core/plugins/org.eclipse.dltk.ui/src/org/eclipse/dltk/internal/ui/editor/SpecificContentAssistAction.java

/*******************************************************************************
 * Copyright (c) 2005, 2006 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.dltk.internal.ui.editor;

import org.eclipse.core.runtime.Assert;
import org.eclipse.core.runtime.CoreException;
import org.eclipse.dltk.core.DLTKLanguageManager;
import org.eclipse.dltk.core.IDLTKLanguageToolkit;
import org.eclipse.dltk.core.IModelElement;
import org.eclipse.dltk.ui.text.completion.CompletionProposalCategory;
import org.eclipse.dltk.ui.text.completion.CompletionProposalComputerRegistry;
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;


/**
 * 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 ScriptEditor 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.dltk.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) {
		ScriptEditor editor;
		if (part instanceof ScriptEditor)
			editor = (ScriptEditor) 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;
		String partitioning = null;
		IModelElement modelElement = EditorUtility.getEditorInputModelElement(this.fEditor, false);
		if (modelElement != null) {
			try {
				IDLTKLanguageToolkit toolkit = DLTKLanguageManager.getLangaugeToolkit(modelElement);
				if (toolkit != null) {
					partitioning = toolkit.getPartitioningID();
				}
			} catch (CoreException e) {
				// TODO Auto-generated catch block
				//e.printStackTrace(); //XXX: always fail on standalone files
			}
		}
		if (partitioning != null) {
			try {
				contentType = TextUtilities.getContentType(document, partitioning, offset, true);
			} catch (BadLocationException x) {
				return false;
			}
		} else {
			contentType = IDocument.DEFAULT_CONTENT_TYPE;
		}
		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));
	}
}