feat(interview): 질문 풀 부활 + 깊이 제어 n/m/k (PR1)

ai/src/ai_server/chain/prompts/question_generation.py

@@ -22,7 +22,8 @@
     "{context}\n"
     "---\n\n"
     "요구 사항:\n"
-    "1. 정확히 {max_questions}개의 질문을 생성합니다.\n"
+    "1. 정확히 {max_questions}개의 질문을 생성하되, **서로 다른 주제/영역**을 다룹니다 "
+    "(각 질문이 일반질문 1개의 씨앗이 되고 뒤에 꼬리질문이 붙으므로 같은 주제 반복 금지).\n"
     "2. 각 질문에 적절한 category 를 부여합니다.\n"
     "3. 직군({job_category})·면접 모드({mode}) 에 맞는 비중으로 카테고리 분배:\n"
     "   - TECHNICAL: CS_FUNDAMENTAL + TECH_CHOICE + PROJECT_DEEP_DIVE 중심.\n"

backend/openapi.json

@@ -2529,6 +2529,18 @@
             "type" : "integer",
             "format" : "int32"
           },
+          "generalQuestionCount" : {
+            "type" : "integer",
+            "format" : "int32",
+            "maximum" : 15,
+            "minimum" : 1
+          },
+          "maxFollowupsPerQuestion" : {
+            "type" : "integer",
+            "format" : "int32",
+            "maximum" : 10,
+            "minimum" : 0
+          },
           "contextDocumentIds" : {
             "type" : "array",
             "items" : {
@@ -2568,6 +2580,14 @@
             "type" : "integer",
             "format" : "int32"
           },
+          "generalQuestionCount" : {
+            "type" : "integer",
+            "format" : "int32"
+          },
+          "maxFollowupsPerQuestion" : {
+            "type" : "integer",
+            "format" : "int32"
+          },
           "status" : {
             "type" : "string",
             "enum" : [ "READY", "IN_PROGRESS", "INTERRUPTED", "COMPLETED", "CANCELLED" ]

backend/src/main/java/com/stackup/stackup/session/application/QuestionsCallbackService.java

@@ -14,6 +14,9 @@
 import com.stackup.stackup.session.domain.InterviewMessageRepository;
 import com.stackup.stackup.session.domain.InterviewSession;
 import com.stackup.stackup.session.domain.InterviewSessionRepository;
+import com.stackup.stackup.session.domain.SessionQuestionPool;
+import com.stackup.stackup.session.domain.SessionQuestionPoolRepository;
+import com.stackup.stackup.session.domain.SessionStatus;
 import java.util.List;
 import lombok.RequiredArgsConstructor;
 import org.slf4j.Logger;
@@ -36,6 +39,7 @@ public class QuestionsCallbackService {
 
     private final InterviewSessionRepository sessionRepository;
     private final InterviewMessageRepository messageRepository;
+    private final SessionQuestionPoolRepository poolRepository;
     private final ProcessedMessageRepository processedMessageRepository;
     private final ApplicationEventPublisher events;
 
@@ -74,35 +78,83 @@ public void apply(QuestionsCallbackEnvelope envelope) {
         markProcessed(envelope.messageId());
     }
 
