sms_feed/crud/viewsets.py

from django.conf.urls import url
from django.contrib.auth.decorators import login_required
from django.core.exceptions import ImproperlyConfigured, ValidationError
from django.db.models.query import QuerySet
from django.http import Http404
from django.urls import reverse
from django.shortcuts import get_object_or_404
from django.views import generic
import django_tables2

import copy
import threading

#import logging
#logger = logging.getLogger("console")

LIST_VIEW_TYPE = 'list'
CREATE_VIEW_TYPE = 'create'
DETAIL_VIEW_TYPE = 'detail'
UPDATE_VIEW_TYPE = 'update'
DELETE_VIEW_TYPE = 'delete'

# Used in the case where a viewset functions only as a nested list view, and
# therefore doesn't require any URLs of its own.
NOT_FOUND_VIEW_TYPE = 'not_found'

INSTANCE_VIEW_TYPES = [DETAIL_VIEW_TYPE, UPDATE_VIEW_TYPE, DELETE_VIEW_TYPE]

class SaveErrorHandlerMixin(object):
    def form_valid(self, form):
        try:
            return super(SaveErrorHandlerMixin, self).form_valid(form)
        except ValidationError as e:
            for field, errors in e:
                form.add_error(field, errors)
            return self.form_invalid(form)

class CrudViewset(object):
    model = None
    queryset = None

    root_breadcrumbs = []

    master_viewset_class = None
    nested_list_view_index = None

    # Setting this to any of the instance view types will cause the master
    # viewset to use its instance_breadcrumb_view_type setting, so the only
    # other value that makes sense is LIST_VIEW_TYPE.
    master_viewset_breadcrumb_view_type = DETAIL_VIEW_TYPE

    # instance_breadcrumb_text.format(instance)
    instance_breadcrumb_text = u"{0}"
    instance_breadcrumb_view_type = DETAIL_VIEW_TYPE

    lookup_field = 'pk'
    lookup_url_kwarg = 'pk'
    lookup_url_kwarg_pattern = r'\d+'

    lookup_regex = None

    view_url_kwarg_names = []

    active_nested_list_view_query_param = 't'

    view_decorator = staticmethod(login_required)

    exclude_views = []

    create_button_text = 'Create'
    create_button_class = 'btn-primary'

    edit_button_text = 'Edit'
    edit_button_class = 'btn-primary'

    delete_button_text = 'Delete'
    delete_button_class = 'btn-danger'

    back_button_text = 'Back'
    back_button_class = 'btn-default'

    base_template_shim = None

    list_view_template_name = None
    create_view_template_name = 'crud/create_view.html'
    detail_view_template_name = 'crud/detail_view.html'
    update_view_template_name = 'crud/update_view.html'
    delete_view_template_name = 'crud/delete_view.html'

    # list_view_title.format(model.verbose_name_plural) if model can be
    # determined. The value is set to None here in case model cannot be
    # determined, in which case a specific value must be provided.
    list_view_title = None

    # create_view_title.format(model.verbose_name) if model can be determined.
    # The value is set to None here in case model cannot be determined, in
    # which case a specific value must be provided.
    create_view_title = None

    # *_view_title.format(view.object)
    detail_view_title = u"{0}"
    update_view_title = u"Edit {0}"
    delete_view_title = u"Delete {0}"

    success_url = None
    create_view_success_url = None
    update_view_success_url = None
    delete_view_success_url = None

    filter_class = None

    form_class = None
    create_view_form_class = None
    update_view_form_class = None

    form_exclude = []
    create_view_form_exclude = None
    update_view_form_exclude = None

    list_view_base_class = generic.ListView
    create_view_base_class = generic.CreateView

    def __init__(self):
        self.master_viewset = None
        self.nested_list_views = []
        self.is_list_view_nested = (self.master_viewset_class is not None) and (self.nested_list_view_index is not None)
        self.list_view_query_param_prefix = self.get_list_view_query_param_prefix()

        # This will be set to an empty string later if no nested list views are
        # linked to this view. We need the value in the detail view before then,
        # however.
        self.nested_list_view_query_param_prefix = self.get_nested_list_view_query_param_prefix()

        # Remove the trailing '-' as django_filter adds it in again.
        self.filter_query_param_prefix = self.list_view_query_param_prefix[:-1]

