Activity API won't update case-related activities due to bad validation

The activity API can (and should) be able to update case-related activities. The problem is the _civicrm_activity_check_params() function, which gets confused when the activity is part of a case. Bypass the validator, and civicrm_activity_update works just fine.

I would volunteer to fix it, but that check_params function is just too messy for me to understand. I have tried reading it several times and really cannot understand what the author was trying to achieve or why it had to be so convoluted.

I guess my solution would be to just re-write the thing. I wrote a really clean and slick (IMHO) validator function for the new case API, which could serve as a good starting point for this (or any) $param validation.