[BE] refactor: 리뷰 랭킹 알고리즘 개선 (#737)

* feat: 리뷰의 랭킹 점수 계산 로직 추가

* test: 리뷰 랭킹 점수 계산 관련 테스트 추가

* refactor: 리뷰 랭킹 기능 수정

* test: 리뷰 랭킹 서비스 테스트 추가

* style: import 와일드카드 제거

* refactor: 좋아요 1개 이상인 리뷰만 랭킹에 들어갈 수 있도록 수정

* refactor: 사용하지 않는 메서드 및 테스트 삭제

* test: findReviewsByFavoriteCountGreaterThanEqual 테스트 추가

* style: ReviewServiceTest 와일드카드 제거

* style: import 정렬 순서 변경

* fix: 충돌 해결

backend/src/main/java/com/funeat/review/application/ReviewService.java

@@ -37,6 +37,7 @@
 import com.funeat.review.specification.SortingReviewSpecification;
 import com.funeat.tag.domain.Tag;
 import com.funeat.tag.persistence.TagRepository;
+import java.util.Comparator;
 import java.util.List;
 import java.util.Optional;
 import java.util.stream.Collectors;
@@ -58,6 +59,8 @@ public class ReviewService {
     private static final int START_INDEX = 0;
     private static final int ONE = 1;
     private static final String EMPTY_URL = "";
+    private static final int RANKING_SIZE = 3;
+    private static final long RANKING_MINIMUM_FAVORITE_COUNT = 1L;
     private static final int REVIEW_PAGE_SIZE = 10;
 
     private final ReviewRepository reviewRepository;
@@ -208,9 +211,10 @@ private Boolean hasNextPage(final List<SortingReviewDto> sortingReviews) {
     }
 
     public RankingReviewsResponse getTopReviews() {
-        final List<Review> rankingReviews = reviewRepository.findTop3ByOrderByFavoriteCountDescIdDesc();
-
-        final List<RankingReviewDto> dtos = rankingReviews.stream()
+        final List<Review> reviews = reviewRepository.findReviewsByFavoriteCountGreaterThanEqual(RANKING_MINIMUM_FAVORITE_COUNT);
+        final List<RankingReviewDto> dtos = reviews.stream()
+                .sorted(Comparator.comparing(Review::calculateRankingScore).reversed())
+                .limit(RANKING_SIZE)
                 .map(RankingReviewDto::toDto)
                 .collect(Collectors.toList());
 

backend/src/main/java/com/funeat/review/domain/Review.java

@@ -4,6 +4,7 @@
 import com.funeat.member.domain.favorite.ReviewFavorite;
 import com.funeat.product.domain.Product;
 import java.time.LocalDateTime;
+import java.time.temporal.ChronoUnit;
 import java.util.ArrayList;
 import java.util.List;
 import java.util.Objects;
@@ -20,6 +21,8 @@
 @Entity
 public class Review {
 
+    private static final double RANKING_GRAVITY = 0.5;
+
     @Id
     @GeneratedValue(strategy = GenerationType.IDENTITY)
     private Long id;
@@ -80,6 +83,18 @@ public Review(final Member member, final Product findProduct, final String image
         this.favoriteCount = favoriteCount;
     }
 
+    public Review(final Member member, final Product findProduct, final String image, final Long rating,
+                  final String content, final Boolean reBuy, final Long favoriteCount, final LocalDateTime createdAt) {
+        this.member = member;
+        this.product = findProduct;
+        this.image = image;
+        this.rating = rating;
+        this.content = content;
+        this.reBuy = reBuy;
+        this.favoriteCount = favoriteCount;
+        this.createdAt = createdAt;
+    }
+
     public void addFavoriteCount() {
         this.favoriteCount++;
     }
@@ -88,6 +103,12 @@ public void minusFavoriteCount() {
         this.favoriteCount--;
     }
 
+    public Double calculateRankingScore() {
+        final long age = ChronoUnit.DAYS.between(createdAt, LocalDateTime.now());
+        final double denominator = Math.pow(age + 1.0, RANKING_GRAVITY);
+        return favoriteCount / denominator;
+    }
+
     public boolean checkAuthor(final Member member) {
         return Objects.equals(this.member, member);
     }

backend/src/main/java/com/funeat/review/persistence/ReviewRepository.java

@@ -5,8 +5,6 @@
 import com.funeat.member.domain.Member;
 import com.funeat.product.domain.Product;
 import com.funeat.review.domain.Review;
-import com.funeat.review.dto.SortingReviewDto;
-import java.time.LocalDateTime;
 import java.util.List;
 import java.util.Optional;
 import org.springframework.data.domain.Page;
@@ -18,8 +16,6 @@
 
 public interface ReviewRepository extends JpaRepository<Review, Long>, ReviewCustomRepository {
 
