/**
    * This file Copyright (c) 2012 Magnolia International
    * Ltd.  (http://www.magnolia-cms.com). All rights reserved.
    *
    *
    * This file is dual-licensed under both the Magnolia
    * Network Agreement and the GNU General Public License.
    * You may elect to use one or the other of these licenses.
    *
   * This file is distributed in the hope that it will be
   * useful, but AS-IS and WITHOUT ANY WARRANTY; without even the
   * implied warranty of MERCHANTABILITY or FITNESS FOR A
   * PARTICULAR PURPOSE, TITLE, or NONINFRINGEMENT.
   * Redistribution, except as permitted by whichever of the GPL
   * or MNA you select, is prohibited.
   *
   * 1. For the GPL license (GPL), you can redistribute and/or
   * modify this file under the terms of the GNU General
   * Public License, Version 3, as published by the Free Software
   * Foundation.  You should have received a copy of the GNU
   * General Public License, Version 3 along with this program;
   * if not, write to the Free Software Foundation, Inc., 51
   * Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
   *
   * 2. For the Magnolia Network Agreement (MNA), this file
   * and the accompanying materials are made available under the
   * terms of the MNA which accompanies this distribution, and
   * is available at http://www.magnolia-cms.com/mna.html
   *
   * Any modifications to this file must keep this entire header
   * intact.
   *
   */
  package info.magnolia.templating.editor.client.widget.button;
  
  import java.util.Arrays;
  import java.util.List;
  
  import com.google.gwt.event.dom.client.ClickEvent;
  import com.google.gwt.event.dom.client.ClickHandler;
  import com.google.gwt.user.client.ui.Button;
  import com.google.gwt.user.client.ui.MenuBar;
  import com.google.gwt.user.client.ui.MenuItem;
  import com.google.gwt.user.client.ui.PopupPanel;
  
  /**
   * A button which, when clicking on it, will display a dropdown menu just beneath. The menu can have different mutually exclusive choices.
   * Each choice corresponds to a {@link MenuItem}. The order in which these options are added in the menu bar is the same in which
   * they are in the list or array passed in to the object's constructor. A menu item can also accept a further {@link MenuBar} as a parameter, thus enabling sub menus.
   * <p>Usage sample:
   * <pre>
   *  ...
   *  // commands are defined elsewhere
   *  MenuItem one = new MenuItem("Option one", true, optionCommandOne);
   *  MenuItem two = new MenuItem("Option two", true, optionCommandTwo);
   *  MenuItem three = new MenuItem("Option three", true, optionCommandThree);
   *
   *  List&lt;MenuItem&gt; options = new ArrayList&lt;MenuItem&gt;();
   *  options.add(one);
   *  options.add(two);
   *  options.add(three);
   *
   *  DropdownButton dropdown = new DropdownButton("My cool caption", options);
   *  ...
   * </pre>
   *
   * @version $Id$
   */
  public class DropdownButton extends Button {
  
      private final PopupPanel dropdownPanel = new PopupPanel(true);
      private final MenuBar dropdownMenuBar = new MenuBar(true);
  
      public DropdownButton(String caption, List<MenuItem> menuItems) {
          super(caption);
          if(menuItems == null) {
              throw new IllegalArgumentException("menuItems cannot be null");
          }
          dropdownMenuBar.setStylePrimaryName("mgnlPreviewMenuDropdown");
          for(MenuItem item: menuItems) {
              item.setStylePrimaryName("mgnlPreviewMenuItem");
              dropdownMenuBar.addItem(item);
          }
          dropdownPanel.setStylePrimaryName("mgnlPreviewMenuPanel");
          //TODO add an onMouseOut event to the menu? This however will make it disappear also when hovering back on the button itself.
          dropdownPanel.add(dropdownMenuBar);
  
          addClickHandler(new ClickHandler() {
              @Override
              public void onClick(ClickEvent event) {
                 onClickCallback(event);
              }
          });
      }
  
      public DropdownButton(String caption, MenuItem... menuItems) {
          this(caption, Arrays.asList(menuItems));
      }
  
     /**
      * Sets the dropdown's position relative to the browser's client area.
      * @param left in px
      * @param top in px
      */
     protected void setDropdownPosition(int left, int top) {
         dropdownPanel.setPopupPosition(left, top);
     }
 
     protected void showDropdown() {
         dropdownMenuBar.setVisible(true);
         dropdownPanel.show();
     }
 
     protected void hideDropdown() {
         dropdownMenuBar.setVisible(false);
         dropdownPanel.hide();
     }
 
     /**
      * Callback method invoked when clicking on the drop-down button. By default the menu will appear just beneath the button, left aligned with it.
      */
     protected void onClickCallback(ClickEvent event) {
         setDropdownPosition(getAbsoluteLeft(), getAbsoluteTop() + getOffsetHeight());
         showDropdown();
     }
 }