Checking Permissions in Permission Groups in the Web Portal

Hi, I'm doing some customisation in the web portal and I want to implement permissions to base this customisation off. What I want is a number of permission groups each with their own permissions. Each permission can be applied to one or more permission groups. I want to query which permissions (not just permission group) the currently logged in user has and change some action, such as viewing or editing particular attributes, depending on which permissions the user has. Is this posisble? And if so, how do I query this information from within the web portal? Thanks for any help.