-    List<Review> findTop3ByOrderByFavoriteCountDescIdDesc();
-
     Long countByProduct(final Product product);
 
     Page<Review> findReviewsByMember(final Member findMember, final Pageable pageable);
@@ -36,4 +32,6 @@ public interface ReviewRepository extends JpaRepository<Review, Long>, ReviewCus
     List<Review> findPopularReviewWithImage(@Param("id") final Long productId, final Pageable pageable);
 
     Optional<Review> findTopByProductOrderByFavoriteCountDescIdDesc(final Product product);
+
+    List<Review> findReviewsByFavoriteCountGreaterThanEqual(final Long favoriteCount);
 }

backend/src/test/java/com/funeat/fixture/ReviewFixture.java

@@ -11,6 +11,7 @@
 import com.funeat.review.dto.ReviewCreateRequest;
 import com.funeat.review.dto.ReviewFavoriteRequest;
 import com.funeat.review.dto.SortingReviewRequest;
+import java.time.LocalDateTime;
 import java.util.List;
 
 @SuppressWarnings("NonAsciiCharacters")
@@ -75,6 +76,11 @@ public class ReviewFixture {
         return new Review(member, product, "test5", 5L, "test", false, count);
     }
 
+    public static Review 리뷰_이미지test5_평점5점_재구매X_생성(final Member member, final Product product, final Long count,
+                                                  final LocalDateTime createdAt) {
+        return new Review(member, product, "test5", 5L, "test", false, count, createdAt);
+    }
+
     public static Review 리뷰_이미지없음_평점1점_재구매X_생성(final Member member, final Product product, final Long count) {
         return new Review(member, product, "", 1L, "test", false, count);
     }

backend/src/test/java/com/funeat/review/application/ReviewServiceTest.java

@@ -1,5 +1,6 @@
 package com.funeat.review.application;
 
+import static com.funeat.fixture.CategoryFixture.카테고리_간편식사_생성;
 import static com.funeat.fixture.CategoryFixture.카테고리_즉석조리_생성;
 import static com.funeat.fixture.ImageFixture.이미지_생성;
 import static com.funeat.fixture.MemberFixture.멤버_멤버1_생성;
@@ -8,6 +9,7 @@
 import static com.funeat.fixture.PageFixture.페이지요청_생성;
 import static com.funeat.fixture.ProductFixture.상품_삼각김밥_가격1000원_평점2점_생성;
 import static com.funeat.fixture.ProductFixture.상품_삼각김밥_가격1000원_평점3점_생성;
+import static com.funeat.fixture.ProductFixture.상품_삼각김밥_가격1000원_평점4점_생성;
 import static com.funeat.fixture.ProductFixture.상품_삼각김밥_가격1000원_평점5점_생성;
 import static com.funeat.fixture.ProductFixture.상품_삼각김밥_가격2000원_평점1점_생성;
 import static com.funeat.fixture.ProductFixture.상품_삼각김밥_가격2000원_평점3점_생성;
@@ -18,6 +20,7 @@
 import static com.funeat.fixture.ReviewFixture.리뷰_이미지test3_평점3점_재구매O_생성;
 import static com.funeat.fixture.ReviewFixture.리뷰_이미지test3_평점3점_재구매X_생성;
 import static com.funeat.fixture.ReviewFixture.리뷰_이미지test4_평점4점_재구매O_생성;
+import static com.funeat.fixture.ReviewFixture.리뷰_이미지test5_평점5점_재구매X_생성;
 import static com.funeat.fixture.ReviewFixture.리뷰_이미지없음_평점1점_재구매O_생성;
 import static com.funeat.fixture.ReviewFixture.리뷰정렬요청_좋아요수_내림차순_생성;
 import static com.funeat.fixture.ReviewFixture.리뷰정렬요청_최신순_생성;
@@ -37,11 +40,15 @@
 import com.funeat.member.exception.MemberException.MemberNotFoundException;
 import com.funeat.product.exception.ProductException.ProductNotFoundException;
 import com.funeat.review.domain.Review;
+import com.funeat.review.dto.RankingReviewDto;
+import com.funeat.review.dto.RankingReviewsResponse;
 import com.funeat.review.dto.MostFavoriteReviewResponse;
 import com.funeat.review.dto.SortingReviewDto;
 import com.funeat.review.exception.ReviewException.NotAuthorOfReviewException;
 import com.funeat.review.exception.ReviewException.ReviewNotFoundException;
 import com.funeat.tag.domain.Tag;
+import java.time.LocalDateTime;
+import java.util.Collections;
 import java.util.List;
 import java.util.Optional;
 import java.util.stream.Collectors;
@@ -1007,6 +1014,155 @@ class getMostFavoriteReview_실패_테스트 {
         }
     }
 
