There are three people, Alex, Brook and Cody. One of whom is a knight, one a knave, and one a spy. The knight always tells the truth, the knave always lies, and the spy can either lie or tell the truth. Alex says: "Cody is a knave." Brook says: "Alex is a knight." Cody says: "I am the spy." Who is the knight, who is the knave, and who is the spy?