package org.apache.log4j.chainsaw.dnd;
   
   
   import org.apache.log4j.Logger;
   import java.awt.datatransfer.DataFlavor;
   import java.awt.Color;
   import java.awt.datatransfer.Transferable;
   import java.awt.dnd.DnDConstants;
   import java.awt.dnd.DropTarget;
  import java.awt.dnd.DropTargetDragEvent;
  import java.awt.dnd.DropTargetDropEvent;
  import java.awt.dnd.DropTargetEvent;
  import java.awt.dnd.DropTargetListener;
  import java.beans.PropertyChangeListener;
  import java.beans.PropertyChangeSupport;
  import java.util.HashMap;
  import java.util.List;
  import java.util.Map;
  
  import javax.swing.BorderFactory;
  import javax.swing.JComponent;
  
  /***
   * This class provides all the functionality to work out when files are dragged onto
   * a particular JComponent instance, and then notifies listeners via
   * the standard PropertyChangesListener semantics to indicate that a list of 
   * files have been dropped onto the target.
   * 
   * If you wish to know whan the files have been dropped, subscribe to the "fileList" property change.
   * 
   * @author psmith
   *
   */
  public class FileDnDTarget implements DropTargetListener{
      /***
       * Logger for this class
       */
      private static final Logger LOG = Logger.getLogger(FileDnDTarget.class);
  
      protected int acceptableActions = DnDConstants.ACTION_COPY;
  
      private DropTarget dropTarget;
      private List fileList;
  
      private JComponent guiTarget;
      private Map dropTargets = new HashMap();
      
      
      private PropertyChangeSupport propertySupport = new PropertyChangeSupport(this);
      /***
       * 
       */
      public FileDnDTarget(JComponent c) {
          this.guiTarget = c;
          dropTarget = new DropTarget(this.guiTarget, this);
      }
      
      public void addDropTargetToComponent(JComponent c){
          dropTargets.put(c, new DropTarget(c, this));
      }
      
      /***
       * @param listener
       */
      public void addPropertyChangeListener(PropertyChangeListener listener) {
          propertySupport.addPropertyChangeListener(listener);
      }
      /***
       * @param propertyName
       * @param listener
       */
      public void addPropertyChangeListener(String propertyName,
              PropertyChangeListener listener) {
          propertySupport.addPropertyChangeListener(propertyName, listener);
      }
  
      /***
       * 
       */
      private void decorateComponent() {
  //        TODO work out a better way of decorating a component
          guiTarget.setBorder(BorderFactory.createLineBorder(Color.black));
      }
  
  
      public void dragEnter(DropTargetDragEvent e) {
          //LOG.debug(dtde);
          if (isDragOk(e) == false) {
              e.rejectDrag();
              return;
          }
          decorateComponent();
  
          e.acceptDrag(acceptableActions);
      }
  
  
      public void dragExit(DropTargetEvent dte) {
          removeComponentDecoration();
     }
 
 
     public void dragOver(DropTargetDragEvent e) {
         //LOG.debug(dtde);
 
         if (isDragOk(e) == false) {
             e.rejectDrag();
             return;
         }
         e.acceptDrag(acceptableActions);
     }
 
     public void drop(DropTargetDropEvent dtde) {
         Transferable transferable = dtde.getTransferable();
         LOG.debug(transferable);
         dtde.acceptDrop(acceptableActions);
         try {
             List list = (List)transferable.getTransferData(DataFlavor.javaFileListFlavor);
             LOG.debug(list);
             setFileList(list);
             dtde.getDropTargetContext().dropComplete(true);
             removeComponentDecoration();
 
         } catch (Exception e) {
             LOG.error("Error with DnD", e);
         }
         
     }
 
     public void dropActionChanged(DropTargetDragEvent dtde) {
         //LOG.debug(dtde);
     }
     /***
      * @return Returns the fileList.
      */
     public final List getFileList() {
         return fileList;
     }
 
     private boolean isDragOk(DropTargetDragEvent e) {
     	DataFlavor[] flavors = new DataFlavor[] { DataFlavor.javaFileListFlavor };
     	DataFlavor chosen = null;
     	for (int i = 0; i < flavors.length; i++) {
     		if (e.isDataFlavorSupported(flavors[i])) {
     			chosen = flavors[i];
     			break;
     		}
     	}
     	/*
     	 * the src does not support any of the StringTransferable flavors
     	 */
     	if (chosen == null) {
     		return false;
     	}
     	// the actions specified when the source
     	// created the DragGestureRecognizer
     	int sa = e.getSourceActions();
     
     	// we're saying that these actions are necessary
     	if ((sa & acceptableActions) == 0)
     		return false;
     	return true;
     }
 
     /***
      * 
      */
     private void removeComponentDecoration() {
         this.guiTarget.setBorder(null);
     }
     /***
      * @param listener
      */
     public void removePropertyChangeListener(PropertyChangeListener listener) {
         propertySupport.removePropertyChangeListener(listener);
     }
     /***
      * @param propertyName
      * @param listener
      */
     public void removePropertyChangeListener(String propertyName,
             PropertyChangeListener listener) {
         propertySupport.removePropertyChangeListener(propertyName, listener);
     }
     
     /***
      * @param fileList The fileList to set.
      */
     private  final void setFileList(List fileList) {
         Object oldValue = this.fileList;
         this.fileList = fileList;
         propertySupport.firePropertyChange("fileList", oldValue, this.fileList);
     }
 }