#usertask

I would like to get all available, unassigned task (assigned_id equal to blank or null) via API using an administrator account/profile.
Reason for this is to create an auto-assign task for users who are currently online or active. Auto-assigning will be based on availability of the user or base on his/her current assign load.

How can i filter this to the API?

How can I obtain the user or possible users in charge of performing the task called Step2 through a Groovy script? (See attached image)