Snap of Fury

This spell is a bit confusing. I wish to make a spell that ends all your cooldowns. But, the amount of cooldown ended makes you take more damage for that period of time.

Example:
Use Snap of Fury.
Ends the 5 second cooldown left on my other spell or spells.
I take more damage for 5 seconds.

How would I design this?

There is no way to detect the cooldown remaining on spells using simple means.
You would have to detect the casting of X spell and then start a repeating timer that would count the seconds.
Then, deal damage based on the value that timer made it to before you cast the refresh spell.
Now at the end or if the spells cooldown finishes, destroy the timer and such to prevent leaks.

At least, that's how I would go about doing it.

If you knew the cooldown time of every spell on the hero explicitly , it could be done.