Recommend movies by shared ratings

Write a function recommendations(user, ratings) that returns a list of movies to recommend to the given user based on shared preferences. Each rating is a triplet [User Name, Movie Name, Rating] where Rating ∈ {1,2,3,4,5} (strings). Define two users as having similar taste if they have both rated the same movie with a 4 or 5. Recommend a movie to the user if the user has not rated it and any similar-taste user rated it a 4 or 5. Ensure the output contains unique movie names and justify any ordering you choose.