onlyIDleft:

I don't see why it won't work with case c. Perhaps I don't understand exactly what you mean. Can you provide a bit more detail or some examples so I can see what you're meaning? If so, I may be able to tweak things up a bit. (It would be best to have a few examples of each of the cases, so we can cover all the corners.)

...roboticus

When your only tool is a hammer, all problems look like your thumb.