PartitionsDividedTester.java

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package jsettlers.logic.map.grid.partition;

import jsettlers.algorithms.interfaces.IContainingProvider;
import jsettlers.algorithms.traversing.borders.BorderTraversingAlgorithm;
import jsettlers.algorithms.traversing.borders.IBorderVisitor;
import jsettlers.common.position.ShortPoint2D;
import jsettlers.common.utils.mutables.MutableInt;
import jsettlers.logic.map.grid.partition.PartitionsListingBorderVisitor.BorderPartitionInfo;

/**
 * This class implements an algorithm used by the {@link PartitionsGrid} to check if two positions of a partition are divided.
 * 
 * @author Andreas Eberle
 * 
 */
final class PartitionsDividedTester {

	/**
	 * Private constructor to prevent the creation of objects.
	 */
	private PartitionsDividedTester() {
	}

	/**
	 * Tests if the given positions (that need to lie on the border of the given partition) are connected by the given partition.
	 * 
	 * @param partitionObjects
	 * @param partitions
	 * @param width
	 * @param partition1
	 * @param partition1Size
	 * @param partition2
	 * @param partition2Size
	 * @return true if both positions are connected by the given partition.<br>
	 *         false if the positions are not connected.
	 */
	public static boolean isPartitionDivided(Partition[] partitionObjects, short[] partitions, short width, BorderPartitionInfo partition1,
			MutableInt partition1Size, BorderPartitionInfo partition2, MutableInt partition2Size) {

		assert partition1.partitionId == partition2.partitionId;

		return posNotOnBorder(partitionObjects, partitions, width, partition1.positionOfPartition,
					partition1.insideNeighborPosition, partition2.positionOfPartition, partition1.partitionId, partition1Size)
				&& posNotOnBorder(partitionObjects, partitions, width, partition2.positionOfPartition,
					partition2.insideNeighborPosition, partition1.positionOfPartition, partition1.partitionId, partition2Size);
	}

	/**
	 * NOTE: The call to this method is different if the given positions are swapped!
	 *
	 * @param partitionObjects
	 * @param partitions
	 * @param width
	 * @param insideStartPosition
	 * @param checkPosition
	 * @param partitionSize
	 * @return
	 */
	private static boolean posNotOnBorder(final Partition[] partitionObjects, final short[] partitions, final short width,
			final ShortPoint2D insideStartPosition, final ShortPoint2D outsideStartPosition, final ShortPoint2D checkPosition,
			final short partitionId, MutableInt partitionSize) {

		final short checkPositionX = checkPosition.x;
		final short checkPositionY = checkPosition.y;

		boolean pos2NotOnBorder = BorderTraversingAlgorithm.traverseBorder(new IContainingProvider() {
			@Override
			public boolean contains(int x, int y) {
				return partitionObjects[partitions[x + y * width]].partitionId == partitionId;
			}
		}, insideStartPosition, outsideStartPosition, new IBorderVisitor() {
			@Override
			public boolean visit(int insideX, int insideY, int outsideX, int outsideY) {
				return checkPositionX != insideX || checkPositionY != insideY;
			}
		}, false, partitionSize);

		return pos2NotOnBorder;
	}
}