I was faced with the same constraints a couple of years ago and came up with an almost verbatim solution. It's an interesting problem where a lot of very subtle

I was faced with the same constraints a couple of years ago and came up with an almost verbatim solution. It's an interesting problem where a lot of very subtle bugs can happen, it's good to know that I went with the same solution as people who put a lot more effort into making sure it is correct.