import java.awt.*;
import java.awt.event.*;
import java.io.InputStream;
import java.util.Arrays;
import javax.comm.CommPortIdentifier;
import javax.comm.SerialPort;

public class GraphicReader extends Frame
{
  private static final int BUFFER_SIZE = 20;
  private static final int CANVAS_WIDTH = 400;
  private static final int CANVAS_HEIGHT = 400;

  public static void main(String[] args)
  {
    try {
      GraphicReader window = new GraphicReader();

      CommPortIdentifier id = CommPortIdentifier.getPortIdentifier("COM2");
      SerialPort port = (SerialPort) id.open("Reader", /*timeout=*/ 20000);
      port.setSerialPortParams(/*baudrate=*/ 9600,
                               SerialPort.DATABITS_8,
                               SerialPort.STOPBITS_1,
                               SerialPort.PARITY_NONE);
      InputStream in = port.getInputStream();

      while (true)
        window.addValue(in.read());

    } catch (Exception e) {
      e.printStackTrace(System.out);
    }
  }

  private PlotCanvas fCanvas = new PlotCanvas();

  GraphicReader()
  {
    super("Graphic Reader");

    addWindowListener(new CloseHandler());
    setResizable(false);
    add(fCanvas);
    pack();
    show();
  }


  void addValue(int value)
  {
    int x = (value & 0x0F) * (CANVAS_WIDTH / 16);
    int y = ((value & 0xF0) >> 4) * (CANVAS_HEIGHT / 16);
    fCanvas.addPoint(x, y);
  }

  class PlotCanvas extends Canvas
  {
    private int[] fPointX = new int[BUFFER_SIZE];
    private int[] fPointY = new int[BUFFER_SIZE];

    PlotCanvas()
    {
      setSize(CANVAS_WIDTH, CANVAS_HEIGHT);
    }

    void addPoint(int x, int y)
    {
      for (int index = 0; index < BUFFER_SIZE-1; index++) {
        fPointX[index] = fPointX[index+1];
        fPointY[index] = fPointY[index+1];
      }
      fPointX[BUFFER_SIZE-1] = x;
      fPointY[BUFFER_SIZE-1] = y;
      repaint();
    }

    public void paint(Graphics g)
    {
      ((Graphics2D) g).setStroke(new BasicStroke(3.0f));
      g.setColor(Color.blue);
      g.drawPolyline(fPointX, fPointY, BUFFER_SIZE);
    }
  }

  class CloseHandler extends WindowAdapter
  {
    public void windowClosing(WindowEvent e)
    {
      System.exit(0);
    }
  }
}