/*******************************************************************************
 * Copyright (c) 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
 *     
 *******************************************************************************/
package org.eclipse.wst.sse.ui.internal.handlers;

import org.eclipse.core.commands.AbstractHandler;
import org.eclipse.core.commands.ExecutionEvent;
import org.eclipse.core.commands.ExecutionException;
import org.eclipse.jface.text.IDocument;
import org.eclipse.jface.text.ITextSelection;
import org.eclipse.jface.text.TextSelection;
import org.eclipse.jface.viewers.ISelection;
import org.eclipse.jface.viewers.ISelectionProvider;
import org.eclipse.ui.IEditorPart;
import org.eclipse.ui.handlers.HandlerUtil;
import org.eclipse.ui.texteditor.ITextEditor;
import org.eclipse.wst.sse.core.internal.provisional.text.IStructuredDocument;

/**
 * This class contains all of the shared functionality for comment handlers
 */
public abstract class AbstractCommentHandler extends AbstractHandler {

	/**
	 * <p>Default constructor must exist because sub classes are created by java reflection</p>
	 */
	public AbstractCommentHandler() {
		super();
	}

	/**
	 * <p>Gets the important information out of the event and passes it onto 
	 * the internal method {@link #processAction}</p>
	 * 
	 * @see org.eclipse.wst.xml.ui.internal.handlers.CommentHandler#execute(org.eclipse.core.commands.ExecutionEvent)
	 */
	public final Object execute(ExecutionEvent event) throws ExecutionException {
		IEditorPart editor = HandlerUtil.getActiveEditor(event);
		ITextEditor textEditor = null;
		if (editor instanceof ITextEditor)
			textEditor = (ITextEditor) editor;
		else {
			Object o = editor.getAdapter(ITextEditor.class);
			if (o != null)
				textEditor = (ITextEditor) o;
		}
		if (textEditor != null) {
			IDocument document = textEditor.getDocumentProvider().getDocument(textEditor.getEditorInput());
			if (document != null && document instanceof IStructuredDocument) {
				// get current text selection
				ITextSelection textSelection = getCurrentSelection(textEditor);
				if (!textSelection.isEmpty()) {
					//call the implementers code to deal with the event
					processAction(textEditor, (IStructuredDocument)document, textSelection);
				}
			}
		}
		return null;
	}

	/**
	 * <p>This method is called by the public {@link #execute} method whenever
	 * the comment handler is invoked.  This method should be used for the
	 * logic of handling the structured comment event.</p>
	 * 
	 * @param textEditor the text editor the initiating event was caused in
	 * @param document the document the text editor is editing
	 * @param textSelection the user selection when the event was caused
	 */
	protected abstract void processAction(ITextEditor textEditor, IStructuredDocument document, ITextSelection textSelection);
	
	/**
	 * <p>Gets the current user selection in the given {@link ITextEditor}</p>
	 * 
	 * @param textEditor get the user selection from here
	 * @return the current user selection in <code>textEdtior</code>
	 */
	private static ITextSelection getCurrentSelection(ITextEditor textEditor) {
		ISelectionProvider provider = textEditor.getSelectionProvider();
		if (provider != null) {
			ISelection selection = provider.getSelection();
			if (selection instanceof ITextSelection) {
				return (ITextSelection) selection;
			}
		}
		return TextSelection.emptySelection();
	}
}