Calvin Harris Rihanna's Next For Me!!!

6/16/2016 2:19 PM PDT

Calvin Harris is pumped for 2 reasons ... he hit the weights Thursday, and he's getting ready for his big moment with Rihanna.

We got Taylor Swift's ex leaving a gym in WeHo, and he could not have been in better spirits ... despite what is now clearly a bitter breakup which he believes involves cheating and lying.

Calvin was pretty talkative -- for Calvin -- telling our photog about his plans with RiRi as some awestruck fans got a big prize.

And check out Calvin's kicks ... Yeezys. You'll recall, Taylor's war with Kanye is back on, and Calvin is clearly a general in the army of the West.