public Film recommendFilm(Person person) {
if (ratings.getPersonalRatings(person).isEmpty()) {
Map<Film, List<Rating>> filmRatings = ratings.filmRatings();
List<Film> films = new ArrayList<Film>();
for (Film f : filmRatings.keySet()) {
films.add(f);
}
Collections.sort(films, new FilmComparator(filmRatings));
return films.get(0);
} else {
Person mostSimilarPerson = findMostSimilarPerson(person);
Film personalBestFilm = getUnwatchedPersonalBestFilm(mostSimilarPerson, person);
if (ratings.getRating(mostSimilarPerson, personalBestFilm).getValue() > 1) {
return personalBestFilm;
} else {
return null;
}
}
}
private int getSimilarity(Person p1, Person p2) {
Map<Film, Rating> p1Review = ratings.getPersonalRatings(p1);
Map<Film, Rating> p2Review = ratings.getPersonalRatings(p2);
int totalSimilarity = 0;
for (Film f : p1Review.keySet()) {
if (p2Review.containsKey(f)) {
totalSimilarity += p1Review.get(f).getValue() * p2Review.get(f).getValue();
}
}
return totalSimilarity;
}
private Person findMostSimilarPerson(Person person) {
List<Person> reviewers = ratings.reviewers();
reviewers.remove(person);
Person mostSimilarPerson = reviewers.get(0);
for (Person p : reviewers) {
if (getSimilarity(person, p) > getSimilarity(person, mostSimilarPerson)) {
mostSimilarPerson = p;
}
}
return mostSimilarPerson;
}
private List<Film> removeWatchedFilms(List<Film> films, Person person) {
Map<Film, Rating> reviews = ratings.getPersonalRatings(person);
Iterator<Film> iterator = films.iterator();
while (iterator.hasNext()) {
if (reviews.containsKey(iterator.next())) {
// delete the object returned by the iterator with its previous method call
iterator.remove();
}
}
return films;
}
private Film getUnwatchedPersonalBestFilm(Person similarPerson, Person personToRecommend) {
Map<Film, Rating> reviews = ratings.getPersonalRatings(similarPerson);
List<Film> films = new ArrayList<Film>();
for (Film f : reviews.keySet()) {
films.add(f);
}
films = removeWatchedFilms(films, personToRecommend);
if (!films.isEmpty()) {
Film personalBestfilm = films.get(0);
for (Film f : films) {
if (reviews.get(f).getValue() > reviews.get(personalBestfilm).getValue()) {
personalBestfilm = f;
}
}
return personalBestfilm;
} else {
return null;
}
}