+    // POOL 콜백: AI 가 만든 일반질문들을 풀에 저장하고 첫 질문을 삽입한다.
     private void applyInitialQuestion(InterviewSession session, QuestionsCallbackPayload payload) {
         List<GeneratedQuestion> questions = payload.questions();
         if (questions == null || questions.isEmpty()) {
             log.warn("callback.questions initial result with no questions. sessionId={}", session.getId());
             return;
         }
-        GeneratedQuestion first = questions.get(0);
-        if (questions.size() > 1) {
-            log.info("callback.questions initial result included extra questions; ignoring extras. sessionId={}, extra={}",
-                session.getId(), questions.size() - 1);
+        if (poolRepository.countBySessionId(session.getId()) > 0) {
+            log.info("callback.questions pool already seeded, skip. sessionId={}", session.getId());
+            return;
+        }
+        int idx = 0;
+        for (GeneratedQuestion q : questions) {
+            poolRepository.save(SessionQuestionPool.of(
+                session.getId(), idx++, q.question(), q.category(), q.targetEvidence(), q.expectedSignal()));
+        }
+        poolRepository.findFirstBySessionIdAndUsedFalseOrderByIdxAsc(session.getId())
+            .ifPresent(first -> insertGeneralFromPool(session, first, "INITIAL_QUESTION_READY"));
+        log.info("callback.questions pool seeded. sessionId={}, poolSize={}", session.getId(), questions.size());
+    }
+
+    // 풀에서 다음 일반질문을 꺼내 삽입(꼬리질문 m개 소진 후 호출). 없으면 종료.
+    @Transactional
+    public void advanceToNextGeneral(Long sessionId) {
+        InterviewSession session = sessionRepository.findById(sessionId).orElse(null);
+        if (session == null || session.getStatus() != SessionStatus.IN_PROGRESS) {
+            return;
         }
+        if (session.isMaxReached()) {
+            endSession(session, "MAX_QUESTIONS_REACHED");
+            return;
+        }
+        poolRepository.findFirstBySessionIdAndUsedFalseOrderByIdxAsc(sessionId).ifPresentOrElse(
+            next -> insertGeneralFromPool(session, next, "GENERAL_QUESTION_READY"),
+            () -> endSession(session, "POOL_EXHAUSTED"));
+    }
+
+    private void insertGeneralFromPool(InterviewSession session, SessionQuestionPool pool, String reason) {
+        pool.markUsed();
+        poolRepository.save(pool);
+        long currentMsgs = messageRepository.countBySession_Id(session.getId());
+        int nextSeq = (int) currentMsgs + 1;
         InterviewMessage message = messageRepository.save(
-            InterviewMessage.interviewer(
-                session, 1, first.question(),
-                first.category(), first.targetEvidence(), first.expectedSignal()
-            )
-        );
+            InterviewMessage.interviewer(session, nextSeq, pool.getQuestion(),
+                pool.getCategory(), pool.getTargetEvidence(), pool.getExpectedSignal()));
         session.incrementQuestionCount();
+        publishQuestionEvents(session, message, reason);
+        maybeAutoEnd(session);
+    }
+
+    private void publishQuestionEvents(InterviewSession session, InterviewMessage message, String reason) {
         events.publishEvent(new QuestionPersistedEvent(
             session.getUser().getId(), session.getId(), message.getId()));
         events.publishEvent(RealtimeNotifyEvent.session(session.getId(), SseEventType.SESSION_MESSAGE, message.getId()));
-        // 사용자 user 채널에도 알림 — frontend 가 documentId/sessionId 사전 인지 없이도 받을 수 있게
-        events.publishEvent(RealtimeNotifyEvent.user(
-            session.getUser().getId(),
-            SseEventType.SESSION_MESSAGE,
-            new SessionMessageNotice(session.getId(), message.getId(), "INITIAL_QUESTION_READY")
-        ));
-        log.info("callback.questions initial question processed. sessionId={}, ignored_extras={}",
-            session.getId(), Math.max(questions.size() - 1, 0));
+        events.publishEvent(RealtimeNotifyEvent.user(session.getUser().getId(), SseEventType.SESSION_MESSAGE,
+            new SessionMessageNotice(session.getId(), message.getId(), reason)));
+    }
+
+    private void maybeAutoEnd(InterviewSession session) {
+        if (session.isMaxReached()) {
+            endSession(session, "MAX_QUESTIONS_REACHED");
+        }
+    }
+
+    private void endSession(InterviewSession session, String reason) {
+        try {
+            session.end();
+            events.publishEvent(RealtimeNotifyEvent.session(session.getId(), SseEventType.SESSION_STATE,
+                new SessionStateNotice(session.getId(), session.getStatus().name(), reason)));
+            events.publishEvent(RealtimeNotifyEvent.user(session.getUser().getId(), SseEventType.SESSION_STATE,
+                new SessionStateNotice(session.getId(), session.getStatus().name(), reason)));
+            events.publishEvent(new SessionEndedEvent(session.getUser().getId(), session.getId(), reason));
+            log.info("session auto-completed. sessionId={}, reason={}", session.getId(), reason);
+        } catch (IllegalStateException e) {
+            log.warn("auto-end skipped — session not IN_PROGRESS. sessionId={}, status={}",
+                session.getId(), session.getStatus());
+        }
     }
 
     private void applyFollowup(InterviewSession session, QuestionsCallbackPayload payload) {
@@ -135,25 +187,8 @@ private void applyFollowup(InterviewSession session, QuestionsCallbackPayload pa
             new SessionMessageNotice(session.getId(), message.getId(), "FOLLOWUP_READY")
         ));
 