+    @Nested
+    class getTopReviews_성공_테스트 {
+
+        @Nested
+        class 리뷰_개수에_대한_테스트 {
+
+            @Test
+            void 전체_리뷰가_하나도_없어도_반환값은_있어야한다() {
+                // given
+                final var expected = RankingReviewsResponse.toResponse(Collections.emptyList());
+
+                // when
+                final var actual = reviewService.getTopReviews();
+
+                // then
+                assertThat(actual).usingRecursiveComparison()
+                        .isEqualTo(expected);
+            }
+
+            @Test
+            void 전체_리뷰가_1개_이상_3개_미만이라도_리뷰가_나와야한다() {
+                // given
+                final var category = 카테고리_간편식사_생성();
+                단일_카테고리_저장(category);
+
+                final var product = 상품_삼각김밥_가격1000원_평점4점_생성(category);
+                단일_상품_저장(product);
+
+                final var member = 멤버_멤버1_생성();
+                단일_멤버_저장(member);
+
+                final var now = LocalDateTime.now();
+                final var review1 = 리뷰_이미지test5_평점5점_재구매X_생성(member, product, 2L, now.minusDays(1L));
+                final var review2 = 리뷰_이미지test5_평점5점_재구매X_생성(member, product, 2L, now);
+                복수_리뷰_저장(review1, review2);
+
+                final var rankingReviewDto1 = RankingReviewDto.toDto(review1);
+                final var rankingReviewDto2 = RankingReviewDto.toDto(review2);
+                final var rankingReviewDtos = List.of(rankingReviewDto2, rankingReviewDto1);
+                final var expected = RankingReviewsResponse.toResponse(rankingReviewDtos);
+
+                // when
+                final var actual = reviewService.getTopReviews();
+
+                // then
+                assertThat(actual).usingRecursiveComparison()
+                        .isEqualTo(expected);
+            }
+
+            @Test
+            void 전체_리뷰_중_랭킹이_높은_상위_3개_리뷰를_구할_수_있다() {
+                // given
+                final var category = 카테고리_간편식사_생성();
+                단일_카테고리_저장(category);
+
+                final var product = 상품_삼각김밥_가격1000원_평점4점_생성(category);
+                단일_상품_저장(product);
+
+                final var member = 멤버_멤버1_생성();
+                단일_멤버_저장(member);
+
+                final var now = LocalDateTime.now();
+                final var review1 = 리뷰_이미지test5_평점5점_재구매X_생성(member, product, 4L, now.minusDays(3L));
+                final var review2 = 리뷰_이미지test5_평점5점_재구매X_생성(member, product, 6L, now.minusDays(2L));
+                final var review3 = 리뷰_이미지test5_평점5점_재구매X_생성(member, product, 4L, now);
+                final var review4 = 리뷰_이미지test5_평점5점_재구매X_생성(member, product, 5L, now);
+                복수_리뷰_저장(review1, review2, review3, review4);
+
+                final var rankingReviewDto1 = RankingReviewDto.toDto(review1);
+                final var rankingReviewDto2 = RankingReviewDto.toDto(review2);
+                final var rankingReviewDto3 = RankingReviewDto.toDto(review3);
+                final var rankingReviewDto4 = RankingReviewDto.toDto(review4);
+                final var rankingReviewDtos = List.of(rankingReviewDto4, rankingReviewDto3, rankingReviewDto2);
+                final var expected = RankingReviewsResponse.toResponse(rankingReviewDtos);
+
+                // when
+                final var actual = reviewService.getTopReviews();
+
+                // then
+                assertThat(actual).usingRecursiveComparison()
+                        .isEqualTo(expected);
+            }
+        }
+
+        @Nested
+        class 리뷰_랭킹_점수에_대한_테스트 {
+
+            @Test
+            void 리뷰_좋아요_수가_같으면_최근_생성된_리뷰의_랭킹을_더_높게_반환한다() {
+                // given
+                final var category = 카테고리_간편식사_생성();
+                단일_카테고리_저장(category);
+
+                final var product = 상품_삼각김밥_가격1000원_평점4점_생성(category);
+                단일_상품_저장(product);
+
+                final var member = 멤버_멤버1_생성();
+                단일_멤버_저장(member);
+
+                final var now = LocalDateTime.now();
+                final var review1 = 리뷰_이미지test5_평점5점_재구매X_생성(member, product, 10L, now.minusDays(9L));
+                final var review2 = 리뷰_이미지test5_평점5점_재구매X_생성(member, product, 10L, now.minusDays(4L));
+                복수_리뷰_저장(review1, review2);
+
+                final var rankingReviewDto1 = RankingReviewDto.toDto(review1);
+                final var rankingReviewDto2 = RankingReviewDto.toDto(review2);
+                final var rankingReviewDtos = List.of(rankingReviewDto2, rankingReviewDto1);
+                final var expected = RankingReviewsResponse.toResponse(rankingReviewDtos);
+
+                // when
+                final var actual = reviewService.getTopReviews();
+
+                // then
+                assertThat(actual).usingRecursiveComparison()
+                        .isEqualTo(expected);
+            }
+
+            @Test
+            void 리뷰_생성_일자가_같으면_좋아요_수가_많은_리뷰의_랭킹을_더_높게_반환한다() {
+                // given
+                final var category = 카테고리_간편식사_생성();
+                단일_카테고리_저장(category);
+
+                final var product = 상품_삼각김밥_가격1000원_평점4점_생성(category);
+                단일_상품_저장(product);
+
+                final var member = 멤버_멤버1_생성();
+                단일_멤버_저장(member);
+
+                final var now = LocalDateTime.now();
+                final var review1 = 리뷰_이미지test5_평점5점_재구매X_생성(member, product, 2L, now.minusDays(1L));
+                final var review2 = 리뷰_이미지test5_평점5점_재구매X_생성(member, product, 4L, now.minusDays(1L));
+                복수_리뷰_저장(review1, review2);
+
+                final var rankingReviewDto1 = RankingReviewDto.toDto(review1);
+                final var rankingReviewDto2 = RankingReviewDto.toDto(review2);
+                final var rankingReviewDtos = List.of(rankingReviewDto2, rankingReviewDto1);
+                final var expected = RankingReviewsResponse.toResponse(rankingReviewDtos);
+
+                // when
+                final var actual = reviewService.getTopReviews();
+
+                // then
+                assertThat(actual).usingRecursiveComparison()
+                        .isEqualTo(expected);
+            }
+        }
+    }
+
     private List<Long> 태그_아이디_변환(final Tag... tags) {
         return Stream.of(tags)
                 .map(Tag::getId)

