It's as hard as 1-2-3

Geometry

A circle with center $O$ has two points $A,B$ on its circumference and one point $P$ inside the circle such that $AP=1$ , $BP=2$ , $OP=3$ , and $\angle APB=90^{\circ}$ . If the area of the circle can be expressed as $\left(\dfrac{a+b\sqrt{c}}{d}\right)\pi$ for positive integers $a,b,c,d$ such that $c$ is square-free and $a,b$ are coprime with $d$ , then find the value of $a+b+c+d$ .