Web interfact to revert snapchots of virtual machine for ctf event

I wanted to setup a web interface that will allow any user to press a button, then that would revert the virtual machine back to its original state so they can work on it from scratch. This is for a capture the flag event where users will be using virtual machines to solve problems, if they make a mistake, then they should be able to restart the vm and return it back to its original state. Can someone guide me on where to start. I'm currently running my virtual machines on xenserver and managed by xen center.

Thank you