+@require_POST
+def revert(request, chunk_id):
+ form = forms.DocumentTextRevertForm(request.POST, prefix="textrevert")
+ if form.is_valid():
+ doc = get_object_or_404(Chunk, pk=chunk_id)
+ if not doc.book.accessible(request):
+ return HttpResponseForbidden("Not authorized.")
+
+ revision = form.cleaned_data['revision']
+
+ comment = form.cleaned_data['comment']
+ comment += "\n#revert to %s" % revision
+
+ if request.user.is_authenticated():
+ author = request.user
+ else:
+ author = None
+
+ before = doc.revision()
+ logger.info("Reverting %s to %s", chunk_id, revision)
+ doc.at_revision(revision).revert(author=author, description=comment)
+
+ return JSONResponse({
+ 'text': doc.materialize() if before != doc.revision() else None,
+ 'meta': {},
+ 'revision': doc.revision(),
+ })
+ else:
+ return JSONFormInvalid(form)
+
+
+@never_cache
+def gallery(request, directory):