I remember our discussion on this. I think this is a little too clumsy.

I adapted a little bit, it can be seen here: 6acd14348dd177c3dae8b0869327e4b6ad8b48a7

We don't need to remember a 'previous topic' because the replacement we do all the time anyway (in the controller, ech was there by default). No the searchcontroller does not care about the topic. Only in the directive to we keep track of the topic.

What do you think?