/*******************************************************************************
 * 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.Dimension;
import org.eclipse.draw2d.geometry.Point;
import org.eclipse.draw2d.geometry.Rectangle;

/**
 * Places a figure relative to a point determined by the subclass. The figure
 * may be placed in some location relative to the point with a configurable
 * amount of spacing.
 */
public abstract class AbstractLocator implements Locator {

	private int relativePosition = PositionConstants.CENTER;
	private int gap;

	/**
	 * Creates a new AbstractLocator.
	 */
	public AbstractLocator() {
	}

	/**
	 * Returns the number of pixels to leave between the figure being located
	 * and the reference point. Only used if {@link #getRelativePosition()}
	 * returns something other than {@link PositionConstants#CENTER}.
	 * 
	 * @return The gap
	 * @since 2.0
	 */
	public int getGap() {
		return gap;
	}

	/**
	 * Returns the reference point in absolute coordinates used to calculate the
	 * location.
	 * 
	 * @return The reference point in absolute coordinates
	 * @since 2.0
	 */
	protected abstract Point getReferencePoint();

	/**
	 * Recalculate the location of the figure according to its desired position
	 * relative to the center point.
	 * 
	 * @param size
	 *            The size of the figure
	 * @param center
	 *            The center point
	 * @return The new bounds
	 * @since 2.0
	 */
	protected Rectangle getNewBounds(Dimension size, Point center) {
		Rectangle bounds = new Rectangle(center, size);

		bounds.x -= bounds.width / 2;
		bounds.y -= bounds.height / 2;

		int xFactor = 0, yFactor = 0;
		int position = getRelativePosition();

		if ((position & PositionConstants.NORTH) != 0)
			yFactor = -1;
		else if ((position & PositionConstants.SOUTH) != 0)
			yFactor = 1;

		if ((position & PositionConstants.WEST) != 0)
			xFactor = -1;
		else if ((position & PositionConstants.EAST) != 0)
			xFactor = 1;

		bounds.x += xFactor * (bounds.width / 2 + getGap());
		bounds.y += yFactor * (bounds.height / 2 + getGap());

		return bounds;
	}

	/**
	 * Returns the position of the figure with respect to the center point.
	 * Possible values can be found in {@link PositionConstants} and include
	 * CENTER, NORTH, SOUTH, EAST, WEST, NORTH_EAST, NORTH_WEST, SOUTH_EAST, or
	 * SOUTH_WEST.
	 * 
	 * @return An int constant representing the relative position
	 * @since 2.0
	 */
	public int getRelativePosition() {
		return relativePosition;
	}

	/**
	 * Recalculates the position of the figure and returns the updated bounds.
	 * 
	 * @param target
	 *            The figure to relocate
	 */
	public void relocate(IFigure target) {
		Dimension prefSize = target.getPreferredSize();
		Point center = getReferencePoint();
		target.translateToRelative(center);
		target.setBounds(getNewBounds(prefSize, center));
	}

	/**
	 * Sets the gap between the reference point and the figure being placed.
	 * Only used if getRelativePosition() returns something other than
	 * {@link PositionConstants#CENTER}.
	 * 
	 * @param i
	 *            The gap
	 * @since 2.0
	 */
	public void setGap(int i) {
		gap = i;
	}

	/**
	 * Sets the position of the figure with respect to the center point.
	 * Possible values can be found in {@link PositionConstants} and include
	 * CENTER, NORTH, SOUTH, EAST, WEST, NORTH_EAST, NORTH_WEST, SOUTH_EAST, or
	 * SOUTH_WEST.
	 * 
	 * @param pos
	 *            The relative position
	 * @since 2.0
	 */
	public void setRelativePosition(int pos) {
		relativePosition = pos;
	}

}