# -*- coding:utf-8 -*
#
# Copyright 2016,2017,2018
# - Skia <skia@libskia.so>
#
# Ce fichier fait partie du site de l'Association des Étudiants de l'UTBM,
# http://ae.utbm.fr.
#
# This program is free software; you can redistribute it and/or modify it under
# the terms of the GNU General Public License a 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 General Public License for more
# details.
#
# You should have received a copy of the GNU General Public License along with
# this program; if not, write to the Free Sofware Foundation, Inc., 59 Temple
# Place - Suite 330, Boston, MA 02111-1307, USA.
#
#

from django.db import models
from django.conf import settings
from django.utils.translation import gettext_lazy as _
from django.core.exceptions import ValidationError
from django.urls import reverse
from django.utils import timezone
from django.utils.functional import cached_property

from datetime import datetime
from itertools import chain
import pytz

from core.models import User, Group
from club.models import Club


class Forum(models.Model):
    """
    The Forum class, made as a tree to allow nice tidy organization

    owner_club allows club members to moderate there own topics
    edit_groups allows to put any group as a forum admin
    view_groups allows some groups to view a forum
    """

    # Those functions prevent generating migration upon settings changes
    def get_default_edit_group():
        return [settings.SITH_GROUP_OLD_SUBSCRIBERS_ID]

    def get_default_view_group():
        return [settings.SITH_GROUP_PUBLIC_ID]

    id = models.AutoField(primary_key=True, db_index=True)
    name = models.CharField(_("name"), max_length=64)
    description = models.CharField(_("description"), max_length=512, default="")
    is_category = models.BooleanField(_("is a category"), default=False)
    parent = models.ForeignKey(
        "Forum",
        related_name="children",
        null=True,
        blank=True,
        on_delete=models.CASCADE,
    )
    owner_club = models.ForeignKey(
        Club,
        related_name="owned_forums",
        verbose_name=_("owner club"),
        default=settings.SITH_MAIN_CLUB_ID,
        on_delete=models.CASCADE,
    )
    edit_groups = models.ManyToManyField(
        Group,
        related_name="editable_forums",
        blank=True,
        default=get_default_edit_group,
    )
    view_groups = models.ManyToManyField(
        Group,
        related_name="viewable_forums",
        blank=True,
        default=get_default_view_group,
    )
    number = models.IntegerField(
        _("number to choose a specific forum ordering"), default=1
    )
    _last_message = models.ForeignKey(
        "ForumMessage",
        related_name="forums_where_its_last",
        verbose_name=_("the last message"),
        null=True,
        on_delete=models.SET_NULL,
    )
    _topic_number = models.IntegerField(_("number of topics"), default=0)

    class Meta:
        ordering = ["number"]

    def clean(self):
        self.check_loop()

    def save(self, *args, **kwargs):
        copy_rights = False
        if self.id is None:
            copy_rights = True
        super(Forum, self).save(*args, **kwargs)
        if copy_rights:
            self.copy_rights()

    def set_topic_number(self):
        self._topic_number = self.get_topic_number()
        self.save()
        if self.parent:
            self.parent.set_topic_number()

    def set_last_message(self):
        topic = (
            ForumTopic.objects.filter(forum__id=self.id)
            .exclude(_last_message=None)
            .order_by("-_last_message__id")
            .first()
        )
        forum = (
            Forum.objects.filter(parent__id=self.id)
            .exclude(_last_message=None)
            .order_by("-_last_message__id")
            .first()
        )
        if topic and forum:
            if topic._last_message_id < forum._last_message_id:
                self._last_message_id = forum._last_message_id
            else:
                self._last_message_id = topic._last_message_id
        elif topic:
            self._last_message_id = topic._last_message_id
        elif forum:
            self._last_message_id = forum._last_message_id
        self.save()
        if self.parent:
            self.parent.set_last_message()

    def apply_rights_recursively(self):
        children = self.children.all()
        for c in children:
            c.copy_rights()
            c.apply_rights_recursively()

    def copy_rights(self):
        """Copy, if possible, the rights of the parent folder"""
        if self.parent is not None:
            self.owner_club = self.parent.owner_club
            self.edit_groups.set(self.parent.edit_groups.all())
            self.view_groups.set(self.parent.view_groups.all())
            self.save()

