from BTrees.Length import Length

def upgrade_ratings(folder):
    """

    upgrades internal data structures of ratings
    object from version .1 -> .3

    needs a fix to Ratings.py to work

    add a meta_type = 'Ratings' first!!!

    """

    res = []

    ratings = self.ZopeFind(folder,
                         obj_metatypes=['Ratings'], 
                         search_sub=1)

    for p,r in ratings:

        data = r._data

        num_votes = len(data)

        r._num_votes = Length(num_votes)

        votesum = 0
        for v in data.values():
            votesum += v

        r._vote_sum = Length(votesum)

        res.append(p)
        
    header = "Fixed up the following ratings - (%s) "%(str(len(ratings)))
    
    body="<br><br><ul><li>%s</li></ul>"%join(res, '</li><li>')
   
    return header+body