+@never_cache
+def embargo_link(request, key, format_, slug):
+ book = get_object_or_404(Book, slug=slug)
+ if format_ not in Book.formats:
+ raise Http404
+ if key != book.preview_key:
+ raise Http404
+ media_file = book.get_media(format_)
+ if not book.preview:
+ return HttpResponseRedirect(media_file.url)
+ return HttpResponse(media_file, content_type=constants.EBOOK_CONTENT_TYPES[format_])
+
+