/**
    * This file Copyright (c) 2012-2018 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.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.AbstractElement;
  
  import com.google.gwt.dom.client.Element;
  import com.google.web.bindery.event.shared.EventBus;
  
  /**
   * Takes care of toggling the visibility of the control-bars in the page-editor based on selections of the elements.
   * This is a fairly optimized and complex implementation considering lots of special corner-cases and side-effects. Don't
   * apply changes here lightly. Seriously.
   * This class should remain state-less. Ideally it should only contain the logic for switching the visibility of
   * control-bars inside the iframe.
   */
  public class FocusModelImpl implements FocusModel {
  
      private final Model model;
      private final EventBus eventBus;
  
      // These elements are only tracked for the toggling of visibility.
      // They should not survive a reload of the page and should not be exposed.
      private MgnlArea selectedAreaElement;
      private MgnlComponent selectedComponentElement;
  
      public FocusModelImpl(EventBus eventBus, Model model) {
          this.eventBus = eventBus;
          this.model = model;
      }
  
      @Override
      public void selectElement(Element element) {
          selectElement(model.getMgnlElement(element));
      }
  
      @Override
      public void selectElement(AbstractElement element) {
          selectElement(model.getMgnlElement(element));
      }
  
      /**
       * Selects the given {@link MgnlElement element} and keeps track of the scroll position before toggling the control-bars
       * for later re-adjustments.
       */
      private void selectElement(MgnlElement mgnlElement) {
  
          if (mgnlElement == null) {
              mgnlElement = model.getRootPage();
          }
  
          // cancel move if click was outside the moving components relatives
          if (model.isMoving()) {
              if (!mgnlElement.isRelated(selectedComponentElement)) {
                  eventBus.fireEvent(new ComponentStopMoveEvent(null, false));
              }
              return; // just cancel the move, no selection
          }
  
          // reset the scroll position unless it's a page.
          ElementScrollPositionPreserver scrollPositionPreserver = null;
         if (!mgnlElement.isPage()) {
             scrollPositionPreserver = mgnlElement.preserve();
         }
 
         doSelectMgnlElement(mgnlElement);
 
         // restoring of the position has to happen after the selection, as that's when the page-height has been changed.
         if (scrollPositionPreserver != null) {
             scrollPositionPreserver.restorePosition();
         }
 
     }
 
     private void doSelectMgnlElement(MgnlElement mgnlElement) {
         MgnlArea area = null;
         MgnlComponent component = null;
 
         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);
 
         // if we're selecting the page, we want this light-greenish look on the root areas, if not, then not.
         togglePageFocus(mgnlElement.isPage());
 
         dispatchElementSelection(mgnlElement);
     }
 
     /**
      * Creates the initial selection of the page-editor when in editing-mode:
      * <pre>
      *     <ul>
      *         <li>Root-areas are visible</li>
      *         <li>Component-placeholders in the root-areas are visible.</li>
      *     </ul>
      * </pre>
      *
      * Opposed to {@link #togglePageFocus(boolean)} this method only needs to be called once, when the iframe is loaded.
      * The reason is that these settings will never be reset by any selections done afterwards.
      */
     @Override
     public void init() {
         for (MgnlArea root : model.getRootAreas()) {
             root.setVisible(true);
 
             if (root.getComponents().isEmpty()) {
                 root.setPlaceHolderVisible(true);
             }
         }
     }
 
     /**
      * Resets the last selected elements. This needs to happen as lot's of the toggling-logic of the displayed bars and
      * their status is based on these. It has no visual effect. This method should ideally go, as the selected elements
      * should automatically be disposed, when the dom changes, e.g. when the iframe reloads.
      */
     @Override
     public void resetFocus() {
         this.selectedAreaElement = null;
         this.selectedComponentElement = null;
     }
 
     /**
      * 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) {
         if (selectedComponentElement == component) {
             return;
         }
         if (selectedComponentElement != null) {
             selectedComponentElement.removeFocus();
         }
         if (component != null) {
             component.setFocus();
         }
         this.selectedComponentElement = component;
     }
 
     /**
      * This method takes care of selecting and deselecting areas.
      *
      * @param area selected area, can be null.
      */
     private void setAreaSelection(MgnlArea area) {
 
         if (selectedAreaElement != null) {
 
             selectedAreaElement.removeFocus();
 
             // always reset current area selection unless area and current area are related
             if (!selectedAreaElement.isRelated(area)) {
 
                 toggleChildComponentVisibility(selectedAreaElement, false);
                 toggleAreaVisibility(selectedAreaElement, false);
             }
 
             // hide child components if area is an ascendant of current area or selectedArea is not
             // a descendant
             else if (selectedAreaElement.getAscendants().contains(area) || (area != null && !area.getDescendants().contains(selectedAreaElement))) {
                 toggleChildComponentVisibility(selectedAreaElement, false);
             }
         }
 
         // set focus on new selected area
         if (area != null) {
             toggleAreaVisibility(area, true);
             toggleChildComponentVisibility(area, true);
 
             area.setFocus(selectedComponentElement != null);
         }
         this.selectedAreaElement = area;
     }
 
     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(false);
         }
 
         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);
         }
     }
 
     /**
      * This toggles the 'initial' focus on the pages root-area elements. That's the light-greenish coloring when the page
      * is loaded or the page gets selected.
      */
     private void togglePageFocus(boolean visible) {
         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()));
         }
     }
 }