Ruby on Rails - Import Data from uncommon formatted CSV

I've got CSV files in the following format;

Category-1-GUID,Product1
,Product2
,Product3
Category-2-GUID,Product4
,Product5

and the task should write following data to the model:

Category-1-GUID,Product1
Category-1-GUID,Product2
Category-1-GUID,Product3
Category-2-GUID,Product4
Category-2-GUID,Product5

I've found Ruby on Rails - Import Data from a CSV file very useful to import the data but this little variance makes me became a blockhead....

Thanks in Advance! Best regards