fix film recommendations after review

src/main/java/ru/yandex/practicum/filmorate/repository/film/FilmRepository.java

@@ -25,7 +25,7 @@ public interface FilmRepository {
 
     Collection<Film> findFilmsOfDirector(long directorId, FilmsSortBy sortFilmsBy);
 
-    Collection<Film> findFilmRecommendations(long userId, long similarUserId);
+    Collection<Film> findFilmRecommendations(long userId, List<Long> similarUserIds);
 
     Collection<Film> searchFilms(String query, List<SearchFilmsBy> searchBy);
 }

src/main/java/ru/yandex/practicum/filmorate/repository/film/JdbcFilmRepository.java

@@ -175,18 +175,19 @@ public Collection<Film> findFilmsOfDirector(long directorId, FilmsSortBy sortFil
     }
 
     @Override
-    public Collection<Film> findFilmRecommendations(long userId, long similarUserId) {
+    public Collection<Film> findFilmRecommendations(long userId, List<Long> similarUserIds) {
         String sqlRecommendations = BASE_SELECT_SQL.concat("""
                 LEFT JOIN likes l ON f.film_id = l.film_id
-                WHERE l.user_id = :similarUserId
+                WHERE l.user_id IN (:similarUserIds)
                   AND f.film_id NOT IN (
                       SELECT film_id FROM likes WHERE user_id = :userId
                   )
                 GROUP BY f.film_id
+                ORDER BY COUNT(DISTINCT l.user_id) DESC
                 """);
 
         MapSqlParameterSource params = new MapSqlParameterSource()
-                .addValue("similarUserId", similarUserId)
+                .addValue("similarUserIds", similarUserIds)
                 .addValue("userId", userId);
 
         return jdbc.query(sqlRecommendations, params, filmRowMapper);

src/main/java/ru/yandex/practicum/filmorate/repository/user/JdbcUserRepository.java

@@ -115,7 +115,7 @@ WHERE u.user_id IN (SELECT user_id2
         return jdbc.query(selectCommonFriendsSql, params, rowMapper);
     }
 
-    public Optional<Long> findSimilarFilmTasteUser(long userId) {
+    public List<Long> findSimilarFilmTasteUsers(long userId) {
         MapSqlParameterSource params = new MapSqlParameterSource()
                 .addValue("userId", userId);
 
@@ -128,15 +128,8 @@ public Optional<Long> findSimilarFilmTasteUser(long userId) {
           AND l2.user_id != :userId
         GROUP BY l2.user_id
         ORDER BY common_like_count DESC
-        LIMIT 1""";
+        LIMIT 5""";
 
-        Long result = jdbc.query(sql, params, rs -> {
-            if (rs.next()) {
-                return rs.getObject("other_user", Long.class);
-            }
-            return null;
-        });
-
-        return Optional.ofNullable(result);
+        return jdbc.query(sql, params, (rs, rowNum) -> rs.getLong("other_user"));
     }
 }

src/main/java/ru/yandex/practicum/filmorate/repository/user/UserRepository.java

@@ -3,6 +3,7 @@
 import ru.yandex.practicum.filmorate.model.User;
 
 import java.util.Collection;
+import java.util.List;
 import java.util.Optional;
 
 public interface UserRepository {
@@ -20,5 +21,5 @@ public interface UserRepository {
 
     Collection<User> findAllCommonFriends(long userId1, long userId2);
 
-    Optional<Long> findSimilarFilmTasteUser(long userId);
+    List<Long> findSimilarFilmTasteUsers(long userId);
 }

src/main/java/ru/yandex/practicum/filmorate/service/recommendation/RecommendationServiceImpl.java

@@ -11,7 +11,7 @@
 
 import java.util.Collection;
 import java.util.Collections;
-import java.util.Optional;
+import java.util.List;
 
 @Service
 @Slf4j
@@ -25,14 +25,13 @@ public Collection<FilmDto> findFilmRecommendations(long userId) {
         userRepository.findById(userId)
                 .orElseThrow(NotFoundException.supplier("User with id %d not found", userId));
 
-        Optional<Long> similarUserOpt = userRepository.findSimilarFilmTasteUser(userId);
+        List<Long> similarUsers = userRepository.findSimilarFilmTasteUsers(userId);
 
-        if (similarUserOpt.isEmpty()) {
+        if (similarUsers.isEmpty()) {
             return Collections.emptyList();
         }
 
-        long similarUserId = similarUserOpt.get();
-        return filmRepository.findFilmRecommendations(userId, similarUserId)
+        return filmRepository.findFilmRecommendations(userId, similarUsers)
                 .stream()
                 .map(FilmMapper::toFilmDto)
                 .toList();