Castaway/shipwrecked sailor

This new humanoid mob would have 10% to spawn on a shipwreck upon chunk loading around the player. If he survives he will try to get to the closest block that is not a water source block. He will trade diamonds or emeralds (or any other valuable item) for food. If you give him a place with a bed to sleep, he lowers the prices of trading. After certain number of trades he runs out of items to sell- forever. However, upon running out of items to trade with, he gives a treasure map.