/*******************************************************************************
 * Copyright (c) 2001, 2010 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
 *     Jens Lukowski/Innoopract - initial renaming/restructuring
 *     
 *******************************************************************************/
package org.eclipse.wst.sse.ui.internal.contentassist;

import org.eclipse.core.runtime.CoreException;
import org.eclipse.core.runtime.IConfigurationElement;
import org.eclipse.core.runtime.IStatus;
import org.eclipse.core.runtime.InvalidRegistryObjectException;
import org.eclipse.core.runtime.Platform;
import org.eclipse.core.runtime.Status;
import org.eclipse.jface.text.ITextViewer;
import org.eclipse.wst.sse.core.StructuredModelManager;
import org.eclipse.wst.sse.core.internal.provisional.IModelManager;
import org.eclipse.wst.sse.core.internal.provisional.IStructuredModel;
import org.eclipse.wst.sse.core.internal.provisional.IndexedRegion;
import org.eclipse.wst.sse.core.internal.provisional.text.IStructuredDocument;
import org.eclipse.wst.sse.core.internal.provisional.text.IStructuredDocumentRegion;
import org.eclipse.wst.sse.ui.internal.SSEUIPlugin;
import org.osgi.framework.Bundle;


/**
 * @author pavery
 *  
 */
public class ContentAssistUtils {

	/**
	 * Returns the closest IndexedRegion for the offset and viewer allowing
	 * for differences between viewer offsets and model positions. note: this
	 * method returns an IndexedRegion for read only
	 * 
	 * @param viewer
	 *            the viewer whose document is used to compute the proposals
	 * @param documentOffset
	 *            an offset within the document for which completions should
	 *            be computed
	 * @return an IndexedRegion
	 */
	public static IndexedRegion getNodeAt(ITextViewer viewer, int documentOffset) {

		if (viewer == null)
			return null;

		IndexedRegion node = null;
		IModelManager mm = StructuredModelManager.getModelManager();
		IStructuredModel model = null;
		if (mm != null)
			model = mm.getExistingModelForRead(viewer.getDocument());
		try {
			if (model != null) {
				int lastOffset = documentOffset;
				node = model.getIndexedRegion(documentOffset);
				while (node == null && lastOffset >= 0) {
					lastOffset--;
					node = model.getIndexedRegion(lastOffset);
				}
			}
		} finally {
			if (model != null)
				model.releaseFromRead();
		}
		return node;
	}

	/**
	 * Returns the closest IStructuredDocumentRegion for the offest and
	 * viewer.
	 * 
	 * @param viewer
	 * @param documentOffset
	 * @return the closest IStructuredDocumentRegion for the offest and
	 *         viewer.
	 */
	public static IStructuredDocumentRegion getStructuredDocumentRegion(ITextViewer viewer, int documentOffset) {
		IStructuredDocumentRegion sdRegion = null;
		if (viewer == null || viewer.getDocument() == null)
			return null;

		int lastOffset = documentOffset;
		IStructuredDocument doc = (IStructuredDocument) viewer.getDocument();
		sdRegion = doc.getRegionAtCharacterOffset(documentOffset);
		while (sdRegion == null && lastOffset >= 0) {
			lastOffset--;
			sdRegion = doc.getRegionAtCharacterOffset(lastOffset);
		}
		return sdRegion;
	}
	
	/**
	 * @return the bundle that defined the {@link IConfigurationElement} that defines
	 * this category.
	 */
	public static Bundle getBundle(IConfigurationElement element) {
		String namespace= element.getDeclaringExtension().getContributor().getName();
		Bundle bundle= Platform.getBundle(namespace);
		return bundle;
	}
	
	/**
	 * <p>Checks that the given attribute value is not <code>null</code>.</p>
	 *
	 * @param value the object to check if not null
	 * @param attribute the attribute
	 * 
	 * @throws InvalidRegistryObjectException if the registry element is no longer valid
	 * @throws CoreException if <code>value</code> is <code>null</code>
	 */
	public static void checkExtensionAttributeNotNull(Object value, String attribute,
			IConfigurationElement element) throws InvalidRegistryObjectException, CoreException {
		
		if (value == null) {
			String message = "The extension \"" + element.getDeclaringExtension().getUniqueIdentifier() + //$NON-NLS-1$
				"\" from plug-in \"" + element.getContributor().getName() + //$NON-NLS-1$
				"\" did not specify a value for the required \"" + attribute + //$NON-NLS-1$
				"\" attribute for the element \"" + element.getName() + "\". Disabling the extension."; //$NON-NLS-1$ //$NON-NLS-2$
			IStatus status= new Status(IStatus.WARNING, SSEUIPlugin.ID, IStatus.OK, message, null);
			throw new CoreException(status);
		}
	}
	
	/**
	 * @param textViewer check to see if this viewer is empty
	 * @return <code>true</code> if there is no text or it's all white space,
	 * <code>false</code> otherwise
	 */
	public static boolean isViewerEmpty(ITextViewer textViewer) {
		boolean isEmpty = false;
		String text = textViewer.getTextWidget().getText();
		if ((text == null) || ((text != null) && text.trim().equals(""))) { //$NON-NLS-1$
			isEmpty = true;
		}
		return isEmpty;
	}

}