/******************************************************************
 * @(#) Linear.java     1.1
 *
 * Copyright (c) 2005 John Miller
 * All Right Reserved
 *-----------------------------------------------------------------
 * Permission to use, copy, modify and distribute this software and
 * its documentation without fee is hereby granted provided that
 * this copyright notice appears in all copies.
 * WE MAKE NO REPRESENTATIONS OR WARRANTIES ABOUT THE SUITABILITY
 * OF THE SOFTWARE, EITHER EXPRESS OR IMPLIED, INCLUDING BUT NOT
 * LIMITED TO THE IMPLIED WARRANTIES OF MERCHANTABILITY, FITNESS
 * FOR A PARTICULAR PURPOSE, OR NON-INFRINGEMENT. WE SHALL NOT BE
 * LIABLE FOR ANY DAMAGES SUFFERED BY ANY USER AS A RESULT OF USING,
 * MODIFYING OR DISTRIBUTING THIS SOFTWARE OR ITS DERIVATIVES.
 *-----------------------------------------------------------------
 *
 * @version     1.1, 28 Sep 2005
 * @author      John Miller
 */

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


/******************************************************************
 * The Linear class displays a line based upon inputs from the
 * command-line and then moves a ball parametrically along the line.
 */
public class Linear extends JFrame
                    implements Runnable
{
    private static final int        STEP = 5;
    private static final Dimension  DIM  = new Dimension (600, 600);

    private Line2D        line;
    private Ellipse2D     ball;
    private Point2D       pos;
    private int           nSteps;
    private double        dx;
    private double        dy;
    private final Thread  displayer;


    /**************************************************************
     * The DisplayPanel inner class is used to place shapes in the
     * drawing region.
     */
    public class DisplayPanel extends JPanel
    {

        /**********************************************************
         * Paint the display panel component.
         * @param  gr  Graphics context.
         */
        public void paintComponent (Graphics gr)
        {
            super.paintComponent (gr);
            Graphics2D gr2 = (Graphics2D) gr;

            gr2.setColor (Color.red);
            gr2.draw (line);

            gr2.setColor (Color.blue);
            ball.setFrame (pos.getX () - 10, pos.getY () - 10, 20, 20);
            gr2.fill (ball);

        } // paintComponent


    } // DisplayPanel inner class


    /**************************************************************
     * Construct a frame.
     * @param  title  Title of frame
     * @param  x1     Point 1's x coordinate
     * @param  y1     Point 1's y coordinate
     * @param  x2     Point 2's x coordinate
     * @param  y2     Point 2's y coordinate
     */
    public Linear (String title, double x1, double y1, double x2, double y2)
    {
        super (title);

        setDefaultCloseOperation (JFrame.EXIT_ON_CLOSE);

        line = new Line2D.Double (x1, y1, x2, y2);

        double distX = x2 - x1;
        double distY = y2 - y1;
        //double dist  = Math.sqrt (distX * distX + distY * distY);
        double dist  = Math.max (Math.abs (distX), Math.abs (distY));

        nSteps = (int) dist / STEP;
        dx     = distX / (double) nSteps;
        dy     = distY / (double) nSteps;

        ball = new Ellipse2D.Double ();
        pos  = new Point2D.Double (x1, y1);

        add (new DisplayPanel ());
        setLocation (100, 100);
        setSize (DIM);
        setVisible (true);
        displayer = new Thread (this, "displayer");
        displayer.start ();

    } // Linear


    /**************************************************************
     * Run method for the display thread.
     * Repeatedly update coordinates, sleep and repaint.
     */
    public void run ()
    {
        for (int i = 0; i < nSteps; i++) {

            pos.setLocation (pos.getX () + dx, pos.getY () + dy);

            System.out.println (" ( " + pos.getX () + " , " + pos.getY () + " ) ");

            try {
                displayer.sleep (75);
            } catch (InterruptedException ex) {
                System.err.println ("Linear.run: sleep failed");
            }; // try

            repaint ();

        }; // for

    } // run


    /**************************************************************
     * Main method for invoking the application.
     * @param  args  Command-line arguments
     */
    public static void main (String [] args)
    {
        if (args.length != 4) {
            System.out.println ("Linear.main: usage: java Linear x1 y1 x2 y2");
            System.exit (0);
        }; // if

        Linear frame = new Linear ("Linear",
                                   Double.parseDouble (args [0]),
                                   Double.parseDouble (args [1]),
                                   Double.parseDouble (args [2]),
                                   Double.parseDouble (args [3]));

    } // main


} // Linear class