[texhax] Positioning that depends on space available in the current line

[Aleksandar Zec]

Hello,

I would like to achieve this effect:

aaaaaaaaaaaaaaaaaaaaaaaaa
aaaaaaaaaaaaaaaaaaaaaaaaa
aaaaaaa             bbbbb

aaaaaaaaaaaaaaaaaaaaaaaaa
aaaaaaaaaaaaaaaaaaaaaaaaa
aaaaaaa
   bbbbbbbbbbbbbbbbbbbbbb

'aaa' is a normal paragraph text. 'bbb' is a signature that should be
positioned

(1) on the right end of the last line if there is enough place;
(2) in the next line if there is not enough place, right aligned.

Any package/trick to do this automatically?

Thank you in advance,
Alex