feat: add diagnostic interview loop

internal/interview/service.go

@@ -0,0 +1,117 @@
+package interview
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"strings"
+	"sync/atomic"
+	"time"
+
+	"tutor/internal/workflows"
+)
+
+var ErrQuestionNotFound = errors.New("diagnostic question not found")
+
+type Service struct {
+	store  Store
+	runner workflows.Runner
+	ids    atomic.Uint64
+}
+
+func NewService(store Store, runner workflows.Runner) *Service {
+	return &Service{store: store, runner: runner}
+}
+
+func (s *Service) CreateSession(_ context.Context, input CreateSessionInput) (Session, error) {
+	if strings.TrimSpace(input.UserID) == "" {
+		return Session{}, errors.New("user_id is required")
+	}
+	if strings.TrimSpace(input.TargetRole) == "" {
+		return Session{}, errors.New("target_role is required")
+	}
+	if len(input.Stack) == 0 {
+		return Session{}, errors.New("stack is required")
+	}
+
+	session := Session{
+		ID:                s.nextID("diag"),
+		UserID:            input.UserID,
+		Track:             BackendDeveloperTrack,
+		Status:            SessionInProgress,
+		TargetRole:        input.TargetRole,
+		Stack:             append([]string(nil), input.Stack...),
+		InterviewTimeline: input.InterviewTimeline,
+		Questions:         BackendDeveloperQuestions(),
+		CreatedAt:         time.Now().UTC(),
+	}
+	return s.store.Create(session)
+}
+
+func (s *Service) GetSession(id string) (Session, error) {
+	return s.store.Get(id)
+}
+
+func (s *Service) SubmitAnswer(ctx context.Context, input SubmitAnswerInput) (Answer, error) {
+	if strings.TrimSpace(input.AnswerText) == "" {
+		return Answer{}, errors.New("answer_text is required")
+	}
+
+	session, err := s.store.Get(input.SessionID)
+	if err != nil {
+		return Answer{}, err
+	}
+
+	question, ok := findQuestion(session.Questions, input.QuestionID)
+	if !ok {
+		return Answer{}, ErrQuestionNotFound
+	}
+
+	answer := Answer{
+		ID:         s.nextID("answer"),
+		QuestionID: input.QuestionID,
+		Text:       input.AnswerText,
+		CreatedAt:  time.Now().UTC(),
+	}
+	grade, err := s.runner.GradeInterviewAnswer(ctx, workflows.GradeAnswerInput{
+		UserID:     session.UserID,
+		QuestionID: question.ID,
+		AnswerID:   answer.ID,
+		AnswerText: answer.Text,
+		Concepts:   question.Concepts,
+	})
+	if err != nil {
+		return Answer{}, err
+	}
+	answer.Grade = grade
+
+	session.Answers = append(session.Answers, answer)
+	if answeredQuestionCount(session.Answers) >= len(session.Questions) {
+		session.Status = SessionComplete
+	}
+	if _, err := s.store.Update(session); err != nil {
+		return Answer{}, err
+	}
+	return answer, nil
+}
+
+func answeredQuestionCount(answers []Answer) int {
+	answered := make(map[string]struct{}, len(answers))
+	for _, answer := range answers {
+		answered[answer.QuestionID] = struct{}{}
+	}
+	return len(answered)
+}
+
+func (s *Service) nextID(prefix string) string {
+	return fmt.Sprintf("%s-%d", prefix, s.ids.Add(1))
+}
+
+func findQuestion(questions []Question, id string) (Question, bool) {
+	for _, question := range questions {
+		if question.ID == id {
+			return question, true
+		}
+	}
+	return Question{}, false
+}