[volume-9] Product Ranking with Redis

apps/commerce-api/src/main/java/com/loopers/application/product/ProductService.java

@@ -7,6 +7,7 @@
 import com.loopers.support.error.CoreException;
 import com.loopers.support.error.ErrorType;
 import java.math.BigDecimal;
+import java.util.List;
 import lombok.RequiredArgsConstructor;
 import org.springframework.cache.annotation.CacheEvict;
 import org.springframework.cache.annotation.Cacheable;
@@ -72,6 +73,21 @@ public Page<ProductInfo> getProductsByBrand(Long brandId, Pageable pageable) {
         });
     }
 
+    /**
+     * 여러 상품 ID로 조회 (랭킹용)
+     */
+    @Transactional(readOnly = true)
+    public List<ProductInfo> findByIds(List<Long> ids) {
+        List<Product> products = productRepository.findByIdIn(ids);
+        // Brand 로딩 및 DTO 변환
+        return products.stream()
+            .map(product -> {
+                product.getBrand().getName();  // Brand 로딩
+                return ProductInfo.from(product);
+            })
+            .toList();
+    }
+
     @Transactional
     @CacheEvict(value = "product", key = "#id")
     public Product updateProduct(Long id, String name, BigDecimal price, Integer stock,

apps/commerce-api/src/main/java/com/loopers/application/ranking/RankingFacade.java

@@ -0,0 +1,93 @@
+package com.loopers.application.ranking;
+
+import com.loopers.application.product.ProductInfo;
+import com.loopers.application.product.ProductService;
+import com.loopers.application.ranking.RankingService.RankingItem;
+import java.math.BigDecimal;
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Map;
+import java.util.stream.Collectors;
+import lombok.RequiredArgsConstructor;
+import lombok.extern.slf4j.Slf4j;
+import org.springframework.stereotype.Service;
+
+/**
+ * 랭킹 + 상품 정보 조합 Facade
+ */
+@Slf4j
+@Service
+@RequiredArgsConstructor
+public class RankingFacade {
+
+    private final RankingService rankingService;
+    private final ProductService productService;
+
+    /**
+     * 일간 랭킹 페이지 조회 (상품 정보 포함)
+     */
+    public List<RankingProductInfo> getDailyRanking(String date, int page, int size) {
+        // 1. Redis ZSET에서 랭킹 조회
+        List<RankingItem> rankingItems = rankingService.getDailyRanking(date, page, size);
+
+        if (rankingItems.isEmpty()) {
+            return List.of();
+        }
+
+        // 2. Product 정보 조회 (Batch)
+        List<Long> productIds = rankingItems.stream()
+            .map(RankingItem::getProductId)
+            .toList();
+
+        Map<Long, ProductInfo> productMap = productService.findByIds(productIds).stream()
+            .collect(Collectors.toMap(ProductInfo::id, p -> p));
+
+        // 3. 랭킹 + 상품 정보 조합
+        List<RankingProductInfo> results = new ArrayList<>();
+        for (RankingItem item : rankingItems) {
+            ProductInfo product = productMap.get(item.getProductId());
+
+            if (product == null) {
+                log.warn("랭킹에 있지만 상품 정보 없음 - productId: {}", item.getProductId());
+                continue;
+            }
+
+            results.add(RankingProductInfo.builder()
+                .rank(item.getRank())
+                .score(item.getScore())
+                .productId(product.id())
+                .productName(product.name())
+                .brandName(product.brand().name())
+                .price(product.price())
+                .stock(product.stock())
+                .likeCount(product.likeCount())
+                .build());
+        }
+
+        return results;
+    }
+
+    /**
+     * 오늘 랭킹 페이지 조회
+     */
+    public List<RankingProductInfo> getTodayRanking(int page, int size) {
+        String today = java.time.LocalDate.now().format(java.time.format.DateTimeFormatter.ofPattern("yyyyMMdd"));
+        return getDailyRanking(today, page, size);
+    }
+
+    /**
+     * 랭킹 + 상품 정보 DTO
+     */
+    @lombok.Getter
+    @lombok.Builder
+    public static class RankingProductInfo {
+        private int rank;               // 순위
+        private Double score;           // 점수
+        private Long productId;         // 상품 ID
+        private String productName;     // 상품명
+        private String brandName;       // 브랜드명
+        private BigDecimal price;       // 가격
+        private Integer stock;          // 재고
+        private Long likeCount;         // 좋아요 수
+    }
+}

apps/commerce-api/src/main/java/com/loopers/application/ranking/RankingService.java

