chess/src/main/java/dev/kske/chess/ui/OverlayComponent.java

package dev.kske.chess.ui;

import java.awt.*;
import java.awt.geom.AffineTransform;
import java.util.ArrayList;
import java.util.List;

import javax.swing.JComponent;

import dev.kske.chess.board.Move;
import dev.kske.chess.board.Position;

/**
 * Project: <strong>Chess</strong><br>
 * File: <strong>OverlayComponent.java</strong><br>
 * Created: <strong>08.07.2019</strong><br>
 *
 * @since Chess v0.1-alpha
 * @author Kai S. K. Engelbart
 */
public class OverlayComponent extends JComponent {

	private static final long serialVersionUID = -7326936060890082183L;

	private final BoardPane boardPane;

	private List<Position> dots;
	private Move arrow;

	/**
	 * Creates an instance of {@link OverlayComponent}.
	 *
	 * @param boardPane the board pane inside which this overlay component is
	 *                  contained
	 */
	public OverlayComponent(BoardPane boardPane) {
		this.boardPane = boardPane;
		dots = new ArrayList<>();
		setSize(boardPane.getPreferredSize());
	}

	@Override
	protected void paintComponent(Graphics g) {
		super.paintComponent(g);

		final int tileSize = boardPane.getTileSize();

		// Draw an arrow representing the last move and mark its position and
		// destination
		if (arrow != null) {
			Point pos = new Point(
				arrow.getPos().x * tileSize + tileSize / 2,
				arrow.getPos().y * tileSize + tileSize / 2
			);
			Point dest = new Point(
				arrow.getDest().x * tileSize + tileSize / 2,
				arrow.getDest().y * tileSize + tileSize / 2
			);

			Graphics2D g2d = (Graphics2D) g;
			g2d.setStroke(new BasicStroke(3));

			g2d.setColor(Color.yellow);
			g2d.drawRect(
				arrow.getPos().x * tileSize,
				arrow.getPos().y * tileSize,
				tileSize,
				tileSize
			);
			g2d.drawRect(
				arrow.getDest().x * tileSize,
				arrow.getDest().y * tileSize,
				tileSize,
				tileSize
			);

			Shape arrowShape = createArrowShape(pos, dest);
			g.setColor(new Color(255, 0, 0, 127));
			g2d.fill(arrowShape);
			g2d.setColor(Color.black);
			g2d.draw(arrowShape);
		}
		// Draw possible moves if a piece was selected
		if (!dots.isEmpty()) {
			g.setColor(Color.green);
			int radius = tileSize / 4;
			for (Position dot : dots)
				g.fillOval(
					dot.x * tileSize + tileSize / 2 - radius / 2,
					dot.y * tileSize + tileSize / 2 - radius / 2,
					radius,
					radius
				);
		}
	}

	private Shape createArrowShape(Point pos, Point dest) {
		Polygon arrowPolygon = new Polygon();
		arrowPolygon.addPoint(-6, 1);
		arrowPolygon.addPoint(3, 1);
		arrowPolygon.addPoint(3, 3);
		arrowPolygon.addPoint(6, 0);
		arrowPolygon.addPoint(3, -3);
		arrowPolygon.addPoint(3, -1);
		arrowPolygon.addPoint(-6, -1);

		Point midPoint = midpoint(pos, dest);

		double rotate = Math.atan2(dest.y - pos.y, dest.x - pos.x);
		double ptDistance = pos.distance(dest);
		double scale = ptDistance / 12.0; // 12 because it's the length of the
											// arrow
											// polygon.

		AffineTransform transform = new AffineTransform();

		transform.translate(midPoint.x, midPoint.y);
		transform.rotate(rotate);
		transform.scale(scale, 5);

		return transform.createTransformedShape(arrowPolygon);
	}

	private Point midpoint(Point p1, Point p2) {
		return new Point(
			(int) ((p1.x + p2.x) / 2.0),
			(int) ((p1.y + p2.y) / 2.0)
		);
	}

	/**
	 * Displays green dots at a list of positions.
	 *
	 * @param dots the positions at which the dots should be displayed
	 */
	public void displayDots(List<Position> dots) {
		this.dots.clear();
		this.dots.addAll(dots);
		repaint();
	}

	/**
	 * Clears all dots displayed at some positions.
	 */
	public void clearDots() {
		dots.clear();
		repaint();
	}

	/**
	 * Displays an arrow from the position to the destination of a move.
	 *
	 * @param arrow the move indicating the arrows position and destination
	 */
	public void displayArrow(Move arrow) {
		this.arrow = arrow;
		repaint();
	}

	/**
	 * Clears the arrow displayed to indicate a move.
	 */
	public void clearArrow() {
		arrow = null;
		repaint();
	}

	/**
	 * @return the size of one board tile in pixels.
	 * @see dev.kske.chess.ui.BoardPane#getTileSize()
	 */
	public int getTileSize() { return boardPane.getTileSize(); }
}