Toyota Repair: brake problem, brake caliper, toyota corolla

Question
i have a 1990 toyota corolla. i heard some break noise while driving more like a grinding, and took the chance to get home, right before i got home i heard a big clunk and the car stopped. so i opened up the brake caliper and saw that my breaks were gone and the cylinder inside the break caliper popped out. i tried to use a clamp and push it back in as i usually do when changing the breaks, but this time it wont go back in. what should i do, buy a new break caliper or is that still usable.  

Answer
I recommend removing the brake caliper from the car, get a seal kit, replace the seal on the piston, clean everything thoroughly, open the brake bleeder valve, lubricate the piston with brake fluid and make sure it goes in straight it should go back in with no trouble. Put everything back together and bleed all the air out.