Implement quiz answer submission and scoring

src/main/java/com/example/questionbank/service/quiz/QuizAttemptService.java

@@ -1,21 +1,32 @@
 package com.example.questionbank.service.quiz;
 
 import com.example.questionbank.domain.Choice;
+import com.example.questionbank.domain.ExamAnswer;
 import com.example.questionbank.domain.ExamAttempt;
 import com.example.questionbank.domain.Question;
 import com.example.questionbank.domain.Subject;
 import com.example.questionbank.domain.User;
 import com.example.questionbank.domain.enumeration.AttemptStatus;
+import com.example.questionbank.domain.enumeration.OptionKey;
+import com.example.questionbank.repository.ExamAnswerRepository;
 import com.example.questionbank.repository.ExamAttemptRepository;
 import com.example.questionbank.repository.QuestionRepository;
 import com.example.questionbank.repository.SubjectRepository;
 import com.example.questionbank.repository.UserRepository;
+import com.example.questionbank.web.rest.dto.AnswerResult;
 import com.example.questionbank.web.rest.dto.ChoiceView;
 import com.example.questionbank.web.rest.dto.ExamAttemptStartResult;
 import com.example.questionbank.web.rest.dto.ExamQuestionView;
+import com.example.questionbank.web.rest.dto.ExamResult;
+import com.example.questionbank.web.rest.dto.SubmitAnswerRequest;
+import com.example.questionbank.web.rest.dto.SubmitExamRequest;
 import java.time.Instant;
+import java.util.ArrayList;
 import java.util.Comparator;
+import java.util.HashSet;
 import java.util.List;
+import java.util.Set;
+import java.util.stream.Collectors;
 import org.springframework.http.HttpStatus;
 import org.springframework.stereotype.Service;
 import org.springframework.transaction.annotation.Transactional;
@@ -25,20 +36,26 @@ import org.springframework.web.server.ResponseStatusException;
 public class QuizAttemptService {
 
     private final ExamAttemptRepository attemptRepository;
+    private final ExamAnswerRepository answerRepository;
     private final SubjectRepository subjectRepository;
     private final QuestionRepository questionRepository;
     private final UserRepository userRepository;
+    private final ExamScoringService scoringService;
 
     public QuizAttemptService(
         ExamAttemptRepository attemptRepository,
+        ExamAnswerRepository answerRepository,
         SubjectRepository subjectRepository,
         QuestionRepository questionRepository,
-        UserRepository userRepository
+        UserRepository userRepository,
+        ExamScoringService scoringService
     ) {
         this.attemptRepository = attemptRepository;
+        this.answerRepository = answerRepository;
         this.subjectRepository = subjectRepository;
         this.questionRepository = questionRepository;
         this.userRepository = userRepository;
+        this.scoringService = scoringService;
     }
 
     // 1. 시험 응시 시작
@@ -74,7 +91,7 @@ public class QuizAttemptService {
         return new ExamAttemptStartResult(saved.getId(), saved.getStartedAt());
     }
 
-    // 2. 시험 문제 조회 (정답은 숨김)
+    // 2. 시험 문제 조회 (정답 숨김)
     @Transactional(readOnly = true)
     public List<ExamQuestionView> getQuestions(Long attemptId, String login) {
         ExamAttempt attempt = getOwnedAttempt(attemptId, login);
@@ -102,7 +119,119 @@ public class QuizAttemptService {
             .toList();
     }
 
