Hey, get ready to be confused @frissdiegurke -- there's a third type of hook, rounding out the behaviours
action hooks are, as @Mega describes, fired when something happens, and NodeBB doesn't care about the response.
filters are fired when plugins might change things. The majority of hooks in NodeBB are filters.
static hooks are fired when you need NodeBB to wait until your plugin is complete in order to do something. There is only one static hook available right now: static:app.load, which is fired on startup.
In this case, since the post is already slated to be deleted, but you want to do something before it is deleted... we may want to consider adding a new hook called static:post.purge.
Sorry for bothering guys, I found it in the source code.
There are two hooks already:
action:group.join
action:group.leave
Both of them takes only one argument:
{ groupName: groupName, uid: uid }
join: https://github.com/NodeBB/NodeBB/blob/master/src/groups.js#L633-L675
leave: https://github.com/NodeBB/NodeBB/blob/master/src/groups.js#L711-L742
Exactly what I'm looking for!
Edit:
action:groups.* hooks in the source code were renamed to
action:group.*
