feat: 유저가 참여한 모임을 취소한다.

src/main/java/net/teumteum/meeting/controller/MeetingController.java

@@ -46,6 +46,13 @@ public MeetingResponse addParticipant(@PathVariable("meetingId") Long meetingId)
         return meetingService.addParticipant(meetingId, userId);
     }
 
+    @DeleteMapping("/{meetingId}/participants")
+    @ResponseStatus(HttpStatus.OK)
+public void deleteParticipant(@PathVariable("meetingId") Long meetingId) {
+        Long userId = securityService.getCurrentUserId();
+        meetingService.cancelParticipant(meetingId, userId);
+    }
+
     @ResponseStatus(HttpStatus.BAD_REQUEST)
     @ExceptionHandler(IllegalArgumentException.class)
     public ErrorResponse handleIllegalArgumentException(IllegalArgumentException illegalArgumentException) {

src/main/java/net/teumteum/meeting/domain/Meeting.java

@@ -55,6 +55,10 @@ public void addParticipant(Long userId) {
         participantUserIds.add(userId);
     }
 
+    public void cancelParticipant(Long userId) {
+        participantUserIds.remove(userId);
+    }
+
     public boolean alreadyParticipant(Long userId) {
         return participantUserIds.contains(userId);
     }
@@ -85,5 +89,4 @@ private void assertTitle() {
     private void assertParticipantUserIds() {
         Assert.isTrue(participantUserIds.size() + 1 <= numberOfRecruits, "최대 참여자 수에 도달한 모임에 참여할 수 없습니다." + "[최대 참여자 수] : " + numberOfRecruits + "[현재 참여자 수] : " + participantUserIds.size());
     }
-
 }

src/main/java/net/teumteum/meeting/service/MeetingService.java

@@ -68,4 +68,20 @@ public MeetingResponse addParticipant(Long meetingId, Long userId) {
         existMeeting.addParticipant(userId);
         return MeetingResponse.of(existMeeting);
     }
+
+    @Transactional
+    public void cancelParticipant(Long meetingId, Long userId) {
+        var existMeeting = meetingRepository.findById(meetingId)
+                .orElseThrow(() -> new IllegalArgumentException("meetingId에 해당하는 모임을 찾을 수 없습니다. \"" + meetingId + "\""));
+
+        if (!existMeeting.isOpen()) {
+            throw new IllegalArgumentException("종료된 모임에서 참여를 취소할 수 없습니다.");
+        }
+
+        if (!existMeeting.alreadyParticipant(userId)) {
+            throw new IllegalArgumentException("참여하지 않은 모임입니다.");
+        }
+
+        existMeeting.cancelParticipant(userId);
+    }
 }

src/test/java/net/teumteum/integration/Api.java

@@ -102,4 +102,10 @@ ResponseSpec joinMeeting(String token, Long meetingId) {
             .exchange();
     }
 
+    ResponseSpec cancelMeeting(String token, Long meetingId) {
+        return webTestClient.delete()
+            .uri("/meetings/" + meetingId + "/participants")
+            .header(HttpHeaders.AUTHORIZATION, token)
+            .exchange();
+    }
 }

src/test/java/net/teumteum/integration/MeetingIntegrationTest.java

@@ -252,4 +252,64 @@ void Return_400_bad_request_if_exceed_max_number_of_recruits_meeting_id_received
                     .expectBody(ErrorResponse.class);
         }
     }
+
+    @Nested
+    @DisplayName("미팅 참여 취소 API는")
+    class Cancel_meeting_api {
+
+        @Test
+        @DisplayName("존재하는 모임의 id가 주어지면, 모임에 참여를 취소한다.")
+        void Cancel_meeting_if_exist_meeting_id_received() {
+            // given
+            var me = repository.saveAndGetUser();
+            var meeting = repository.saveAndGetOpenMeeting();
+
+            loginContext.setUserId(me.getId());
+            api.joinMeeting(VALID_TOKEN, meeting.getId());
+            // when
+            var result = api.cancelMeeting(VALID_TOKEN, meeting.getId());
+            // then
+            result.expectStatus().isOk();
+        }
+
+        @Test
+        @DisplayName("참여하지 않은 모임의 id가 주어지면, 400 Bad Request를 응답한다.")
+        void Return_400_bad_request_if_not_joined_meeting_id_received() {
+            // given
+            var me = repository.saveAndGetUser();
+            var meeting = repository.saveAndGetOpenMeeting();
+
+            loginContext.setUserId(me.getId());
+            // when
+            var result = api.cancelMeeting(VALID_TOKEN, meeting.getId());
+            // then
+            Assertions.assertThat(result.expectStatus().isBadRequest()
+                            .expectBody(ErrorResponse.class)
+                            .returnResult()
+                            .getResponseBody()
+                    )
+                    .extracting(ErrorResponse::getMessage)
+                    .isEqualTo("참여하지 않은 모임입니다.");
+        }
+
+        @Test
+        @DisplayName("종료된 모임의 id가 주어진다면, 400 Bad Request를 응답한다.")
+        void Return_400_bad_request_if_closed_meeting_id_received() {
+            // given
+            var me = repository.saveAndGetUser();
+            var meeting = repository.saveAndGetCloseMeeting();
+
+            loginContext.setUserId(me.getId());
+            // when
+            var result = api.cancelMeeting(VALID_TOKEN, meeting.getId());
+            // then
+            Assertions.assertThat(result.expectStatus().isBadRequest()
+                            .expectBody(ErrorResponse.class)
+                            .returnResult()
+                            .getResponseBody()
+                    )
+                    .extracting(ErrorResponse::getMessage)
+                    .isEqualTo("종료된 모임에서 참여를 취소할 수 없습니다.");
+        }
+    }
 }