Bundesliga strugglers Borussia Dortmund have agreed to sign Slovenia international Kevin Kampl in January.
Cardiff have agreed to sell Norwegian midfielder Mats Daehli to Freiburg in January.
The 21-year-old had over a year left to run on his existing deal but the club were keen to tie him to a longer-term agreement.
Alfei, who has spent most of the season on loan at Wrexham, said: "I'm absolutely delighted. It's good to know the club has faith in me and there is nowhere I would rather be than Swansea."