@Data
@Entity
public class ExportTask {
    @Id
    private String taskId;

    private String fileName;
    private String status; // WAITING, RUNNING, SUCCESS, FAILED
    private String downloadUrl;
    private LocalDateTime createTime;
    private LocalDateTime finishTime;
    private String errorMessage;
}

@RestController
@RequestMapping("/export")
public class ExportController {

    @Autowired
    private ExportService exportService;

    @PostMapping("/start")
    public ResponseEntity<String> startExport(@RequestBody ExportRequest request) {
        String taskId = exportService.initExportTask(request);
        return ResponseEntity.ok(taskId);
    }

    @GetMapping("/status/{taskId}")
    public ResponseEntity<ExportTask> getStatus(@PathVariable String taskId) {
        return ResponseEntity.ok(exportService.getExportStatus(taskId));
    }
}

@Service
public class ExportService {

    @Autowired
    private TaskExecutor taskExecutor;

    @Autowired
    private ExportTaskRepository exportTaskRepository;

    public String initExportTask(ExportRequest request) {
        String taskId = UUID.randomUUID().toString();
        ExportTask task = new ExportTask();
        task.setTaskId(taskId);
        task.setStatus("WAITING");
        task.setCreateTime(LocalDateTime.now());
        exportTaskRepository.save(task);

        taskExecutor.execute(() -> doExport(task, request));
        return taskId;
    }

    public void doExport(ExportTask task, ExportRequest request) {
        try {
            task.setStatus("RUNNING");
            exportTaskRepository.save(task);

            String filePath = ExcelExporter.exportToExcel(request); // 核心導出邏輯

            task.setStatus("SUCCESS");
            task.setDownloadUrl(filePath);
        } catch (Exception e) {
            task.setStatus("FAILED");
            task.setErrorMessage(e.getMessage());
        } finally {
            task.setFinishTime(LocalDateTime.now());
            exportTaskRepository.save(task);
        }
    }

    public ExportTask getExportStatus(String taskId) {
        return exportTaskRepository.findById(taskId).orElseThrow();
    }
}

public class ExcelExporter {

    public static String exportToExcel(ExportRequest request) throws IOException {
        String filename = "export_" + System.currentTimeMillis() + ".xlsx";
        String filePath = "/data/export/" + filename;

        List<MyData> dataList = fetchData(request); // 分頁拉取數(shù)據(jù)

        try (OutputStream os = new FileOutputStream(filePath)) {
            ExcelWriter writer = EasyExcel.write(os, MyData.class).build();
            WriteSheet sheet = EasyExcel.writerSheet("Data").build();

            int page = 1;
            while (true) {
                List<MyData> pageData = fetchPageData(page++);
                if (pageData.isEmpty()) break;
                writer.write(pageData, sheet);
            }
            writer.finish();
        }

        return filePath;
    }
}