from datetime import timedelta

from django.core.exceptions import PermissionDenied
from django.db.models import F, Q
from django.http import Http404
from django.utils import timezone
from django.utils.translation import ugettext as _
from django.utils.translation import ugettext_lazy

from misago.acl import add_acl
from misago.conf import settings
from misago.core.shortcuts import paginate, pagination_dict
from misago.readtracker import threadstracker
from misago.threads.models import Thread
from misago.threads.participants import make_participants_aware
from misago.threads.permissions import exclude_invisible_threads
from misago.threads.serializers import ThreadsListSerializer
from misago.threads.subscriptions import make_subscription_aware
from misago.threads.utils import add_categories_to_items


__all__ = ['ForumThreads', 'PrivateThreads', 'filter_read_threads_queryset']


LISTS_NAMES = {
    'all': None,
    'my': ugettext_lazy("Your threads"),
    'new': ugettext_lazy("New threads"),
    'unread': ugettext_lazy("Unread threads"),
    'subscribed': ugettext_lazy("Subscribed threads"),
    'unapproved': ugettext_lazy("Unapproved content"),
}

LIST_DENIED_MESSAGES = {
    'my': ugettext_lazy("You have to sign in to see list of threads that you have started."),
    'new': ugettext_lazy("You have to sign in to see list of threads you haven't read."),
    'unread': ugettext_lazy("You have to sign in to see list of threads with new replies."),
    'subscribed': ugettext_lazy("You have to sign in to see list of threads you are subscribing."),
    'unapproved': ugettext_lazy("You have to sign in to see list of threads with unapproved posts."),
}


class ViewModel(object):
    def __init__(self, request, category, list_type, page):
        self.allow_see_list(request, category, list_type)

        category_model = category.unwrap()

        base_queryset = self.get_base_queryset(request, category.categories, list_type)
        threads_categories = [category_model] + category.subcategories

        threads_queryset = self.get_remaining_threads_queryset(base_queryset, category_model, threads_categories)

        list_page = paginate(threads_queryset, page, settings.MISAGO_THREADS_PER_PAGE, settings.MISAGO_THREADS_TAIL)
        paginator = pagination_dict(list_page)

        if list_page.number > 1:
            threads = list(list_page.object_list)
        else:
            pinned_threads = list(self.get_pinned_threads(base_queryset, category_model, threads_categories))
            threads = list(pinned_threads) + list(list_page.object_list)

        if list_type in ('new', 'unread'):
            # we already know all threads on list are unread
            threadstracker.make_unread(threads)
        else:
            threadstracker.make_threads_read_aware(request.user, threads)

        add_categories_to_items(category_model, category.categories, threads)

        add_acl(request.user, threads)
        make_subscription_aware(request.user, threads)

        self.filter_threads(request, threads)

        # set state on object for easy access from hooks
        self.category = category
        self.threads = threads
        self.list_type = list_type
        self.paginator = paginator

    def allow_see_list(self, request, category, list_type):
        if list_type not in LISTS_NAMES:
            raise Http404()

        if request.user.is_anonymous:
            if list_type in LIST_DENIED_MESSAGES:
                raise PermissionDenied(LIST_DENIED_MESSAGES[list_type])
        else:
            if list_type == 'unapproved' and not request.user.acl['can_see_unapproved_content_lists']:
                raise PermissionDenied(_("You don't have permission to see unapproved content lists."))

    def get_list_name(self, list_type):
        return LISTS_NAMES[list_type]

    def get_base_queryset(self, request, threads_categories, list_type):
        return get_threads_queryset(request.user, threads_categories, list_type).order_by('-last_post_id')

    def get_pinned_threads(self, queryset, category, threads_categories):
        return []

    def get_remaining_threads_queryset(self, queryset, category, threads_categories):
        return []

    def filter_threads(self, request, threads):
        pass # hook for custom thread types to add features to extend threads

    def get_frontend_context(self):
        context = {
            'THREADS': {
                'results': ThreadsListSerializer(self.threads, many=True).data,
                'subcategories': [c.pk for c in self.category.children]
            },
        }

        context['THREADS'].update(self.paginator)
        return context

    def get_template_context(self):
        return {
            'list_name': self.get_list_name(self.list_type),
            'list_type': self.list_type,

