The chord did it

In the circle $G$ , the midpoint of the radius $FG$ is $H$ and $AB\perp EF$ at $H$ . The semicircle with $AB$ as diameter intersects $EF$ in $I$ , line $AI$ intersects circle $G$ in $C$ and line $BI$ intersects the circle $G$ at $D$ , then chord $BC$ is drawn.

If the radius of the circle $G$ is $r$ , then find length of chord $BC$ .