Radial movement range for turn based strategy game

Hi.

I want to create a movement system for a turn based strategy game which isn't grid based. The units should have a certain movement range in which they can move. The basic thing is pretty easy but how can I adjust (and draw) the movement area considering obstacles?

I added an image. The black dot is the character, the red outline is the max range, the blie the adjusted one and the grren block is the obstacle. It's not accurate but should show what I'm trying to achieve.

What would be the best approach to that?

Thanks in advance.