/*******************************************************************************
 * Copyright (c) 2000, 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.draw2d;

import org.eclipse.draw2d.geometry.Point;

/**
 * Base class for implementing a connection router. This class provides stubs
 * for constraint usage, and some utility methods.
 */
public abstract class AbstractRouter implements ConnectionRouter {

	private static final Point START = new Point();
	private static final Point END = new Point();

	/**
	 * Returns the constraint for the given Connection.
	 * 
	 * @param connection
	 *            The connection
	 * @return The constraint
	 * @since 2.0
	 */
	public Object getConstraint(Connection connection) {
		return null;
	}

	/**
	 * A convenience method for obtaining a connection's endpoint. The
	 * connection's endpoint is a point in absolute coordinates obtained by
	 * using its source and target {@link ConnectionAnchor}. The returned Point
	 * is a static singleton that is reused to reduce garbage collection. The
	 * caller may modify this point in any way. However, the point will be
	 * reused and its values overwritten during the next call to this method.
	 * 
	 * @param connection
	 *            The connection
	 * @return The endpoint
	 * @since 2.0
	 */
	protected Point getEndPoint(Connection connection) {
		Point ref = connection.getSourceAnchor().getReferencePoint();
		return END.setLocation(connection.getTargetAnchor().getLocation(ref));
	}

	/**
	 * A convenience method for obtaining a connection's start point. The
	 * connection's startpoint is a point in absolute coordinates obtained by
	 * using its source and target {@link ConnectionAnchor}. The returned Point
	 * is a static singleton that is reused to reduce garbage collection. The
	 * caller may modify this point in any way. However, the point will be
	 * reused and its values overwritten during the next call to this method.
	 * 
	 * @param conn
	 *            The connection
	 * @return The start point
	 * @since 2.0
	 */
	protected Point getStartPoint(Connection conn) {
		Point ref = conn.getTargetAnchor().getReferencePoint();
		return START.setLocation(conn.getSourceAnchor().getLocation(ref));
	}

	/**
	 * Causes the router to discard any cached information about the given
	 * Connection.
	 * 
	 * @param connection
	 *            The connection to invalidate
	 * @since 2.0
	 */
	public void invalidate(Connection connection) {
	}

	/**
	 * Removes the given Connection from this routers list of Connections it is
	 * responsible for.
	 * 
	 * @param connection
	 *            The connection to remove
	 * @since 2.0
	 */
	public void remove(Connection connection) {
	}

	/**
	 * Sets the constraint for the given Connection.
	 * 
	 * @param connection
	 *            The connection
	 * @param constraint
	 *            The constraint
	 * @since 2.0
	 */
	public void setConstraint(Connection connection, Object constraint) {
	}

}