        # Cache the get_filter_class result in an instance attribute, which will
        # hide the class attribute of the same name.
        self.filter_class = self.get_filter_class()

        self.base_view_mixin = None
        self.views = {}

        self.exclude_views = set(self.exclude_views)
        if self.is_list_view_nested:
            self.exclude_views.add(LIST_VIEW_TYPE)

        if self.model is None:
            queryset = self.get_queryset(None)
            if isinstance(queryset, QuerySet):
                self.model = queryset.model
        elif self.queryset is None:
            # It's the user's problem if they define 'model' and override
            # 'get_queryset' at the same time.
            self.queryset = self.model._default_manager.all()
        else:
            raise ImproperlyConfigured("%s contains definitions for both 'model' and 'queryset', but only one or the other is allowed" % self.__class__.__name__)

        # If model is None then list_view_title and create_view_title will be
        # left with their default values (which are None by default and will
        # cause the corresponding getters to raise an error).
        if self.model is not None:
            if self.list_view_title is None:
                self.list_view_title = u"{0}"
            self.list_view_title = self.list_view_title.format(self.model._meta.verbose_name_plural.title())

            if self.create_view_title is None:
                self.create_view_title = u"Create {0}"
            self.create_view_title = self.create_view_title.format(self.model._meta.verbose_name.title())

        self.generate_list_view()
        self.generate_create_view()
        self.generate_detail_view()
        self.generate_update_view()
        self.generate_delete_view()

        self.is_view_enabled = {view_type: view is not None for view_type, view in self.views.items()}

        # For convenience.
        if not self.is_view_enabled[DETAIL_VIEW_TYPE] and (self.instance_breadcrumb_view_type == DETAIL_VIEW_TYPE):
            self.instance_breadcrumb_view_type = UPDATE_VIEW_TYPE

    @staticmethod
    def reverse_with_query_params(viewname, *args, **kwargs):
        query_params = kwargs.pop('query_params', None)
        url = reverse(viewname, *args, **kwargs)
        if query_params:
            url += '?' + query_params.urlencode()
        return url

    @staticmethod
    def get_parent_url_name(url_name, remove_count=1):
        return ':'.join(url_name.split(':')[:-remove_count])

    @staticmethod
    def derive_view_url_kwarg_names(master_viewset_class):
        return master_viewset_class.view_url_kwarg_names + [master_viewset_class.lookup_url_kwarg]

    @classmethod
    def depth(cls):
        return 0 if cls.master_viewset_class is None else cls.master_viewset_class.depth() + 1

    def get_master_object(self, view, instance):
        raise ImproperlyConfigured("%s requires an implementation of 'get_master_object'" % self.__class__.__name__)

    def get_list_view_query_param_prefix_core(self, relative_depth):
        # The prefix must include a trailing '-' to match the way django_filter
        # handles prefixes.
        prefix = 'd%d-' % (self.depth() + relative_depth)
        if self.is_list_view_nested and (relative_depth == 0):
            return '%s%d-' % (prefix, self.nested_list_view_index)
        else:
            return prefix

    def get_list_view_query_param_prefix(self):
        return self.get_list_view_query_param_prefix_core(0)

    def get_nested_list_view_query_param_prefix(self):
        return self.get_list_view_query_param_prefix_core(1)

    def remove_list_view_query_params_core(self, GET, prefix):
        if prefix != '':
            filtered = GET.copy()
            for key in filtered.keys():
                if key.startswith(prefix):
                    filtered.pop(key, None)
            return filtered
        return GET

    def remove_list_view_query_params(self, GET):
        return self.remove_list_view_query_params_core(GET, self.list_view_query_param_prefix)

    def remove_nested_list_view_query_params(self, GET):
        return self.remove_list_view_query_params_core(GET, self.nested_list_view_query_param_prefix)

    def get_view_url_kwargs(self, view_type, view, instance=None):
        kwargs = {name: view.kwargs[name] for name in self.view_url_kwarg_names}
        if view_type in INSTANCE_VIEW_TYPES:
            if isinstance(instance, dict):
                kwargs[self.lookup_url_kwarg] = instance.get(self.lookup_field)
            else:
                kwargs[self.lookup_url_kwarg] = getattr(instance, self.lookup_field)
        return kwargs

