package com.eloquentix.soundpure.web.page.migration;

import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.Future;

import org.apache.wicket.AttributeModifier;
import org.apache.wicket.Component;
import org.apache.wicket.ajax.AjaxRequestTarget;
import org.apache.wicket.ajax.AjaxSelfUpdatingTimerBehavior;
import org.apache.wicket.ajax.IAjaxIndicatorAware;
import org.apache.wicket.ajax.markup.html.AjaxLink;
import org.apache.wicket.extensions.ajax.markup.html.AjaxIndicatorAppender;
import org.apache.wicket.markup.html.basic.Label;
import org.apache.wicket.markup.html.panel.Panel;
import org.apache.wicket.model.AbstractReadOnlyModel;
import org.apache.wicket.model.IModel;
import org.apache.wicket.model.Model;
import org.apache.wicket.util.time.Duration;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * A kind of button used to execute long running process & notifying about the progress.
 *
 * @author Alex Objelean
 */
@SuppressWarnings("serial")
public abstract class ProcessExecutorPanel
  extends Panel implements IAjaxIndicatorAware {
  private static final Logger LOG = LoggerFactory.getLogger(ProcessExecutorPanel.class);

  /**
   * Indicates if the process is still running.
   */
  private boolean everStarted = false;
  private Component status;
  private transient Future<?> future;
  private AjaxIndicatorAppender ajaxIndicator;
  public ProcessExecutorPanel(final String id) {
    super(id);
    addComponents();
  }

  private void addComponents() {
    add(getStatus());
    add(getButton());
    add(ajaxIndicator = new AjaxIndicatorAppender());
  }

  /**
   * {@inheritDoc}
   */
  @Override
  public String getAjaxIndicatorMarkupId() {
    return ajaxIndicator.getMarkupId();
  }

  private Component getButton() {
    final Component button = new AjaxLink<Void>("button") {
      @Override
      public void onClick(final AjaxRequestTarget target) {
        target.addComponent(getStatus());
        if (isProcessRunning()) {
          target.appendJavascript("alert('still in progress')");
        } else {
          status.add(getSelfUpdatingBehavior());
          everStarted = true;
          future = start();
        }
      }
    };
    button.add(new AttributeModifier("value", getButtonText()));
    return button;
  }

  protected IModel<String> getButtonText() {
      return Model.of("Execute");
  }

  /**
   * Start execution, immediately returning a future.
   */
  protected abstract Future<?> start();

  /**
   * @return if the process is still running.
   */
  private boolean isProcessRunning() {
    return future != null && !future.isDone();
  }

  /**
   * @return component displaying the current status of the process.
   */
  private Component getStatus() {
    if (status == null) {
      final IModel<String> model = new AbstractReadOnlyModel<String>() {
        @Override
        public String getObject() {
          return isProcessRunning() ? "in progress" : "complete";
        }
      };
      status = new Label("status", model) {
        @Override
        public boolean isVisible() {
          return everStarted;
        }
      };
      status.setOutputMarkupPlaceholderTag(true);
      status.setOutputMarkupId(true);
    }
    return status;
  }

  private AjaxSelfUpdatingTimerBehavior getSelfUpdatingBehavior() {
    return new AjaxSelfUpdatingTimerBehavior(Duration.seconds(2)) {
      @Override
      protected void onPostProcessTarget(final AjaxRequestTarget target) {
        if (!isProcessRunning()) {
          stop();
          status.remove(this);
        }
      }
    };
  }
}