first of all, is it hard to create??because i am just a newbie here.

or can you guys just tell me the algo/logic needed to construct that ai.because i want to learn creating my own script..

thanks in advance..

create global variable which determine player attack. Then your ai knew then player attack and can defend or do else stuff don't know what is global variable? read this http://tutorial.3dgamestudio.net/ article workshop24: Variables II