[Spell] Buff Priority - I have receipts for everything!

[Devalut]

I have an ability that places a temporary buff on a unit, if the unit is damaged it will consume the buff and heal it for X amount.

I have multiple variants of this ability that can be cast, only one should fire and heal the target unit, and I would be absolutely pleased as punch if it were to be in order that I choose, either by what order they were last cast or by that of an arbitrary value (lowest buff duration, highest heal value, etc.)

Example:

UnitB casts 10 second BuffB on Footman, UnitA casts 60 second BuffA on Footman.

So with the effect already defined in my opening, BuffB should take priority over BuffA, however if the cast order is reversed and BuffA is cast before BuffB, BuffA Should fire!


ETA: I'm no stranger to Variables, hurt me plenty with your suggestions, but efficiency should take priority!

 

[Astrella]

You could trigger it removing the old buff or by another condition.

 

[Devalut]

But I need a way of defining whats considered old.
Ex: How can you tell if the inner fire on your footman was cast before the frost armor?

ETA: How about a dispel ability that removes the oldest negative/positive buff on the target?