content: /*******************************************************************************
   * Copyright (c) 2000, 2008 IBM Corporation and others.
   * All rights reserved. This program and the accompanying materials
   * are made available under the terms of the Eclipse Public License v1.0
   * which accompanies this distribution, and is available at
   * http://www.eclipse.org/legal/epl-v10.html
   *
   * Contributors:
   *     IBM Corporation - initial API and implementation
   *******************************************************************************/
  package org.eclipse.wst.jsdt.ui.actions;
  
  import java.util.ArrayList;
  import java.util.Iterator;
  import java.util.List;
  
  import org.eclipse.core.resources.IResource;
  import org.eclipse.core.runtime.Assert;
  import org.eclipse.core.runtime.IAdaptable;
  import org.eclipse.core.runtime.ListenerList;
  import org.eclipse.jface.viewers.ISelection;
  import org.eclipse.jface.viewers.ISelectionChangedListener;
  import org.eclipse.jface.viewers.ISelectionProvider;
  import org.eclipse.jface.viewers.IStructuredSelection;
  import org.eclipse.jface.viewers.SelectionChangedEvent;
  import org.eclipse.jface.viewers.StructuredSelection;
  import org.eclipse.wst.jsdt.core.IJavaScriptElement;
  
  
  
  /**
   * A converting selection provider is a special selection provider which converts
   * a selection before notifying any listeners. Additional it converts the selection
   * on <code>getSelection</code> and <code>setSelection</code>. The default strategy
   * used to adapt the elements of the selection to {@link IJavaScriptElement} or a {@link IResource},
   * but implementors can override this behavior.
   *   
   *
   * Provisional API: This class/interface is part of an interim API that is still under development and expected to
   * change significantly before reaching stability. It is being made available at this early stage to solicit feedback
   * from pioneering adopters on the understanding that any code that uses this API will almost certainly be broken
   * (repeatedly) as the API evolves.
   */
  public class ConvertingSelectionProvider implements ISelectionProvider {
  
  	private final ISelectionProvider fProvider;
  	private SelectionChangedListener fListener;
  	
  	private class SelectionChangedListener implements ISelectionChangedListener {
  		
  		ListenerList fListeners= new ListenerList();
  		
  		public void selectionChanged(SelectionChangedEvent event) {
  			ISelection selection= convertFrom(event.getSelection());
  			SelectionChangedEvent newEvent= new SelectionChangedEvent(ConvertingSelectionProvider.this, selection);
  			Object[] listeners= fListeners.getListeners();
  			for (int i= 0; i < listeners.length; i++) {
  				((ISelectionChangedListener)listeners[i]).selectionChanged(newEvent);
  			}
  		}
  		public void addListener(ISelectionChangedListener listener) {
  			fListeners.add(listener);
  		}
  		public void removeListener(ISelectionChangedListener listener) {
  			fListeners.remove(listener);
  		}
  		public boolean isEmpty() {
  			return fListeners.isEmpty();
  		}
  	}
  	
  	/**
  	 * Creates a {@link ConvertingSelectionProvider} to convert from a given selection provider
  	 * using the default mechanism.
  	 * 
  	 * @param provider the provider to covert from and to
  	 */
  	public ConvertingSelectionProvider(ISelectionProvider provider) {
  		Assert.isNotNull(provider);
  		fProvider= provider;
  	}
  	
  	/**
  	 * Converts the given original viewer selection into a new
  	 * selection. The default behavior adapts the elements in the selection
  	 * first to {@link IJavaScriptElement} then to {@link IResource}.
  	 * Implementors want to override this method. 
  	 * 
  	 * @param viewerSelection the original viewer selection
  	 * 
  	 * @return the new selection to be used
  	 */
  	public ISelection convertFrom(ISelection viewerSelection) {
  		return convertFromUsingDefaultMechanism(viewerSelection);
  	}
  
  
  	private ISelection convertFromUsingDefaultMechanism(ISelection viewerSelection) {
  		if (! (viewerSelection instanceof IStructuredSelection))
  			return viewerSelection;
  		IStructuredSelection selection= (IStructuredSelection)viewerSelection;
  		List result= new ArrayList(selection.size());
  		for (Iterator iter= selection.iterator(); iter.hasNext();) {
  			Object element= iter.next();
  			if (element instanceof IResource || element instanceof IJavaScriptElement) {
  				result.add(element);
  			} else if (element instanceof IAdaptable) {
  				IAdaptable adaptable= (IAdaptable)element;
  				IJavaScriptElement jElement= (IJavaScriptElement)adaptable.getAdapter(IJavaScriptElement.class);
  				if (jElement != null) {
  					result.add(jElement);
  				} else {
  					IResource resource= (IResource)adaptable.getAdapter(IResource.class);
  					if (resource != null) {
  						result.add(resource);
  					} else {
  						result.add(element);
  					}
  				}
  			} else {
  				result.add(element);
  			}
  		}
  		return new StructuredSelection(result);
  	}
  
  	/**
  	 * Converts a selection to a viewer selection. The default implementation does not convert
  	 * the selection. Implementors want to override this behavior. 
  	 * 
  	 * @param selection the selection to convert
  	 * 
  	 * @return a viewer selection
  	 */
  	public ISelection convertTo(ISelection selection) {
  		return selection;
  	}
  	
  	
  	/**
  	 * {@inheritDoc}
  	 */
  	public final ISelection getSelection() {
  		return convertFrom(fProvider.getSelection());
  	}
  
  	/**
  	 * {@inheritDoc}
  	 */
  	public final void setSelection(ISelection selection) {
  		fProvider.setSelection(convertTo(selection));
  	}
  	
  	/**
  	 * {@inheritDoc}
  	 */
  	public void addSelectionChangedListener(ISelectionChangedListener listener) {
  		if (fListener == null) {
  			fListener= new SelectionChangedListener();
  			fProvider.addSelectionChangedListener(fListener);
  		}
  		fListener.addListener(listener);
  	}
  	
  	/**
  	 * {@inheritDoc}
  	 */
  	public void removeSelectionChangedListener(ISelectionChangedListener listener) {
  		if (fListener == null)
  			return;
  		fListener.removeListener(listener);
  		if (fListener.isEmpty()) {
  			fProvider.removeSelectionChangedListener(fListener);
  			fListener= null;
  		}
  	}
  }
  