-        // maxQuestions 도달 시 자동 종료 (plan §A-4)
-        Integer max = session.getMaxQuestions();
-        if (max != null && session.getTotalQuestionCount() != null
-            && session.getTotalQuestionCount() >= max) {
-            try {
-                session.end();
-                events.publishEvent(RealtimeNotifyEvent.session(session.getId(), SseEventType.SESSION_STATE,
-                    new SessionStateNotice(session.getId(), session.getStatus().name(), "MAX_QUESTIONS_REACHED")));
-                events.publishEvent(RealtimeNotifyEvent.user(session.getUser().getId(), SseEventType.SESSION_STATE,
-                    new SessionStateNotice(session.getId(), session.getStatus().name(), "MAX_QUESTIONS_REACHED")));
-                events.publishEvent(new SessionEndedEvent(
-                    session.getUser().getId(), session.getId(), "MAX_QUESTIONS_REACHED"));
-                log.info("session auto-completed on max questions. sessionId={}, max={}",
-                    session.getId(), max);
-            } catch (IllegalStateException e) {
-                log.warn("auto-end skipped — session not IN_PROGRESS. sessionId={}, status={}",
-                    session.getId(), session.getStatus());
-            }
-        }
+        // maxQuestions(k) 도달 시 자동 종료.
+        maybeAutoEnd(session);
 
         log.info("callback.questions FOLLOWUP processed. sessionId={}, msg={}, totalQ={}",
             session.getId(), message.getId(), session.getTotalQuestionCount());

backend/src/main/java/com/stackup/stackup/session/application/SessionFollowupRequester.java

@@ -9,6 +9,7 @@
 import com.stackup.stackup.session.domain.InterviewMessage;
 import com.stackup.stackup.session.domain.InterviewMessageRepository;
 import com.stackup.stackup.session.domain.InterviewSession;
+import com.stackup.stackup.session.domain.MessageRole;
 import com.stackup.stackup.session.domain.SessionContextRepository;
 import java.util.List;
 import lombok.RequiredArgsConstructor;
@@ -33,6 +34,7 @@ public class SessionFollowupRequester {
     private final RabbitMqProperties properties;
     private final InterviewMessageRepository messageRepository;
     private final SessionContextRepository contextRepository;
+    private final QuestionsCallbackService questionsCallbackService;
 
     @Transactional(propagation = Propagation.REQUIRES_NEW)
     @TransactionalEventListener(phase = TransactionPhase.AFTER_COMMIT)
@@ -54,6 +56,19 @@ public void onAnswerSubmitted(AnswerSubmittedEvent event) {
         // 최근 대화 히스토리 (중복 질문 회피). 시퀀스 순 → 마지막 N개.
         List<InterviewMessage> ordered =
             messageRepository.findBySession_IdOrderBySequenceNumberAsc(session.getId());
+
+        // 깊이 제어: 현재 일반질문 아래 꼬리질문 수(depth) 가 m 이상이면
+        // 꼬리질문 대신 풀의 다음 일반질문으로 넘어간다(없으면 종료). AI 호출 불필요.
+        int depth = currentFollowupDepth(ordered);
+        int maxFollowups = session.getMaxFollowupsPerQuestion() != null
+            ? session.getMaxFollowupsPerQuestion() : 2;
+        if (depth >= maxFollowups) {
+            log.info("followup depth reached (m={}) — advancing to next general. sessionId={}",
+                maxFollowups, session.getId());
+            questionsCallbackService.advanceToNextGeneral(session.getId());
+            return;
+        }
+
         List<HistoryItem> history = ordered.stream()
             .skip(Math.max(0, ordered.size() - HISTORY_MAX))
             .map(m -> new HistoryItem(m.getRole().name(), m.getContent()))
@@ -80,4 +95,21 @@ public void onAnswerSubmitted(AnswerSubmittedEvent event) {
         log.info("generate.followup published. sessionId={}, parent={}, answer={}",
             session.getId(), parent.getId(), answer.getId());
     }
+
+    // 현재 일반질문(INTERVIEWER + parent null) 이후 달린 꼬리질문(INTERVIEWER + parent 있음) 수.
+    // 새 일반질문이 나오면 0 으로 리셋된다.
+    private int currentFollowupDepth(List<InterviewMessage> ordered) {
+        int depth = 0;
+        for (InterviewMessage m : ordered) {
+            if (m.getRole() != MessageRole.INTERVIEWER) {
+                continue;
+            }
+            if (m.getParentMessage() == null) {
+                depth = 0;            // 일반질문 → 리셋
+            } else {
+                depth++;              // 꼬리질문 → 증가
+            }
+        }
+        return depth;
+    }
 }

