/**
    * This file Copyright (c) 2012-2016 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.ui.vaadin.gwt.client.editor.model.focus;
  
  import info.magnolia.ui.vaadin.gwt.client.editor.dom.MgnlArea;
  import info.magnolia.ui.vaadin.gwt.client.editor.dom.MgnlComponent;
  import info.magnolia.ui.vaadin.gwt.client.editor.dom.MgnlElement;
  import info.magnolia.ui.vaadin.gwt.client.editor.dom.MgnlPage;
  import info.magnolia.ui.vaadin.gwt.client.editor.event.ComponentStopMoveEvent;
  import info.magnolia.ui.vaadin.gwt.client.editor.event.SelectElementEvent;
  import info.magnolia.ui.vaadin.gwt.client.editor.jsni.scroll.ElementScrollPositionPreserver;
  import info.magnolia.ui.vaadin.gwt.client.editor.model.Model;
  import info.magnolia.ui.vaadin.gwt.client.shared.AreaElement;
  import info.magnolia.ui.vaadin.gwt.client.shared.ComponentElement;
  
  import com.google.web.bindery.event.shared.EventBus;
  
  /**
   * Helper class to keep track of selected items. Welcome to the MindTwister.
   */
  public class FocusModelImpl implements FocusModel {
  
      private final Model model;
  
      private final EventBus eventBus;
  
      private boolean rootSelected = false;
  
      private AreaElement selectedAreaElement = null;
  
      private ComponentElement selectedComponentElement = null;
  
      public FocusModelImpl(EventBus eventBus, Model model) {
          super();
          this.eventBus = eventBus;
          this.model = model;
      }
  
      @Override
      public void selectElement(MgnlElement mgnlElement) {
          if (mgnlElement == null) {
              mgnlElement = model.getRootPage();
          }
  
          final MgnlComponent currentlySelected = getSelectedComponent();
          final MgnlComponent componentToPreserve = mgnlElement.isComponent() ? (MgnlComponent) mgnlElement : currentlySelected;
  
          ElementScrollPositionPreserver scrollPositionPreserver = null;
          if (componentToPreserve != null) {
              scrollPositionPreserver = componentToPreserve.preserve();
          }
  
          doSelectMgnlElement(mgnlElement);
  
          if (scrollPositionPreserver != null) {
              scrollPositionPreserver.restorePosition();
          }
      }
  
      private void doSelectMgnlElement(MgnlElement mgnlElement) {
          if (model.isMoving()) {
              // cancel move if click was outside the moving components relatives or null
              if (!mgnlElement.isRelated(getSelectedComponent())) {
                  eventBus.fireEvent(new ComponentStopMoveEvent(null, false));
              }
          } else {
              MgnlPage page = null;
              MgnlArea area = null;
             MgnlComponent component = null;
 
             // if there is no mapping, we select the page
             if (mgnlElement == null) {
                 page = model.getRootPage();
             } else {
                 if (mgnlElement.isComponent()) {
                     component = (MgnlComponent) mgnlElement;
                     area = mgnlElement.getParentArea();
                 } else if (mgnlElement.isArea()) {
                     area = (MgnlArea) mgnlElement;
                 }
             }
             // first set the component, then set the area. the selected component is used for setting
             // the current area class.
             setComponentSelection(component);
             setAreaSelection(area);
             setPageSelection(page);
 
             dispatchElementSelection(mgnlElement);
         }
     }
 
     @Override
     public void init() {
         for (MgnlArea root : model.getRootAreas()) {
             root.setVisible(true);
 
             if (root.getComponents().isEmpty()) {
                 root.setPlaceHolderVisible(true);
             }
         }
 
         tryRestoreSelection();
     }
 
     private void tryRestoreSelection() {
         MgnlElement selectedElement = getSelectedComponent();
         if (selectedElement == null) {
             selectedElement = getSelectedArea();
         }
 
         if (selectedElement == null) {
             selectedElement = model.getRootPage();
         }
 
         selectedComponentElement = null;
         selectedAreaElement = null;
 
         selectElement(selectedElement);
     }
 
     @Override
     public MgnlArea getSelectedArea() {
         return (MgnlArea) model.getMgnlElement(selectedAreaElement);
     }
 
