优化目录结构

backend/src/main/java/com/openisle/service/UserVisitService.java

@@ -0,0 +1,61 @@
+package com.openisle.service;
+
+import com.openisle.model.User;
+import com.openisle.model.UserVisit;
+import com.openisle.repository.UserRepository;
+import com.openisle.repository.UserVisitRepository;
+import lombok.RequiredArgsConstructor;
+import org.springframework.stereotype.Service;
+
+import java.time.LocalDate;
+import java.util.LinkedHashMap;
+import java.util.Map;
+
+@Service
+@RequiredArgsConstructor
+public class UserVisitService {
+    private final UserVisitRepository userVisitRepository;
+    private final UserRepository userRepository;
+
+    public boolean recordVisit(String username) {
+        User user = userRepository.findByUsername(username)
+                .orElseThrow(() -> new com.openisle.exception.NotFoundException("User not found"));
+        LocalDate today = LocalDate.now();
+        return userVisitRepository.findByUserAndVisitDate(user, today).map(v -> false).orElseGet(() -> {
+            UserVisit visit = new UserVisit();
+            visit.setUser(user);
+            visit.setVisitDate(today);
+            userVisitRepository.save(visit);
+            return true;
+        });
+    }
+
+    public long countVisits(String username) {
+        User user = userRepository.findByUsername(username)
+                .orElseThrow(() -> new com.openisle.exception.NotFoundException("User not found"));
+        return userVisitRepository.countByUser(user);
+    }
+
+    public long countDau(LocalDate date) {
+        LocalDate d = date != null ? date : LocalDate.now();
+        return userVisitRepository.countByVisitDate(d);
+    }
+
+    public Map<LocalDate, Long> countDauRange(LocalDate start, LocalDate end) {
+        Map<LocalDate, Long> result = new LinkedHashMap<>();
+        if (start == null || end == null || start.isAfter(end)) {
+            return result;
+        }
+        var list = userVisitRepository.countRange(start, end);
+        for (var obj : list) {
+            LocalDate d = (LocalDate) obj[0];
+            Long c = (Long) obj[1];
+            result.put(d, c);
+        }
+        // fill zero counts for missing dates
+        for (LocalDate d = start; !d.isAfter(end); d = d.plusDays(1)) {
+            result.putIfAbsent(d, 0L);
+        }
+        return result;
+    }
+}