Take the door off its track. Lay it down on a flat, even surface to work on it.
Screw in one metal mending brace at the top of the door, one in the middle about even with the door handle, and one at the bottom with a power drill.
Paint the braces to match the door with a paintbrush.
Screw one door hinge to the top, one to the middle and one to the bottom of the door. Adjust the door on the door frame as needed so that the door opens properly. Attach the other side of the hinges to the wall or door frame.