    _club_memberships = {}  # This cache is particularly efficient:

    # divided by 3 the number of requests on the main forum page
    # after the first load
    def is_owned_by(self, user):
        if user.is_anonymous:
            return False
        if user.is_in_group(pk=settings.SITH_GROUP_FORUM_ADMIN_ID):
            return True
        try:
            m = Forum._club_memberships[self.id][user.id]
        except:
            m = self.owner_club.get_membership_for(user)
            try:
                Forum._club_memberships[self.id][user.id] = m
            except:
                Forum._club_memberships[self.id] = {}
                Forum._club_memberships[self.id][user.id] = m
        if m:
            return m.role > settings.SITH_MAXIMUM_FREE_ROLE
        return False

    def check_loop(self):
        """Raise a validation error when a loop is found within the parent list"""
        objs = []
        cur = self
        while cur.parent is not None:
            if cur in objs:
                raise ValidationError(_("You can not make loops in forums"))
            objs.append(cur)
            cur = cur.parent

    def __str__(self):
        return "%s" % (self.name)

    def get_full_name(self):
        return "/".join(
            chain.from_iterable(
                [[parent.name for parent in self.get_parent_list()], [self.name]]
            )
        )

    def get_absolute_url(self):
        return reverse("forum:view_forum", kwargs={"forum_id": self.id})

    @cached_property
    def parent_list(self):
        return self.get_parent_list()

    def get_parent_list(self):
        l = []
        p = self.parent
        while p is not None:
            l.append(p)
            p = p.parent
        return l

    @property
    def topic_number(self):
        return self._topic_number

    def get_topic_number(self):
        number = self.topics.all().count()
        for c in self.children.all():
            number += c.topic_number
        return number

    @cached_property
    def last_message(self):
        return self._last_message

    def get_children_list(self):
        l = [self.id]
        for c in self.children.all():
            l.append(c.id)
            l += c.get_children_list()
        return l


class ForumTopic(models.Model):
    forum = models.ForeignKey(Forum, related_name="topics", on_delete=models.CASCADE)
    author = models.ForeignKey(
        User, related_name="forum_topics", on_delete=models.CASCADE
    )
    description = models.CharField(_("description"), max_length=256, default="")
    subscribed_users = models.ManyToManyField(
        User, related_name="favorite_topics", verbose_name=_("subscribed users")
    )
    _last_message = models.ForeignKey(
        "ForumMessage",
        related_name="+",
        verbose_name=_("the last message"),
        null=True,
        on_delete=models.SET_NULL,
    )
    _title = models.CharField(_("title"), max_length=64, blank=True)
    _message_number = models.IntegerField(_("number of messages"), default=0)

    class Meta:
        ordering = ["-_last_message__date"]

    def save(self, *args, **kwargs):
        super(ForumTopic, self).save(*args, **kwargs)
        self.forum.set_topic_number()  # Recompute the cached value
        self.forum.set_last_message()

    def is_owned_by(self, user):
        return self.forum.is_owned_by(user)

    def can_be_edited_by(self, user):
        return user.can_edit(self.forum)

    def can_be_viewed_by(self, user):
        return user.can_view(self.forum)

    def __str__(self):
        return "%s" % (self.title)

    def get_absolute_url(self):
        return reverse("forum:view_topic", kwargs={"topic_id": self.id})

    def get_first_unread_message(self, user):
        try:
            msg = (
                self.messages.exclude(readers=user)
                .filter(date__gte=user.forum_infos.last_read_date)
                .order_by("id")
                .first()
            )
            return msg
        except:
            return None

