Linux scripting - how do I wait for CD/DVD medium to load before reading/mounting?

I'm putting together a quick-and-dirty script to read 100s of CD/DVDs onto a NAS. It takes care of ejecting and loading the tray, but I haven't figured out a simple way to wait/block for the medium to become available to the OS after inserting the tray. - eject -t exits as soon as the tray closes - mount will fail with *No medium found* if it's run immediately after eject, but also when it's run 15 seconds later. The discs are fairly old and some take considerable time to become available, so I'd like to avoid the "sleep for 2 minutes" non-solution. Any ideas? Using ubuntu 18.04.