    def get_view_url(self, view_type, view, GET, instance=None):
        if self.is_list_view_nested and (view_type == LIST_VIEW_TYPE):
            return self.master_viewset.get_view_url(self.master_viewset.instance_breadcrumb_view_type, view, GET, view.cached_objects[self.master_viewset])
        else:
            return self.reverse_with_query_params(self.url_name_prefix + view_type, kwargs=self.get_view_url_kwargs(view_type, view, instance), query_params=self.remove_nested_list_view_query_params(GET) if view_type == LIST_VIEW_TYPE else GET)

    def get_root_breadcrumbs(self, view):
        return self.root_breadcrumbs

    def get_list_view_breadcrumb(self, view, GET, instance=None):
        return {
            'text': self.get_list_view_title(view),
            'url': self.get_view_url(LIST_VIEW_TYPE, view, GET)
        }

    def get_instance_breadcrumb_text(self, view, instance):
        return self.instance_breadcrumb_text.format(instance)

    def get_breadcrumbs(self, view_type, view, GET):
        breadcrumbs = []

        if self.master_viewset is None:
            breadcrumbs += self.get_root_breadcrumbs(view)
        else:
            breadcrumbs += self.master_viewset.get_breadcrumbs(self.master_viewset_breadcrumb_view_type, view, GET if self.is_list_view_nested else self.remove_list_view_query_params(GET))

        instance = view.cached_objects[self]

        # The list view of nested viewsets is part of the detail view of the
        # master viewset, and the breadcrumb will already have been added above.
        if not self.is_list_view_nested and self.is_view_enabled[LIST_VIEW_TYPE]:
            breadcrumbs.append(self.get_list_view_breadcrumb(view, GET, instance))

        if view_type in INSTANCE_VIEW_TYPES:
            breadcrumbs += [{
                'text': self.get_instance_breadcrumb_text(view, instance),
                'url': self.get_view_url(self.instance_breadcrumb_view_type, view, GET, instance)
            }]

        return breadcrumbs

    def get_list_view_title(self, view):
        if self.list_view_title is None:
            raise ImproperlyConfigured("%s requires either a definition of 'list_view_title' or an implementation of 'get_list_view_title'" % self.__class__.__name__)
        return self.list_view_title

    def get_create_view_title(self, view):
        if self.create_view_title is None:
            raise ImproperlyConfigured("%s requires either a definition of 'create_view_title' or an implementation of 'get_create_view_title'" % self.__class__.__name__)
        return self.create_view_title

    def get_detail_view_title(self, view):
        return self.detail_view_title.format(view.object)

    def get_update_view_title(self, view):
        return self.update_view_title.format(view.object)

    def get_delete_view_title(self, view):
        return self.delete_view_title.format(view.object)

    """
    If get_queryset is overridden to return an iterable rather than a QuerySet
    you must provide an implementation of:

        get_object(self, view, queryset=None)

    in order for instance views to work correctly. You can also provide an
    implementation of:

        delete_object(self, view, request, *args, **kwargs)
    
    to implement custom deletion logic.
    """
    def get_queryset(self, view):
        if self.queryset is None:
            raise ImproperlyConfigured("%s requires either a definition of 'model' or 'queryset', or an implementation of 'get_queryset'" % self.__class__.__name__)
        return self.queryset

    def get_object(self, view, queryset=None):
        if queryset is None:
            queryset = self.get_queryset(view)
        queryset = queryset.filter(**{self.lookup_field: view.kwargs[self.lookup_url_kwarg]})
        return get_object_or_404(queryset)

    def get_create_view_object(self, view):
        return None

    def add_context_data(self, view, context):
        pass

    def add_list_view_context_data(self, view, GET, context):
        pass

    def create_view_form_valid(self, view, form):
        pass

    def update_view_form_valid(self, view, form):
        pass

    def get_filter_class(self):
        return self.filter_class

    def get_form_class(self):
        if self.form_class is None:
            raise ImproperlyConfigured("%s requires a definition of either 'form_class' or the appropriate combination of 'create_view_form_class' and 'update_view_form_class'" % self.__class__.__name__)
        return self.form_class

    def get_create_view_form_class(self):
        if self.create_view_form_class is None:
            return self.get_form_class()
        return self.create_view_form_class

    def get_update_view_form_class(self):
        if self.update_view_form_class is None:
            return self.get_form_class()
        return self.update_view_form_class

