+@register.assignment_tag(takes_context=True)
+def choose_cite(context, ctx=None):
+ """Choose a cite for main page, for book or for set of tags."""
+ try:
+ request = context['request']
+ assert request.user.is_staff
+ assert 'choose_cite' in request.GET
+ cite = Cite.objects.get(pk=request.GET['choose_cite'])
+ except (AssertionError, Cite.DoesNotExist):
+ if ctx is None:
+ cites = Cite.objects.all()
+ elif isinstance(ctx, Book):
+ cites = ctx.cite_set.all()
+ if not cites.exists():
+ cites = cites_for_tags([ctx.book_tag()])
+ else:
+ cites = cites_for_tags(ctx)
+ stickies = cites.filter(sticky=True)
+ count = stickies.count()
+ if count:
+ cite = stickies[randint(0, count - 1)]
+ else:
+ count = cites.count()
+ if count:
+ cite = cites[randint(0, count - 1)]
+ else:
+ cite = None
+ return cite
+
+