#26 pharmacy: direction service - haversine formula

road/src/main/java/com/example/road/direction/entity/Direction.java

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+package com.example.road.direction.entity;
+
+import com.example.road.BaseTimeEntity;
+import lombok.AllArgsConstructor;
+import lombok.Builder;
+import lombok.Getter;
+import lombok.NoArgsConstructor;
+
+import javax.persistence.Entity;
+import javax.persistence.GeneratedValue;
+import javax.persistence.GenerationType;
+import javax.persistence.Id;
+
+@Entity(name = "direction")
+@AllArgsConstructor
+@NoArgsConstructor
+@Builder
+@Getter
+public class Direction extends BaseTimeEntity {
+
+    @Id
+    @GeneratedValue(strategy = GenerationType.IDENTITY)
+    private Long id;
+
+    // 고객
+    private String inputAddress;
+    private double inputLatitude;
+    private double inputLongitude;
+
+    // 약국
+    private String targetPharmacyName;
+    private String targetAddress;
+    private double targetLatitude;
+    private double targetLongitude;
+
+    // 거리
+    private double distance;
+}

road/src/main/java/com/example/road/direction/service/DirectionService.java

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+package com.example.road.direction.service;
+
+import com.example.road.api.dto.DocumentDto;
+import com.example.road.direction.entity.Direction;
+import com.example.road.pharmacy.service.PharmacySearchService;
+import lombok.RequiredArgsConstructor;
+import lombok.extern.slf4j.Slf4j;
+import org.springframework.stereotype.Service;
+
+import java.util.Collections;
+import java.util.Comparator;
+import java.util.List;
+import java.util.Objects;
+import java.util.stream.Collectors;
+
+@Slf4j
+@Service
+@RequiredArgsConstructor
+public class DirectionService {
+
+    private static final int MAX_SEARCH_COUNT = 3;
+    private static final double RADIUS_KM = 10.0;
+
+    private final PharmacySearchService pharmacySearchService;
+
+    public List<Direction> buildDirectionList(DocumentDto documentDto) {
+
+        if (Objects.isNull(documentDto)) {
+            return Collections.emptyList();
+        }
+
+        return pharmacySearchService.searchPharmacyDtoList()
+                .stream().map(pharmacyDto ->
+                    Direction.builder()
+                            .inputAddress(documentDto.getAddressName())
+                            .inputLatitude(documentDto.getLatitude())
+                            .inputLongitude(documentDto.getLongitude())
+                            .targetPharmacyName(pharmacyDto.getPharmacyName())
+                            .targetAddress(pharmacyDto.getPharmacyAddress())
+                            .targetLatitude(pharmacyDto.getLatitude())
+                            .targetLongitude(pharmacyDto.getLongitude())
+                            .distance(
+                                    calculateDistance(
+                                            documentDto.getLatitude(), documentDto.getLongitude(),
+                                            pharmacyDto.getLatitude(), pharmacyDto.getLongitude()
+                                    )
+                            )
+                            .build()
+                )
+                .filter(direction -> direction.getDistance() <= RADIUS_KM)
+                .sorted(Comparator.comparing(Direction::getDistance))
+                .limit(MAX_SEARCH_COUNT)
+                .collect(Collectors.toList());
+    }
+
+    // Haversine formula
+    private double calculateDistance(double lat1, double lon1, double lat2, double lon2) {
+        lat1 = Math.toRadians(lat1);
+        lon1 = Math.toRadians(lon1);
+        lat2 = Math.toRadians(lat2);
+        lon2 = Math.toRadians(lon2);
+
+        double earthRadius = 6371; //Kilometers
+        return earthRadius * Math.acos(Math.sin(lat1) * Math.sin(lat2) + Math.cos(lat1) * Math.cos(lat2) * Math.cos(lon1 - lon2));
+    }
+}

road/src/main/java/com/example/road/pharmacy/dto/PharmacyDto.java

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+package com.example.road.pharmacy.dto;
+
+import lombok.AllArgsConstructor;
+import lombok.Builder;
+import lombok.Getter;
+import lombok.NoArgsConstructor;
+
+@Getter
+@Builder
+@AllArgsConstructor
+@NoArgsConstructor
+public class PharmacyDto {
+
+    private Long id;
+    private String pharmacyName;
+    private String pharmacyAddress;
+    private double latitude;
+    private double longitude;
+}

road/src/main/java/com/example/road/pharmacy/service/PharmacySearchService.java

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+package com.example.road.pharmacy.service;
+
+import com.example.road.pharmacy.dto.PharmacyDto;
+import com.example.road.pharmacy.entity.Pharmacy;
+import lombok.RequiredArgsConstructor;
+import lombok.extern.slf4j.Slf4j;
+import org.springframework.stereotype.Service;
+
+import java.util.List;
+import java.util.stream.Collectors;
+
+@Slf4j
+@Service
+@RequiredArgsConstructor
+public class PharmacySearchService {
+
+    private final PharmacyRepositoryService pharmacyRepositoryService;
+
+    public List<PharmacyDto> searchPharmacyDtoList() {
+
+        return pharmacyRepositoryService.findAll()
+                .stream()
+                .map(this::convertToPharmacyDto)
+                .collect(Collectors.toList());
+    }
+
+    private PharmacyDto convertToPharmacyDto(Pharmacy pharmacy) {
+        return PharmacyDto.builder()
+                .id(pharmacy.getId())
+                .pharmacyAddress(pharmacy.getPharmacyAddress())
+                .pharmacyName(pharmacy.getPharmacyName())
+                .latitude(pharmacy.getLatitude())
+                .longitude(pharmacy.getLongitude())
+                .build();
+    }
+}