add load and save methods

internal/services/story_service/service.go

@@ -15,16 +15,38 @@ type StoryService struct {
 }
 
 func NewStoryService(filepath string) (*StoryService, error) {
+	s := &StoryService{}
+	if err := s.Load(filepath); err != nil {
+		return nil, err
+	}
+	return s, nil
+}
+
+func (s *StoryService) Load(filepath string) error {
 	data, err := os.ReadFile(filepath)
 	if err != nil {
-		return nil, fmt.Errorf("story file %s not found", filepath)
+		return fmt.Errorf("story file %s not found", filepath)
 	}
 	log.Printf("load story from: %s", filepath)
 	story := &Story{}
 	if err := json.Unmarshal(data, story); err != nil {
-		return nil, err
+		return err
 	}
-	return &StoryService{story: story}, nil
+	s.story = story
+	return nil
+}
+
+func (s *StoryService) Save(filepath string) error {
+	story := s.story
+	data, err := json.Marshal(story)
+	if err != nil {
+		return err
+	}
+	if err := os.WriteFile(filepath, data, 0x777); err != nil {
+		return err
+	}
+	log.Printf("save story to: %s", filepath)
+	return nil
 }
 
 func (s *StoryService) GetPlace(code string) *Place {