Front driver side wheel is leaking bra...

Front driver side wheel is leaking brake fluid all over wheel well and behind wheel is wet, I lost brakes, I put fluid in and made it home safely and got under truck to see where the leak was. brake line is dry and not leaking, However, when facing the front of the vehicle, the rear of the front tire is a metal part that is leaking pretty bad from the bottom, Ive been told it is a wheel cylinder, but My father belives it is a caliper. I need to know if it is a caliper so I can get the part to fix it or not.