Don't implement strumming patterns! I've watched my wife trying to learn guitar pursing her lips saying up-down-up-up-down to herself and it just sounds robotic. Once you can play the chords smoothly enough strumming just happens. Even better, everyone seems to strum their own way (i cant sing so i strum a lot to compensate, whereas i have a friend with a beautiful voice who barely touches the strings)
That up-down-up-up-down whilst keeping the hand moving sets up different rythms and is an important skill. Especially if you're trying to learn a particular song - which will sound totally different if you get that wrong. Of course, you can get away without learning it like a lot of stuff on the guitar but you just won't be as good.
IMHO, strumming patterns are something that you (as a beginner) need to experiment with to see what sounds just right. Eventually you end up not thinking about it anymore.
Maybe an algorithm that could identify for ex first played note - meaning bass or first string and continue the same with other chords. After that you know where to start. Also there are only few strumming patterns and if you know the measure it should be easier. Just an idea.