verbose_name=_("view groups")
    )
    edit_groups = models.ManyToManyField(
        Group, related_name="editable_albums", verbose_name=_("edit groups")
    )
    event_date = models.DateField(
        _("event date"),
        help_text=_("The date on which the photos in this album were taken"),
        default=timezone.localdate,
    )

    objects = AlbumQuerySet.as_manager()

    class Meta:
        verbose_name = _("album")
        constraints = [
            models.UniqueConstraint(
                fields=["name", "parent"], name="unique_album_name_if_same_parent"
            )
        ]

    def __str__(self):
        return f"Album {self.name}"

    def save(self, *args, **kwargs):
        super().save(*args, **kwargs)
        for user in User.objects.filter(
            groups__id__in=[settings.SITH_GROUP_SAS_ADMIN_ID]
        ):
            Notification(
                user=user,
                url=reverse("sas:moderation"),
                type="SAS_MODERATION",
                param="1",
            ).save()

    def get_absolute_url(self):
        return reverse("sas:album", kwargs={"album_id": self.id})

    def get_download_url(self):
        return reverse("sas:album_preview", kwargs={"album_id": self.id})

    def generate_thumbnail(self):
        p = self.pictures.order_by("?").first() or self.children.order_by("?").first()
        if p and p.thumbnail:
            self.thumbnail = p.thumbnail
            self.thumbnail.name = f"{self.name}/thumb.webp"
            self.save()


class PictureQuerySet(models.QuerySet):
    def viewable_by(self, user: User) -> Self:
        """Filter the pictures that this user can view.

        Warning:
            Calling this queryset method may add several additional requests.
        """
        if user.is_root or user.is_in_group(pk=settings.SITH_GROUP_SAS_ADMIN_ID):
            return self.all()
        if user.was_subscribed:
            return self.filter(is_moderated=True)
        return self.filter(people__user_id=user.id, is_moderated=True)


class Picture(SasFile):
    name = models.CharField(_("file name"), max_length=256)
    parent = models.ForeignKey(
        Album,
        related_name="pictures",
        verbose_name=_("album"),
        on_delete=models.CASCADE,
    )
    thumbnail = models.FileField(
        upload_to=get_thumbnail_directory,
        verbose_name=_("thumbnail"),
        unique=True,
        max_length=256,
    )
    original = models.FileField(
        upload_to=get_directory,
        verbose_name=_("original image"),
        max_length=256,
        unique=True,
    )
    compressed = models.FileField(
        upload_to=get_compressed_directory,
        verbose_name=_("compressed image"),
        max_length=256,
        unique=True,
    )
    created_at = models.DateTimeField(default=timezone.now)
    owner = models.ForeignKey(
        User,
        related_name="owned_pictures",
        verbose_name=_("owner"),
        on_delete=models.PROTECT,
    )

    is_moderated = models.BooleanField(_("is moderated"), default=False)
    asked_for_removal = models.BooleanField(_("asked for removal"), default=False)
    moderator = models.ForeignKey(
        User,
        related_name="moderated_pictures",
        null=True,
        blank=True,
        on_delete=models.SET_NULL,
    )

    objects = PictureQuerySet.as_manager()

    def __str__(self):
        return self.name

    def save(self, *args, **kwargs):
        if self._state.adding:
            self.generate_thumbnails()
        super().save(*args, **kwargs)

    def get_absolute_url(self):
        return reverse("sas:picture", kwargs={"picture_id": self.id})

    def get_download_url(self):
        return reverse("sas:download", kwargs={"picture_id": self.id})

    def get_download_compressed_url(self):
        return reverse("sas:download_compressed", kwargs={"picture_id": self.id})

    def get_download_thumb_url(self):
        return reverse("sas:download_thumb", kwargs={"picture_id": self.id})

    @property
    def is_vertical(self):
        # original, compressed and thumbnail image have all three the same ratio,
        # so the smallest one is used to tell if the image is vertical
        im = Image.open(BytesIO(self.thumbnail.read()))
        (w, h) = im.size
        return w < h

    def generate_thumbnails(self):
        im = Image.open(self.original)
        with contextlib.suppress(Exception):
            im = exif_auto_rotate(im)
        # convert the compressed image and the thumbnail into webp
        # the HD version of the image doesn't need to be optimized, because :
        # - it isn't frequently queried
        # - optimizing large images takes a lot of time, which greatly hinders the UX
        # - photographers usually already optimize their images
        thumb = resize_image(im, 200, "webp")
        compressed = resize_image(im, 1200, "webp")
        self.thumbnail = thumb
        self.thumbnail.name = self.name
        self.compressed = compressed
        self.compressed.name = self.name

    def rotate(self, degree):
        for field in self.original, self.compressed, self.thumbnail:
            with open(field.file, "r+b") as file:
                if file:
                    im = Image.open(BytesIO(file.read()))
                    file.seek(0)
                    im = im.rotate(degree, expand=True)
                    im.save(
                        fp=file,
                        format=self.mime_type.split("/")[-1].upper(),
                        quality=90,
                        optimize=True,
                        progressive=True,
                    )


def sas_notification_callback(notif):
    count = Picture.objects.filter(is_moderated=False).count()
    if count:
        notif.viewed = False
    else:
        notif.viewed = True
    notif.param = "%s" % count
    notif.date = timezone.now()


class PeoplePictureRelation(models.Model):
    """The PeoplePictureRelation class makes the connection between User and Picture."""

    user = models.ForeignKey(
        User,
        verbose_name=_("user"),
        related_name="pictures",
        on_delete=models.CASCADE,
    )
    picture = models.ForeignKey(
        Picture,
        verbose_name=_("picture"),
        related_name="people",
        on_delete=models.CASCADE,
    )

    class Meta:
        unique_together = ["user", "picture"]

    def __str__(self):
        return f"Moderation request by {self.user.get_short_name()} - {self.picture}"


class PictureModerationRequest(models.Model):
    """A request to remove a Picture from the SAS."""

    created_at = models.DateTimeField(auto_now_add=True)
    author = models.ForeignKey(
        User,
        verbose_name=_("Author"),
        related_name="moderation_requests",
        on_delete=models.CASCADE,
    )
    picture = models.ForeignKey(
        Picture,
        verbose_name=_("Picture"),
        related_name="moderation_requests",
        on_delete=models.CASCADE,
    )
    reason = models.TextField(
        verbose_name=_("Reason"),
        default="",
        help_text=_("Why do you want this image to be removed ?"),
    )

    class Meta:
        verbose_name = _("Picture moderation request")
        verbose_name_plural = _("Picture moderation requests")
        constraints = [
            models.UniqueConstraint(
                fields=["author", "picture"], name="one_request_per_user_per_picture"
            )
        ]

    def __str__(self):
        return f"Moderation request by {self.author.get_short_name()}"