BJS2-77373 | Участвовать в событии (#2952)

* create CRUD operations for event participants

* pr fixes

* pr fixes

---------

Co-authored-by: JolyGolden <[email protected]>
Co-authored-by: Kateryna <[email protected]>

Author: 3 people

src/main/java/school/faang/user_service/conrtoller/event/EventParticipationController.java

@@ -0,0 +1,41 @@
+package school.faang.user_service.conrtoller.event;
+
+import jakarta.validation.constraints.Positive;
+import lombok.RequiredArgsConstructor;
+import org.springframework.http.HttpStatus;
+import org.springframework.validation.annotation.Validated;
+import org.springframework.web.bind.annotation.*;
+import school.faang.user_service.dto.UserDto;
+import school.faang.user_service.service.EventParticipationService;
+
+import java.util.List;
+
+@Validated
+@RestController
+@RequestMapping("/events/{eventId}")
+@RequiredArgsConstructor
+public class EventParticipationController {
+    private final EventParticipationService eventParticipationService;
+
+    @ResponseStatus(HttpStatus.NO_CONTENT)
+    @PostMapping("/participants/{userId}")
+    public void registerParticipant(@PathVariable @Positive long eventId, @PathVariable @Positive long userId) {
+        eventParticipationService.registerParticipant(eventId, userId);
+    }
+
+    @ResponseStatus(HttpStatus.NO_CONTENT)
+    @DeleteMapping("/participants/{userId}")
+    public void unregisterParticipant(@PathVariable @Positive long eventId, @PathVariable @Positive long userId) {
+        eventParticipationService.unregisterParticipant(eventId, userId);
+    }
+
+    @GetMapping("/participants")
+    public List<UserDto> getParticipants(@PathVariable @Positive long eventId) {
+        return eventParticipationService.getParticipants(eventId);
+    }
+
+    @GetMapping("/participants/count")
+    public Integer getParticipantsCount(@PathVariable @Positive long eventId) {
+        return eventParticipationService.getParticipantsCount(eventId);
+    }
+}

src/main/java/school/faang/user_service/dto/UserDto.java

@@ -11,4 +11,4 @@ public class UserDto {
     private Long id;
     private String username;
     private String email;
-}
+}

src/main/java/school/faang/user_service/mapper/ParticipantMapper.java

@@ -0,0 +1,10 @@
+package school.faang.user_service.mapper;
+
+import org.mapstruct.Mapper;
+import school.faang.user_service.dto.UserDto;
+import school.faang.user_service.entity.User;
+
+@Mapper(componentModel = "spring")
+public interface ParticipantMapper {
+    UserDto toDto(User user);
+}

src/main/java/school/faang/user_service/service/EventParticipationService.java

@@ -0,0 +1,53 @@
+package school.faang.user_service.service;
+
+import com.sun.jdi.request.DuplicateRequestException;
+import jakarta.transaction.Transactional;
+import lombok.RequiredArgsConstructor;
+import org.springframework.stereotype.Service;
+import school.faang.user_service.dto.UserDto;
+import school.faang.user_service.mapper.ParticipantMapper;
+import school.faang.user_service.repository.event.EventParticipationRepository;
+
+import java.util.List;
+
+@Service
+@RequiredArgsConstructor
+public class EventParticipationService {
+    private final EventParticipationRepository eventParticipationRepository;
+    private final ParticipantMapper participantMapper;
+
+    @Transactional
+    public void registerParticipant(long eventId, long userId) {
+        if (isParticipantRegistered(eventId, userId)) {
+            throw new DuplicateRequestException("User is already registered for this event");
+        }
+        eventParticipationRepository.register(eventId, userId);
+    }
+
+    @Transactional
+    public void unregisterParticipant(long eventId, long userId) {
+        if (isParticipantRegistered(eventId, userId)) {
+            throw new IllegalStateException("User is not registered for this event");
+        }
+        eventParticipationRepository.unregister(eventId, userId);
+    }
+
+    public List<UserDto> getParticipants(long eventId) {
+        return eventParticipationRepository
+                .findAllParticipantsByEventId(eventId)
+                .stream()
+                .map(participantMapper::toDto)
+                .toList();
+    }
+
+    public Integer getParticipantsCount(long eventId) {
+        return eventParticipationRepository.countParticipants(eventId);
+    }
+
+    private boolean isParticipantRegistered(long eventId, long userId) {
+        return eventParticipationRepository
+                .findAllParticipantsByEventId(eventId)
+                .stream()
+                .anyMatch(user -> user.getId() == userId);
+    }
+}