Lava/water reactions and rain in cauldrons

Where should I look to find where cauldrons collect water while it's raining (random tick) and lava/water reactions are? If it exists, is there anything for the composter as well (sorry for asking so much)? I should note that I'm a newbie and have only done the most basic of stuff in relation to datapacks, I just can't find anything anywhere about these sorts of things ;-v-.