    def get_form_exclude(self, view):
        return self.form_exclude

    def get_create_view_form_exclude(self, view):
        if self.create_view_form_exclude is None:
            return self.get_form_exclude(view)
        return self.create_view_form_exclude

    def get_update_view_form_exclude(self, view):
        if self.update_view_form_exclude is None:
            return self.get_form_exclude(view)
        return self.update_view_form_exclude

    def get_create_view_form_initial(self, view):
        return {}

    def get_update_view_form_initial(self, view):
        return {}

    def get_create_button_text(self):
        return self.create_button_text

    def get_create_button_class(self):
        return self.create_button_class

    def get_edit_button_text(self):
        return self.edit_button_text

    def get_edit_button_class(self):
        return self.edit_button_class

    def get_delete_button_text(self):
        return self.delete_button_text

    def get_delete_button_class(self):
        return self.delete_button_class

    def get_back_button_text(self):
        return self.back_button_text

    def get_back_button_class(self):
        return self.back_button_class

    def get_relative_view_url(self, url_name_suffix, remove_url_name_components=0, kwargs=None, query_params=None):
        if remove_url_name_components > 0:
            # url_name_prefix has a trailing colon so we always need to remove
            # an extra component.
            url_name_prefix = self.get_parent_url_name(self.url_name_prefix, remove_url_name_components + 1) + ':'
        else:
            url_name_prefix = self.url_name_prefix

        return self.reverse_with_query_params(url_name_prefix + url_name_suffix, kwargs=kwargs, query_params=query_params)

    def get_success_url(self, view):
        if self.success_url is None:
            return self.get_view_url(LIST_VIEW_TYPE, view, view.request.GET)
        return self.success_url

    def get_create_view_success_url(self, view):
        if self.create_view_success_url is None:
            return self.get_success_url(view)
        return self.create_view_success_url

    def get_update_view_success_url(self, view):
        if self.update_view_success_url is None:
            return self.get_success_url(view)
        return self.update_view_success_url

    def get_delete_view_success_url(self, view):
        if self.delete_view_success_url is None:
            return self.get_success_url(view)
        return self.delete_view_success_url

    def get_base_view_mixin(self):
        if self.base_view_mixin is None:
            class BaseViewMixin(object):
                viewset = self
                view_type = None
                final_breadcrumb = None
                pk_url_kwarg = viewset.lookup_url_kwarg

                def get_queryset(self):
                    return self.viewset.get_queryset(self)

                def get_view_title(self):
                    raise NotImplementedError

                def get_cached_object(self, viewset=None):
                    return self.cached_objects[self.viewset if viewset is None else viewset]

                def get_object(self, *args, **kwargs):
                    return self.cached_objects[self.viewset]

                def populate_object_cache(self, instance):
                    # Populate a cache of objects for all viewsets in the
                    # master-detail chain so all lookup logic is in one place
                    # and we don't have to worry about accidentally doing
                    # the same lookup twice in other functions.
                    viewset = self.viewset
                    viewset_object = instance
                    self.cached_objects = {viewset: viewset_object}
                    while viewset.master_viewset is not None:
                        if viewset_object is None:
                            viewset_object = viewset.master_viewset.get_object(self)
                        else:
                            viewset_object = viewset.get_master_object(self, viewset_object)
                        viewset = viewset.master_viewset
                        self.cached_objects[viewset] = viewset_object

                def get_context_data(self, *args, **kwargs):
                    context = super(BaseViewMixin, self).get_context_data(*args, **kwargs)
                    viewset = self.viewset

                    breadcrumbs = viewset.get_breadcrumbs(self.view_type, self, self.request.GET)
                    if self.final_breadcrumb is not None:
                        breadcrumbs.append(
                            {
                                'text': self.final_breadcrumb,
                                # Includes the query string.
                                'url': self.request.get_full_path()
                            }
                        )

                    context['base_template_shim'] = viewset.base_template_shim
                    context['breadcrumbs'] = breadcrumbs
                    context['query_string'] = self.request.GET.urlencode()
                    context['view_title'] = self.get_view_title()
                    context['is_view_enabled'] = viewset.is_view_enabled
                    context['actions'] = []

