from django.views.generic.detail import DetailView
from django.views.generic.edit import UpdateView, CreateView, DeleteView
from django.views.generic.list import ListView
from django.core import exceptions
from django.core.exceptions import ImproperlyConfigured
from django.http import Http404, HttpResponseRedirect


class GuardedDetailView(DetailView):
    def get(self, request, **kwargs):
        self.object = self.get_object()
        self.check_permission(request.user, self.object)
        context = self.get_context_data(object=self.object)
        return self.render_to_response(context)


class GuardedUpdateView(UpdateView):
    def get(self, request, *args, **kwargs):
        self.object = self.get_object()
        self.check_permission(request.user, self.object)
        return super(GuardedUpdateView, self).get(request, *args, **kwargs)

    def post(self, request, *args, **kwargs):
        self.object = self.get_object()
        self.check_permission(request.user, self.object)
        return super(GuardedUpdateView, self).post(request, *args, **kwargs)


class GuardedCreateView(CreateView):
    def post(self, request, *args, **kwargs):
        self.object = None
        form_class = self.get_form_class()
        form = self.get_form(form_class)
        if form.is_valid():
            self.ensure_permissions(request.user, form.instance)
            return self.form_valid(form)
        else:
            return self.form_invalid(form)

class GuardedDeleteView(DeleteView):
    def get(self, request, *args, **kwargs):
        self.object = self.get_object()
        self.check_permission(request.user, self.object)
        return super(DeleteView, self).get(request, *args, **kwargs)

    def delete(self, request, *args, **kwargs):
        self.object = self.get_object()
        self.check_permission(request.user, self.object)
        self.object.delete()
        return HttpResponseRedirect(self.get_success_url())


class OwnedCreateView(GuardedCreateView):
    
    owner = None
    
    def ensure_permissions(self, user, object):
        setattr(object, self.owner, user)

    
class OwnedDetailView(GuardedDetailView):
    
    owner = None
    
    def check_permission(self, user, object):
        if getattr(object, self.owner) != user:
            raise exceptions.PermissionDenied()


class OwnedUpdateView(GuardedUpdateView):
    
    owner = None
    
    def check_permission(self, user, object):
        if getattr(object, self.owner) != user:
            raise exceptions.PermissionDenied()

class OwnedDeleteView(GuardedDeleteView):
    
    owner = None
    
    def check_permission(self, user, object):
        if getattr(object, self.owner) != user:
            raise exceptions.PermissionDenied()


class OwnedListView(ListView):
    
    owner = None
    
    def get_queryset_perm(self, user):
        """
        Get the list of items for this view. This must be an interable, and may
        be a queryset (in which qs-specific behavior will be enabled).
        """
        if self.queryset is not None:
            queryset = self.queryset
            if hasattr(queryset, '_clone'):
                queryset = queryset._clone()
        elif self.model is not None:
            lookup_args = { self.owner: user }
            queryset = self.model._default_manager.filter(**lookup_args)
        else:
            raise ImproperlyConfigured(u"'%s' must define 'queryset' or 'model'"
                                       % self.__class__.__name__)
        return queryset

    def get(self, request, *args, **kwargs):
        self.object_list = self.get_queryset_perm(request.user)
        allow_empty = self.get_allow_empty()
        if not allow_empty and len(self.object_list) == 0:
            raise Http404(_(u"Empty list and '%(class_name)s.allow_empty' is False.")
                          % {'class_name': self.__class__.__name__})
        context = self.get_context_data(object_list=self.object_list)
        return self.render_to_response(context)