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.internal.ui.viewsupport;
  
  import java.util.ArrayList;
  import java.util.HashMap;
  import java.util.List;
  import java.util.Stack;
  
  import org.eclipse.core.resources.IResource;
  import org.eclipse.swt.widgets.Item;
  import org.eclipse.swt.widgets.Widget;
  import org.eclipse.wst.jsdt.core.IJavaScriptUnit;
  import org.eclipse.wst.jsdt.core.IJavaScriptElement;
  
  /**
   * Helper class for updating error markers and other decorators that work on resources.
   * Items are mapped to their element's underlying resource.
   * Method <code>resourceChanged</code> updates all items that are affected from the changed
   * elements.
   */
  public class ResourceToItemsMapper {
  	
  	public static interface IContentViewerAccessor {
  		public void doUpdateItem(Widget item);
  	}
  	
  
  	private static final int NUMBER_LIST_REUSE= 10;
  
  	// map from resource to item
  	private HashMap fResourceToItem;
  	private Stack fReuseLists;
  	
  	private IContentViewerAccessor fContentViewerAccess;
  
  	public ResourceToItemsMapper(IContentViewerAccessor viewer) {
  		fResourceToItem= new HashMap();
  		fReuseLists= new Stack();
  		
  		fContentViewerAccess= viewer;
  	}
  
  	/**
  	 * Must be called from the UI thread.
  	 * @param changedResource Changed resource
  	 */
  	public void resourceChanged(IResource changedResource) {
  		Object obj= fResourceToItem.get(changedResource);
  		if (obj == null) {
  			// not mapped
  		} else if (obj instanceof Item) {
  			updateItem((Item) obj);
  		} else { // List of Items
  			List list= (List) obj;
  			for (int k= 0; k < list.size(); k++) {
  				updateItem((Item) list.get(k));
  			}
  		}
  	}
  		
  	private void updateItem(Item item) {
  		if (!item.isDisposed()) {
  			fContentViewerAccess.doUpdateItem(item);
  		}
  	}
  
  	/**
  	 * Adds a new item to the map.
  	 * @param element Element to map
  	 * @param item The item used for the element
  	 */
  	public void addToMap(Object element, Item item) {
  		IResource resource= getCorrespondingResource(element);
  		if (resource != null) {
  			Object existingMapping= fResourceToItem.get(resource);
  			if (existingMapping == null) {
  				fResourceToItem.put(resource, item);
  			} else if (existingMapping instanceof Item) {
  				if (existingMapping != item) {
  					List list= getNewList();
  					list.add(existingMapping);
  					list.add(item);
  					fResourceToItem.put(resource, list);
  				}
  			} else { // List			
  				List list= (List) existingMapping;
  				if (!list.contains(item)) {
  					list.add(item);
  				}
  			}
  		}
  	}
  
  	/**
  	 * Removes an element from the map.
  	 * @param element The data element
  	 * @param item The table or tree item
  	 */	
  	public void removeFromMap(Object element, Item item) {
  		IResource resource= getCorrespondingResource(element);
  		if (resource != null) {
  			Object existingMapping= fResourceToItem.get(resource);
  			if (existingMapping == null) {
  				return;
  			} else if (existingMapping instanceof Item) {
  				fResourceToItem.remove(resource);
  			} else { // List
  				List list= (List) existingMapping;
  				list.remove(item);
  				if (list.isEmpty()) {
  					fResourceToItem.remove(list);
  					releaseList(list);
  				}
  			}
  		}
  	}
  	
  	private List getNewList() {
  		if (!fReuseLists.isEmpty()) {
  			return (List) fReuseLists.pop();
  		}
  		return new ArrayList(2);
  	}
  	
  	private void releaseList(List list) {
  		if (fReuseLists.size() < NUMBER_LIST_REUSE) {
  			fReuseLists.push(list);
  		}
  	}
  	
  	/**
  	 * Clears the map.
  	 */
  	public void clearMap() {
  		fResourceToItem.clear();
  	}
  	
  	/**
  	 * Tests if the map is empty
  	 * @return Returns if there are mappings
  	 */
  	public boolean isEmpty() {
  		return fResourceToItem.isEmpty();
  	}	
  	
  	/**
  	 * Method that decides which elements can have error markers
  	 * Returns null if an element can not have error markers.
  	 * @param element The input element
  	 * @return Returns the corresponding resource or null
  	 */	
  	private static IResource getCorrespondingResource(Object element) {
  		if (element instanceof IJavaScriptElement) {
  			IJavaScriptElement elem= (IJavaScriptElement) element;
  			IResource res= elem.getResource();
  			if (res == null) {
  				IJavaScriptUnit cu= (IJavaScriptUnit) elem.getAncestor(IJavaScriptElement.JAVASCRIPT_UNIT);
  				if (cu != null) {
  					// elements in compilation units are mapped to the underlying resource of the original cu
  					res= cu.getResource();
  				}
  			}
  			return res; 
  		} else if (element instanceof IResource) {
  			return (IResource) element;
  		}
  		return null;
  	}
  	
  }
  