                    if (self.view_type != LIST_VIEW_TYPE) and (viewset.is_list_view_nested or viewset.is_view_enabled[LIST_VIEW_TYPE]):
                        context['actions'].append(
                            [
                                {
                                    'type': 'button',
                                    'text': viewset.get_back_button_text(),
                                    'url': viewset.get_view_url(LIST_VIEW_TYPE, self, self.request.GET),
                                    'button_class': viewset.get_back_button_class()
                                }
                            ]
                        )

                    viewset.add_context_data(self, context)

                    return context

            self.base_view_mixin = BaseViewMixin

        return self.base_view_mixin

    def get_decorated_view(self, view_class):
        view = view_class.as_view()
        if self.view_decorator is not None:
            view = self.view_decorator(view)
        view.viewset = self
        return view

    def is_view_generated(self, view_type):
        if view_type in self.views:
            return True
        if view_type in self.exclude_views:
            self.views[view_type] = None
            return True
        return False

    def generate_list_view(self):
        if self.is_view_generated(LIST_VIEW_TYPE):
            return

        class ListView(self.get_base_view_mixin(), self.list_view_base_class):
            viewset = self
            view_type = LIST_VIEW_TYPE
            template_name = self.list_view_template_name
            filter = None

            def dispatch(self, request, *args, **kwargs):
                self.populate_object_cache(None)
                return super(ListView, self).dispatch(request, *args, **kwargs)

            def get_view_title(self):
                return self.viewset.get_list_view_title(self)

            def get_context_data(self, *args, **kwargs):
                context = super(ListView, self).get_context_data(*args, **kwargs)
                if self.filter is not None:
                    context['filter'] = self.filter
                self.viewset.add_list_view_context_data(self, self.request.GET, context)
                return context

        if self.filter_class is not None:
            filter_class = self.filter_class
            prefix = self.filter_query_param_prefix

            # NOTE: This will only be called if base_list_view_class is a
            # ListView, not a TemplateView.
            def get_queryset(self):
                # Sanity check: verify that get_queryset() is called only once
                # per request.
                if self.filter is not None:
                    raise RuntimeError("ListView.get_queryset() was called more than once")
                self.filter = filter_class(self.request.GET, super(ListView, self).get_queryset(), prefix=prefix)
                return self.filter.qs

            ListView.get_queryset = get_queryset

        self.views[LIST_VIEW_TYPE] = self.get_decorated_view(ListView)

    def generate_create_view(self):
        if self.is_view_generated(CREATE_VIEW_TYPE):
            return

        class CreateView(SaveErrorHandlerMixin, self.get_base_view_mixin(), self.create_view_base_class):
            viewset = self
            view_type = CREATE_VIEW_TYPE
            form_class = self.get_create_view_form_class()
            template_name = self.create_view_template_name
            final_breadcrumb = 'Create'

            def dispatch(self, request, *args, **kwargs):
                self.populate_object_cache(self.viewset.get_create_view_object(self))
                return super(CreateView, self).dispatch(request, *args, **kwargs)

            def get_view_title(self):
                return self.viewset.get_create_view_title(self)

            def get_context_data(self, *args, **kwargs):
                context = super(CreateView, self).get_context_data(*args, **kwargs)
                context['form_exclude'] = self.viewset.get_create_view_form_exclude(self)
                return context

            def form_valid(self, form):
                self.viewset.create_view_form_valid(self, form)
                return super(CreateView, self).form_valid(form)

            def get_initial(self):
                return self.viewset.get_create_view_form_initial(self)

            def get_form(self, form_class=None):
                form = super(CreateView, self).get_form(form_class)
                form.view = self
                customise = getattr(form, 'customise_for_view', None)
                if customise is not None:
                    customise(self)
                return form

            def get_success_url(self):
                return self.viewset.get_create_view_success_url(self)

        self.views[CREATE_VIEW_TYPE] = self.get_decorated_view(CreateView)

    def generate_detail_view(self):
        if self.is_view_generated(DETAIL_VIEW_TYPE):
            return

        active_nested_list_view_query_param = self.nested_list_view_query_param_prefix + self.active_nested_list_view_query_param

        class DetailView(self.get_base_view_mixin(), generic.DetailView):
            viewset = self
            view_type = DETAIL_VIEW_TYPE
            template_name = self.detail_view_template_name