            'threads': self.threads,
            'paginator': self.paginator
        }


class ForumThreads(ViewModel):
    def get_pinned_threads(self, queryset, category, threads_categories):
        if category.level:
            return list(queryset.filter(weight=2)) + list(queryset.filter(
                weight=1,
                category__in=threads_categories
            ))
        else:
            return queryset.filter(weight=2)

    def get_remaining_threads_queryset(self, queryset, category, threads_categories):
        if category.level:
            return queryset.filter(
                weight=0,
                category__in=threads_categories,
            )
        else:
            return queryset.filter(
                weight__lt=2,
                category__in=threads_categories,
            )


class PrivateThreads(ViewModel):
    def get_base_queryset(self, request, threads_categories, list_type):
        queryset = super(PrivateThreads, self).get_base_queryset(request, threads_categories, list_type)

        # limit queryset to threads we are participant of
        participated_threads = request.user.threadparticipant_set.values('thread_id')

        if request.user.acl['can_moderate_private_threads']:
            queryset = queryset.filter(
                Q(id__in=participated_threads) | Q(has_reported_posts=True))
        else:
            queryset = queryset.filter(id__in=participated_threads)

        return queryset

    def get_remaining_threads_queryset(self, queryset, category, threads_categories):
        return queryset.filter(category__in=threads_categories)

    def filter_threads(self, request, threads):
        make_participants_aware(request.user, threads)


"""
Thread queryset utils
"""
def get_threads_queryset(user, categories, list_type):
    queryset = exclude_invisible_threads(user, categories, Thread.objects)

    if list_type == 'all':
        return queryset
    else:
        return filter_threads_queryset(user, categories, list_type, queryset)


def filter_threads_queryset(user, categories, list_type, queryset):
    if list_type == 'my':
        return queryset.filter(starter=user)
    elif list_type == 'subscribed':
        subscribed_threads = user.subscription_set.values('thread_id')
        return queryset.filter(id__in=subscribed_threads)
    elif list_type == 'unapproved':
        return queryset.filter(has_unapproved_posts=True)
    elif list_type in ('new', 'unread'):
        return filter_read_threads_queryset(user, categories, list_type, queryset)
    else:
        return queryset


def filter_read_threads_queryset(user, categories, list_type, queryset):
    # grab cutoffs for categories
    cutoff_date = timezone.now() - timedelta(days=settings.MISAGO_READTRACKER_CUTOFF)

    if cutoff_date < user.joined_on:
        cutoff_date = user.joined_on

    categories_dict = {}
    for record in user.categoryread_set.filter(category__in=categories):
        if record.last_read_on > cutoff_date:
            categories_dict[record.category_id] = record.last_read_on

    if list_type == 'new':
        # new threads have no entry in reads table
        # AND were started after cutoff date
        read_threads = user.threadread_set.filter(
            category__in=categories
        ).values('thread_id')

        condition = Q(last_post_on__lte=cutoff_date)
        condition = condition | Q(id__in=read_threads)

        if categories_dict:
            for category_id, category_cutoff in categories_dict.items():
                condition = condition | Q(
                    category_id=category_id,
                    last_post_on__lte=category_cutoff,
                )

        return queryset.exclude(condition)
    elif list_type == 'unread':
        # unread threads were read in past but have new posts
        # after cutoff date
        read_threads = user.threadread_set.filter(
            category__in=categories,
            thread__last_post_on__gt=cutoff_date,
            last_read_on__lt=F('thread__last_post_on')
        ).values('thread_id')

        queryset = queryset.filter(id__in=read_threads)

        # unread threads have last reply after read/cutoff date
        if categories_dict:
            conditions = None

            for category_id, category_cutoff in categories_dict.items():
                condition = Q(
                    category_id=category_id,
                    last_post_on__lte=category_cutoff,
                )
                if conditions:
                    conditions = conditions | condition
                else:
                    conditions = condition

            return queryset.exclude(conditions)
        else:
            return queryset