Get player attack cooldown

So, we all now about the +1.9 combat sistem. Well, I want to know how to get the player "attack cooldown"
When you attack, a sword-like bar apparear showing you how much time is left for the next attack, and if you attack before the bar is full, the damage dealed is less
I want to know how to get how much of that bar you have / miss for various procedures, as a procedure like "when hitting a mob: deal 3 damage" will always deal the 3 points of damage, even when spamming
I guess is a NTB, but I don't know what one is