views.py

__copyright__ = "Copyright © Stichting SciPost (SciPost Foundation)"
__license__ = "AGPL v3"


from django import forms
from django.contrib import messages
from django.contrib.auth.models import Group
from django.contrib.auth.mixins import LoginRequiredMixin, UserPassesTestMixin
from django.contrib.contenttypes.models import ContentType
from django.core.exceptions import PermissionDenied
from django.http import Http404
from django.shortcuts import get_object_or_404, redirect
from django.urls import reverse, reverse_lazy
from django.utils import timezone
from django.views.generic.detail import DetailView
from django.views.generic.edit import CreateView, UpdateView, DeleteView
from django.views.generic.list import ListView

from guardian.mixins import PermissionRequiredMixin
from guardian.shortcuts import (assign_perm, remove_perm,
    get_objects_for_user, get_perms, get_users_with_perms, get_groups_with_perms)

from .models import Forum, Meeting, Post
from .forms import (ForumForm, ForumGroupPermissionsForm, ForumOrganizationPermissionsForm,
                    MeetingForm, PostForm)

from scipost.mixins import PermissionsMixin


class ForumCreateView(PermissionsMixin, CreateView):
    permission_required = 'forums.add_forum'
    model = Forum
    form_class = ForumForm
    template_name = 'forums/forum_form.html'
    success_url = reverse_lazy('forums:forums')

    def get_initial(self):
        initial = super().get_initial()
        parent_model = self.kwargs.get('parent_model')
        parent_content_type = None
        parent_object_id = self.kwargs.get('parent_id')
        if parent_model == 'forum':
            parent_content_type = ContentType.objects.get(app_label='forums', model='forum')
        initial.update({
            'moderators': self.request.user,
            'parent_content_type': parent_content_type,
            'parent_object_id': parent_object_id,
        })
        return initial


class MeetingCreateView(ForumCreateView):
    model = Meeting
    form_class = MeetingForm


class ForumUpdateView(PermissionRequiredMixin, UpdateView):
    permission_required = 'forums.update_forum'
    model = Forum
    form_class = ForumForm
    template_name = 'forums/forum_form.html'


class ForumDeleteView(PermissionRequiredMixin, DeleteView):
    permission_required = 'forums.delete_forum'
    model = Forum
    success_url = reverse_lazy('forums:forums')

    def delete(self, request, *args, **kwargs):
        """
        A Forum can only be deleted if it does not have any descendants.
        Upon deletion, all object-level permissions associated to the
        Forum are explicitly removed, to avoid orphaned permissions.
        """
        forum = get_object_or_404(Forum, slug=self.kwargs.get('slug'))
        groups_perms_dict = get_groups_with_perms(forum, attach_perms=True)
        if forum.child_forums.all().count() > 0:
            messages.warning(request, 'A Forum with descendants cannot be deleted.')
            return redirect(forum.get_absolute_url())
        for group, perms_list in groups_perms_dict.items():
            for perm in perms_list:
                remove_perm(perm, group, forum)
        return super().delete(request, *args, **kwargs)


class ForumDetailView(PermissionRequiredMixin, DetailView):
    permission_required = 'forums.can_view_forum'
    model = Forum
    template_name = 'forums/forum_detail.html'

    def get_context_data(self, *args, **kwargs):
        context = super().get_context_data(*args, **kwargs)
        context['groups_with_perms'] = get_groups_with_perms(self.object).order_by('name')
        context['users_with_perms'] = get_users_with_perms(self.object)
        context['group_permissions_form'] = ForumGroupPermissionsForm()
        context['organization_permissions_form'] = ForumOrganizationPermissionsForm()
        return context


class ForumPermissionsView(PermissionRequiredMixin, UpdateView):
    permission_required = 'forums.can_change_forum'
    model = Forum
    form_class = ForumGroupPermissionsForm
    template_name = 'forums/forum_permissions.html'

    def get_context_data(self, *args, **kwargs):
        context = super().get_context_data(*args, **kwargs)
        try:
            context['group'] = Group.objects.get(pk=self.kwargs.get('group_id'))
        except Group.DoesNotExist:
            pass
        return context

