[Release] 거래소별 가격 비교 API 추가 (#111)

src/main/java/com/membershipflow/course/controller/CourseController.java

@@ -4,6 +4,7 @@
 import com.membershipflow.course.dto.CourseListItemResponse;
 import com.membershipflow.course.dto.RankingItemResponse;
 import com.membershipflow.course.dto.RankingPageResponse;
+import com.membershipflow.course.dto.SourceComparisonItem;
 import com.membershipflow.course.entity.CourseType;
 import com.membershipflow.course.entity.MembershipType;
 import com.membershipflow.course.service.CourseService;
@@ -51,6 +52,14 @@ public ResponseEntity<RankingPageResponse> ranking(
         return ResponseEntity.ok(courseService.getRanking(period, sort, courseType, page, clampedSize));
     }
 
+    // /courses/source-comparison 이 /courses/{courseId} 보다 먼저 위치해야 경로 충돌 없음
+    @GetMapping("/source-comparison")
+    public ResponseEntity<List<SourceComparisonItem>> sourceComparison(
+            @RequestParam(defaultValue = "10") int limit) {
+        int clampedLimit = Math.min(limit, 50);
+        return ResponseEntity.ok(courseService.getSourceComparison(clampedLimit));
+    }
+
     @GetMapping("/{courseId}")
     public ResponseEntity<CourseDetailResponse> detail(@PathVariable Long courseId) {
         return ResponseEntity.ok(courseService.getDetail(courseId));

src/main/java/com/membershipflow/course/dto/SourceComparisonItem.java

@@ -0,0 +1,12 @@
+package com.membershipflow.course.dto;
+
+public record SourceComparisonItem(
+        Long courseId,
+        String name,
+        String region,
+        String courseType,
+        Long dongaPrice,
+        Long dongbuPrice,
+        Long diffAmount,   // dongbu - donga (원 단위)
+        Double diffRate    // 차이 비율 (%)
+) {}

src/main/java/com/membershipflow/course/service/CourseService.java

@@ -6,6 +6,7 @@
 import com.membershipflow.course.dto.CourseListItemResponse;
 import com.membershipflow.course.dto.RankingItemResponse;
 import com.membershipflow.course.dto.RankingPageResponse;
+import com.membershipflow.course.dto.SourceComparisonItem;
 import com.membershipflow.course.entity.CourseType;
 import com.membershipflow.course.entity.MembershipCourse;
 import com.membershipflow.course.entity.MembershipType;
@@ -166,6 +167,38 @@ public RankingPageResponse getRanking(String period, String sort,
         return new RankingPageResponse(content, page, size, totalElements, toIndex < totalElements);
     }
 
+    public List<SourceComparisonItem> getSourceComparison(int limit) {
+        List<Object[]> rows = priceService.getLatestByTwoSources("동아골프", "동부회원권");
+
+        List<Long> courseIds = rows.stream()
+                .map(r -> ((Number) r[0]).longValue())
+                .toList();
+
+        Map<Long, MembershipCourse> courseMap = courseRepository.findAllById(courseIds).stream()
+                .collect(Collectors.toMap(MembershipCourse::getId, c -> c));
+
+        return rows.stream()
+                .map(r -> {
+                    long courseId  = ((Number) r[0]).longValue();
+                    long dongaPrice = ((Number) r[1]).longValue();
+                    long dongbuPrice = ((Number) r[2]).longValue();
+                    long diffAmount  = dongbuPrice - dongaPrice;
+                    double diffRate  = dongaPrice == 0 ? 0
+                            : Math.round((double) diffAmount / dongaPrice * 10000d) / 100d;
+
+                    MembershipCourse c = courseMap.get(courseId);
+                    if (c == null) return null;
+                    return new SourceComparisonItem(
+                            courseId, c.getName(), c.getRegion(),
+                            c.getCourseType() != null ? c.getCourseType().name() : null,
+                            dongaPrice, dongbuPrice, diffAmount, diffRate);
+                })
+                .filter(item -> item != null)
+                .sorted((a, b) -> Double.compare(Math.abs(b.diffRate()), Math.abs(a.diffRate())))
+                .limit(limit)
+                .toList();
+    }
+
     private Double calcChangeRate(PriceHistory latest, PriceHistory base) {
         if (latest == null || base == null || base.getPrice() == 0) return null;
         double rate = (double) (latest.getPrice() - base.getPrice()) / base.getPrice() * 100;

src/main/java/com/membershipflow/price/repository/PriceHistoryRepository.java

@@ -125,6 +125,26 @@ WHERE course_id IN (:courseIds)
             """, nativeQuery = true)
     List<PriceHistory> findCurrentPriceForRanking(@Param("courseIds") List<Long> courseIds);
 
+    // 소스 비교용: 두 소스 모두 최신가가 있는 종목 조회
+    @Query(value = """
+            SELECT ph.course_id,
+                   MAX(CASE WHEN cs.name = :sourceA THEN ph.price END) AS price_a,
+                   MAX(CASE WHEN cs.name = :sourceB THEN ph.price END) AS price_b
+            FROM (
+                SELECT id, course_id, source_id, price,
+                       ROW_NUMBER() OVER (PARTITION BY course_id, source_id ORDER BY collected_at DESC, id DESC) AS rn
+                FROM price_history
+            ) ph
+            JOIN crawl_source cs ON cs.id = ph.source_id
+            WHERE ph.rn = 1
+              AND cs.name IN (:sourceA, :sourceB)
+            GROUP BY ph.course_id
+            HAVING price_a IS NOT NULL AND price_b IS NOT NULL
+            """, nativeQuery = true)
+    List<Object[]> findLatestByTwoSources(
+            @Param("sourceA") String sourceA,
+            @Param("sourceB") String sourceB);
+
     // 랭킹용 기준 시점 가격 (period 시작 시점 가장 근접 레코드)
     @Query(value = """
             SELECT ph.id, ph.course_id, ph.source_id, ph.price, ph.collected_at, ph.collect_run_id

src/main/java/com/membershipflow/price/service/PriceService.java

@@ -106,6 +106,10 @@ public Map<Long, PriceHistory> getCurrentPriceBatch(List<Long> courseIds) {
                 .collect(Collectors.toMap(ph -> ph.getCourse().getId(), ph -> ph));
     }
 
+    public List<Object[]> getLatestByTwoSources(String sourceA, String sourceB) {
+        return priceHistoryRepository.findLatestByTwoSources(sourceA, sourceB);
+    }
+
     public Map<Long, PriceHistory> getBasePriceBatch(List<Long> courseIds, LocalDateTime baseTime) {
         long periodDays = java.time.temporal.ChronoUnit.DAYS.between(baseTime, LocalDateTime.now());
         long windowDays = Math.max(7, periodDays);