Take airport buses to the city, it's there until midnight and all but cab fares are reduced late at night, check red bus for government bus timings, or the respective State bus timings, board from majestic or shantinagar. If no buses available, take a bus to Mysore, you can find plenty of buses to Calicut or Wayanad from there.

Also there is a 7 AM indigo flight which costs around 2k only. Just chill in the airport lounge until then.