/**
    * This file Copyright (c) 2013-2014 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.workbench.tree.drop;
  
  import static info.magnolia.jcr.util.NodeUtil.*;
  
  import info.magnolia.jcr.util.NodeUtil;
  import info.magnolia.ui.vaadin.integration.jcr.JcrItemAdapter;
  import info.magnolia.ui.workbench.tree.HierarchicalJcrContainer;
  import info.magnolia.ui.workbench.tree.MoveHandler;
  import info.magnolia.ui.workbench.tree.MoveLocation;
  
  import java.util.Arrays;
  import java.util.Collection;
  import java.util.Iterator;
  import java.util.Set;
  
  import javax.jcr.Item;
  import javax.jcr.Node;
  import javax.jcr.Property;
  import javax.jcr.RepositoryException;
  
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  import com.vaadin.event.DataBoundTransferable;
  import com.vaadin.event.Transferable;
  import com.vaadin.event.dd.DragAndDropEvent;
  import com.vaadin.event.dd.DropHandler;
  import com.vaadin.event.dd.acceptcriteria.AcceptCriterion;
  import com.vaadin.event.dd.acceptcriteria.ServerSideCriterion;
  import com.vaadin.shared.ui.dd.VerticalDropLocation;
  import com.vaadin.ui.AbstractSelect.AbstractSelectTargetDetails;
  import com.vaadin.ui.TreeTable;
  
  /**
   * Vaadin {@link DropHandler} for moving JCR nodes and properties in trees, with Drag and Drop.
   * <p>
   * Additionally, the dropping conditions can be restricted, by implementing a {@link DropConstraint}
   * and configuring it in the {@link info.magnolia.ui.workbench.definition.WorkbenchDefinition WorkbenchDefinition}.
   */
  public class TreeViewDropHandler implements MoveHandler, DropHandler {
  
      private final Logger log = LoggerFactory.getLogger(getClass());
  
      private TreeTable tree;
      private DropConstraint constraint;
      private AcceptCriterion serverSideCriterion;
  
      public TreeViewDropHandler() {
          createAcceptCriterion();
      }
  
      public TreeViewDropHandler(TreeTable tree, DropConstraint constraint) {
          this.tree = tree;
          this.constraint = constraint;
          createAcceptCriterion();
      }
  
      @Override
      public void drop(DragAndDropEvent dropEvent) {
          // Called whenever a drop occurs on the component
  
          // Make sure the drag source is the same tree
          Transferable t = dropEvent.getTransferable();
  
          // First acceptance criteria.
          // Make sure the drag source is the same tree
         if (t.getSourceComponent() != tree || !(t instanceof DataBoundTransferable)) {
             return;
         }
 
         AbstractSelectTargetDetails target = (AbstractSelectTargetDetails) dropEvent.getTargetDetails();
         // Get id's of the target item
         Object targetItemId = target.getItemIdOver();
         // On which side of the target the item was dropped
         VerticalDropLocation location = target.getDropLocation();
         if (location == null) {
             log.debug("DropLocation is null. Do nothing.");
             return;
         }
         // Get id's of the dragged items
         Iterator<Object> selected = getItemIdsToMove(dropEvent).iterator();
         while (selected.hasNext()) {
             Object sourceItemId = selected.next();
             moveNode(sourceItemId, targetItemId, location);
         }
     }
 
     /**
      * Returns a collection of itemIds to move:
      * <ul>
      * <li>all <em>selected</em> itemIds if and only if the dragging node is <em>also</em> selected</li>
      * <li>only the dragging itemId if it's not selected</li>.
      * </ul>
      */
     private Collection<Object> getItemIdsToMove(DragAndDropEvent dropEvent) {
         Transferable t = dropEvent.getTransferable();
         Object draggingItemId = ((DataBoundTransferable) t).getItemId();
 
         // all selected itemIds if and only if the dragging node is also selected
         Set<Object> selectedItemIds = (Set<Object>) ((TreeTable) t.getSourceComponent()).getValue();
         if (selectedItemIds.contains(draggingItemId)) {
             return selectedItemIds;
         }
 
         // only the dragging itemId if it's not selected
         return Arrays.asList(draggingItemId);
     }
 
     /**
      * Accept dragged Elements.
      */
     @Override
     public AcceptCriterion getAcceptCriterion() {
         return serverSideCriterion;
     }
 
     /**
      * Move a node within a tree onto, above or below another node depending on
      * the drop location.
      *
      * @param sourceItemId
      * id of the item to move
      * @param targetItemId
      * id of the item onto which the source node should be moved
      * @param location
      * VerticalDropLocation indicating where the source node was
      * dropped relative to the target node
      */
     private void moveNode(Object sourceItemId, Object targetItemId, VerticalDropLocation location) {
         log.debug("DropLocation: {}", location.name());
         // Get Item from tree
         HierarchicalJcrContainer container = (HierarchicalJcrContainer) tree.getContainerDataSource();
         JcrItemAdapter sourceItem = (JcrItemAdapter) container.getItem(sourceItemId);
         JcrItemAdapter targetItem = (JcrItemAdapter) container.getItem(targetItemId);
 