@@ -0,0 +1,129 @@
+package com.loopers.application.ranking;
+
+import java.time.LocalDate;
+import java.time.format.DateTimeFormatter;
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Set;
+import lombok.RequiredArgsConstructor;
+import lombok.extern.slf4j.Slf4j;
+import org.springframework.data.redis.core.RedisTemplate;
+import org.springframework.data.redis.core.ZSetOperations.TypedTuple;
+import org.springframework.stereotype.Service;
+
+/**
+ * 랭킹 조회 서비스 (Redis ZSET 조회)
+ */
+@Slf4j
+@Service
+@RequiredArgsConstructor
+public class RankingService {
+
+    private final RedisTemplate<String, String> redisTemplate;
+
+    private static final String DAILY_PREFIX = "ranking:all:";
+    private static final String HOURLY_PREFIX = "ranking:realtime:";
+    private static final DateTimeFormatter DATE_FORMATTER = DateTimeFormatter.ofPattern("yyyyMMdd");
+
+    /**
+     * 일간 랭킹 Top-N 조회
+     *
+     * @param date 조회 날짜 (yyyyMMdd)
+     * @param page 페이지 번호 (1부터 시작)
+     * @param size 페이지 크기
+     * @return 랭킹 아이템 목록
+     */
+    public List<RankingItem> getDailyRanking(String date, int page, int size) {
+        String key = DAILY_PREFIX + date;
+        return getRanking(key, page, size);
+    }
+
+    /**
+     * 오늘 일간 랭킹 Top-N 조회
+     */
+    public List<RankingItem> getTodayRanking(int page, int size) {
+        String today = LocalDate.now().format(DATE_FORMATTER);
+        return getDailyRanking(today, page, size);
+    }
+
+    /**
+     * 특정 상품의 일간 랭킹 순위 조회
+     *
+     * @param date 조회 날짜
+     * @param productId 상품 ID
+     * @return 순위 (1부터 시작, 없으면 null)
+     */
+    public Long getProductRank(String date, Long productId) {
+        String key = DAILY_PREFIX + date;
+        String member = productId.toString();
+
+        Long rank = redisTemplate.opsForZSet().reverseRank(key, member);
+        return rank != null ? rank + 1 : null;  // 0-based → 1-based
+    }
+
+    /**
+     * 오늘 특정 상품의 랭킹 순위 조회
+     */
+    public Long getProductRankToday(Long productId) {
+        String today = LocalDate.now().format(DATE_FORMATTER);
+        return getProductRank(today, productId);
+    }
+
+    /**
+     * 특정 상품의 점수 조회
+     */
+    public Double getProductScore(String date, Long productId) {
+        String key = DAILY_PREFIX + date;
+        String member = productId.toString();
+
+        return redisTemplate.opsForZSet().score(key, member);
+    }
+
+    /**
+     * ZSET에서 랭킹 조회 (내부 공통 로직)
+     */
+    private List<RankingItem> getRanking(String key, int page, int size) {
+        // 페이지 계산 (1-based → 0-based)
+        int start = (page - 1) * size;
+        int end = start + size - 1;
+
+        // ZREVRANGE로 점수 높은 순으로 조회
+        Set<TypedTuple<String>> results = redisTemplate.opsForZSet()
+            .reverseRangeWithScores(key, start, end);
+
+        if (results == null || results.isEmpty()) {
+            log.debug("랭킹 조회 결과 없음 - key: {}, page: {}, size: {}", key, page, size);
+            return List.of();
+        }
+
+        List<RankingItem> items = new ArrayList<>();
+        int rank = start + 1;  // 순위는 1부터 시작
+
+        for (TypedTuple<String> tuple : results) {
+            Long productId = Long.parseLong(tuple.getValue());
+            Double score = tuple.getScore();
+
+            items.add(RankingItem.builder()
+                .rank(rank++)
+                .productId(productId)
+                .score(score)
+                .build());
+        }
+
+        log.info("랭킹 조회 완료 - key: {}, page: {}, size: {}, count: {}",
+            key, page, size, items.size());
+
+        return items;
+    }
+
+    /**
+     * 랭킹 아이템 DTO
+     */
+    @lombok.Getter
+    @lombok.Builder
+    public static class RankingItem {
+        private int rank;           // 순위 (1부터 시작)
+        private Long productId;     // 상품 ID
+        private Double score;       // 점수
+    }
+}

apps/commerce-api/src/main/java/com/loopers/interfaces/api/product/ProductV1Controller.java

@@ -2,6 +2,7 @@
 
 import com.loopers.application.product.ProductInfo;
 import com.loopers.application.product.ProductService;
+import com.loopers.application.ranking.RankingService;
 import com.loopers.application.useraction.UserActionService;
 import com.loopers.domain.product.Product;
 import com.loopers.interfaces.api.ApiResponse;
@@ -25,6 +26,7 @@ public class ProductV1Controller implements ProductV1ApiSpec {
 
     private final ProductService productService;
     private final UserActionService userActionService;
+    private final RankingService rankingService;
 
