import json
import swapper

from django.views.generic import base, detail, edit
from django.http import Http404, HttpResponseRedirect
from django.shortcuts import redirect
from django.core.exceptions import ImproperlyConfigured
from django.contrib.contenttypes.models import ContentType
from django.contrib.auth.mixins import UserPassesTestMixin
#from django.http import HttpResponseRedirect, HttpResponseBadRequest

from .decorators import register_view
from .forms import PageForm, SectionForm, SectionFormSet

Page = swapper.load_model('cms', 'Page')
Section = swapper.load_model('cms', 'Section')

@register_view(Section)
class SectionView:
    '''Generic section view'''
    template_name = 'cms/sections/section.html'

    def setup(self, request, section):
        '''Initialize request and section attributes'''
        self.request = request
        self.section = section

    def get_context_data(self, **kwargs):
        '''Override this to customize a section's context'''
        return kwargs

class SectionFormView(edit.FormMixin, SectionView):
    '''Generic section with associated form'''

    def post(self, request):
        '''Process form'''
        form = self.get_form()
        if form.is_valid():
            form.save(request)
            return redirect(self.get_success_url())
        return form

class SectionFormSetView(SectionView):
    '''Generic section with associated formset'''

    formset_class = None

    def post(self, request):
        '''Process form'''
        formset = self.get_formset()
        if formset.is_valid():
            formset.save(request)
            return redirect(self.get_success_url())
        return formset

    def get_formset(self):
        # todo: handle initials!
        return self.formset_class()

    def get_context_data(self, **kwargs):
        if 'formset' not in kwargs:
            kwargs['formset'] = self.get_formset()
        return super().get_context_data(**kwargs)

class PageView(detail.DetailView):
    '''View of a page with heterogeneous (polymorphic) sections'''
    model = Page
    template_name = 'cms/page.html'

    def setup(self, *args, slug='', **kwargs):
        '''Supply a default argument for slug'''
        super().setup(*args, slug=slug, **kwargs)

    def initialize_section(self, section):
        section.view = section.__class__.view_class()
        section.view.setup(self.request, section)
        section.context = section.view.get_context_data(
            request = self.request,
            section = section,
        )

    def get(self, request, *args, **kwargs):
        '''Initialize sections and render final response'''
        try:
            page = self.object = self.get_object()
        except Http404:
            if self.request.user.has_perm('cms_page_create'):
                return redirect('cms:updatepage', self.kwargs['slug'])
            else:
                raise
        context = self.get_context_data(**kwargs)
        sections = page.sections.all()
        for section in sections:
            self.initialize_section(section)
        context.update({
            'page': page,
            'sections': sections,
        })
        return self.render_to_response(context)

    def post(self, request, **kwargs):
        '''Initialize sections and call the post() function of the correct
        section view'''
        try:
            pk = int(self.request.POST.get('section'))
        except:
            return HttpResponseBadRequest()

        page = self.object = self.get_object()
        context = self.get_context_data(**kwargs)
        sections = page.sections.all()
        for section in sections:
            self.initialize_section(section)
            if section.pk == pk:
                result = section.view.post(request)
                if isinstance(result, HttpResponseRedirect):
                    return result
                section.context['form'] = result

        context.update({
            'page': page,
            'sections': sections,
        })
        return self.render_to_response(context)

    def get_context_data(self, **kwargs):
        context = super().get_context_data(**kwargs)
        pages = Page.objects.filter(menu=True)
        context.update({
            'pages': pages,
        })
        return context

class EditPage(UserPassesTestMixin, edit.ModelFormMixin, base.TemplateResponseMixin, base.View):
    model = Page
    form_class = PageForm
    template_name = 'cms/edit.html'

    def test_func(self):
        return self.request.user.has_perm('cms_page_change')

    def setup(self, *args, slug='', **kwargs):
        '''Supply a default argument for slug'''
        super().setup(*args, slug=slug, **kwargs)

    def get_form_kwargs(self):
        kwargs = super().get_form_kwargs()
        kwargs.update({
            'label_suffix': '',
            'initial': {'slug': self.kwargs['slug']},
        })
        return kwargs

    def get_context_data(self, **kwargs):
        context = super().get_context_data(**kwargs)
        if 'formset' not in context:
            context['formset'] = SectionFormSet(instance=self.object, form_kwargs={'label_suffix': ''})
        fields_per_type = {}
        for model, _ in Section.TYPES:
            ctype = ContentType.objects.get(
                app_label = Section._meta.app_label,
                model = model.lower(),
            )
            fields_per_type[ctype.model] = ['type', 'number'] + ctype.model_class().fields

        context.update({
            'fields_per_type': json.dumps(fields_per_type),
        })
        return context

    def get_object(self):
        try:
            return super().get_object()
        except:
            return None

    def get(self, request, *args, **kwargs):
        self.object = self.get_object()
        return self.render_to_response(self.get_context_data())

    def post(self, request, *args, **kwargs):
        self.object = self.get_object()
        form = self.get_form()
        if form.is_valid():
            page = form.save()
            formset = SectionFormSet(request.POST, request.FILES, instance=page)
            if formset.is_valid():
                if formset.save():
                    if page.slug and not page.sections.exists(): # anymore
                        page.delete()
                        return HttpResponseRedirect('/')
                    return HttpResponseRedirect(page.get_absolute_url())
                else:
                    # TODO: show sensible error
                    formset.errors.append([{}, {'title': ['You have to add sections']}])
        formset = SectionFormSet(request.POST, request.FILES)
        return self.render_to_response(self.get_context_data(form=form, formset=formset))

class CreatePage(EditPage):
    def get_object(self):
        pass

class UpdatePage(EditPage):
    pass