feat: 인기상품 조회 API 구현

Author: Kimjipang

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

@@ -0,0 +1,70 @@
+package com.loopers.application;
+
+import com.loopers.interfaces.api.ranking.RankingV1Dto;
+import lombok.RequiredArgsConstructor;
+import org.springframework.data.redis.core.StringRedisTemplate;
+import org.springframework.data.redis.core.ZSetOperations;
+import org.springframework.stereotype.Component;
+
+import java.time.LocalDate;
+import java.time.ZoneId;
+import java.time.format.DateTimeFormatter;
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Set;
+
+@Component
+@RequiredArgsConstructor
+public class RankingFacade {
+    private final StringRedisTemplate redisTemplate;
+    private static final ZoneId KST = ZoneId.of("Asia/Seoul");
+    private static final DateTimeFormatter YYYYMMDD = DateTimeFormatter.BASIC_ISO_DATE;
+
+    public RankingV1Dto.ProductRankingPageResponse getDailyProductRanking(int page, int size) {
+        if (page < 1) page = 1;
+        if (size < 1) size = 20;
+
+        String date = LocalDate.now(KST).format(YYYYMMDD);
+
+        String key = "ranking:all:" + date;
+        ZSetOperations<String, String> zset = redisTemplate.opsForZSet();
+
+        Long total = zset.size(key);
+        long totalElements = (total == null) ? 0 : total;
+
+        if (totalElements == 0) {
+            return new RankingV1Dto.ProductRankingPageResponse(date, page, size, 0, 0, List.of());
+        }
+
+        long start = (long) (page - 1) * size;
+        long end = start + size - 1;
+
+        if (start >= totalElements) {
+            int totalPages = (int) Math.ceil((double) totalElements / size);
+            return new RankingV1Dto.ProductRankingPageResponse(date, page, size, totalElements, totalPages, List.of());
+        }
+
+        Set<ZSetOperations.TypedTuple<String>> tuples =
+                zset.reverseRangeWithScores(key, start, end);
+
+        List<RankingV1Dto.ProductRankingResponse> items = new ArrayList<>();
+        if (tuples != null) {
+            long rank = start + 1;
+            for (var t : tuples) {
+                String member = t.getValue();
+                Double score = t.getScore();
+                if (member == null || score == null) continue;
+
+                items.add(new RankingV1Dto.ProductRankingResponse(
+                        rank++,
+                        Long.parseLong(member),
+                        score
+                ));
+            }
+        }
+
+        int totalPages = (int) Math.ceil((double) totalElements / size);
+        return new RankingV1Dto.ProductRankingPageResponse(date, page, size, totalElements, totalPages, items);
+    }
+
+}

apps/commerce-streamer/src/main/java/com/loopers/interfaces/api/ranking/RankingV1ApiSpec.java

@@ -0,0 +1,9 @@
+package com.loopers.interfaces.api.ranking;
+
+import com.loopers.interfaces.api.ApiResponse;
+
+public interface RankingV1ApiSpec {
+
+    ApiResponse<RankingV1Dto.ProductRankingPageResponse> getDailyProductRanking(int size, int page);
+
+}

apps/commerce-streamer/src/main/java/com/loopers/interfaces/api/ranking/RankingV1Controller.java

@@ -0,0 +1,27 @@
+package com.loopers.interfaces.api.ranking;
+
+import com.loopers.application.RankingFacade;
+import com.loopers.interfaces.api.ApiResponse;
+import lombok.RequiredArgsConstructor;
+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;
+
+@RestController
+@RequestMapping("/api/v1/rankings")
+@RequiredArgsConstructor
+public class RankingV1Controller implements RankingV1ApiSpec {
+    private final RankingFacade rankingFacade;
+
+    @GetMapping
+    @Override
+    public ApiResponse<RankingV1Dto.ProductRankingPageResponse> getDailyProductRanking(
+            @RequestParam int size,
+            @RequestParam int page
+    ) {
+        RankingV1Dto.ProductRankingPageResponse response = rankingFacade.getDailyProductRanking(page, size);
+
+        return ApiResponse.success(response);
+    }
+}

apps/commerce-streamer/src/main/java/com/loopers/interfaces/api/ranking/RankingV1Dto.java

@@ -0,0 +1,20 @@
+package com.loopers.interfaces.api.ranking;
+
+import java.util.List;
+
+public class RankingV1Dto {
+    public record ProductRankingResponse(
+            Long rank,
+            Long productId,
+            double score
+    ) {}
+
+    public record ProductRankingPageResponse(
+            String date,
+            int page,
+            int size,
+            long totalElements,
+            int totalPages,
+            List<ProductRankingResponse> items
+    ) {}
+}