🚀 메이트 참여 삭제 API 구현

src/main/java/team/silvertown/masil/mate/controller/MateParticipantController.java

@@ -9,6 +9,7 @@
 import lombok.RequiredArgsConstructor;
 import org.springframework.http.ResponseEntity;
 import org.springframework.security.core.annotation.AuthenticationPrincipal;
+import org.springframework.web.bind.annotation.DeleteMapping;
 import org.springframework.web.bind.annotation.PathVariable;
 import org.springframework.web.bind.annotation.PostMapping;
 import org.springframework.web.bind.annotation.PutMapping;
@@ -70,4 +71,24 @@ public ResponseEntity<Void> acceptParticipant(
             .build();
     }
 
+    @DeleteMapping("/api/v1/mates/{id}/participants/{participantId}")
+    @Operation(summary = "메이트 참여 요청 거절/취소")
+    @ApiResponse(
+        responseCode = "204",
+        description = "메이트 참여 요청 거절/취소 성공"
+    )
+    public ResponseEntity<Void> deleteById(
+        @AuthenticationPrincipal
+        Long userId,
+        @PathVariable
+        Long id,
+        @PathVariable
+        Long participantId
+    ) {
+        mateService.deleteParticipantById(userId, id, participantId);
+
+        return ResponseEntity.noContent()
+            .build();
+    }
+
 }

src/main/java/team/silvertown/masil/mate/service/MateService.java

@@ -1,6 +1,7 @@
 package team.silvertown.masil.mate.service;
 
 import java.util.List;
+import java.util.Optional;
 import java.util.function.Supplier;
 import lombok.RequiredArgsConstructor;
 import org.locationtech.jts.geom.Point;
@@ -130,6 +131,22 @@ public void acceptParticipation(Long authorId, Long id, Long participantId) {
         mateParticipant.acceptParticipant();
     }
 
+    @Transactional
+    public void deleteParticipantById(Long userId, Long id, Long participantId) {
+        User user = userRepository.findById(userId)
+            .orElseThrow(getNotFoundException(MateErrorCode.USER_NOT_FOUND));
+        Optional<MateParticipant> mateParticipant = mateParticipantRepository.findById(
+            participantId);
+
+        if (mateParticipant.isEmpty()) {
+            return;
+        }
+
+        MateValidator.validateParticipantDeletion(user, id, mateParticipant.get());
+
+        mateParticipantRepository.delete(mateParticipant.get());
+    }
+
     private Supplier<DataNotFoundException> getNotFoundException(ErrorCode errorCode) {
         return () -> new DataNotFoundException(errorCode);
     }

src/main/java/team/silvertown/masil/mate/validator/MateValidator.java

@@ -10,6 +10,7 @@
 import team.silvertown.masil.mate.domain.Mate;
 import team.silvertown.masil.mate.domain.MateParticipant;
 import team.silvertown.masil.mate.exception.MateErrorCode;
+import team.silvertown.masil.user.domain.User;
 
 @NoArgsConstructor(access = AccessLevel.PRIVATE)
 public final class MateValidator extends Validator {
@@ -59,6 +60,22 @@ public static void validateParticipantAcceptance(
         validateParticipantUnderMate(mateId, mate);
     }
 
+    public static void validateParticipantDeletion(
+        User user,
+        Long mateId,
+        MateParticipant mateParticipant
+    ) {
+        Mate mate = mateParticipant.getMate();
+
+        validateParticipantUnderMate(mateId, mate);
+
+        boolean isNotOwner = !user.equals(mateParticipant.getUser());
+
+        if (isNotOwner) {
+            validateAuthForManipulation(user.getId(), mate);
+        }
+    }
+
     private static void validateParticipantUnderMate(
         Long mateId,
         Mate mate

src/test/java/team/silvertown/masil/mate/service/MateServiceTest.java

@@ -8,6 +8,7 @@
 import java.util.ArrayList;
 import java.util.Collections;
 import java.util.List;
+import java.util.Optional;
 import org.assertj.core.api.ThrowableAssert.ThrowingCallable;
 import org.junit.jupiter.api.BeforeEach;
 import org.junit.jupiter.api.DisplayNameGeneration;
@@ -619,4 +620,108 @@ private String getLastLatestCursor(int skipSize) {
             .withMessage(MateErrorCode.PARTICIPATING_AROUND_SIMILAR_TIME.getMessage());
     }
 
