from django.core.paginator import Paginator, InvalidPage
from django.core.exceptions import ImproperlyConfigured
from django.http import Http404
from django.utils.encoding import smart_str
from django.views.generic.base import TemplateResponseMixin, View

class MultipleObjectMixin(object):
    allow_empty = True
    queryset = None
    model = None
    paginate_by = None
    context_object_name = None

    def get_queryset(self):
        """
        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:
            queryset = self.model._default_manager.all()
        else:
            raise ImproperlyConfigured(u"'%s' must define 'queryset' or 'model'"
                                       % self.__class__.__name__)
        return queryset

    def paginate_queryset(self, queryset, page_size):
        """
        Paginate the queryset, if needed.
        """
        if queryset.count() > page_size:
            paginator = Paginator(queryset, page_size, allow_empty_first_page=self.get_allow_empty())
            page = self.kwargs.get('page', None) or self.request.GET.get('page', 1)
            try:
                page_number = int(page)
            except ValueError:
                if page == 'last':
                    page_number = paginator.num_pages
                else:
                    raise Http404("Page is not 'last', nor can it be converted to an int.")
            try:
                page = paginator.page(page_number)
                return (paginator, page, page.object_list, True)
            except InvalidPage:
                raise Http404(u'Invalid page (%s)' % page_number)
        else:
            return (None, None, queryset, False)

    def get_paginate_by(self, queryset):
        """
        Get the number of items to paginate by, or ``None`` for no pagination.
        """
        return self.paginate_by

    def get_allow_empty(self):
        """
        Returns ``True`` if the view should display empty lists, and ``False``
        if a 404 should be raised instead.
        """
        return self.allow_empty

    def get_context_object_name(self, object_list):
        """
        Get the name of the item to be used in the context.
        """
        if self.context_object_name:
            return self.context_object_name
        elif hasattr(object_list, 'model'):
            return smart_str(object_list.model._meta.verbose_name_plural)
        else:
            return None

    def get_context_data(self, **kwargs):
        """
        Get the context for this view.
        """
        queryset = kwargs.pop('object_list')
        page_size = self.get_paginate_by(queryset)
        if page_size:
            paginator, page, queryset, is_paginated = self.paginate_queryset(queryset, page_size)
            context = {
                'paginator': paginator,
                'page_obj': page,
                'is_paginated': is_paginated,
                'object_list': queryset
            }
        else:
            context = {
                'paginator': None,
                'page_obj': None,
                'is_paginated': False,
                'object_list': queryset
            }
        context.update(kwargs)
        context_object_name = self.get_context_object_name(queryset)
        if context_object_name is not None:
            context[context_object_name] = queryset
        return context


class BaseListView(MultipleObjectMixin, View):
    def get(self, request, *args, **kwargs):
        self.object_list = self.get_queryset()
        allow_empty = self.get_allow_empty()
        if not allow_empty and len(self.object_list) == 0:
            raise Http404(u"Empty list and '%s.allow_empty' is False."
                          % self.__class__.__name__)
        context = self.get_context_data(object_list=self.object_list)
        return self.render_to_response(context)

class MultipleObjectTemplateResponseMixin(TemplateResponseMixin):
    template_name_suffix = '_list'

    def get_template_names(self):
        """
        Return a list of template names to be used for the request. Must return
        a list. May not be called if get_template is overridden.
        """
        names = super(MultipleObjectTemplateResponseMixin, self).get_template_names()

        # If the list is a queryset, we'll invent a template name based on the
        # app and model name. This name gets put at the end of the template
        # name list so that user-supplied names override the automatically-
        # generated ones.
        if hasattr(self.object_list, 'model'):
            opts = self.object_list.model._meta
            names.append("%s/%s%s.html" % (opts.app_label, opts.object_name.lower(), self.template_name_suffix))

        return names

class ListView(MultipleObjectTemplateResponseMixin, BaseListView):
    """
    Render some list of objects, set by `self.model` or `self.queryset`.
    `self.queryset` can actually be any iterable of items, not just a queryset.
    """