backend/src/main/java/com/stackup/stackup/session/application/SessionQuestionsRequester.java

@@ -38,7 +38,7 @@ public class SessionQuestionsRequester {
     private static final JsonMapper JSON = JsonMapper.builder().build();
     private static final TypeReference<List<String>> TECH_STACK_TYPE = new TypeReference<>() {};
     private static final long MAX_MARKDOWN_BYTES = 200_000L;  // envelope 비대화 방지
-    private static final int INITIAL_QUESTION_COUNT = 1;
+    private static final int DEFAULT_GENERAL_QUESTION_COUNT = 3;
 
     private final RabbitMessagePublisher publisher;
     private final RabbitMqProperties properties;
@@ -49,21 +49,23 @@ public class SessionQuestionsRequester {
     @TransactionalEventListener(phase = TransactionPhase.AFTER_COMMIT)
     public void onSessionCreated(SessionCreatedEvent event) {
         List<DocumentContext> documents = buildDocumentContexts(event.contextDocumentIds());
+        int generalCount = event.generalQuestionCount() != null
+            ? event.generalQuestionCount() : DEFAULT_GENERAL_QUESTION_COUNT;
         GenerateQuestionsPayload payload = new GenerateQuestionsPayload(
             event.sessionId(),
             event.mode(),
             event.jobCategory(),
             documents,
-            INITIAL_QUESTION_COUNT,
+            generalCount,
             event.maxQuestions()
         );
         publisher.publishToAi(
             properties.routingKeys().generateQuestions(),
             payload,
             new MessageContext(event.userId(), event.sessionId(), null, null)
         );
-        log.info("generate.questions published. sessionId={}, doc_count={}, initial_count={}, max={}",
-            event.sessionId(), documents.size(), INITIAL_QUESTION_COUNT, event.maxQuestions());
+        log.info("generate.questions published. sessionId={}, doc_count={}, general_count={}, max={}",
+            event.sessionId(), documents.size(), generalCount, event.maxQuestions());
     }
 
     private List<DocumentContext> buildDocumentContexts(List<Long> documentIds) {

backend/src/main/java/com/stackup/stackup/session/application/SessionService.java

@@ -50,7 +50,9 @@ public SessionResult create(Long userId, SessionCreateCommand command) {
             command.mode(),
             command.jobCategory(),
             command.maxQuestions(),
-            command.maxDurationMinutes()
+            command.maxDurationMinutes(),
+            command.generalQuestionCount(),
+            command.maxFollowupsPerQuestion()
         ));
 
         List<Long> linkedIds = linkContexts(session, userId, command.contextDocumentIds());
@@ -62,6 +64,7 @@ public SessionResult create(Long userId, SessionCreateCommand command) {
             session.getMode(),
             session.getJobCategory(),
             session.getMaxQuestions(),
+            session.getGeneralQuestionCount(),
             linkedIds
         ));
         return SessionResult.of(session, linkedIds);

backend/src/main/java/com/stackup/stackup/session/application/dto/SessionCreateCommand.java

