Update user story ranks from raw data using data in a json field

gistfile1.txt

Map<String, Id> rank = new Map<String, Id>();
Map<Id, User_Story__c> stories = new Map<Id, User_Story__c>([
    select Id, Customer_Story_ID__c, Customer_Story_Raw_Data__c
    from User_Story__c
    where Project__r.Name = 'projectname'
]);
for (User_Story__c us : stories.values()) {
    if (String.isBlank(us.Customer_Story_Raw_Data__c)) continue;
    Map<String, Object> data = (Map<String, Object>)JSON.deserializeUntyped(us.Customer_Story_Raw_Data__c);
	// rally DragAndDropRank is not unique, so combine with id 
    String key = (String)data.get('DragAndDropRank') + us.Customer_Story_ID__c;
    rank.put(key, us.Id);
}
List<String> sortedRanks = new List<String>();
sortedRanks.addAll(rank.KeySet());
sortedRanks.sort();
List<User_Story__c> toUpsert = new List<User_Story__c>();
for (Integer i=0; i<sortedRanks.size(); i++) {
    String thisRank = sortedRanks.get(i);
    toUpsert.add(
    	new User_Story__c(
        	Id = rank.get(thisRank),
            Rank__c = i
        )
    );
}
upsert toUpsert;