            def dispatch(self, request, *args, **kwargs):
                self.populate_object_cache(self.viewset.get_object(self))
                return super(DetailView, self).dispatch(request, *args, **kwargs)

            def get_view_title(self):
                return self.viewset.get_detail_view_title(self)

            def get_context_data(self, *args, **kwargs):
                context = super(DetailView, self).get_context_data(*args, **kwargs)

                viewset = self.viewset

                action_group = []
                if viewset.is_view_enabled[UPDATE_VIEW_TYPE]:
                    edit_button_text = viewset.get_edit_button_text()
                    if edit_button_text is not None:
                        action_group.append(
                            {
                                'type': 'button',
                                'id': 'id_edit_button',
                                'url': viewset.get_view_url(UPDATE_VIEW_TYPE, self, self.request.GET, self.get_cached_object()),
                                'text': edit_button_text,
                                'button_class': viewset.get_edit_button_class()
                            }
                        )

                if viewset.is_view_enabled[DELETE_VIEW_TYPE]:
                    delete_button_text = viewset.get_delete_button_text()
                    if delete_button_text is not None:
                        action_group.append(
                            {
                                'type': 'button',
                                'id': 'id_delete_button',
                                'url': viewset.get_view_url(DELETE_VIEW_TYPE, self, self.request.GET, self.get_cached_object()),
                                'text': delete_button_text,
                                'button_class': viewset.get_delete_button_class()
                            }
                        )

                if action_group:
                    context['actions'].append(action_group)

                context['nested_list_views'] = []
                if self.viewset.nested_list_views:
                    active_index = self.request.GET.get(active_nested_list_view_query_param, '')
                    have_active = False
                    for nested_viewset in self.viewset.nested_list_views:
                        index = str(nested_viewset.nested_list_view_index)
                        active = index == active_index
                        have_active = have_active or active
                        GET = self.request.GET.copy()
                        GET[active_nested_list_view_query_param] = index
                        nested_context = {
                            'active': active,
                            'id': 't' + index,
                            'caption': nested_viewset.get_list_view_title(self),
                            'actions': []
                        }
                        nested_viewset.add_list_view_context_data(self, GET, nested_context)
                        context['nested_list_views'].append(nested_context)
                    if not have_active:
                        context['nested_list_views'][0]['active'] = True

                return context

        self.views[DETAIL_VIEW_TYPE] = self.get_decorated_view(DetailView)

    def generate_update_view(self):
        if self.is_view_generated(UPDATE_VIEW_TYPE):
            return

        class UpdateView(SaveErrorHandlerMixin, self.get_base_view_mixin(), generic.UpdateView):
            viewset = self
            view_type = UPDATE_VIEW_TYPE
            form_class = self.get_update_view_form_class()
            template_name = self.update_view_template_name
            final_breadcrumb = None if self.instance_breadcrumb_view_type == UPDATE_VIEW_TYPE else 'Update'

            def dispatch(self, request, *args, **kwargs):
                self.populate_object_cache(self.viewset.get_object(self))
                return super(UpdateView, self).dispatch(request, *args, **kwargs)

            def get_view_title(self):
                return self.viewset.get_update_view_title(self)

            def get_context_data(self, *args, **kwargs):
                context = super(UpdateView, self).get_context_data(*args, **kwargs)

                viewset = self.viewset

                if viewset.is_view_enabled[DELETE_VIEW_TYPE]:
                    delete_button_text = viewset.get_delete_button_text()
                    if delete_button_text is not None:
                        context['actions'].append(
                            [
                                {
                                    'type': 'button',
                                    'url': viewset.get_view_url(DELETE_VIEW_TYPE, self, self.request.GET, self.get_cached_object()),
                                    'text': delete_button_text,
                                    'button_class': viewset.get_delete_button_class()
                                }
                            ]
                        )

                context['form_exclude'] = self.viewset.get_update_view_form_exclude(self)
                return context

            def form_valid(self, form):
                self.viewset.update_view_form_valid(self, form)
                return super(UpdateView, self).form_valid(form)

            def get_initial(self):
                return self.viewset.get_update_view_form_initial(self)

            def get_form(self, form_class=None):
                form = super(UpdateView, self).get_form(form_class)
                form.view = self
                customise = getattr(form, 'customise_for_view', None)
                if customise is not None:
                    customise(self)
                return form

