$page = (isset($_GET['page'])) ? intval($_GET['page']) : 0;

from django import forms
 
class ListForm(forms.Form):
    feed = forms.IntegerField(required=False)
    category = forms.IntegerField(required=False)
    since = forms.DateTimeField(required=False)
    count = forms.IntegerField(required=False)
    page = forms.IntegerField(required=False)
    include_content = forms.BooleanField(required=False)
 
def list(request, format='json'):
    form = ListForm(request.user, request.GET)
 
    if form.is_valid():
       articles = Article.objects.filter(feed__in=form.cleaned_data['feeds']
                                                  ).order_by('-time')[page*count:page*count+count]
       return HttpResponse(json.dumps({'status': 'OK',
                                        'count': len(articles),
                                        'articles': articles}))
    else:
	return HttpResponseBadRequest(json.dumps({'status': 'ERROR'}))

def form_valid(form_type, data_type):
    def inner(view_func):
        def wrapper(request, *args, **kwargs):
            form = form_type(request.__getattribute__(data_type))
 
            if form.is_valid():
                request.form = form
                return view_func(request, *args, **kwargs)
            else:
                return HttpResponseBadRequest(json.dumps({'status': 'ERROR'}))
        return wraps(view_func)(wrapper)
    return inner
 
## the usage goes like so
@form_valid(ImageForm, 'GET')
def image(request):
    blob = BlobInfo.gql("WHERE filename='%s' LIMIT 1" % request.form.cleaned_data['id'])[0]
 
    return HttpResponse(BlobReader(blob.key()).read(),
                        content_type=blob.content_type)

## this enables us to handle <a class="zem_slink freebase/en/comma-separated_values" title="Comma-separated values" rel="wikipedia" href="http://en.wikipedia.org/wiki/Comma-separated_values">comma separated values</a> seamlessly
    def clean_feed(self):
        try:
            feed = [int(id) for id in str(self.cleaned_data['feed']).split(',')]
        except (AttributeError, ValueError, KeyError):
            feed = None
        return feed
 
## automagically parsing json parameters can be done too
    def clean_feeds(self):
        feeds = json.loads(self.cleaned_data['feeds'])
        if type(feeds) != list:
            raise forms.ValidationError("list of feeds expected")
        return feeds
 
## or how about logging in the user while we're checking the user/pass is correct
## don't manually log in users unless you know at least somewhat what you're doing, usually django handles this
    def clean(self):
        cleaned_data = self.cleaned_data
 
        if len(self.errors) != 0:
            return cleaned_data
 
        user = authenticate(username=cleaned_data['email'],
                            password=cleaned_data['password'])
        if user is None:
            del cleaned_data['email']
            del cleaned_data['password']
            raise forms.ValidationError('Bad login')
        else:
            cleaned_data['user'] = user
 
        return cleaned_data
 
## now the strangest thing, when you have to handle grabbing data by different parameters
##(like being given a set of feed ids, or a feed category id, you can do this by returning
## a QuerySet in the form's cleaned_data
def clean(self):
        cleaned_data = self.cleaned_data
 
        if not (cleaned_data.get('feed', None) != None or cleaned_data.get('category', None) != None):
            raise forms.ValidationError("feed or category required")
 
        if cleaned_data['feed'] != None:
            user_feeds = UserFeed.objects.filter(user=self.user,
                                                 id__in=cleaned_data['feed'])
        else:
            user_feeds = UserFeed.objects.filter(user=self.user,
                                                 categories__contains="'%d'" % cleaned_data['category'])
 
        cleaned_data['feeds'] = map(lambda f: f.id,
                                    Feed.objects.filter(id__in=map(lambda f: f.feed, user_feeds)))
 
        reverse_feeds = {}
        for feed in user_feeds:
            reverse_feeds[feed.feed] = feed.id
        cleaned_data['reverse_feeds'] = reverse_feeds
 
        return cleaned_data