+    @Test
+    void 사용자가_본인의_메이트_참여자_삭제를_성공한다() {
+        // given
+        Mate mate = mateRepository.save(MateTexture.createDependentMate(author, post));
+        User user = userRepository.save(UserTexture.createValidUser());
+        MateParticipant participant = mateParticipantRepository.save(
+            MateTexture.createMateParticipant(user, mate, ParticipantStatus.REQUESTED));
+
+        // when
+        mateService.deleteParticipantById(user.getId(), mate.getId(), participant.getId());
+
+        // then
+        Optional<MateParticipant> expected = mateParticipantRepository.findById(
+            participant.getId());
+
+        assertThat(expected).isEmpty();
+    }
+
+    @Test
+    void 메이트_작성자가_다른_사용자의_메이트_참여_삭제를_성공한다() {
+        // given
+        Mate mate = mateRepository.save(MateTexture.createDependentMate(author, post));
+        User user = userRepository.save(UserTexture.createValidUser());
+        MateParticipant participant = mateParticipantRepository.save(
+            MateTexture.createMateParticipant(user, mate, ParticipantStatus.REQUESTED));
+
+        // when
+        mateService.deleteParticipantById(author.getId(), mate.getId(), participant.getId());
+
+        // then
+        Optional<MateParticipant> expected = mateParticipantRepository.findById(
+            participant.getId());
+
+        assertThat(expected).isEmpty();
+    }
+
+    @Test
+    void 존재하지_않는_참여자면_예외를_발생시키지_않는다() {
+        // given
+        Mate mate = mateRepository.save(MateTexture.createDependentMate(author, post));
+        long invalidId = MateTexture.getRandomId();
+
+        // when
+        ThrowingCallable delete = () -> mateService.deleteParticipantById(author.getId(),
+            mate.getId(), invalidId);
+
+        // then
+        assertThatNoException().isThrownBy(delete);
+    }
+
+    @Test
+    void 로그인_사용자가_없으면_메이트_참여자_삭제를_실패한다() {
+        // given
+        Mate mate = mateRepository.save(MateTexture.createDependentMate(author, post));
+        User user = userRepository.save(UserTexture.createValidUser());
+        MateParticipant participant = mateParticipantRepository.save(
+            MateTexture.createMateParticipant(user, mate, ParticipantStatus.REQUESTED));
+        long invalidId = MateTexture.getRandomId();
+
+        // when
+        ThrowingCallable delete = () -> mateService.deleteParticipantById(invalidId, mate.getId(),
+            participant.getId());
+
+        // then
+        assertThatExceptionOfType(DataNotFoundException.class).isThrownBy(delete)
+            .withMessage(MateErrorCode.USER_NOT_FOUND.getMessage());
+    }
+
+    @Test
+    void 메이트와_참여자의_메이트가_다르면_메이트_참여자_삭제를_실패한다() {
+        // given
+        Mate mate = mateRepository.save(MateTexture.createDependentMate(author, post));
+        User user = userRepository.save(UserTexture.createValidUser());
+        MateParticipant participant = mateParticipantRepository.save(
+            MateTexture.createMateParticipant(user, mate, ParticipantStatus.REQUESTED));
+        Mate anotherMate = mateRepository.save(MateTexture.createDependentMate(author, post));
+
+        // when
+        ThrowingCallable delete = () -> mateService.deleteParticipantById(user.getId(),
+            anotherMate.getId(), participant.getId());
+
+        // then
+        assertThatExceptionOfType(BadRequestException.class).isThrownBy(delete)
+            .withMessage(MateErrorCode.PARTICIPANT_MATE_NOT_MATCHING.getMessage());
+    }
+
+    @Test
+    void 로그인한_사용자가_메이트_작성자도_아니고_본인도_아니면_삭제를_실패한다() {
+        // given
+        Mate mate = mateRepository.save(MateTexture.createDependentMate(author, post));
+        User user = userRepository.save(UserTexture.createValidUser());
+        MateParticipant participant = mateParticipantRepository.save(
+            MateTexture.createMateParticipant(user, mate, ParticipantStatus.REQUESTED));
+        User anotherUser = userRepository.save(UserTexture.createValidUser());
+
+        // when
+        ThrowingCallable delete = () -> mateService.deleteParticipantById(anotherUser.getId(),
+            mate.getId(), participant.getId());
+
+        //then
+        assertThatExceptionOfType(ForbiddenException.class).isThrownBy(delete)
+            .withMessage(MateErrorCode.USER_NOT_AUTHORIZED_FOR_MATE.getMessage());
+    }
+
 }