backend/src/test/java/com/funeat/review/domain/ReviewTest.java

@@ -0,0 +1,40 @@
+package com.funeat.review.domain;
+
+import static com.funeat.fixture.CategoryFixture.카테고리_간편식사_생성;
+import static com.funeat.fixture.MemberFixture.멤버_멤버1_생성;
+import static com.funeat.fixture.ProductFixture.상품_삼각김밥_가격1000원_평점1점_생성;
+import static com.funeat.fixture.ReviewFixture.리뷰_이미지test5_평점5점_재구매X_생성;
+import static org.assertj.core.api.Assertions.assertThat;
+
+import java.time.LocalDateTime;
+import org.junit.jupiter.api.DisplayNameGeneration;
+import org.junit.jupiter.api.DisplayNameGenerator;
+import org.junit.jupiter.api.Nested;
+import org.junit.jupiter.api.Test;
+
+@SuppressWarnings("NonAsciiCharacters")
+@DisplayNameGeneration(DisplayNameGenerator.ReplaceUnderscores.class)
+class ReviewTest {
+
+    @Nested
+    class calculateRankingScore_성공_테스트 {
+
+        @Test
+        void 리뷰_좋아요_수와_리뷰_생성_시간으로_해당_리뷰의_랭킹_점수를_구할_수_있다() {
+            // given
+            final var member = 멤버_멤버1_생성();
+            final var category = 카테고리_간편식사_생성();
+            final var product = 상품_삼각김밥_가격1000원_평점1점_생성(category);
+            final var favoriteCount = 4L;
+            final var review = 리뷰_이미지test5_평점5점_재구매X_생성(member, product, favoriteCount, LocalDateTime.now().minusDays(1L));
+
+            final var expected = favoriteCount / Math.pow(2.0, 0.5);
+
+            // when
+            final var actual = review.calculateRankingScore();
+
+            // then
+            assertThat(actual).isEqualTo(expected);
+        }
+    }
+}