import com.haulmont.cuba.gui.backgroundwork.BackgroundWorkProgressWindow;

public class StudentBrowse extends StandardLookup<Student> {

    @Inject
    private Table<Student> studentsTable;

    @Inject
    private EmailService emailService;

    @Subscribe("studentsTable.sendEmail")
    public void onStudentsTableSendEmail(Action.ActionPerformedEvent event) {
        Set<Student> selected = studentsTable.getSelected();
        if (selected.isEmpty()) {
            return;
        }
        BackgroundTask<Integer, Void> task = new EmailTask(selected);
        BackgroundWorkProgressWindow.show(task, (1)
                "Sending reminder emails", "Please wait while emails are being sent",
                selected.size(), true, true (2)
        );
    }

    private class EmailTask extends BackgroundTask<Integer, Void> { (3)
        private Set<Student> students; (4)

        public EmailTask(Set<Student> students) {
            super(10, TimeUnit.MINUTES, StudentBrowse.this); (5)
            this.students = students;
        }

        @Override
        public Void run(TaskLifeCycle<Integer> taskLifeCycle) throws Exception {
            int i = 0;
            for (Student student : students) {
                if (taskLifeCycle.isCancelled()) { (6)
                    break;
                }
                emailService.sendEmail(student.getEmail(), "Reminder", "Don't forget, the exam is tomorrow",
                        EmailInfo.TEXT_CONTENT_TYPE);

                i++;
                taskLifeCycle.publish(i); (7)
            }
            return null;
        }
    }
}

@UiController("playground_RankMonitor")
@UiDescriptor("rank-monitor.xml")
public class RankMonitor extends Screen {
    @Inject
    private Notifications notifications;
    @Inject
    private Label<String> refreshTimeLabel;
    @Inject
    private CollectionContainer<Rank> ranksDc;
    @Inject
    private RankService rankService;
    @Inject
    private CheckBox onlyActiveBox;
    @Inject
    private Logger log;
    @Inject
    private TimeSource timeSource;
    @Inject
    private Timer refreshTimer;

    private BackgroundTaskWrapper<Void, List<Rank>> refreshTaskWrapper = new BackgroundTaskWrapper<>(); (1)

    @Subscribe
    public void onBeforeShow(BeforeShowEvent event) {
        refreshTimer.setDelay(5000);
        refreshTimer.setRepeating(true);
        refreshTimer.start();
    }

    @Subscribe("onlyActiveBox")
    public void onOnlyActiveBoxValueChange(HasValue.ValueChangeEvent<Boolean> event) {
        refreshTaskWrapper.restart(new RefreshScreenTask()); (2)
    }

    @Subscribe("refreshTimer")
    public void onRefreshTimerTimerAction(Timer.TimerActionEvent event) {
        refreshTaskWrapper.restart(new RefreshScreenTask()); (3)
    }

    public class RefreshScreenTask extends BackgroundTask<Void, List<Rank>> { (4)
        private boolean onlyActive; (5)
        protected RefreshScreenTask() {
            super(30, TimeUnit.SECONDS, RankMonitor.this);
            onlyActive = onlyActiveBox.getValue();
        }

        @Override
        public List<Rank> run(TaskLifeCycle<Void> taskLifeCycle) throws Exception {
            List<Rank> data = rankService.loadActiveRanks(onlyActive); (6)
            return data;
        }

        @Override
        public void done(List<Rank> result) { (7)
            List<Rank> mutableItems = ranksDc.getMutableItems();
            mutableItems.clear();
            mutableItems.addAll(result);

            String hhmmss = new SimpleDateFormat("HH:mm:ss").format(timeSource.currentTimestamp());
            refreshTimeLabel.setValue("Last time refreshed: " + hhmmss);
        }

        @Override
        public boolean handleTimeoutException() { (8)
            displayRefreshProblem();
            return true;
        }

        @Override
        public boolean handleException(Exception ex) { (9)
            log.debug("Auto-refresh error", ex);
            displayRefreshProblem();
            return true;
        }

        private void displayRefreshProblem() {
            if (!refreshTimeLabel.getValue().endsWith("(outdated)")) {
                refreshTimeLabel.setValue(refreshTimeLabel.getValue() + " (outdated)");
            }
            notifications.create(Notifications.NotificationType.TRAY)
                    .withCaption("Problem refreshing data")
                    .withHideDelayMs(10_000)
                    .show();
        }
    }
}