@@ -11,6 +11,8 @@ public record SessionCreateCommand(
     JobCategory jobCategory,
     Integer maxQuestions,
     Integer maxDurationMinutes,
+    Integer generalQuestionCount,
+    Integer maxFollowupsPerQuestion,
     List<Long> contextDocumentIds
 ) {
 }

backend/src/main/java/com/stackup/stackup/session/application/dto/SessionResult.java

@@ -15,6 +15,8 @@ public record SessionResult(
     JobCategory jobCategory,
     Integer maxQuestions,
     Integer maxDurationMinutes,
+    Integer generalQuestionCount,
+    Integer maxFollowupsPerQuestion,
     SessionStatus status,
     Integer totalQuestionCount,
     Instant startedAt,
@@ -32,6 +34,8 @@ public static SessionResult of(InterviewSession session, List<Long> documentIds)
             session.getJobCategory(),
             session.getMaxQuestions(),
             session.getMaxDurationMinutes(),
+            session.getGeneralQuestionCount(),
+            session.getMaxFollowupsPerQuestion(),
             session.getStatus(),
             session.getTotalQuestionCount(),
             session.getStartedAt(),

backend/src/main/java/com/stackup/stackup/session/application/event/SessionCreatedEvent.java

@@ -11,6 +11,7 @@ public record SessionCreatedEvent(
     SessionMode mode,
     JobCategory jobCategory,
     Integer maxQuestions,
+    Integer generalQuestionCount,
     List<Long> contextDocumentIds
 ) {
 }

backend/src/main/java/com/stackup/stackup/session/domain/InterviewSession.java

@@ -60,6 +60,14 @@ public class InterviewSession extends BaseSoftDeleteEntity {
     @Column(name = "max_duration_minutes", nullable = false)
     private Integer maxDurationMinutes = 60;
 
+    // 일반질문 수(n). 서로 다른 주제로 풀에서 꺼내 묻는다.
+    @Column(name = "general_question_count", nullable = false)
+    private Integer generalQuestionCount = 3;
+
+    // 일반질문 1개당 최대 꼬리질문 수(m).
+    @Column(name = "max_followups_per_question", nullable = false)
+    private Integer maxFollowupsPerQuestion = 2;
+
     @Column(nullable = false, length = 20)
     @Enumerated(EnumType.STRING)
     private SessionStatus status = SessionStatus.READY;
@@ -75,7 +83,8 @@ public class InterviewSession extends BaseSoftDeleteEntity {
 
     private InterviewSession(User user, String title, String memo, SessionMode mode,
                              JobCategory jobCategory,
-                             Integer maxQuestions, Integer maxDurationMinutes) {
+                             Integer maxQuestions, Integer maxDurationMinutes,
+                             Integer generalQuestionCount, Integer maxFollowupsPerQuestion) {
         this.user = user;
         this.title = title;
         this.memo = memo;
@@ -87,18 +96,26 @@ private InterviewSession(User user, String title, String memo, SessionMode mode,
         if (maxDurationMinutes != null) {
             this.maxDurationMinutes = maxDurationMinutes;
         }
+        if (generalQuestionCount != null) {
+            this.generalQuestionCount = generalQuestionCount;
+        }
+        if (maxFollowupsPerQuestion != null) {
+            this.maxFollowupsPerQuestion = maxFollowupsPerQuestion;
+        }
     }
 
     public static InterviewSession create(User user, String title, String memo, SessionMode mode,
                                           JobCategory jobCategory,
-                                          Integer maxQuestions, Integer maxDurationMinutes) {
+                                          Integer maxQuestions, Integer maxDurationMinutes,
+                                          Integer generalQuestionCount, Integer maxFollowupsPerQuestion) {
         if (user == null) {
             throw new IllegalArgumentException("user must not be null");
         }
         if (mode == null || jobCategory == null) {
             throw new IllegalArgumentException("mode/jobCategory must not be null");
         }
-        return new InterviewSession(user, title, memo, mode, jobCategory, maxQuestions, maxDurationMinutes);
+        return new InterviewSession(user, title, memo, mode, jobCategory,
+            maxQuestions, maxDurationMinutes, generalQuestionCount, maxFollowupsPerQuestion);
     }
 
     public void start() {