         // Sorting goes as
         // - If dropped ON a node, we append it as a child
         // - If dropped on the TOP part of a node, we move/add it before
         // the node
         // - If dropped on the BOTTOM part of a node, we move/add it
         // after the node
 
         if (location == VerticalDropLocation.MIDDLE) {
             if (constraint.allowedAsChild(sourceItem, targetItem)) {
                 // move first in the container
                 moveItem(sourceItem, targetItem, MoveLocation.INSIDE);
                 container.setParent(sourceItemId, targetItemId);
             }
         } else {
             Object parentId = container.getParent(targetItemId);
             if (location == VerticalDropLocation.TOP) {
                 if (parentId != null && constraint.allowedBefore(sourceItem, targetItem)) {
                     // move first in the container
                     moveItem(sourceItem, targetItem, MoveLocation.BEFORE);
                     container.setParent(sourceItemId, parentId);
                 }
             } else if (location == VerticalDropLocation.BOTTOM) {
                 if (parentId != null && constraint.allowedAfter(sourceItem, targetItem)) {
                     moveItem(sourceItem, targetItem, MoveLocation.AFTER);
                     container.setParent(sourceItemId, parentId);
                 }
             }
         }
     }
 
     /**
      * Create a serverSide {@link AcceptCriterion} based on the {@link DropConstraint} implementation.
      */
     private void createAcceptCriterion() {
         serverSideCriterion = new ServerSideCriterion() {
 
             @Override
             public boolean accept(DragAndDropEvent dragEvent) {
                 boolean res = true;
                 Iterator<Object> selected = getItemIdsToMove(dragEvent).iterator();
                 while (selected.hasNext()) {
                     Object sourceItemId = selected.next();
                     HierarchicalJcrContainer container = (HierarchicalJcrContainer) tree.getContainerDataSource();
                     JcrItemAdapter sourceItem = (JcrItemAdapter) container.getItem(sourceItemId);
                     res &= constraint.allowedToMove(sourceItem);
                 }
                 return res;
             }
         };
 
     }
 
     /**
      * Performs check for moving items. Evaluates true when first node is of type Node and source and target are not same.
      */
     public boolean basicMoveCheck(Item source, Item target) {
         try {
             // target must be node, to allow moving in
             if (!target.isNode()) {
                 return false;
             }
             // Source and origin are the same... do nothing
             if (target.getPath().equals(source.getPath()) && target.getSession().getWorkspace().getName().equals(source.getSession().getWorkspace().getName())) {
                 return false;
             }
             // Source can not be a child of target.
             return !NodeUtil.isSame((Node) target, source.getParent());
         } catch (RepositoryException re) {
             log.debug("Cannot determine whether drag and drop is possible due to: {}", re.getMessage(), re);
             return false;
         }
     }
 
     /**
      * Performs move of the source node into target node or next to target node depending on the value of MoveLocation.
      * Move is performed in session-write mode and as such requires explicit call to session.save() after performing the operation.
      */
     public void moveNode(Node nodeToMove, Node newParent, MoveLocation location) throws RepositoryException {
         if (!basicMoveCheck(nodeToMove, newParent)) {
             return;
         }
         switch (location) {
         case INSIDE:
             String newPath = combinePathAndName(newParent.getPath(), nodeToMove.getName());
             nodeToMove.getSession().move(nodeToMove.getPath(), newPath);
             break;
         case BEFORE:
             moveNodeBefore(nodeToMove, newParent);
             break;
         case AFTER:
             moveNodeAfter(nodeToMove, newParent);
             break;
         }
     }
 
     /**
      * Performs move of the source node or property into target node or next to target node depending on the value of MoveLocation.
      * This method will persist move by calling session.save() explicitly. And will return true/false depending on whether move was successful or not.
      */
     @Override
     public boolean moveItem(com.vaadin.data.Item source, com.vaadin.data.Item target, MoveLocation location) {
         Item sourceItem = ((JcrItemAdapter) source).getJcrItem();
         Item targetItem = ((JcrItemAdapter) target).getJcrItem();
         if (!basicMoveCheck(sourceItem, targetItem)) {
             return false;
         }
         try {
             final Node targetNode = (Node) targetItem;
             if (sourceItem.isNode()) {
                 moveNode((Node) sourceItem, targetNode, location);
             } else {
                 NodeUtil.moveProperty((Property) sourceItem, targetNode);
             }
             sourceItem.getSession().save();
             return true;
         } catch (RepositoryException re) {
             log.debug("Cannot execute drag and drop action", re);
             return false;
         }
     }
 
     @Override
     public DropHandler asDropHandler() {
         return this;
     }
 }