    @cached_property
    def last_message(self):
        return self._last_message

    @cached_property
    def title(self):
        return self._title


class ForumMessage(models.Model):
    """
    "A ForumMessage object represents a message in the forum" -- Cpt. Obvious
    """

    topic = models.ForeignKey(
        ForumTopic, related_name="messages", on_delete=models.CASCADE
    )
    author = models.ForeignKey(
        User, related_name="forum_messages", on_delete=models.CASCADE
    )
    title = models.CharField(_("title"), default="", max_length=64, blank=True)
    message = models.TextField(_("message"), default="")
    date = models.DateTimeField(_("date"), default=timezone.now)
    readers = models.ManyToManyField(
        User, related_name="read_messages", verbose_name=_("readers")
    )
    _deleted = models.BooleanField(_("is deleted"), default=False)

    class Meta:
        ordering = ["-date"]

    def __str__(self):
        return "%s (%s) - %s" % (self.id, self.author, self.title)

    def save(self, *args, **kwargs):
        self._deleted = self.is_deleted()  # Recompute the cached value
        super(ForumMessage, self).save(*args, **kwargs)
        if self.is_last_in_topic():
            self.topic._last_message_id = self.id
        if self.is_first_in_topic() and self.title:
            self.topic._title = self.title
        self.topic._message_number = self.topic.messages.count()
        self.topic.save()

    def is_first_in_topic(self):
        return bool(self.id == self.topic.messages.order_by("date").first().id)

    def is_last_in_topic(self):
        return bool(self.id == self.topic.messages.order_by("date").last().id)

    def is_owned_by(self, user):
        if user.is_anonymous:
            return False
        # Anyone can create a topic: it's better to
        # check the rights at the forum level, since it's more controlled
        return self.topic.forum.is_owned_by(user) or user.id == self.author.id

    def can_be_edited_by(self, user):
        return user.can_edit(self.topic.forum)

    def can_be_viewed_by(self, user):
        # No need to check the real rights since it's already done by the Topic view
        # and it impacts performances too much
        return not self._deleted

    def can_be_moderated_by(self, user):
        return self.topic.forum.is_owned_by(user) or user.id == self.author.id

    def get_absolute_url(self):
        return reverse("forum:view_message", kwargs={"message_id": self.id})

    def get_url(self):
        return (
            self.topic.get_absolute_url()
            + "?page="
            + str(self.get_page())
            + "#msg_"
            + str(self.id)
        )

    def get_page(self):
        return (
            int(
                self.topic.messages.filter(id__lt=self.id).count()
                / settings.SITH_FORUM_PAGE_LENGTH
            )
            + 1
        )

    def mark_as_read(self, user):
        try:  # Need the try/except because of AnonymousUser
            if not self.is_read(user):
                self.readers.add(user)
        except:
            pass

    def is_read(self, user):
        return (self.date < user.forum_infos.last_read_date) or (
            user in self.readers.all()
        )

    def is_deleted(self):
        meta = self.metas.exclude(action="EDIT").order_by("-date").first()
        if meta:
            return meta.action == "DELETE"
        return False


MESSAGE_META_ACTIONS = [
    ("EDIT", _("Message edited by")),
    ("DELETE", _("Message deleted by")),
    ("UNDELETE", _("Message undeleted by")),
]


class ForumMessageMeta(models.Model):
    user = models.ForeignKey(
        User, related_name="forum_message_metas", on_delete=models.CASCADE
    )
    message = models.ForeignKey(
        ForumMessage, related_name="metas", on_delete=models.CASCADE
    )
    date = models.DateTimeField(_("date"), default=timezone.now)
    action = models.CharField(_("action"), choices=MESSAGE_META_ACTIONS, max_length=16)

    def save(self, *args, **kwargs):
        super(ForumMessageMeta, self).save(*args, **kwargs)
        self.message._deleted = self.message.is_deleted()
        self.message.save()


class ForumUserInfo(models.Model):
    """
    This currently stores only the last date a user clicked "Mark all as read".
    However, this can be extended with lot of user preferences dedicated to a
    user, such as the favourite topics, the signature, and so on...
    """

    user = models.OneToOneField(
        User, related_name="_forum_infos", on_delete=models.CASCADE
    )
    last_read_date = models.DateTimeField(
        _("last read date"),
        default=datetime(
            year=settings.SITH_SCHOOL_START_YEAR, month=1, day=1, tzinfo=pytz.UTC
        ),
    )

    def __str__(self):
        return str(self.user)