import java.awt.*;
import javax.swing.*;

public class NumberDisplay extends JComponent {
	public static final int DIGIT_WIDTH = 11;
	public static final int DIGIT_HEIGHT = 21;
	public static final int BACKDROP_WIDTH = 41;
	public static final int BACKDROP_HEIGHT = 25;
	public static final int MINUS_INDEX = 10;

	private static final int[] DIGIT_X = {28, 15, 2};
	private static final int DIGIT_Y = 2;

	public final Image BACKDROP;
	public final Image[] DIGITS;

	private int num;
	private boolean negative;

	public NumberDisplay(Image backdrop, Image[] digits) {
		BACKDROP = backdrop;
		DIGITS = digits;
		setPreferredSize(new Dimension(BACKDROP_WIDTH, BACKDROP_HEIGHT));
	}

	public void setNum(int num) {
		setClamped(num);
		repaint();
	}

	private void setClamped(int num) {
		// Clamp all number assignments between -99 and 999, inclusive
		if (num < 0) {
			this.num = Math.min(-num, 99);
			negative = true;
		} else {
			this.num = Math.min(num, 999);
			negative = false;
		}
	}

	@Override
	public void paintComponent(Graphics g) {
		g.drawImage(BACKDROP, 0, 0, this);
		// Preserve the original num for divison, in case we repaint twice
		// without updating the number
		int num = this.num;
		for (int i = 0; i < 3; i++) {
			int digitsIndex;
			if (negative && i == 2)
				digitsIndex = MINUS_INDEX;
			else
				digitsIndex = num % 10;
			g.drawImage(DIGITS[digitsIndex], DIGIT_X[i], DIGIT_Y, this);
			num /= 10;
		}
	}
}