[feat] 약속 참여 가능자 목록 API 구현

src/main/java/org/kkumulkkum/server/controller/ParticipantController.java

@@ -5,6 +5,7 @@
 import org.kkumulkkum.server.annotation.IsParticipant;
 import org.kkumulkkum.server.annotation.UserId;
 import org.kkumulkkum.server.dto.participant.request.PreparationInfoDto;
+import org.kkumulkkum.server.dto.participant.response.AvailableParticipantsDto;
 import org.kkumulkkum.server.dto.participant.response.LateComersDto;
 import org.kkumulkkum.server.dto.participant.response.ParticipantsDto;
 import org.kkumulkkum.server.dto.participant.response.PreparationStatusDto;
@@ -61,6 +62,15 @@ public ResponseEntity<ParticipantsDto> getParticipants(
         return ResponseEntity.ok().body(participantService.getParticipants(promiseId));
     }
 
+    @IsParticipant(promiseIdParamIndex = 1)
+    @GetMapping("/v1/promises/{promiseId}/members")
+    public ResponseEntity<AvailableParticipantsDto> getAvailableParticipants(
+            @UserId final Long userId,
+            @PathVariable("promiseId") final Long promiseId
+    ) {
+        return ResponseEntity.ok().body(participantService.getAvailableParticipants(userId, promiseId));
+    }
+
     @PatchMapping("/v1/promises/{promiseId}/times")
     public ResponseEntity<Void> inputPreparationInfo(
             @UserId final Long userId,

src/main/java/org/kkumulkkum/server/dto/participant/response/AvailableParticipantsDto.java

@@ -0,0 +1,36 @@
+package org.kkumulkkum.server.dto.participant.response;
+
+import org.kkumulkkum.server.dto.member.response.MemberDto;
+
+import java.util.List;
+public record AvailableParticipantsDto(
+        List<AvailableParticipantDto> members
+) {
+    public static AvailableParticipantsDto of(List<MemberDto> members, List<Long> participantIds) {
+        List<AvailableParticipantDto> participantDtos = members.stream()
+                .map(member -> new AvailableParticipantDto(
+                        member.memberId(),
+                        member.name(),
+                        member.profileImg(),
+                        //모임 내 멤버가 약속 참여중인 멤버 리스트 안에 있으면 true, 아니면 false
+                        participantIds.contains(member.memberId())
+                )).toList();
+        return new AvailableParticipantsDto(participantDtos);
+    }
+
+    public record AvailableParticipantDto(
+            Long memberId,
+            String name,
+            String profileImg,
+            boolean isParticipant
+    ) {
+        public static AvailableParticipantDto of(Long memberId, String name, String profileImg, boolean isParticipant) {
+            return new AvailableParticipantDto(
+                    memberId,
+                    name,
+                    profileImg,
+                    isParticipant
+            );
+        }
+    }
+}

src/main/java/org/kkumulkkum/server/repository/MemberRepository.java

@@ -44,4 +44,14 @@ SELECT CASE WHEN EXISTS (
             JOIN Promise p ON p.meeting.id = mt.id
             WHERE p.id = :promiseId AND u.id = :userId""")
     Member findByUserIdAndPromiseId(Long userId, Long promiseId);
+
+    @Query("""
+            SELECT new org.kkumulkkum.server.dto.member.response.MemberDto
+            (m.id, ui.name, ui.profileImg)
+            FROM Member m
+            JOIN m.meeting mt
+            JOIN FETCH UserInfo ui ON m.user.id = ui.user.id
+            JOIN Promise p ON p.meeting.id = mt.id
+            WHERE p.id = :promiseId""")
+    List<MemberDto> findAllByPromiseId(Long promiseId);
 }

src/main/java/org/kkumulkkum/server/service/member/MemberRetreiver.java

@@ -53,4 +53,8 @@ public Member findByUserIdAndPromiseId(
     ) {
         return memberRepository.findByUserIdAndPromiseId(userId, promiseId);
     }
+
+    public List<MemberDto> findAllByPromiseId(final Long promiseId) {
+        return memberRepository.findAllByPromiseId(promiseId);
+    }
 }

src/main/java/org/kkumulkkum/server/service/participant/ParticipantService.java

@@ -2,8 +2,10 @@
 
 import lombok.RequiredArgsConstructor;
 import lombok.extern.slf4j.Slf4j;
+import org.kkumulkkum.server.domain.Member;
 import org.kkumulkkum.server.domain.Participant;
 import org.kkumulkkum.server.domain.Promise;
+import org.kkumulkkum.server.dto.member.response.MemberDto;
 import org.kkumulkkum.server.dto.participant.ParticipantStatusUserInfoDto;
 import org.kkumulkkum.server.dto.participant.request.PreparationInfoDto;
 import org.kkumulkkum.server.dto.participant.response.*;
@@ -12,6 +14,7 @@
 import org.kkumulkkum.server.external.FcmService;
 import org.kkumulkkum.server.external.dto.FcmMessageDto;
 import org.kkumulkkum.server.external.enums.FcmContent;
+import org.kkumulkkum.server.service.member.MemberRetreiver;
 import org.kkumulkkum.server.service.promise.PromiseRetriever;
 import org.springframework.stereotype.Service;
 import org.springframework.transaction.annotation.Transactional;
@@ -30,6 +33,7 @@ public class ParticipantService {
     private final ParticipantRetriever participantRetriever;
     private final ParticipantEditor participantEditor;
     private final PromiseRetriever promiseRetriever;
+    private final MemberRetreiver memberRetreiver;
     private final ParticipantRemover participantRemover;
     private final FcmService fcmService;
 
@@ -107,6 +111,25 @@ public ParticipantsDto getParticipants(final Long promiseId) {
         return ParticipantsDto.from(sortedParticipants);
     }
 
+    @Transactional(readOnly = true)
+    public AvailableParticipantsDto getAvailableParticipants(
+            final Long userId,
+            final Long promiseId
+    ) {
+        //모임 내 멤버 목록
+        List<MemberDto> members = memberRetreiver.findAllByPromiseId(promiseId);
+        //나 제외
+        Member authenticatedMember = memberRetreiver.findByUserIdAndPromiseId(userId, promiseId);
+        members.removeIf(member -> member.memberId().equals(authenticatedMember.getId()));
+
+        //약속에 참여 중인 멤버 id들 가져오기
+        List<Long> participantIds = participantRetriever.findAllByPromiseId(promiseId).stream()
+                                                                .map(participant -> participant.getMember().getId())
+                                                                .toList();
+
+        return AvailableParticipantsDto.of(members, participantIds);
+    }
+
     @Transactional
     public void insertPreparationInfo(
             final Long userId,