            def get_success_url(self):
                return self.viewset.get_update_view_success_url(self)

        self.views[UPDATE_VIEW_TYPE] = self.get_decorated_view(UpdateView)

    def generate_delete_view(self):
        if self.is_view_generated(DELETE_VIEW_TYPE):
            return

        class DeleteView(self.get_base_view_mixin(), generic.DeleteView):
            viewset = self
            view_type = DELETE_VIEW_TYPE
            template_name = self.delete_view_template_name
            final_breadcrumb = 'Delete'

            def dispatch(self, request, *args, **kwargs):
                self.populate_object_cache(self.viewset.get_object(self))
                return super(DeleteView, self).dispatch(request, *args, **kwargs)

            def get_view_title(self):
                return self.viewset.get_delete_view_title(self)

            def get_success_url(self):
                return self.viewset.get_delete_view_success_url(self)

        if getattr(self, 'delete_object', None) is not None:
            def delete(self, request, *args, **kwargs):
                return self.viewset.delete_object(self, request, *args, **kwargs)

            DeleteView.delete = delete

        self.views[DELETE_VIEW_TYPE] = self.get_decorated_view(DeleteView)

    @classmethod
    def urls(cls):
        viewset = cls()

        lookup_regex = r'(?P<' + viewset.lookup_url_kwarg + '>' + viewset.lookup_url_kwarg_pattern + ')/' if viewset.lookup_regex is None else viewset.lookup_regex

        patterns = []

        def append_pattern(pattern, view_type):
            view = viewset.views[view_type]
            if view is not None:
                patterns.append(url(pattern, view, name=view_type))

        append_pattern(r'^$', LIST_VIEW_TYPE)
        append_pattern(r'^create/$', CREATE_VIEW_TYPE)
        append_pattern(lookup_regex + '$', DETAIL_VIEW_TYPE)
        append_pattern(lookup_regex + 'update/$', UPDATE_VIEW_TYPE)
        append_pattern(lookup_regex + 'delete/$', DELETE_VIEW_TYPE)

        if not patterns:
            # If a viewset functions only as a nested list view then it will
            # not define any views of its own. We need at least one view URL
            # to be defined in order to discover the viewset via link_viewsets,
            # however, so we simply define a dummy one.
            def not_found(request, *args, **kwargs):
                raise Http404('Not found')
            not_found.viewset = viewset
            patterns.append(url(r'^$', not_found, name=NOT_FOUND_VIEW_TYPE))

        return patterns

    @staticmethod
    def link_viewsets(views):
        viewsets = {}

        for view_function, url_pattern, view_name in views:
            viewset = getattr(view_function, 'viewset', None)
            if viewset is not None:
                viewset_class = viewset.__class__
                if viewset_class in viewsets:
                    # TODO: we can remove this restriction by passing a name/ID
                    # to the CrudViewset.urls() function to use in the viewset
                    # constructor, and then specifying that name/ID instead of
                    # the class for master or nested viewsets.
                    # OR we could just create derived viewset classes for each
                    # case.
                    if viewset != viewsets[viewset_class]:
                        raise ImproperlyConfigured("%s.urls() is called multiple times (see TODO in code)" % viewset_class.__name__)
                else:
                    viewset.url_name_prefix = CrudViewset.get_parent_url_name(view_name) + ':'
                    viewsets[viewset_class] = viewset

        for viewset_class, viewset in viewsets.items():
            if viewset.master_viewset_class is not None:
                # Sanity check.
                if viewset.master_viewset is not None:
                    raise RuntimeError("%s already has a master viewset" % viewset_class.__name__)

                viewset.master_viewset = viewsets.get(viewset.master_viewset_class, None)
                if viewset.master_viewset is None:
                    raise ImproperlyConfigured("%s does not have an associated URL" % viewset.master_viewset_class.__name__)

                if viewset.nested_list_view_index is not None:
                    for i, nested_viewset in enumerate(viewset.master_viewset.nested_list_views):
                        if viewset.nested_list_view_index < nested_viewset.nested_list_view_index:
                            viewset.master_viewset.nested_list_views.insert(i, viewset)
                            break
                        elif viewset.nested_list_view_index == nested_viewset.nested_list_view_index:
                            raise ImproperlyConfigured("%s and %s have the same value for nested_list_view_index", viewset.__class__.__name__, nested_viewset.__class__.__name__)
                    else:
                        viewset.master_viewset.nested_list_views.append(viewset)

