I have an Alfresco document reference; what I'm looking for is a way to access workflow attached to that document and finish it (or progress it to the next transition) through Javascript.

Almost every example on the web shows how to start workflow, and from the dashlet I could call task command processor (/alfresco/command/task/end/[/transition]) if I knew the task ID, but how do I do the same thing from server-side web script starting only from the document reference?

There must be a way to access workflows from document and manage them programatically.