# documentação Django 2.0.8

# Código fonte para django.contrib.syndication.views

    from calendar import timegm

    from django.conf import settings
    from django.contrib.sites.shortcuts import get_current_site
    from django.core.exceptions import ImproperlyConfigured, ObjectDoesNotExist
    from django.http import Http404, HttpResponse
    from django.template import TemplateDoesNotExist, loader
    from django.utils import feedgenerator
    from django.utils.encoding import iri_to_uri
    from django.utils.html import escape
    from django.utils.http import http_date
    from django.utils.timezone import get_default_timezone, is_naive, make_aware

    def add_domain(domain, url, secure=False):
        protocol = 'https' if secure else 'http'
        if url.startswith('//'):
            # Support network-path reference (see #16753) - RSS requires a protocol
            url = '%s:%s' % (protocol, url)
        elif not url.startswith(('http://', 'https://', 'mailto:')):
            url = iri_to_uri('%s://%s%s' % (protocol, domain, url))
        return url

    class FeedDoesNotExist(ObjectDoesNotExist):
        pass

    class Feed:
        feed_type = feedgenerator.DefaultFeed
        title_template = None
        description_template = None

        def __call__(self, request, *args, **kwargs):
            try:
                obj = self.get_object(request, *args, **kwargs)
            except ObjectDoesNotExist:
                raise Http404('Feed object does not exist.')
            feedgen = self.get_feed(obj, request)
            response = HttpResponse(content_type=feedgen.content_type)
            if hasattr(self, 'item_pubdate') or hasattr(self, 'item_updateddate'):
                # if item_pubdate or item_updateddate is defined for the feed, set
                # header so as ConditionalGetMiddleware is able to send 304 NOT MODIFIED
                response['Last-Modified'] = http_date(
                    timegm(feedgen.latest_post_date().utctimetuple()))
            feedgen.write(response, 'utf-8')
            return response

        def item_title(self, item):
            # Titles should be double escaped by default (see #6533)
            return escape(str(item))

        def item_description(self, item):
            return str(item)

        def item_link(self, item):
            try:
                return item.get_absolute_url()
            except AttributeError:
                raise ImproperlyConfigured(
                    'Give your %s class a get_absolute_url() method, or define an '
                    'item_link() method in your Feed class.' % item.__class__.__name__
                )

        def item_enclosures(self, item):
            enc_url = self._get_dynamic_attr('item_enclosure_url', item)
            if enc_url:
                enc = feedgenerator.Enclosure(
                    url=str(enc_url),
                    length=str(self._get_dynamic_attr('item_enclosure_length', item)),
                    mime_type=str(self._get_dynamic_attr('item_enclosure_mime_type', item)),
                )
                return [enc]
            return []

        def _get_dynamic_attr(self, attname, obj, default=None):
            try:
                attr = getattr(self, attname)
            except AttributeError:
                return default
            if callable(attr):
                # Check co_argcount rather than try/excepting the function and
                # catching the TypeError, because something inside the function
                # may raise the TypeError. This technique is more accurate.
                try:
                    code = attr.__code__
                except AttributeError:
                    code = attr.__call__.__code__
                if code.co_argcount == 2:       # one argument is 'self'
                    return attr(obj)
                else:
                    return attr()
            return attr

        def feed_extra_kwargs(self, obj):
            """
            Return an extra keyword arguments dictionary that is used when
            initializing the feed generator.
            """
            return {}

        def item_extra_kwargs(self, item):
            """
            Return an extra keyword arguments dictionary that is used with
            the `add_item` call of the feed generator.
            """
            return {}

        def get_object(self, request, *args, **kwargs):
            return None

        def get_context_data(self, **kwargs):
            """
            Return a dictionary to use as extra context if either
            ``self.description_template`` or ``self.item_template`` are used.

            Default implementation preserves the old behavior
            of using {'obj': item, 'site': current_site} as the context.
            """
            return {'obj': kwargs.get('item'), 'site': kwargs.get('site')}

        def get_feed(self, obj, request):
            """
            Return a feedgenerator.DefaultFeed object, fully populated, for
            this feed. Raise FeedDoesNotExist for invalid parameters.
            """
            current_site = get_current_site(request)

            link = self._get_dynamic_attr('link', obj)
            link = add_domain(current_site.domain, link, request.is_secure())

            feed = self.feed_type(
                title=self._get_dynamic_attr('title', obj),
                subtitle=self._get_dynamic_attr('subtitle', obj),
                link=link,
                description=self._get_dynamic_attr('description', obj),
                language=settings.LANGUAGE_CODE,
                feed_url=add_domain(
                    current_site.domain,
                    self._get_dynamic_attr('feed_url', obj) or request.path,
                    request.is_secure(),
                ),
                author_name=self._get_dynamic_attr('author_name', obj),
                author_link=self._get_dynamic_attr('author_link', obj),
                author_email=self._get_dynamic_attr('author_email', obj),
                categories=self._get_dynamic_attr('categories', obj),
                feed_copyright=self._get_dynamic_attr('feed_copyright', obj),
                feed_guid=self._get_dynamic_attr('feed_guid', obj),
                ttl=self._get_dynamic_attr('ttl', obj),
                **self.feed_extra_kwargs(obj)
            )

            title_tmp = None
            if self.title_template is not None:
                try:
                    title_tmp = loader.get_template(self.title_template)
                except TemplateDoesNotExist:
                    pass

            description_tmp = None
            if self.description_template is not None:
                try:
                    description_tmp = loader.get_template(self.description_template)
                except TemplateDoesNotExist:
                    pass

            for item in self._get_dynamic_attr('items', obj):
                context = self.get_context_data(item=item, site=current_site,
                                                obj=obj, request=request)
                if title_tmp is not None:
                    title = title_tmp.render(context, request)
                else:
                    title = self._get_dynamic_attr('item_title', item)
                if description_tmp is not None:
                    description = description_tmp.render(context, request)
                else:
                    description = self._get_dynamic_attr('item_description', item)
                link = add_domain(
                    current_site.domain,
                    self._get_dynamic_attr('item_link', item),
                    request.is_secure(),
                )
                enclosures = self._get_dynamic_attr('item_enclosures', item)
                author_name = self._get_dynamic_attr('item_author_name', item)
                if author_name is not None:
                    author_email = self._get_dynamic_attr('item_author_email', item)
                    author_link = self._get_dynamic_attr('item_author_link', item)
                else:
                    author_email = author_link = None

                tz = get_default_timezone()

                pubdate = self._get_dynamic_attr('item_pubdate', item)
                if pubdate and is_naive(pubdate):
                    pubdate = make_aware(pubdate, tz)

                updateddate = self._get_dynamic_attr('item_updateddate', item)
                if updateddate and is_naive(updateddate):
                    updateddate = make_aware(updateddate, tz)

                feed.add_item(
                    title=title,
                    link=link,
                    description=description,
                    unique_id=self._get_dynamic_attr('item_guid', item, link),
                    unique_id_is_permalink=self._get_dynamic_attr(
                        'item_guid_is_permalink', item),
                    enclosures=enclosures,
                    pubdate=pubdate,
                    updateddate=updateddate,
                    author_name=author_name,
                    author_email=author_email,
                    author_link=author_link,
                    categories=self._get_dynamic_attr('item_categories', item),
                    item_copyright=self._get_dynamic_attr('item_copyright', item),
                    **self.item_extra_kwargs(item)
                )
            return feed