        for viewset in viewsets.values():
            # Prevents unnecessary processing in
            # remove_nested_list_view_query_params() if there are no nested list
            # views.
            if not viewset.nested_list_views:
                viewset.nested_list_view_query_param_prefix = ''


class Tables2ListViewMixin(object):
    list_view_base_class = generic.TemplateView
    list_view_template_name = 'crud/tables2_list_view.html'
    detail_view_template_name = 'crud/tables2_detail_view.html'

    tables2_class = None
    tables2_context_variable_name = 'table'
    tables2_paginator_query_string_variable_name = 'paginator_query_string'
    tables2_template = 'django_tables2/bootstrap.html'
    tables2_attributes = {}
    tables2_meta_attributes = {}
    tables2_page_field = 'p'
    tables2_per_page_field = 'c'
    tables2_order_by_field = 's'
    tables2_clickable_rows = False
    tables2_clickable_row_class = 'clickable-row'
    tables2_clickable_row_view_type = DETAIL_VIEW_TYPE

    def __init__(self, *args, **kwargs):
        super(Tables2ListViewMixin, self).__init__(*args, **kwargs)

        # For convenience.
        if not self.is_view_enabled[DETAIL_VIEW_TYPE] and (self.tables2_clickable_row_view_type == DETAIL_VIEW_TYPE):
            self.tables2_clickable_row_view_type = UPDATE_VIEW_TYPE

        if self.tables2_class is None:
            meta = type('Meta', (object,), self.tables2_meta_attributes)

            attrs = copy.copy(self.tables2_attributes)
            attrs['Meta'] = meta

            self.tables2_class = type('Table', (django_tables2.Table,), attrs)

        try:
            my_attrs = copy.copy(self.tables2_class.Meta.attrs)
        except AttributeError:
            my_attrs = {}

        my_attrs['class'] = my_attrs.get('class', 'table table-bordered table-striped table-hover')

        class DerivedTable(self.tables2_class):
            class Meta(self.tables2_class.Meta):
                model = self.model
                template = self.tables2_template
                page_field = self.list_view_query_param_prefix + self.tables2_page_field
                per_page_field = self.list_view_query_param_prefix + self.tables2_per_page_field
                order_by_field = self.list_view_query_param_prefix + self.tables2_order_by_field
                attrs = my_attrs

        # This will create an instance variable containing the class and
        # leave the original class variable unchanged.
        self.tables2_class = DerivedTable

    def add_list_view_context_data(self, view, GET, context):
        super(Tables2ListViewMixin, self).add_list_view_context_data(view, GET, context)

        # Sanity check: get_queryset() will not have been called yet as we
        # are using a TemplateView instead of a ListView.
        if 'object_list' in context:
            raise RuntimeError("Context contains an 'object_list' key")

        if self.filter_class is None:
            queryset = self.get_queryset(view)
        else:
            context['filter'] = self.filter_class(GET, self.get_queryset(view), prefix=self.filter_query_param_prefix)
            queryset = context['filter'].qs

        table_kwargs = {}
        if self.tables2_clickable_rows:
            table_kwargs['row_attrs'] = {
                'class': self.tables2_clickable_row_class,
                'data-href': lambda record: self.get_view_url(self.tables2_clickable_row_view_type, view, GET, record)
            }

        table = self.tables2_class(queryset, **table_kwargs)
        django_tables2.RequestConfig(view.request).configure(table)
        table.viewset = self
        table.view = view
        table.GET = GET

        paginator_query_params = GET.copy()
        paginator_query_params.pop(table.page_field, None)

        context[self.tables2_context_variable_name] = table
        context[self.tables2_paginator_query_string_variable_name] = paginator_query_params.urlencode()

        if self.is_view_enabled[CREATE_VIEW_TYPE]:
            create_button_text = self.get_create_button_text()
            if create_button_text is not None:
                context['actions'].append(
                    [
                        {
                            'type': 'button',
                            'id': self.list_view_query_param_prefix + 'create_button',
                            'url': self.get_view_url(CREATE_VIEW_TYPE, view, GET),
                            'text': create_button_text,
                            'button_class': self.get_create_button_class()
                        }
                    ]
                )