feat(grpc): add support for fetching empty classrooms

Implement the `TASK_TYPE_GET_EMPTY_CLASSROOM` task type to allow users to fetch available classroom information.

- Add `TASK_TYPE_GET_EMPTY_CLASSROOM` to the `TaskType` enum in protobuf.
- Define `GetEmptyClassroomPayload` and `EmptyClassroomResultData` messages.
- Implement `getEmptyClassrooms`

grpc/handler.go

@@ -58,6 +58,8 @@ func (h *TaskHandler) Execute(task *pb.Task) *pb.TaskResult {
 		data, err = h.getExams(context.Background(), task.Payload)
 	case pb.TaskType_TASK_TYPE_LOGIN:
 		data, err = h.login(context.Background(), task.Payload)
+	case pb.TaskType_TASK_TYPE_GET_EMPTY_CLASSROOM:
+		data, err = h.getEmptyClassrooms(context.Background(), task.Payload)
 	default:
 		result.Status = pb.TaskStatus_TASK_STATUS_FAILED
 		result.ErrorMessage = fmt.Sprintf("未知的任务类型: %v", task.Type)
@@ -383,3 +385,55 @@ func convertExams(exams []parser.ExamEntry) []*pb.Exam {
 	}
 	return result
 }
+
+func (h *TaskHandler) getEmptyClassrooms(ctx context.Context, payload []byte) ([]byte, error) {
+	var req pb.GetEmptyClassroomPayload
+	if err := json.Unmarshal(payload, &req); err != nil {
+		return nil, apperr.New("parse_payload", err, "解析任务载荷失败")
+	}
+
+	log := slog.With("username", req.Username, "semester", req.Semester)
+	log.Info("获取空教室任务")
+
+	httpClient, err := createHTTPClient()
+	if err != nil {
+		return nil, err
+	}
+
+	cfg := config.Get()
+	setTWFIDCookie(httpClient, cfg.BaseURL, "")
+
+	if err := executeLogin(ctx, httpClient, req.Username, req.Password); err != nil {
+		return nil, err
+	}
+
+	classrooms, err := parser.FetchEmptyClassrooms(httpClient, req.Semester, req.WeekStart, req.WeekEnd, req.CampusCode)
+	if err != nil {
+		return nil, apperr.New("fetch_empty_classrooms", err, "获取空教室失败")
+	}
+
+	pbClassrooms := convertEmptyClassrooms(classrooms)
+
+	result := &pb.EmptyClassroomResultData{
+		StudentId:  req.Username,
+		Semester:   req.Semester,
+		Classrooms: pbClassrooms,
+	}
+
+	log.Info("空教室获取成功", "classroom_count", len(pbClassrooms))
+	return json.Marshal(result)
+}
+
+func convertEmptyClassrooms(entries []parser.EmptyClassroomEntry) []*pb.EmptyClassroomEntry {
+	result := make([]*pb.EmptyClassroomEntry, 0, len(entries))
+	for _, e := range entries {
+		result = append(result, &pb.EmptyClassroomEntry{
+			Classroom: e.Classroom,
+			Weekday:   e.Weekday,
+			Periods:   e.Periods,
+			Term:      e.Term,
+			Weeks:     e.Weeks,
+		})
+	}
+	return result
+}