from django.core.exceptions import ImproperlyConfigured, ObjectDoesNotExist

from django.template import Context, loader, Template, TemplateDoesNotExist

from django.contrib.sites.models import Site, RequestSite

from django.utils import feedgenerator

from django.utils.encoding import smart_unicode, iri_to_uri

from django.conf import settings         

from django.template import RequestContext

def add_domain(domain, url):

    if not (url.startswith('http://') or url.startswith('https://')):

        # 'url' must already be ASCII and URL-quoted, so no need for encoding

        # conversions here.

        url = iri_to_uri(u'http://%s%s' % (domain, url))

    return url

class FeedDoesNotExist(ObjectDoesNotExist):

    pass

class Feed(object):

    item_pubdate = None

    item_enclosure_url = None

    feed_type = feedgenerator.DefaultFeed

    title_template = None

    description_template = None

    def __init__(self, slug, request):

        self.slug = slug

        self.request = request

        self.feed_url = request.path

        self.title_template_name = self.title_template or ('feeds/%s_title.html' % slug)

        self.description_template_name = self.description_template or ('feeds/%s_description.html' % slug)

    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 __get_dynamic_attr(self, attname, obj, default=None):

        try:

            attr = getattr(self, attname)

        except AttributeError:

            return default

        if callable(attr):

            # Check func_code.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.

            if hasattr(attr, 'func_code'):

                argcount = attr.func_code.co_argcount

            else:

                argcount = attr.__call__.func_code.co_argcount

            if argcount == 2: # one argument is 'self'

                return attr(obj)

            else:

                return attr()

        return attr

    def get_object(self, bits):

        return None

    def get_feed(self, url=None):

        """

        Returns a feedgenerator.DefaultFeed object, fully populated, for

        this feed. Raises FeedDoesNotExist for invalid parameters.

        """

        if url:

            bits = url.split('/')

        else:

            bits = []

        try:

            obj = self.get_object(bits)

        except ObjectDoesNotExist:

            raise FeedDoesNotExist

        if Site._meta.installed:

            current_site = Site.objects.get_current()

        else:

            current_site = RequestSite(self.request)

        link = self.__get_dynamic_attr('link', obj)

        link = add_domain(current_site.domain, link)

        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.decode(),

            feed_url = add_domain(current_site.domain,

                                  self.__get_dynamic_attr('feed_url', obj)),

            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),

        )

        try:

            title_tmp = loader.get_template(self.title_template_name)

        except TemplateDoesNotExist:

            title_tmp = Template('{{ obj }}')

        try:

            description_tmp = loader.get_template(self.description_template_name)

        except TemplateDoesNotExist:

            description_tmp = Template('{{ obj }}')

        for item in self.__get_dynamic_attr('items', obj):

            link = add_domain(current_site.domain, self.__get_dynamic_attr('item_link', item))

            enc = None

            enc_url = self.__get_dynamic_attr('item_enclosure_url', item)

            if enc_url:

                enc = feedgenerator.Enclosure(

                    url = smart_unicode(enc_url),

                    length = smart_unicode(self.__get_dynamic_attr('item_enclosure_length', item)),

                    mime_type = smart_unicode(self.__get_dynamic_attr('item_enclosure_mime_type', 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

            feed.add_item(

                title = title_tmp.render(RequestContext(self.request, {'obj': item, 'site': current_site})),

                link = link,

                description = description_tmp.render(RequestContext(self.request, {'obj': item, 'site': current_site})),

                unique_id = self.__get_dynamic_attr('item_guid', item, link),

                enclosure = enc,

                pubdate = self.__get_dynamic_attr('item_pubdate', item),

                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),

            )

        return feed