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.corext.refactoring.rename;
  
  import org.eclipse.jface.text.IRegion;
  import org.eclipse.jface.text.Region;
  import org.eclipse.wst.jsdt.core.dom.ASTNode;
  import org.eclipse.wst.jsdt.core.dom.JavaScriptUnit;
  import org.eclipse.wst.jsdt.core.dom.IBinding;
  import org.eclipse.wst.jsdt.core.dom.Name;
  import org.eclipse.wst.jsdt.core.dom.SimpleName;
  import org.eclipse.wst.jsdt.core.dom.VariableDeclaration;
  import org.eclipse.wst.jsdt.core.dom.VariableDeclarationStatement;
  import org.eclipse.wst.jsdt.internal.corext.dom.Selection;
  import org.eclipse.wst.jsdt.internal.corext.dom.SelectionAnalyzer;
  
  public class TempDeclarationFinder {
  
  	//no instances
  	private TempDeclarationFinder(){}
  	
  	/**
  	 * @return <code>null</code> if the selection is invalid or does not cover a temp
  	 * declaration or reference.
  	 */
  	public static VariableDeclaration findTempDeclaration(JavaScriptUnit cu, int selectionOffset, int selectionLength) {
  		TempSelectionAnalyzer analyzer= new TempSelectionAnalyzer(selectionOffset, selectionLength);
  		cu.accept(analyzer);
  		
  		ASTNode[] selected= analyzer.getSelectedNodes();
  		if (selected == null || selected.length != 1)
  			return null;
  			
  		ASTNode selectedNode= selected[0];
  		if (selectedNode instanceof VariableDeclaration)
  			return (VariableDeclaration)selectedNode;
  		
  		if (selectedNode instanceof Name){
  			Name reference= (Name)selectedNode;
  			IBinding binding= reference.resolveBinding();
  			if (binding == null)
  				return null;
  			ASTNode declaringNode= cu.findDeclaringNode(binding);
  			if (declaringNode instanceof VariableDeclaration)
  				return (VariableDeclaration)declaringNode;
  			else
  				return null;	
  		} else if (selectedNode instanceof VariableDeclarationStatement){
  			VariableDeclarationStatement vds= (VariableDeclarationStatement)selectedNode;
  			if (vds.fragments().size() != 1)
  				return null;
  			return (VariableDeclaration)vds.fragments().get(0);
  		}
  		return null;
  	} 
  	
  	/*
  	 * Class used to extract selected nodes from an AST.
  	 * Subclassing <code>SelectionAnalyzer</code> is needed to support activation 
  	 * when only a part of the <code>VariableDeclaration</code> node is selected
  	 */
  	private static class TempSelectionAnalyzer extends SelectionAnalyzer {
  
  		private ASTNode fNode;
  
  		TempSelectionAnalyzer(int selectionOffset, int selectionLength){
  			super(Selection.createFromStartLength(selectionOffset, selectionLength), true);
  		}
  
  		//overridden
  		public boolean visitNode(ASTNode node) {
  			if (node instanceof VariableDeclaration)	
  				return visitVariableDeclaration((VariableDeclaration)node);
  			else if (node instanceof SimpleName)
  					return visitSimpleName((SimpleName)node);
  			else
  				return super.visitNode(node);
  		}
  		
  		private boolean addNodeAndStop(ASTNode node){
  			fNode= node;
  			return false;
  		}
  		
  		private boolean visitSimpleName(SimpleName name) {
  			if (getSelection().coveredBy(name))
  				return addNodeAndStop(name);
  			return super.visitNode(name);				
  		}
  		
  		private boolean visitVariableDeclaration(VariableDeclaration vd) {
  			if (vd.getInitializer() != null){
  				int start= vd.getStartPosition();
  				IRegion declarationRange= new Region(start, vd.getInitializer().getStartPosition() - start);
  				if (getSelection().coveredBy(declarationRange))
  					return addNodeAndStop(vd);
  				else 
  					return super.visitNode(vd);
  			} else {
  				if (getSelection().coveredBy(vd))
  					return addNodeAndStop(vd);
  				else 
  					return super.visitNode(vd);
  			}
  		}
  		
  		//overridden
  		public ASTNode[] getSelectedNodes() {
  			if (fNode != null)
  				return new ASTNode[] { fNode };
  			return super.getSelectedNodes();
  		}
  	}
  
  }
  