package sk.stuba.fiit.perconik.ui.plugin;

import java.util.concurrent.atomic.AtomicBoolean;

import org.eclipse.jface.dialogs.MessageDialog;
import org.eclipse.swt.widgets.Display;
import org.eclipse.swt.widgets.Shell;
import org.eclipse.ui.IStartup;
import org.eclipse.ui.IWorkbenchWindow;

import org.osgi.framework.BundleContext;

import sk.stuba.fiit.perconik.eclipse.ui.Windows;
import sk.stuba.fiit.perconik.eclipse.ui.plugin.UserInterfacePlugin;
import sk.stuba.fiit.perconik.environment.java.JavaVerificationException;
import sk.stuba.fiit.perconik.osgi.framework.Versions;

import static sk.stuba.fiit.perconik.osgi.framework.Versions.Component.MAJOR;
import static sk.stuba.fiit.perconik.osgi.framework.Versions.Component.MINOR;

/**
 * The <code>Activator</code> class controls the plug-in life cycle.
 *
 * <p><b>Warning:</b> Users should not explicitly instantiate this class.
 *
 * @author Pavol Zbell
 * @since 1.0
 */
public final class Activator extends UserInterfacePlugin {
  /**
   * The plug-in identifier.
   */
  public static final String PLUGIN_ID = "sk.stuba.fiit.perconik.ui";

  /**
   * The shared instance.
   */
  private static volatile Activator plugin;

  /**
   * Indicates whether UI environment is verified or not.
   */
  private static final AtomicBoolean verified = new AtomicBoolean(false);

  /**
   * The constructor.
   */
  public Activator() {}

  /**
   * Gets the shared instance.
   * @return the shared instance or {@code null}
   */
  public static Activator defaultInstance() {
    synchronized (Activator.class) {
      return plugin;
    }
  }

  /**
   * Plug-in early startup.
   *
   * <p><b>Warning:</b> Users should not explicitly instantiate this class.
   *
   * @author Pavol Zbell
   * @since 1.0
   */
  public static final class Startup implements IStartup {
    /**
     * The constructor.
     */
    public Startup() {}

    /**
     * Processes supplied extensions and starts core services.
     */
    public void earlyStartup() {
      verifyJava();
    }
  }

  static void verifyJava() {
    if (!verified.compareAndSet(false, true)) {
      return;
    }

    try {
      sk.stuba.fiit.perconik.environment.plugin.Activator.defaultInstance().verifyJava();
    } catch (final JavaVerificationException e) {
      final Runnable dialog = new Runnable() {
        public final void run() {
          IWorkbenchWindow window = Windows.getActiveWindow();

          Shell shell = window != null ? window.getShell() : Display.getDefault().getActiveShell();

          String title = "PerConIK Core for Eclipse Platform";
          String message = "PerConIK Extension requires Java ";

          message += Versions.toString(e.getRequiredJavaVersion(), MAJOR, MINOR);
          message += " or greater but Java ";
          message += Versions.toString(e.getDetectedJavaVersion(), MAJOR, MINOR);
          message += " was detected.";
          message += " Extension is not active, please launch Eclipse on Java ";
          message += Versions.toString(e.getRequiredJavaVersion(), MAJOR, MINOR);
          message += " again.";

          MessageDialog.openWarning(shell, title, message);
        }
      };

      Display.getDefault().syncExec(dialog);
    }
  }

  /**
   * Starts this plug-in.
   *
   * <p><b>Warning:</b> Users must never explicitly call this method.
   */
  @Override
  public void start(final BundleContext context) throws Exception {
    super.start(context);

    plugin = this;

    verifyJava();
  }

  /**
   * Stops this plug-in.
   *
   * <p><b>Warning:</b> Users must never explicitly call this method.
   */
  @Override
  public void stop(final BundleContext context) throws Exception {
    plugin = null;

    super.stop(context);
  }
}