Bash if grep or grep elif grep? So confused

Here is what I am trying to do. I want to grep(maybe?) a file for keywords based on what I find do blah.

if grep "env=" does not exist OR "env=" exists but is null file.name; then
env=prod 
elif grep "env=dev" OR "env=qa" file.name; then
env=dev/qa respectivly

I was trying some grep command but was getting stuck with that