/*******************************************************************************
 * Copyright (c) 2004, 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.gef.ui.actions;

import java.util.Arrays;

import org.eclipse.jface.action.Action;

import org.eclipse.gef.EditPart;
import org.eclipse.gef.EditPartViewer;
import org.eclipse.gef.internal.GEFMessages;
import org.eclipse.gef.internal.ui.rulers.GuideEditPart;
import org.eclipse.gef.internal.ui.rulers.RulerEditPart;
import org.eclipse.gef.rulers.RulerProvider;

/**
 * An Action that creates a guide on a ruler and reveals it.
 * 
 * @author Pratik Shah
 * @since 3.0
 */
public class CreateGuideAction extends Action {

	private EditPartViewer viewer;

	/**
	 * Constructor
	 * 
	 * @param ruler
	 *            the viewer for the ruler on which the guide is to be created
	 */
	public CreateGuideAction(EditPartViewer ruler) {
		super(GEFMessages.Create_Guide_Label);
		viewer = ruler;
		setToolTipText(GEFMessages.Create_Guide_Tooltip);
	}

	/**
	 * @see org.eclipse.jface.action.IAction#run()
	 */
	public void run() {
		RulerProvider provider = ((RulerEditPart) viewer.getRootEditPart()
				.getChildren().get(0)).getRulerProvider();

		// Determine where the guide should be created
		int[] positions = provider.getGuidePositions();
		Arrays.sort(positions);
		int index = 0;
		int newPosition = GuideEditPart.MIN_DISTANCE_BW_GUIDES + 1;
		int desiredDifference = (GuideEditPart.MIN_DISTANCE_BW_GUIDES * 2) + 1;
		boolean found = positions.length > 0
				&& positions[0] > desiredDifference;
		while (index < positions.length - 1 && !found) {
			if (positions[index + 1] - positions[index] > desiredDifference) {
				newPosition += positions[index];
				found = true;
			}
			index++;
		}
		if (!found && positions.length > 0)
			newPosition += positions[positions.length - 1];

		// Create the guide and reveal it
		viewer.getEditDomain().getCommandStack()
				.execute(provider.getCreateGuideCommand(newPosition));
		viewer.reveal((EditPart) viewer.getEditPartRegistry().get(
				provider.getGuideAt(newPosition)));
	}

}