-    // 3. 응시 기록이 로그인한 사용자 본인의 것인지 확인
+    // 3. 답안 제출 및 자동 채점
+    @Transactional
+    public ExamResult submit(Long attemptId, String login, SubmitExamRequest request) {
+        ExamAttempt attempt = getOwnedAttempt(attemptId, login);
+
+        if (attempt.getStatus() != AttemptStatus.IN_PROGRESS) {
+            throw new ResponseStatusException(HttpStatus.CONFLICT, "이미 제출된 응시입니다.");
+        }
+
+        Set<Long> seenQuestionIds = new HashSet<>();
+
+        Set<Long> requiredQuestionIds = questionRepository
+            .findAllBySubjectIdAndActiveTrue(attempt.getSubject().getId())
+            .stream()
+            .map(Question::getId)
+            .collect(Collectors.toSet());
+
+        List<AnswerResult> results = new ArrayList<>();
+        int totalScore = 0;
+
+        for (SubmitAnswerRequest answerRequest : request.answers()) {
+            // 동일한 문제를 중복 제출했는지 확인
+            if (!seenQuestionIds.add(answerRequest.questionId())) {
+                throw new ResponseStatusException(HttpStatus.BAD_REQUEST, "중복 제출된 문항이 있습니다.");
+            }
+
+            // 제출한 문제 조회
+            Question question = questionRepository
+                .findById(answerRequest.questionId())
+                .orElseThrow(() -> new ResponseStatusException(HttpStatus.NOT_FOUND, "문항을 찾을 수 없습니다."));
+
+            // 현재 과목에 속한 활성 문제인지 확인
+            if (!Boolean.TRUE.equals(question.getActive()) || !question.getSubject().getId().equals(attempt.getSubject().getId())) {
+                throw new ResponseStatusException(HttpStatus.BAD_REQUEST, "응시할 수 없는 문항입니다.");
+            }
+
+            // 보기 4개와 정답 1개가 올바르게 등록됐는지 확인
+            List<Choice> choices = new ArrayList<>(question.getChoices());
+
+            List<Choice> correctChoices = choices
+                .stream()
+                .filter(choice -> Boolean.TRUE.equals(choice.getCorrect()))
+                .toList();
+
+            Set<OptionKey> optionKeys = choices.stream().map(Choice::getOptionKey).collect(Collectors.toSet());
+
+            if (choices.size() != 4 || optionKeys.size() != 4 || correctChoices.size() != 1) {
+                throw new ResponseStatusException(HttpStatus.CONFLICT, "문항의 선택지 구성이 올바르지 않습니다.");
+            }
+
+            // 사용자가 선택한 보기 찾기
+            OptionKey selectedOption = answerRequest.selectedOption();
+
+            Choice selectedChoice =
+                selectedOption == null
+                    ? null
+                    : choices
+                          .stream()
+                          .filter(choice -> choice.getOptionKey() == selectedOption)
+                          .findFirst()
+                          .orElseThrow(() ->
+                              new ResponseStatusException(HttpStatus.BAD_REQUEST, "해당 문항에 존재하지 않는 선택지입니다.")
+                          );
+
+            // 앞에서 만든 ExamScoringService로 채점
+            ExamScoringService.ScoringResult score = scoringService.score(correctChoices.getFirst().getOptionKey(), selectedOption);
+
+            // 문제·해설·선택 답안의 스냅샷 저장
+            ExamAnswer answer = new ExamAnswer();
+            answer.setAttempt(attempt);
+            answer.setQuestion(question);
+            answer.setQuestionTextSnapshot(question.getPrompt());
+            answer.setExplanationSnapshot(question.getExplanation());
+            answer.setSelectedOption(selectedOption);
+            answer.setSelectedContentSnapshot(selectedChoice == null ? null : selectedChoice.getContent());
+            answer.setCorrect(score.correct());
+            answer.setAwardedPoints(score.awardedPoints());
+
+            answerRepository.save(answer);
+
+            // 총점 계산
+            totalScore += score.awardedPoints();
+
+            // 응시자에게 반환할 채점 결과 만들기
+            results.add(
+                new AnswerResult(
+                    question.getId(),
+                    question.getPrompt(),
+                    selectedOption,
+                    selectedChoice == null ? null : selectedChoice.getContent(),
+                    score.correct(),
+                    score.awardedPoints(),
+                    question.getExplanation()
+                )
+            );
+        }
+
+        // 모든 활성 문제를 제출했는지 확인
+        if (!seenQuestionIds.equals(requiredQuestionIds)) {
+            throw new ResponseStatusException(HttpStatus.BAD_REQUEST, "과목의 모든 활성 문항을 빠짐없이 제출해야 합니다.");
+        }
+
+        // 시험 제출 완료 처리
+        Instant submittedAt = Instant.now();
+
+        attempt.setScore(totalScore);
+        attempt.setSubmittedAt(submittedAt);
+        attempt.setStatus(AttemptStatus.SUBMITTED);
+
+        return new ExamResult(attempt.getId(), totalScore, submittedAt, results);
+    }
+
+    // 4. 응시 기록 소유자 확인
     private ExamAttempt getOwnedAttempt(Long attemptId, String login) {
         ExamAttempt attempt = attemptRepository
             .findById(attemptId)