    def get_initial(self, *args, **kwargs):
        initial = super().get_initial(*args, **kwargs)
        try:
            group = Group.objects.get(pk=self.kwargs.get('group_id'))
            perms = get_perms (group, self.object)
            initial['group'] = group.id
            initial['can_view'] = 'can_view_forum' in perms
            initial['can_post'] = 'can_post_to_forum' in perms
        except Group.DoesNotExist:
            pass
        return initial

    def form_valid(self, form):
        if form.cleaned_data['can_view']:
            assign_perm('can_view_forum', form.cleaned_data['group'], self.object)
        else:
            remove_perm('can_view_forum', form.cleaned_data['group'], self.object)
        if form.cleaned_data['can_post']:
            assign_perm('can_post_to_forum', form.cleaned_data['group'], self.object)
        else:
            remove_perm('can_post_to_forum', form.cleaned_data['group'], self.object)
        return super().form_valid(form)


class ForumListView(LoginRequiredMixin, ListView):
    model = Forum
    template_name = 'forum_list.html'

    def get_queryset(self):
        queryset = get_objects_for_user(self.request.user, 'forums.can_view_forum').anchors()
        return queryset


class PostCreateView(UserPassesTestMixin, CreateView):
    """
    First step of a two-step Post creation process.
    This view, upon successful POST, redirects to the
    PostConfirmCreateView confirmation view.

    To transfer form data from this view to the next (confirmation) one,
    two session variables are used, ``post_subject`` and ``post_text``.
    """
    model = Post
    form_class= PostForm

    def test_func(self):
        if self.request.user.has_perm('forums.add_forum'):
            return True
        forum = get_object_or_404(Forum, slug=self.kwargs.get('slug'))
        if self.request.user.has_perm('can_post_to_forum', forum):
            return True
        else:
            raise PermissionDenied

    def get_initial(self, *args, **kwargs):
        initial = super().get_initial(*args, **kwargs)
        parent_model = self.kwargs.get('parent_model')
        parent_object_id = self.kwargs.get('parent_id')
        subject = ''
        if parent_model == 'forum':
            parent_content_type = ContentType.objects.get(app_label='forums', model='forum')
        elif parent_model == 'post':
            parent_content_type = ContentType.objects.get(app_label='forums', model='post')
            parent = parent_content_type.get_object_for_this_type(pk=parent_object_id)
            if parent.subject.startswith('Re: ...'):
                subject = parent.subject
            elif parent.subject.startswith('Re:'):
                subject = '%s%s' % ('Re: ...', parent.subject.lstrip('Re:'))
            else:
                subject = 'Re: %s' % parent.subject
        else:
            raise Http404
        initial.update({
            'posted_by': self.request.user,
            'posted_on': timezone.now(),
            'parent_content_type': parent_content_type,
            'parent_object_id': parent_object_id,
            'subject': subject,
        })
        return initial

    def form_valid(self, form):
        """
        Save the form data to session variables only, redirect to confirmation view.
        """
        self.request.session['post_subject'] = form.cleaned_data['subject']
        self.request.session['post_text'] = form.cleaned_data['text']
        return redirect(reverse('forums:post_confirm_create',
                                kwargs={'slug': self.kwargs.get('slug'),
                                        'parent_model': self.kwargs.get('parent_model'),
                                        'parent_id': self.kwargs.get('parent_id')}))


class PostConfirmCreateView(PostCreateView):
    """
    Second (confirmation) step of Post creation process.

    Upon successful POST, the Post object is saved and the
    two session variables ``post_subject`` and ``post_text`` are deleted.
    """
    form_class = PostForm
    template_name = 'forums/post_confirm_create.html'

    def get_form(self, form_class=None):
        form = super().get_form(form_class)
        form.fields['subject'].widget = forms.HiddenInput()
        form.fields['text'].widget = forms.HiddenInput()
        return form

    def get_initial(self, *args, **kwargs):
        initial = super().get_initial(*args, **kwargs)
        initial.update({
            'subject': self.request.session.get('post_subject'),
            'text': self.request.session.get('post_text'),
        })
        return initial

    def form_valid(self, form):
        """
        After deleting the session variables used for the confirmation step,
        simply perform the form_valid calls of form_valid from ancestor classes
        ModelFormMixin and FormMixin, due to the fact that the form_valid
        method in the PostCreateView superclass was overriden to a redirect.
        """
        del self.request.session['post_subject']
        del self.request.session['post_text']
        self.object = form.save()
        return redirect(self.get_success_url())