     @Override
     public MgnlComponent getSelectedComponent() {
         return (MgnlComponent) model.getMgnlElement(selectedComponentElement);
     }
 
     @Override
     public void clearSelection() {
         this.selectedAreaElement = null;
         this.selectedComponentElement = null;
         doSelectMgnlElement(model.getRootPage());
     }
 
     /**
      * Takes care of the selection of components. keeps track of last selected element and toggles
      * the focus. If a null-value is passed it will reset the currently selected component.
      *
      * @param component the MgnlElement component, can be null.
      */
     private void setComponentSelection(MgnlComponent component) {
         MgnlComponent currentComponent = getSelectedComponent();
         if (currentComponent == component) {
             return;
         }
         if (currentComponent != null) {
             currentComponent.removeFocus();
         }
         if (component != null) {
             component.setFocus();
         }
         this.selectedComponentElement = component == null ? null : component.getTypedElement();
     }
 
     /**
      * This method takes care of selecting and deselecting areas.
      *
      * @param area selected area, can be null.
      */
     private void setAreaSelection(MgnlArea area) {
         MgnlArea selectedArea = getSelectedArea();
         MgnlComponent currentComponent = getSelectedComponent();
 
         if (selectedArea != null) {
 
             selectedArea.removeFocus();
 
             // always reset current area selection unless area and current area are related
             if (!selectedArea.isRelated(area)) {
 
                 toggleChildComponentVisibility(selectedArea, false);
                 toggleAreaVisibility(selectedArea, false);
             }
 
             // hide child components if area is an ascendant of current area or selectedArea is not
             // a descendant
             else if (selectedArea.getAscendants().contains(area) || (area != null && !area.getDescendants().contains(selectedArea))) {
                 toggleChildComponentVisibility(selectedArea, false);
             }
         }
 
         // set focus on new selected area
         if (area != null) {
             toggleAreaVisibility(area, true);
             toggleChildComponentVisibility(area, true);
 
             area.setFocus((currentComponent != null));
         }
         this.selectedAreaElement = area == null ? null : area.getTypedElement();
     }
 
     private void toggleAreaVisibility(MgnlArea area, boolean visible) {
 
         MgnlArea parentArea = area.getParentArea();
         if (parentArea != null) {
             toggleAreaVisibility(parentArea, visible);
             toggleChildComponentVisibility(parentArea, visible);
 
         }
         // root areas are always visible
         if (!model.getRootAreas().contains(area)) {
             area.setVisible(visible);
         }
 
         toggleNestedAreasVisibility(area, visible);
     }
 
     private void toggleChildComponentVisibility(MgnlArea area, boolean visible) {
 
         // do not hide empty root areas placeholder
         if (!model.getRootAreas().contains(area) || !area.getComponents().isEmpty()) {
             area.setPlaceHolderVisible(visible);
         }
 
         // hide
         if (!visible && !area.getComponents().isEmpty()) {
             area.setPlaceHolderVisible(visible);
         }
 
 
         for (MgnlComponent component : area.getComponents()) {
 
             // toggle all child-components editbar visibility - does this case occur?
             component.setVisible(visible);
 
 
             // toggle all child-components-area visibility
             for (MgnlArea childArea : component.getAreas()) {
                 childArea.setVisible(visible);
                 toggleNestedAreasVisibility(childArea, visible);
             }
         }
     }
 
     private void toggleNestedAreasVisibility(MgnlArea area, boolean visible) {
         for (MgnlArea childArea : area.getAreas()) {
             childArea.setVisible(visible);
             toggleNestedAreasVisibility(childArea, visible);
         }
     }
 
     private void setPageSelection(MgnlPage page) {
         boolean visible = true;
         if (page == null) {
             visible = false;
         }
 
         this.rootSelected = !this.rootSelected;
         for (MgnlArea root : model.getRootAreas()) {
             root.toggleInitFocus(visible);
         }
     }
 
     private void dispatchElementSelection(MgnlElement mgnlElement) {
         mgnlElement = (mgnlElement != null) ? mgnlElement : model.getRootPage();
         if (mgnlElement != null) {
             eventBus.fireEvent(new SelectElementEvent(mgnlElement.getTypedElement()));
         }
     }
 }