     @PostMapping
     @Override
@@ -55,7 +57,11 @@ public ApiResponse<ProductV1Dto.ProductResponse> getProduct(
         }
 
         ProductInfo productInfo = productService.getProduct(productId);
-        ProductV1Dto.ProductResponse response = ProductV1Dto.ProductResponse.from(productInfo);
+
+        // 오늘의 랭킹 순위 조회
+        Long rank = rankingService.getProductRankToday(productId);
+
+        ProductV1Dto.ProductResponse response = ProductV1Dto.ProductResponse.from(productInfo, rank);
         return ApiResponse.success(response);
     }
 

apps/commerce-api/src/main/java/com/loopers/interfaces/api/product/ProductV1Dto.java

@@ -44,7 +44,8 @@ public record ProductResponse(
         Integer stock,
         String description,
         BrandResponse brand,
-        Long likeCount
+        Long likeCount,
+        Long rank  // 오늘의 랭킹 순위 (없으면 null)
     ) {
         public static ProductResponse from(ProductInfo info) {
             return new ProductResponse(
@@ -54,7 +55,21 @@ public static ProductResponse from(ProductInfo info) {
                 info.stock(),
                 info.description(),
                 BrandResponse.from(info.brand()),
-                info.likeCount()
+                info.likeCount(),
+                null  // 기본값 null
+            );
+        }
+
+        public static ProductResponse from(ProductInfo info, Long rank) {
+            return new ProductResponse(
+                info.id(),
+                info.name(),
+                info.price(),
+                info.stock(),
+                info.description(),
+                BrandResponse.from(info.brand()),
+                info.likeCount(),
+                rank
             );
         }
     }

apps/commerce-api/src/main/java/com/loopers/interfaces/api/ranking/RankingApi.java

@@ -0,0 +1,75 @@
+package com.loopers.interfaces.api.ranking;
+
+import com.loopers.application.ranking.RankingFacade;
+import com.loopers.application.ranking.RankingFacade.RankingProductInfo;
+import io.swagger.v3.oas.annotations.Operation;
+import io.swagger.v3.oas.annotations.Parameter;
+import io.swagger.v3.oas.annotations.tags.Tag;
+import java.time.LocalDate;
+import java.time.format.DateTimeFormatter;
+import java.util.List;
+import lombok.RequiredArgsConstructor;
+import org.springframework.http.ResponseEntity;
+import org.springframework.web.bind.annotation.GetMapping;
+import org.springframework.web.bind.annotation.RequestMapping;
+import org.springframework.web.bind.annotation.RequestParam;
+import org.springframework.web.bind.annotation.RestController;
+
+/**
+ * 랭킹 API
+ */
+@Tag(name = "Ranking", description = "상품 랭킹 API")
+@RestController
+@RequestMapping("/api/v1/rankings")
+@RequiredArgsConstructor
+public class RankingApi {
+
+    private final RankingFacade rankingFacade;
+
+    private static final DateTimeFormatter DATE_FORMATTER = DateTimeFormatter.ofPattern("yyyyMMdd");
+
+    @Operation(
+        summary = "일간 랭킹 조회",
+        description = "특정 날짜의 상품 랭킹을 페이지 단위로 조회합니다."
+    )
+    @GetMapping
+    public ResponseEntity<RankingResponse> getRankings(
+        @Parameter(description = "조회 날짜 (yyyyMMdd), 미입력 시 오늘", example = "20250123")
+        @RequestParam(required = false) String date,
+
+        @Parameter(description = "페이지 번호 (1부터 시작)", example = "1")
+        @RequestParam(defaultValue = "1") int page,
+
+        @Parameter(description = "페이지 크기", example = "20")
+        @RequestParam(defaultValue = "20") int size
+    ) {
+        // 날짜 검증
+        String targetDate = validateAndGetDate(date);
+
+        // 랭킹 조회
+        List<RankingProductInfo> rankings = rankingFacade.getDailyRanking(targetDate, page, size);
+
+        return ResponseEntity.ok(new RankingResponse(
+            targetDate,
+            page,
+            size,
+            rankings
+        ));
+    }
+
+    /**
+     * 날짜 검증 및 변환
+     */
+    private String validateAndGetDate(String date) {
+        if (date == null || date.isBlank()) {
+            return LocalDate.now().format(DATE_FORMATTER);
+        }
+
+        try {
+            LocalDate.parse(date, DATE_FORMATTER);
+            return date;
+        } catch (Exception e) {
+            throw new IllegalArgumentException("날짜 형식이 올바르지 않습니다. (yyyyMMdd)");
+        }
+    }
+}