content: /*******************************************************************************
   * Copyright (c) 2005, 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.javaeditor;
  
  
  import org.eclipse.core.runtime.Assert;
  import org.eclipse.jface.action.Action;
  import org.eclipse.jface.text.BadLocationException;
  import org.eclipse.jface.text.IDocument;
  import org.eclipse.jface.text.ITextOperationTarget;
  import org.eclipse.jface.text.ITextSelection;
  import org.eclipse.jface.text.TextUtilities;
  import org.eclipse.jface.text.source.ISourceViewer;
  import org.eclipse.jface.viewers.ISelection;
  import org.eclipse.ui.IEditorPart;
  import org.eclipse.ui.texteditor.IDocumentProvider;
  import org.eclipse.ui.texteditor.ITextEditor;
  import org.eclipse.ui.texteditor.IUpdate;
  import org.eclipse.wst.jsdt.internal.ui.text.java.CompletionProposalCategory;
  import org.eclipse.wst.jsdt.internal.ui.text.java.CompletionProposalComputerRegistry;
  import org.eclipse.wst.jsdt.ui.text.IJavaScriptPartitions;
  
  /**
   * Action to run content assist on a specific proposal category.
   * 
   * 
   */
  final class SpecificContentAssistAction extends Action implements IUpdate {
  	/**
  	 * The category represented by this action.
  	 */
  	private final CompletionProposalCategory fCategory;
  	/**
  	 * The content assist executor.
  	 */
  	private final SpecificContentAssistExecutor fExecutor= new SpecificContentAssistExecutor(CompletionProposalComputerRegistry.getDefault());
  	/**
  	 * The editor.
  	 */
  	private JavaEditor fEditor;
  	
  	/**
  	 * Creates a new action for a certain proposal category.
  	 * 
  	 * @param category
  	 */
  	public SpecificContentAssistAction(CompletionProposalCategory category) {
  		fCategory= category;
  		setText(category.getName());
  		setImageDescriptor(category.getImageDescriptor());
  		setActionDefinitionId("org.eclipse.wst.jsdt.ui.specific_content_assist.command"); //$NON-NLS-1$
  	}
  
  	/*
  	 * @see org.eclipse.jface.action.Action#run()
  	 */
  	public void run() {
  		ITextEditor editor= getActiveEditor();
  		if (editor == null)
  			return;
  		
  		fExecutor.invokeContentAssist(editor, fCategory.getId());
  		
  		return;
  	}
  
  	private ITextEditor getActiveEditor() {
  		return fEditor;
  	}
  
  	/**
  	 * Sets the active editor part.
  	 * 
  	 * @param part the editor, possibly <code>null</code>
  	 */
  	public void setActiveEditor(IEditorPart part) {
  		JavaEditor editor;
  		if (part instanceof JavaEditor)
  			editor= (JavaEditor) part;
  		else
  			editor= null;
  		fEditor= editor;
  		setEnabled(computeEnablement(fEditor));
  	}
  	
  	private boolean computeEnablement(ITextEditor editor) {
  		if (editor == null)
  			return false;
  		ITextOperationTarget target= (ITextOperationTarget) editor.getAdapter(ITextOperationTarget.class);
  		boolean hasContentAssist= target != null && target.canDoOperation(ISourceViewer.CONTENTASSIST_PROPOSALS);
  		if (!hasContentAssist)
  			return false;
  		
  		ISelection selection= editor.getSelectionProvider().getSelection();
  		return isValidSelection(selection);
  	}
  
      /**
  	 * Computes the partition type at the selection start and checks whether the proposal category
  	 * has any computers for this partition.
  	 * 
  	 * @param selection the selection
  	 * @return <code>true</code> if there are any computers for the selection
  	 */
      private boolean isValidSelection(ISelection selection) {
      	if (!(selection instanceof ITextSelection))
      		return false;
      	int offset= ((ITextSelection) selection).getOffset();
      	
      	IDocument document= getDocument();
      	if (document == null)
      		return false;
      	
      	String contentType;
      	try {
  	        contentType= TextUtilities.getContentType(document, IJavaScriptPartitions.JAVA_PARTITIONING, offset, true);
          } catch (BadLocationException x) {
          	return false;
          }
          
          return fCategory.hasComputers(contentType);
      }
      
  	private IDocument getDocument() {
  		Assert.isTrue(fEditor != null);
  	    IDocumentProvider provider= fEditor.getDocumentProvider();
  	    if (provider == null)
  	    	return null;
  	    
  		IDocument document= provider.getDocument(fEditor.getEditorInput());
  	    return document;
      }
  
  	/*
       * @see org.eclipse.ui.texteditor.IUpdate#update()
       */
      public void update() {
      	setEnabled(computeEnablement(fEditor));
      }
  }
  