Assignment move strategy

gistfile1.coffee

  update_assignment: (token, assignment, cb) ->
    # Pull the assignment from the current course,
    # push it onto the new one, save it,
    # and finally update the assignment fields. 
    Course.update {
      owner: token.username
      assignments: assignment._id
    },
    {
      $pull: {assignments: assignment._id}
    },
    {},
    (err, num_affected) =>
      Course
        .findOne({'owner': token.username, '_id': assignment.course})
        .run (err, course) =>
          course.assignments.push assignment._id
          course.save (err) =>
            Assignment.update {
                owner: token.username
                _id: assignment._id
              },
              {
                title: assignment.title
                date: assignment.date
                details: assignment.details
                done: assignment.done
                archived: assignment.archived
              },
              {},
              cb